WO2020039229A1 - Photocatalytic water splitting by combining semiconductor nano-structures with fabricated metal and/or metal alloy or waste metal and/or metal alloy to generate hydrogen gas - Google Patents
Photocatalytic water splitting by combining semiconductor nano-structures with fabricated metal and/or metal alloy or waste metal and/or metal alloy to generate hydrogen gas Download PDFInfo
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- WO2020039229A1 WO2020039229A1 PCT/IB2018/056265 IB2018056265W WO2020039229A1 WO 2020039229 A1 WO2020039229 A1 WO 2020039229A1 IB 2018056265 W IB2018056265 W IB 2018056265W WO 2020039229 A1 WO2020039229 A1 WO 2020039229A1
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- titanium dioxide
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
- C01B3/042—Decomposition of water
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
- B01J21/063—Titanium; Oxides or hydroxides thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/133—Renewable energy sources, e.g. sunlight
Definitions
- This invention is related to photocatalytic water splitting method by combining semiconductor nano-structures (SNSs) with metal and/or metal alloy to generate hydrogen gas.
- SNSs semiconductor nano-structures
- This method of the invention comprises
- Photon wave and particle like, bundle or packet of energy from the sun of light with sufficient frequency, excites semiconductor nano-structures, it produces a negative charge (electron) and positive charge (hole). Electrons hop to the conduction band (CB) by absorbing the energy of the photons and leaving the holes in the valence band (VB). These exited electrons generated from the photons are called photoelectrons which reduce the hydrogen atoms of water molecules and form hydrogen gas while the positively charge holes oxidize the oxygen atoms of the water molecules to form oxygen gas.
- CB conduction band
- VB valence band
- Metal and/or Metal alloy is the obstacle to the recombination of negatively charge photoelectrons with positively charge holes with respect to the attractive electrical properties of the metal and/or metal alloy which allows transfer the stream of photoelectrons from the semiconductor nano structures to the metal and/or metal alloy. This effect leads and increase the redox reactions by acting metal and/or metal alloy as a best photoelectron acceptor and barrier to the rapid recombination process of photoelectrons and holes in order to increase the yield of hydrogen gas. BACKGROUND ART OF THE INVENTION.
- the electron can rapidly transfer to the metal/metal alloy and hydrogen generation ensues.
- the photocatalysts illumination of photon it is subjected to separate positive and negative charge from each other due to the electrical property of the metal and/or metal alloy.
- one type of charge leaves the semiconductor material and occupy the metal and/or metal alloy and the opposite charge remains in the semiconductor material.
- this charge separation between the metal and/or metal alloy and semiconductor nanostructures rapid recombination process decrease by increasing the redox reactions, leads to the more yield of hydrogen gas.
- researchers who are interested about photocatalytic hydrogen generation around the world are attempting to invent low cost, high efficient and environmentally friendly hydrogen generation system and they have enormous disadvantages as below.
- CdSe-Au and CdSe-Pt nanodumbbells were prepared in international publication number WO 2008/102351 A2 as a photocatalysts and here describes when a photon absorb with sufficient energy by semiconductor region of nanodumbbell it is subjected to separate charge particle.
- inventors were grown Cadmium Selenide (CdSe) nano rods by using high temperature pyrolysis. In the pyrolysis process they have used suitable precursors with a coordinating solvent containing a mixture of trioctylphosphineoxide and phosphonic acid. And used the AuCl 3 and PtCl 4 as a gold and platinum source.
- Various methods are account of preparation of semiconductor structures and/or size such as aerosol process, sol gel method, inert gas condensation, chemical vapor deposition, electrochemical plating so on.
- Nagaveni et al. given the comparison description about photocatalytic activity between of size, nanocrystal structures and Degussa P-25 nanoparticles of titanium dioxide by giving precise details to understand the variation of the band gap energy in order to size and nanocrystal structure. They were pursued solution combustion method to develop titanium dioxide nanocrystals.
- This variation of structures and sizes lead to avoid poor respond of visible light of solar radiation.
- photocatalytic activity is stiffen to short time of period and it is disadvantage. Rapid recombination is also reduce the life time of photoactivity of this nanostructures.
- Titanium dioxide ( Ti0 2 ) has considerable properties when compared with other semiconductors such as ZnO, Fe 2 0 3 , W 0 3 , CdS, CdSe and SiC so on.
- Ti0 2 Is reliable semiconductor able to utilize as photocatalyst because of its high chemical stability, non-corrosive, environmentally friendly, photostability, nontoxicity, abundant, redox efficiency, and cost efficiency.
- Another photocatalytic water splitting system under visible light performed by preparing mixture of Pt- W0 3 and the Pt-SrTi0 3 (Cr-Ta doped) as photocatalyst in Nal or NaI0 3 aqueous solution by Sayama et al.
- titanium dioxide utilize by taking the advance of semiconductor properties which have discussed above.
- nano structures of titanium dioxide was synthesized by following hydrothermal process of P-25 of Ti0 2 .
- the mixed-phase Ti0 2 nanocomposit was prepared by hydrothermal method by Li et al. This process cannot use industrially due to several chemicals employing and various treatment steps and they were not included water splitting ability of the photocatalyst.
- titania (Ti0 2 ) nanotubes photocatalyst Another good approach to the synthesis of titania (Ti0 2 ) nanotubes photocatalyst was published by Akilavasan et al. They were used hydrothermal method and performed hydrothermal process on Degussa P25 Ti0 2 nanoparticles. In this experiment they were pursued several treatment steps to achieve the titanium dioxide nanotubes as an ultimate goal and here they were used only one temperature 150 C° (423.15 k) for the hydrothermal process. This hydrothermal method has good potential in order to make titania nanoparticles but above method is too long and it consume the time. In the present invention also use the hydrothermal method to synthesis titanium dioxide nanostructures but with range of temperatures and very short treatment process also pH control is unnecessary.
- the present invention describes the method to development and utility of photocatalyst which is based on semiconductor and metal and/or metal alloy combination.
- Photocatalyst absorb the photon of the light, photon with sufficient energy excites the valance electron in order to increase the kinetic energy of the valance electron.
- This excited electron leave the valance band of the semiconductor due to its high energy and find the suitable quantum state for this energy in order to make nearly free or free electrons which are allowed to produce the stream of electrons in the semiconductor.
- the energy level(s) which the photoexcited electrons are occupied is known as conduction band (CB).
- a photocatalyst comprises a titanium dioxide nanostructures and metal and/or metal alloy. Titanium dioxide nanocomposite was synthesized from the simple hydrothermal method by using P25 (Degussa) titanium dioxide nanoparticles as the starting material.
- Synthesized titanium dioxide nanostructures was mixed with the metal and/or metal alloy of the cleaned beer can by using spraying method or any other suitable methods or by following simple mixing method and ethanol, methanol, water or any other suitable chemicals can be used as a solvent and/or mixing agents.
- Various particle sizes and structures and/or any other shapes of metal and/or metal alloy of cleaned and/or non cleaned beer cans could be used.
- Different ratios in any parameters of titanium dioxide nanostructures and metal and/or metal alloy of beer cans able to be used.
- This photocatalyst can be mix/combined with any other photocatalysts which are exist in the universe in order to make different photocatalysts.
- Photocatalytic activity of photocatalyst is observed in the single structure and the bulk of the structures. According to the preparation method of photocatalyst, it is absorb the wide range of wave length in the electromagnetic spectrum. The absorption capacity is wider from visible to near infrared region (UV absorption is obvious). The minimum hydrogen volume generating rate of the 3g of catalyst is 1.6874 ml / min.
- Electrons jump to the conduction band (CB) by absorbing photon energy while holes are remaining in the valance band (VB).
- Photoexcited electron in the semiconductor material able to donates this electron to any other species which prefer to accept the electron.
- photoexcited hole reduces by oxidizing any other species that prefer to oxidize. Accordingly, following problems are occur.
- Titanium dioxide is inexpensive, nontoxic and abundant semiconductor.
- Ti0 2 is a good promising semiconductor because of its photostability. So in this invention used these properties as advantages for water splitting and/or any kind of oxidation and reduction system.
- the sodium hydroxide (NaOH) which use in hydrothermal process increase the pH of water and/or aqueous media by releasing hydroxyl (OH-) groups, these hydroxyl groups able to come closer and donate the electron(s) to the hole(s). Both two mechanism minimize the rapid recombination of photoexcited electron and hole.
- the hydroxyl (-OH) groups alter the polarity on titanium dioxide nanostructures which makes the solubility of these nanostructures in a water and/or polar solution.
- the different nanostructures and sizes lead to absorb various wavelength of incident light to excite more electrons in the semiconductor nanostructures, using the metal and/or metal alloy conductor and hydroxyl groups act as a barrier in order to minimize or stop the rapid recombination of photoelectrons and photoexcited holes.
- the rate of redox reaction is increase due to above facts.
- metal and/or metal alloy collect more photoexcited electrons and release the electron(s) for the reduction purpose so the reaction take place even in the dark, metal and/or metal alloy and hydroxyl groups minimized or stop the recombination those ensure the life time and production ability of the photocatalytic system.
- Metal and/or metal alloy is highly corrosive. Nevertheless, by combining with this non corrosive titanium dioxide nanostructures the metal and/or metal alloy protect from the corrosion and the waste metal and/or metal alloy is resist to the corrosion. So in the sea water the photocatalytic activity ensure with same rate.
- Waste metal and/or metal alloy made to achieve the non-corrosive property with combining metal complex. So this property is highly regarded in this invention.
- Photocatalyst able to change the physical property (nanoparticles, microparticles, layers, powder, dust so on) upon the purpose without reducing the rate of redox reaction. So it is easy to handle and transport.
- the row materials can be used again for the same purpose by following the same preparation methods.
- Hydroxyl groups alter the polarity on photocatalyst in order to disperse in the water and/or any aqueous solution.
- Beer cans can find everywhere around the environment, in this invention beer can use as the metal and/or metal alloy source and it is reduce the environmental pollution, cleaning cost and labor hours.
- Beer cans are non-corrosive so directly able to use beer can as a metal and/or metal alloy without further modification for achieve non-corrosive properties it save the time and cost.
- Titanium dioxide nanostructures and metal and/or metal alloy of beer cans both are non- corrosive so in any aqueous medium the photocatalyst is being stable and ensure the redox reaction in order to achieve ultimate goal.
- Any stirring techniques can use to disperse titanium dioxide in the sodium hydroxide aqueous solution.
- Titanium dioxide and beer cans are abundant then the photocatalyst is reliable and promising for the water splitting or any other purpose which required the property of this photocatalyst.
- Hydrogen is a green energy generating hydrogen by using waste beer cans accelerate the rate of development of green energy world like a catalyst.
- this invention is inexpensive, environmentally friendly, stable, wide usability, non-corrosive, time saving, reliable, non-toxic, re-usable, promising so on and very simple water splitting method able to use in vast industrial application.
- the titanium dioxide nanostructures there is at least one nanostructure combine with the metal and/or metal region which absorb the visible to near infrared region.
- the at least one semiconductor nanoregion absorbed by a wave length range of 200 nm to 3 mhi.
- the at least one semiconductor nanoregion absorb the wave length of 380 nm to 1.1 mth.
- the at least one semiconductor nanoregion absorb the wave length of 380nm to 420 nm.
- other elemental semiconductors and/or their compositions and/or alloy thereof such as Si, Ge and some elements from the groups V and VI such as P, S, Se, Te etc. and Eu and Mn and binary compound such as GaAs, ZnSe, ZnS, ZnTe, HgS, HgSe, HgTe, CdSe, CdS, CdTe, Pbl 2 and MoS 2 and binary compound formed from groups IV and VI elements such as PbS, PbTe, SnS so on and the oxides semiconductors such as CuO, Cu0 2 , Cu 2 0, Si0 2 and La 2 Cu0 4 and alloy thereof such as CdZnSe, CdSeTe, ZnCdSe, SbSI, AgGaS 2 , ZnSiP 2 , As 2 Se 3 and Cd 1-x Mn x Te and mixtures thereof and organic semiconductors such as polyacetylene [(CH 2 ) n ], polydiacetylene [(CH
- the same nanostructures and different nanocomposite combined with same metal and/or metal alloy and/or different metal and/or metal alloy are discuss herein as a nanoregion absorbed the photon energy and excite the electron to ensure the photocatalytic activity.
- At least one grain of metal and/or metal alloy is combined with at least one titanium dioxide nanoregion. In some other embodiments, at least two grains of metal and/or metal alloy are combined with at least one titanium dioxide nanoregion.
- the metal and/or metal alloy can be produce my mixing different composition/ratios of the metal which used in to production of beer cans.
- the metal and/or metal alloy can be made by using different combination and/or different ratios of Al, Mg, Mn, Cu, Si, Fe, Zn, Ga, V , Ti and alloy thereof.
- the metal and/or metal alloy can be made by combining with above metal and/or different composition of above metal by mixing with different metal and/or metal alloy composition and/or any suitable element(s).
- the metal and/or metal alloy can be made by combining different metal such as Pt, Mo, Ru, Rh, W, Ag, Au, Zn, Hg, Cn, In, Tl, Nh, Sn, Pb, As, Sb, Bi, Me, Po, Fl, Lv, As, Ts, Hf, Rf, Ba, Cs, Fr, Rb, Se, I, Te, Os, Hs, Bh, Db, Ta, Ir, Re, Na, Li, element in lanthanide series and actinide series etc. and/or metal alloy thereof and any suitable element(s) and alloy thereof with metal and/or metal alloy of beer cans and/or red bull cans or any other waste metal and/or metal alloy.
- different metal such as Pt, Mo, Ru, Rh, W, Ag, Au, Zn, Hg, Cn, In, Tl, Nh, Sn, Pb, As, Sb, Bi, Me, Po, Fl, Lv, As, Ts, Hf, Rf, Ba, Cs
- any transition metal and or any metal and alloy thereof and there are non-limiting instances of semiconductors and mixtures thereof and metal and metal alloy and mixtures thereof could be investigate with the present photocatalyst and there are various non-limited processing techniques and methods to fabrication of this photocatalyst and mixtures thereof such as chemical vapor deposition method, hydrothermal methods, ion implantation method, Czochralski Method, Birdman Method, Metal-Organic chemical vapor deposition, Molecular beam epitaxy and Liquid phase epitaxy, spraying methods, sintering methods/techniques, cooling methods/techniques so on.
- processing techniques and methods to fabrication of this photocatalyst and mixtures thereof such as chemical vapor deposition method, hydrothermal methods, ion implantation method, Czochralski Method, Birdman Method, Metal-Organic chemical vapor deposition, Molecular beam epitaxy and Liquid phase epitaxy, spraying methods, sintering methods/techniques, cooling methods/techniques so on.
- the temperature 100 °C to 170 °C or above 170 °C and time 6 hours to 72 hours or above 72 hours, different temperature and different time combination thereof for the hydrothermal process are different temperature and different time combination thereof for the hydrothermal process.
- same temperature with different time combinations for the hydrothermal process same temperature with different time combinations for the hydrothermal process.
- different amount of Degussa P25 titanium dioxide nanoparticles dispersed in the different concentrations of sodium hydroxide aqueous solution above 10 M or below 10 M.
- the various composition of titanium dioxide nanostructures can be obtain by applying different temperature and time combinations and different volume of Teflon lined autoclave for the hydrothermal method.
- the metal and/or metal alloy can select from the waste such as beer cans, red bull cans and/or any other cans which made by beer can composition and/or red bull can composition and/or any other suitable metal and/or metal alloy and/or metal and/or metal alloy sheets of beer cans and/or red bull can or any other suitable metal and/or metal alloy and/or mixture thereof.
- Metal and/or Metal alloy is accept the electron and make the electron rich surface and act as a barrier to the rapid recombination process of electron and hole. This phenomenon ensure the life time of oxidative and reductive reactions in order to splitting water to oxygen and hydrogen. So the combining with low cost metal and/or metal alloy with this synthesized semiconductor facilitate the utilization of the present invention in industrial purpose.
- Fig. 1 shows the gas chromatography data of hydrogen generation volume in milliliter of 30 ml of water and 3 g of photocatalyst at the room temperature.
- Fig. 2 shows the gas chromatography data of the hydrogen generation volume in milliliter of 30 ml of water and 3g of photocatalyst at the room temperature, after seventeen hours and ten minutes from the end point value of time axis of the Fig. 1.
- Fig. 3 shows the gas chromatography data of the hydrogen generation volume in milliliter of 30 ml of water and 3g of photocatalyst at the room temperature, after twenty three hours from the end point value of time axis of the Fig. 2.
- Fig. 4 shows the hydrogen generation in micromole of 30 ml of water and 3 g of photocatalyst at the room temperature.
- Fig. 5 shows the hydrogen generation in micromole of 30 ml of water and 3 g of photocatalyst at the room temperature, after seventeen hours and ten minutes from the end point value of time axis of the Fig. 4.
- Fig. 6 shows the hydrogen generation in micromole of 30 ml of water and 3 g of photocatalyst at the room temperature, after twenty three hours from the end point value of time axis of the Fig. 5.
- P25 titanium dioxide nanoparticles were used as a titanium dioxide source in order to synthesis of titanium dioxide nanostructures as a semiconductor material.
- 4 g and 6 g (or different amount ) of P25 titanium dioxide nanoparticles were dispersed in 21 ml and 31.5 ml of 10 M (or above 10 M) of sodium hydroxide (NaOH) aqueous solution by using magnetic stirrer for about 30 minutes respectively. After 30 minutes (or > 5 minutes), the mixtures were transferred into Teflon lined autoclave with capacity 28 ml and 42 ml respectively. After that, Teflon autoclaves were kept at 170 °C for 24 hours in a furnace. Then, after the hydrothermal process the product was ready for the combine with waste metal and/or metal alloy without further treatments.
- NaOH sodium hydroxide
- any kind of beer cans as a waste metal and/or metal alloy (and/or red bull can or any other suitable waste metal and/or metal alloy) and beer cans were cleaned by using sand paper and/or suitable chemical or method.
- Synthesized titanium dioxide nanocomposite ( ⁇ 4g wet) was dispersed in approximately 40 ml of ethanol by using magnetic stirrer for about 5 minutes and it was transferred into a solution container of spray gun. This nanocomposite was sprayed by using air compressor onto the both sides of cleaned beer can and obtained a thin layer of titanium dioxide nanocomposite on the clean beer can. After that, it was kept at 420 °C for 3 hours in an oven.
- the synthesized titanium dioxide nanocomposite was mixed with various size of cleaned beer can such as nanoparticle, microparticle, powder, dust, small pieces so on and mixture thereof. Titanium dioxide nanoparticles and various states of beer can were mixed in different ratios in weight such as, Ti0 2 nanoparticle: beer can particle, 1 : 1, 2: 1, 1:2 and 3: 1 so on. Mixtures were sintered to the same temperature and time in an oven as above. After, photocatalytic activity was performed.
- Sodium hydroxide concentration equal or higher than 10 M (> 10 M) is more preferred for the hydrothermal process.
- temperature and time combinations were performed in an oven. Temperature from 412 °C to 450 °C and from 1 to 5 hour(s) any combination is more preferred for the oven.
- nanostructures or“nanocomposite” used because of there may be various structures and sizes such as nano rods, nanosheets, nanocylinders so on.
- the synthesized nanocomposite there may be a various type of structures and sizes, absorb the different wavelength of light.
- Hydroxyl groups alter the polarity on the nanostructures in order to dissolve in water and/or aqueous media.
- Hydroxyl groups increase the pH of media, travel to the nanostructure and oxidize and minimize the rapid recombination, Increase the redox reaction. Hydrogen production ensure.
- Beer cans used as waste metal and/or metal alloy reduce the environmental pollution and reduce the cost and time and increase the efficiency of the hydrogen production.
- Corrosion resistance is another benefit of the beer can.
- Beer can, metal and/or metal alloy collect the photoelectron and donate to the hydrogen atom to reduce to hydrogen molecule.
- Photoexcited electron occupy the metal and/or metal alloy of beer can by leaving the titania nanostructure and reduce the recombination process and increase the redox reaction.
- the redox reactions ensure in the dark due to collection of photoexcited electrons in the metal and/or metal alloy of beer can.
- Metal and/or metal alloy can be made by mixing the different ratio of element which in beer can.
- the catalytic activity of synthesized photocatalyst was studied in room temperature and dark.
- the gas chromatography was carried out and the hydrogen production of 3g of photocatalyst in 30 ml of distilled water and the ratio of Ti0 2 nanostructures to beer can particles were 2: 1 and hydrogen generation rate is 1.6874 ml / min
- the photocatalyst has wide range of industrial applications due to its chemical, physical and other properties such as high chemical stability, non-corrosive, inexpensive, environmentally friendly, extensive life span, non-toxic, reaction efficiency, low synthesis process, high solar to hydrogen conversion efficiency, easy to handle, easy transportation and simple so on. According to the beautiful properties of the photocatalyst it is a reliable and promising source for the photo-oxidation and photo-reduction or photocatalytic applications and also light induce charge separation such as electrochemical and photovoltaic cell.
- the present invention has great potential for the photocatalytic water splitting to generate hydrogen gas as an energy carrier for all kind of energy requirement.
- photocatalyst absorb the photon energy and split the water molecule in to the hydrogen and oxygen by using reduction and oxidation half reaction known as redox reaction. So the ultimate product of this invention solve the big problem of the world by releasing the hydrogen molecules as an energy carrier. So as an energy carrier hydrogen gas employ enormous industrial applications are discuss herein below.
- Fossil fuel which used in combustion engine can replace by hydrogen gas to do the same thing but in high efficiency and hydrogen release more energy than fossil fuel (petrol, diesel etc.) and the product is the pure water of this reaction. No harmful gases.
- Hydrogen fuel cell convert the hydrogen molecule in to the protons and release the electrons to produce the electric current for any purpose which can utilized electric current. Protons are travel through the proton exchange membrane and react with oxygen in order to make the water molecule. Hydrogen fuel cell can use for the electrical vehicle and can connect to the electrical grid for the electricity.
- Combustion energy of hydrogen can use as a heat energy to produce the energy to water for make the steam for a steam power plant.
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Abstract
There are various type of energy sources on the earth. Some of energies are derived from the resources like the sun and the wind that can easily be replenished, those energies known as renewable energies. Nonrenewable resources are energy sources like petroleum, natural gas, coal, and nuclear energy that take millions of years to form. They cannot be recreated over a short period of time. Wind, fire, water (hydro power), geothermal energy, marine (Ocean) and bioenergy power are some examples for the renewable energy sources. There is a hazard of nonrenewable energy sources and various disadvantages are account. The demand for energy not decreases. Environmental friendly, inexpensive, efficient renewable energy sources are the most important for the green world. The invented photocatalytic water splitting method introduce as a novel and competent approach to generate hydrogen as an energy carrier as a foremost energy in the green world. Degussa P25 nanoparticles are disperse in the sodium hydroxide aqueous solution (≥10 M) and hydrothermal process was performed under the range of temperature and time combinations and synthesized titanium dioxide was sprayed on the cleaned beer can and/or mixed with the various sizes of metal and/or metal alloy of beer can and mixture thereof and sintering process was performed under the various temperature and time combinations. The photocatalytic activity was performed in the room temperature as well as in the dark. Hydrogen generation was measured by using gas chromatography (GC) and other characterization was done by XRD, UV-VIS spectroscopy and SEM. The gas chromatography result shows the efficiency of photocatalytic hydrogen generation and the hydrogen generation rate can be controlled by changing the various parameters of the catalyst as well as the treatment conditions.
Description
PHOTOCATALYTIC WATER SPLITTING BY COMBINING SEMICONDUCTOR NANO STRUCTURES WITH FABRICATED METAL AND/OR METAL ALLOY OR WASTE METAL AND/OR METAL ALLOY TO GENERATE HYDROGEN GAS
TECHNICAL FIELD OF THE INVENTION.
This invention is related to photocatalytic water splitting method by combining semiconductor nano-structures (SNSs) with metal and/or metal alloy to generate hydrogen gas.
This method of the invention comprises
Unlike conductors, the electronic structure of semiconductor materials are different. In conductors there are virtually/nearly free electrons, external voltage exert the force on those electrons and directed to flow of electrons in order to make the electric current. Nevertheless, there is an energy gap also known as band gap ( Eg ) which separates valance band (VB) and conduction band (CB) of semiconductors.
Photon (wave and particle like, bundle or packet of energy from the sun) of light with sufficient frequency, excites semiconductor nano-structures, it produces a negative charge (electron) and positive charge (hole). Electrons hop to the conduction band (CB) by absorbing the energy of the photons and leaving the holes in the valence band (VB). These exited electrons generated from the photons are called photoelectrons which reduce the hydrogen atoms of water molecules and form hydrogen gas while the positively charge holes oxidize the oxygen atoms of the water molecules to form oxygen gas.
Metal and/or Metal alloy is the obstacle to the recombination of negatively charge photoelectrons with positively charge holes with respect to the attractive electrical properties of the metal and/or metal alloy which allows transfer the stream of photoelectrons from the semiconductor nano structures to the metal and/or metal alloy. This effect leads and increase the redox reactions by acting metal and/or metal alloy as a best photoelectron acceptor and barrier to the rapid recombination process of photoelectrons and holes in order to increase the yield of hydrogen gas.
BACKGROUND ART OF THE INVENTION.
Nature has stored solar energy in the form of mineral organic compounds or in fossil fuels such as coal, petroleum, and natural gas over millions of years of biological and non-biological processes . All living things they consume energy in an enormous way. Among those, the human beings use the fossil fuel for their daily requirement, as instances travelling, cooking, generating electricity and agricultural used etc. Hence there is a high demand to the energy and the demand is directly proportional to the population around the earth but fossil fuels are inversely proportional to the population and it is catastrophic. Considering this phenomenon fossil fuels are depleting gradually and steadily. Carbon dioxide (C02) and other harmful gasses emitted destroy the equilibrium of the system of earth while using of fossil fuels. Hence the generating reliable, inexpensive and environmentally friendly green energy from the renewable sources such as solar power, water and wind is more attractive. The amount of solar radiation that reach the earth in a year exceeds our current annual energy need more than ten thousand folds. A promising approach is to utilize incoming solar radiation for photocatalytic generation of molecule hydrogen from water. Photocatalytic hydrogen production from water by utilizing solar radiation is inexpensive, environmentally friendly and by using small plant area can produce more hydrogen are some advantages. Hydrogen gas is an excellent energy source, with the product of its being again water, thereby making it free of greenhouse gases. These scenarios hold the attention on photocatalytic hydrogen generation as an energy carrier.
Efficient hydrogen generation as an energy carrier by using quanta of light (photon), and photocatalysts hydrogen generation from water has been a challenge to humans. Researchers, they are working to harness solar power to split the water molecule by inserting photocatalysts to generate hydrogen as an inexpensive and environmentally friendly energy carrier. Photocatalytic synthesis of hydrogen gas from water requires the transfer of electrons to the hydrogen atom so- called reduction of hydrogen atom, while the holes interact with the oxygen or are scavenged by other molecules known as oxidation of oxygen atom. Nevertheless, before any of this can happen, the photogenerated electrons and holes must be quickly separated from each other. However, ultimate energy derivation from the renewable sources should satisfy the natural equilibrium of the earth.
There is a high demand on efficient photocatalyst, the search for photocatalysts has been a long time quest in the field of Science. Semiconductor nanostructures have been investigated for their photocatalytic activity. Illumination of the sufficient photons of the light produce electrons and holes. Nevertheless, rapid recombination decrease the rate of reduction and oxidation reactions in the photocatalysts. Hence hydrogen generation rate decrease. The need of polar molecule being attached to the semiconductor nanostructures as surface ligands in order to make the semiconductor nanostructures water-soluble is one of problem to generate sufficient hydrogen and it is advantage to the rapid recombination process. These ligand forest make it difficult for the holes to interact with water or other large scavenger molecules.
If the semiconducting nanostructures are decorated with the metal and/or metal alloy, such as metal platinum, nickel and palladium etc., the electron can rapidly transfer to the metal/metal alloy and hydrogen generation ensues. When the photocatalysts illumination of photon it is subjected to separate positive and negative charge from each other due to the electrical property of the metal and/or metal alloy. In this scenario one type of charge leaves the semiconductor material and occupy the metal and/or metal alloy and the opposite charge remains in the semiconductor material. According to this charge separation between the metal and/or metal alloy and semiconductor nanostructures rapid recombination process decrease by increasing the redox reactions, leads to the more yield of hydrogen gas. However, researchers who are interested about photocatalytic hydrogen generation around the world are attempting to invent low cost, high efficient and environmentally friendly hydrogen generation system and they have enormous disadvantages as below.
In United States patent US 6,533,033 B l Amendola et al. Used the metal hydrides to generate hydrogen gas and in this patent preferred following borohydrides sodium borohydride, lithium borohydride, potassium borohydride, ammonium borohydride, tetramethyl ammonium borohydride, quaternary borohydrides and mixtures thereof generate hydrogen and borate by reaction with water, and this chemical reaction occurs very slowly unless a catalyst is used. This invention provides methods of preparation of catalyst to increase generate hydrogen by using Anionic Exchange Resin substrate, Cationic Exchange Resin substrate, Ceramic and/or carbon Substrate, Electro Chemical Plating and Chemical Vapor Deposition so on. In those techniques, due to high treatment steps it consumes high processing time, using various kind of chemicals and
expensive metal hydrides, expensive metal and/or metal alloy and using expensive complex machinery to develop the catalyst are minimizing or act as obstacles to utilization of hydrogen gas and cannot use these methods in vast industrial and commercial purpose. However, this methods do not deal with the renewable energy sources and semiconductor nanostructures different from the photocatalyst system from the present invention.
CdSe-Au and CdSe-Pt nanodumbbells (NDBs) were prepared in international publication number WO 2008/102351 A2 as a photocatalysts and here describes when a photon absorb with sufficient energy by semiconductor region of nanodumbbell it is subjected to separate charge particle. In this invention, inventors were grown Cadmium Selenide (CdSe) nano rods by using high temperature pyrolysis. In the pyrolysis process they have used suitable precursors with a coordinating solvent containing a mixture of trioctylphosphineoxide and phosphonic acid. And used the AuCl3 and PtCl4 as a gold and platinum source. In here the separation of Cadmium Selenide nano rods and making of NDBs have several steps those are consumed the time when compare with present invention also gold and platinum sources are somehow expensive and using lot of chemicals and treatment processes make a barrier to the commercial purpose and utilization of hydrogen gas as a sustainable energy in a huge industrial sector.
Still suffer from lack of efficient, environmentally friendly, inexpensive, long term and simple photocatalytic hydrogen production system for industrial sector to achieve renewable energy goal for the green planet. Upon above facts the present invention present the fascinating, reliable, efficient, environmental friendly, inexpensive, long term, re-usable and very simple photocatalytic system for the green world and it is magnificence. When a photon incident with a sufficient energy semiconductor material absorb the photon and produce the negative (electron) and positive (hole) charge. Photoelectron hops to the conduction band and hole occupy in the valance band this precious behavior occurs in the semiconductor material and it depends on the band gap of the semiconductor material. To overcome this energy gap to be a conductive the energy of the incident photon must have the same energy as band gap at all of certain semiconductor material.
Sun distributes its energy in various range of wave length. There is a unique magnitude of the energy of specific wave length. Nevertheless, the energy gap of the certain semiconductor can vary under the structure and/or size. Various methods are account of preparation of semiconductor structures and/or size such as aerosol process, sol gel method, inert gas condensation, chemical
vapor deposition, electrochemical plating so on. Nagaveni et al. given the comparison description about photocatalytic activity between of size, nanocrystal structures and Degussa P-25 nanoparticles of titanium dioxide by giving precise details to understand the variation of the band gap energy in order to size and nanocrystal structure. They were pursued solution combustion method to develop titanium dioxide nanocrystals. This variation of structures and sizes lead to avoid poor respond of visible light of solar radiation. However, photocatalytic activity is stiffen to short time of period and it is disadvantage. Rapid recombination is also reduce the life time of photoactivity of this nanostructures.
Titanium dioxide ( Ti02) has considerable properties when compared with other semiconductors such as ZnO, Fe203, W 03, CdS, CdSe and SiC so on. Ti02 Is reliable semiconductor able to utilize as photocatalyst because of its high chemical stability, non-corrosive, environmentally friendly, photostability, nontoxicity, abundant, redox efficiency, and cost efficiency. Another photocatalytic water splitting system under visible light performed by preparing mixture of Pt- W03 and the Pt-SrTi03 (Cr-Ta doped) as photocatalyst in Nal or NaI03 aqueous solution by Sayama et al. Another approached to investigate an infrared photon active catalytic system for the conversion of solar energy to chemical energy by using Ag20/Ti02 composite photocatalyst for water splitting experimentally introduced by Gannoruwa et al. Several treatment steps and various chemicals consume the time and money respectively, even if production life time of hydrogen is long. In industrial sector low cost, efficient, environmentally friendly and simple persistent hydrogen production methods are preferred.
By deep concerning upon above facts the present invention introduce environmentally friendly, inexpensive and long term simple hydrogen generation method for the utilization of hydrogen as a sustainable energy, for a green world. In this photocatalytic water splitting system titanium dioxide utilize by taking the advance of semiconductor properties which have discussed above. In this experiment nano structures of titanium dioxide was synthesized by following hydrothermal process of P-25 of Ti02. The mixed-phase Ti02 nanocomposit was prepared by hydrothermal method by Li et al. This process cannot use industrially due to several chemicals employing and various treatment steps and they were not included water splitting ability of the photocatalyst.
Another good approach to the synthesis of titania (Ti02) nanotubes photocatalyst was published by Akilavasan et al. They were used hydrothermal method and performed hydrothermal process
on Degussa P25 Ti02 nanoparticles. In this experiment they were pursued several treatment steps to achieve the titanium dioxide nanotubes as an ultimate goal and here they were used only one temperature 150 C° (423.15 k) for the hydrothermal process. This hydrothermal method has good potential in order to make titania nanoparticles but above method is too long and it consume the time. In the present invention also use the hydrothermal method to synthesis titanium dioxide nanostructures but with range of temperatures and very short treatment process also pH control is unnecessary.
The effect of pH variation from 3.0 to 14.7 by adjusting the NaOH concentration is leads to decrease of recombination rate because of the small-sized hydroxyl anion present in large quantities in highly alkaline conditions easily diffuses to the nanorod surface was investigated by Simon et al. This process has the same problems as described above but the present invention insert the simple method which involve both two mechanism (alkaline condition and metal and/or metal alloy) to minimize the recombination of photoexcited holes and photoelectrons. There are various semiconductor crystal growth techniques. For example, Czochralski Method, Birdman Method, Metal-Organic chemical vapor deposition, Molecular beam epitaxy and Liquid phase epitaxy so on. Nevertheless, in present invention titanium dioxide nanostructures growth by pursuing simple hydrothermal process.
SUMMARY OF THE INVENTION
The present invention describes the method to development and utility of photocatalyst which is based on semiconductor and metal and/or metal alloy combination. Photocatalyst absorb the photon of the light, photon with sufficient energy excites the valance electron in order to increase the kinetic energy of the valance electron. This excited electron leave the valance band of the semiconductor due to its high energy and find the suitable quantum state for this energy in order to make nearly free or free electrons which are allowed to produce the stream of electrons in the semiconductor. The energy level(s) which the photoexcited electrons are occupied is known as conduction band (CB). When the electrons excited from the valance band (VB) to the conduction band it is generated the positively charge holes in the valance band and the energy difference between top of the VB and bottom of the CB is known as band gap or energy gap (Eg) of the semiconductor. This photoexcited electrons and holes utilized for the enormous purposes.
This energy gap or band gap of semiconductors changes due to its structures and sizes so on. This characteristics of the semiconductors are the advantages for a photoactivity and/or any other purposes. In accordance with the present invention a photocatalyst comprises a titanium dioxide nanostructures and metal and/or metal alloy. Titanium dioxide nanocomposite was synthesized from the simple hydrothermal method by using P25 (Degussa) titanium dioxide nanoparticles as the starting material. Synthesized titanium dioxide nanostructures was mixed with the metal and/or metal alloy of the cleaned beer can by using spraying method or any other suitable methods or by following simple mixing method and ethanol, methanol, water or any other suitable chemicals can be used as a solvent and/or mixing agents. Various particle sizes and structures and/or any other shapes of metal and/or metal alloy of cleaned and/or non cleaned beer cans could be used. Different ratios in any parameters of titanium dioxide nanostructures and metal and/or metal alloy of beer cans able to be used. This photocatalyst can be mix/combined with any other photocatalysts which are exist in the universe in order to make different photocatalysts. Photocatalytic activity of photocatalyst is observed in the single structure and the bulk of the structures. According to the preparation method of photocatalyst, it is absorb the wide range of wave length in the electromagnetic spectrum. The absorption capacity is wider from visible to near infrared region (UV absorption is obvious). The minimum hydrogen volume generating rate of the 3g of catalyst is 1.6874 ml / min. The technical problems and solutions of the invention are generally can be discussed as below,
Technical Problem
Electrons jump to the conduction band (CB) by absorbing photon energy while holes are remaining in the valance band (VB). Photoexcited electron in the semiconductor material able to donates this electron to any other species which prefer to accept the electron. On the other hand photoexcited hole reduces by oxidizing any other species that prefer to oxidize. Accordingly, following problems are occur.
01. Selecting the suitable, reliable, environmentally friendly, abundant, inexpensive, non-toxic material with semiconductor properties.
02. Reducing the ban gap or energy gap (Eg) by using suitable and minimum treatment synthesis method.
03. Minimizing or stopping the rapid recombination of photoexcited electron and hole.
04. Solubility in water and/or aqueous medium.
05. Increasing the reaction rate of redox reaction.
06. Production ability and Life time of redox reaction(s) (day and/or night).
07. Making the non-corrosive photocatalyst.
08. Selecting the waste metal and/or metal alloy.
09. Transportation and easy handling of the photocatalyst.
10. Re -usability.
Technical Solution.
01. Titanium dioxide is inexpensive, nontoxic and abundant semiconductor. As a photoactive material, Ti02 is a good promising semiconductor because of its photostability. So in this invention used these properties as advantages for water splitting and/or any kind of oxidation and reduction system.
02. Can obtain various nanostructures and sizes composite of Titanium dioxide in order to make different band gap by using simple low temperature hydrothermal method.
03. Photoexcited electron(s) transferred to the metal and/or metal alloy by leaving opposite charge(s) in the titanium dioxide nanostructure(s). The sodium hydroxide (NaOH) which use in hydrothermal process increase the pH of water and/or aqueous media by releasing hydroxyl (OH-) groups, these hydroxyl groups able to come closer and donate the electron(s) to the hole(s). Both two mechanism minimize the rapid recombination of photoexcited electron and hole.
04. The hydroxyl (-OH) groups alter the polarity on titanium dioxide nanostructures which makes the solubility of these nanostructures in a water and/or polar solution.
05. The different nanostructures and sizes lead to absorb various wavelength of incident light to excite more electrons in the semiconductor nanostructures, using the metal and/or metal alloy conductor and hydroxyl groups act as a barrier in order to minimize or stop the rapid recombination of photoelectrons and photoexcited holes. The rate of redox reaction is increase due to above facts.
06. More electrons are excited due to absorption of the wide range of wave length by titanium dioxide nanostructures. Therefore metal and/or metal alloy collect more photoexcited electrons and release the electron(s) for the reduction purpose so the reaction take place
even in the dark, metal and/or metal alloy and hydroxyl groups minimized or stop the recombination those ensure the life time and production ability of the photocatalytic system.
07. Metal and/or metal alloy is highly corrosive. Nevertheless, by combining with this non corrosive titanium dioxide nanostructures the metal and/or metal alloy protect from the corrosion and the waste metal and/or metal alloy is resist to the corrosion. So in the sea water the photocatalytic activity ensure with same rate.
08. Waste metal and/or metal alloy made to achieve the non-corrosive property with combining metal complex. So this property is highly regarded in this invention.
09. Photocatalyst able to change the physical property (nanoparticles, microparticles, layers, powder, dust so on) upon the purpose without reducing the rate of redox reaction. So it is easy to handle and transport.
10. After photocatalytic activity the row materials can be used again for the same purpose by following the same preparation methods.
Advantages effects
01. Very low treatment steps and few of chemicals save the time and cost (in this method only two chemicals used those are sodium hydroxide and ethanol except titanium dioxide).
02. Sodium hydroxide release the hydroxyl groups to the media which is reduce the hole by decreasing the rapid recombination process.
03. Hydroxyl groups alter the polarity on photocatalyst in order to disperse in the water and/or any aqueous solution.
04. Sodium hydroxide use for the synthesis of titanium dioxide nanostructures.
05. Sodium hydroxide employing as an individual substance to do all above (02, 03, 04) three very important task of this invention in order to reduce the number of chemicals and cost.
06. Beer cans can find everywhere around the environment, in this invention beer can use as the metal and/or metal alloy source and it is reduce the environmental pollution, cleaning cost and labor hours.
07. Without following any of processing method and without using any of high cost metal hydrogen production and/or redox reaction process ensure by using beer can.
08. Metal and/or metal alloy of beer can separated the photoexcited electrons from the semiconductor material and increase the redox reaction.
09. Beer cans are non-corrosive so directly able to use beer can as a metal and/or metal alloy without further modification for achieve non-corrosive properties it save the time and cost.
10. Titanium dioxide nanostructures and metal and/or metal alloy of beer cans, both are non- corrosive so in any aqueous medium the photocatalyst is being stable and ensure the redox reaction in order to achieve ultimate goal.
11. Any stirring techniques can use to disperse titanium dioxide in the sodium hydroxide aqueous solution.
12. Easy to increase the surface area of beer can by crushing or using any suitable method it not required expensive, time consume or high laboratory facilities to get the nanostructures, microstructures, and various sizes of beer can.
13. Those structures and/or sizes of beer cans, able to mix with titanium dioxide nanostructures very easily without following any of complex methods.
14. Titanium dioxide and beer cans are abundant then the photocatalyst is reliable and promising for the water splitting or any other purpose which required the property of this photocatalyst.
15. Hydrogen is a green energy generating hydrogen by using waste beer cans accelerate the rate of development of green energy world like a catalyst.
16. However, this invention is inexpensive, environmentally friendly, stable, wide usability, non-corrosive, time saving, reliable, non-toxic, re-usable, promising so on and very simple water splitting method able to use in vast industrial application.
Thus, efficient photocatalytic activity is ensured due to the absorption of a wide range of wave lengths by the titanium dioxide nanostructures. There is at least one nanostructure combine with the metal and/or metal region which absorb the visible to near infrared region.
In some embodiments, the at least one semiconductor nanoregion absorbed by a wave length range of 200 nm to 3 mhi.
In some other embodiments, the at least one semiconductor nanoregion absorbed in a wave length of 200 nm to 380 nm.
In further embodiments, the at least one semiconductor nanoregion absorbed in a wave length of 200 nm to 420 nm.
In still other embodiments, the at least one semiconductor nanoregion absorb the wave length of 380 nm to 1.1 mth.
In still further embodiments, the at least one semiconductor nanoregion absorb the wave length of 380nm to 420 nm.
In still some other embodiments, there are different band gap and different Fermi energy levels in the titanium dioxide nanoregion.
In still some further embodiments, there are same band gaps and same Fermi energy levels in the titanium dioxide nanoregion.
In another embodiments, other elemental semiconductors and/or their compositions and/or alloy thereof such as Si, Ge and some elements from the groups V and VI such as P, S, Se, Te etc. and Eu and Mn and binary compound such as GaAs, ZnSe, ZnS, ZnTe, HgS, HgSe, HgTe, CdSe, CdS, CdTe, Pbl2 and MoS2 and binary compound formed from groups IV and VI elements such as PbS, PbTe, SnS so on and the oxides semiconductors such as CuO, Cu02, Cu20, Si02 and La2Cu04 and alloy thereof such as CdZnSe, CdSeTe, ZnCdSe, SbSI, AgGaS2, ZnSiP2, As2Se3 and Cd1-xMnxTe and mixtures thereof and organic semiconductors such as polyacetylene [(CH2)n], polydiacetylene and polypyrrole so on. Any other semiconductors can mix with titanium dioxide nanostructures or individually or mixtures thereof can mix with metal and/or meatal alloy of beer can in order to make different photocatalysts.
The enhancement of the light absorption of titanium dioxide nanostructures pursuing the efficient photocatalytic activity in order to increase the hydrogen production rate by increasing rate of redox reaction. The same nanostructures and different nanocomposite combined with same metal and/or metal alloy and/or different metal and/or metal alloy are discuss herein as a nanoregion absorbed the photon energy and excite the electron to ensure the photocatalytic activity.
In some embodiments, at least one grain of metal and/or metal alloy is combined with at least one titanium dioxide nanoregion.
In some other embodiments, at least two grains of metal and/or metal alloy are combined with at least one titanium dioxide nanoregion.
In further embodiments, the metal and/or metal alloy can be produce my mixing different composition/ratios of the metal which used in to production of beer cans.
In still some embodiments, the metal and/or metal alloy can be made by using different combination and/or different ratios of Al, Mg, Mn, Cu, Si, Fe, Zn, Ga, V , Ti and alloy thereof.
In still further embodiments, the metal and/or metal alloy can be made by combining with above metal and/or different composition of above metal by mixing with different metal and/or metal alloy composition and/or any suitable element(s).
In still some further embodiments, the metal and/or metal alloy can be made by combining different metal such as Pt, Mo, Ru, Rh, W, Ag, Au, Zn, Hg, Cn, In, Tl, Nh, Sn, Pb, As, Sb, Bi, Me, Po, Fl, Lv, As, Ts, Hf, Rf, Ba, Cs, Fr, Rb, Se, I, Te, Os, Hs, Bh, Db, Ta, Ir, Re, Na, Li, element in lanthanide series and actinide series etc. and/or metal alloy thereof and any suitable element(s) and alloy thereof with metal and/or metal alloy of beer cans and/or red bull cans or any other waste metal and/or metal alloy.
Any transition metal and or any metal and alloy thereof and there are non-limiting instances of semiconductors and mixtures thereof and metal and metal alloy and mixtures thereof could be investigate with the present photocatalyst and there are various non-limited processing techniques and methods to fabrication of this photocatalyst and mixtures thereof such as chemical vapor deposition method, hydrothermal methods, ion implantation method, Czochralski Method, Birdman Method, Metal-Organic chemical vapor deposition, Molecular beam epitaxy and Liquid phase epitaxy, spraying methods, sintering methods/techniques, cooling methods/techniques so on.
In some embodiments, the temperature 100 °C to 170 °C or above 170 °C and time 6 hours to 72 hours or above 72 hours, different temperature and different time combination thereof for the hydrothermal process.
In some other embodiments, same temperature with different time combinations for the hydrothermal process.
In further embodiments, different amount of Degussa P25 titanium dioxide nanoparticles dispersed in the different concentrations of sodium hydroxide aqueous solution (above 10 M or below 10 M).
The various composition of titanium dioxide nanostructures can be obtain by applying different temperature and time combinations and different volume of Teflon lined autoclave for the hydrothermal method.
In some embodiments, the metal and/or metal alloy can select from the waste such as beer cans, red bull cans and/or any other cans which made by beer can composition and/or red bull can composition and/or any other suitable metal and/or metal alloy and/or metal and/or metal alloy sheets of beer cans and/or red bull can or any other suitable metal and/or metal alloy and/or mixture thereof.
Metal and/or Metal alloy is accept the electron and make the electron rich surface and act as a barrier to the rapid recombination process of electron and hole. This phenomenon ensure the life time of oxidative and reductive reactions in order to splitting water to oxygen and hydrogen. So the combining with low cost metal and/or metal alloy with this synthesized semiconductor facilitate the utilization of the present invention in industrial purpose.
DESCRIPTION OF DRAWING
In order to understand the utilization and practical applicability and for the clarification of the invention following descriptions are carried out.
Fig. 1 shows the gas chromatography data of hydrogen generation volume in milliliter of 30 ml of water and 3 g of photocatalyst at the room temperature.
Fig. 2 shows the gas chromatography data of the hydrogen generation volume in milliliter of 30 ml of water and 3g of photocatalyst at the room temperature, after seventeen hours and ten minutes from the end point value of time axis of the Fig. 1.
Fig. 3 shows the gas chromatography data of the hydrogen generation volume in milliliter of 30 ml of water and 3g of photocatalyst at the room temperature, after twenty three hours from the end point value of time axis of the Fig. 2.
Fig. 4 shows the hydrogen generation in micromole of 30 ml of water and 3 g of photocatalyst at the room temperature.
Fig. 5 shows the hydrogen generation in micromole of 30 ml of water and 3 g of photocatalyst at the room temperature, after seventeen hours and ten minutes from the end point value of time axis of the Fig. 4.
Fig. 6 shows the hydrogen generation in micromole of 30 ml of water and 3 g of photocatalyst at the room temperature, after twenty three hours from the end point value of time axis of the Fig. 5.
Mode for Invention
In the present invention explained photocatalytic water splitting method to generate hydrogen molecule (H2) as a basic ultimate goal. In this method, solar power convert to the hydrogen energy or chemical energy by using titanium dioxide nanostructures combining with waste metal and/or metal alloy as photocatalyst. Synthesized titanium dioxide nanostructures shows the great photocatalytic activity when combine with metal and/or metal alloy. The treated P25 titanium dioxide nano particles have shown remarkable improvement in photocatalytic activity due to various nanostructures and sizes. Low temperature and simple hydrothermal method was employed to synthesis process of titanium dioxide nanostructures. Methods and experimental are discuss herein below.
Experimental Section
Synthesis of titanium dioxide nanostructures
In this invention P25 titanium dioxide nanoparticles were used as a titanium dioxide source in order to synthesis of titanium dioxide nanostructures as a semiconductor material. In this method, 4 g and 6 g (or different amount ) of P25 titanium dioxide nanoparticles were dispersed in 21 ml and 31.5 ml of 10 M (or above 10 M) of sodium hydroxide (NaOH) aqueous solution by using
magnetic stirrer for about 30 minutes respectively. After 30 minutes (or > 5 minutes), the mixtures were transferred into Teflon lined autoclave with capacity 28 ml and 42 ml respectively. After that, Teflon autoclaves were kept at 170 °C for 24 hours in a furnace. Then, after the hydrothermal process the product was ready for the combine with waste metal and/or metal alloy without further treatments.
Fabrication of photocatalyst.
In present invention, it was used any kind of beer cans as a waste metal and/or metal alloy (and/or red bull can or any other suitable waste metal and/or metal alloy) and beer cans were cleaned by using sand paper and/or suitable chemical or method. Synthesized titanium dioxide nanocomposite (~4g wet) was dispersed in approximately 40 ml of ethanol by using magnetic stirrer for about 5 minutes and it was transferred into a solution container of spray gun. This nanocomposite was sprayed by using air compressor onto the both sides of cleaned beer can and obtained a thin layer of titanium dioxide nanocomposite on the clean beer can. After that, it was kept at 420 °C for 3 hours in an oven. Also the synthesized titanium dioxide nanocomposite was mixed with various size of cleaned beer can such as nanoparticle, microparticle, powder, dust, small pieces so on and mixture thereof. Titanium dioxide nanoparticles and various states of beer can were mixed in different ratios in weight such as, Ti02 nanoparticle: beer can particle, 1 : 1, 2: 1, 1:2 and 3: 1 so on. Mixtures were sintered to the same temperature and time in an oven as above. After, photocatalytic activity was performed.
This experiment was done under wide range of temperature and/or time. These conditions, novelties and characterization of photocatalyst may discuss herein below.
01. In hydrothermal process 100 °C to 170 °C and 10 to 72 hours temperature and time combinations were selected for the furnace. Temperature higher than 170 °C and time higher than 72 hours consume the energy and time. Hence within 130 °C to 170 °C and 24 hours to 72 hours temperature and time any of combinations are more preferred for the hydrothermal process.
02. Sodium hydroxide concentration equal or higher than 10 M (> 10 M) is more preferred for the hydrothermal process.
In the sintering process from 100 °C to 500 °C and from 1 to 8 hours temperature and time combinations were performed in an oven. Temperature from 412 °C to 450 °C and from 1 to 5 hour(s) any combination is more preferred for the oven.
The word“nanostructures” or“nanocomposite” used because of there may be various structures and sizes such as nano rods, nanosheets, nanocylinders so on.
In the synthesized nanocomposite there may be a various type of structures and sizes, absorb the different wavelength of light.
Sodium hydroxide used as a multi task agent in this invention.
Sodium hydroxide used for the construction of titanium dioxide nanostructures as only one cooperative chemical in the hydrothermal process.
Hydroxyl groups alter the polarity on the nanostructures in order to dissolve in water and/or aqueous media.
Hydroxyl groups increase the pH of media, travel to the nanostructure and oxidize and minimize the rapid recombination, Increase the redox reaction. Hydrogen production ensure.
Beer cans used as waste metal and/or metal alloy. Hence, reduce the environmental pollution and reduce the cost and time and increase the efficiency of the hydrogen production.
Corrosion resistance is another benefit of the beer can.
Hydrogen production ensure even in the sea water because of corrosion resistance of both titanium dioxide nanostructures and beer cans.
Beer can, metal and/or metal alloy collect the photoelectron and donate to the hydrogen atom to reduce to hydrogen molecule.
Photoexcited electron occupy the metal and/or metal alloy of beer can by leaving the titania nanostructure and reduce the recombination process and increase the redox reaction. The redox reactions ensure in the dark due to collection of photoexcited electrons in the metal and/or metal alloy of beer can.
Various sizes and there mixtures of beer metal and/or metal alloy increase the surface area and it leads to increase connection with water molecule and increase the rate of redox reaction.
17. Metal and/or metal alloy can be made by mixing the different ratio of element which in beer can.
18. Any other suitable elements and/or compositions can be mixed with the beer cans element composition.
19. Various photocatalyst could mixed together with this photocatalyst in order to make different photocatalyst.
Catalytic activity.
The catalytic activity of synthesized photocatalyst was studied in room temperature and dark. The gas chromatography was carried out and the hydrogen production of 3g of photocatalyst in 30 ml of distilled water and the ratio of Ti02 nanostructures to beer can particles were 2: 1 and hydrogen generation rate is 1.6874 ml / min
Industrial applicability
The present invention, the photocatalyst has wide range of industrial applications due to its chemical, physical and other properties such as high chemical stability, non-corrosive, inexpensive, environmentally friendly, extensive life span, non-toxic, reaction efficiency, low synthesis process, high solar to hydrogen conversion efficiency, easy to handle, easy transportation and simple so on. According to the magnificent properties of the photocatalyst it is a reliable and promising source for the photo-oxidation and photo-reduction or photocatalytic applications and also light induce charge separation such as electrochemical and photovoltaic cell.
Mainly, the present invention has great potential for the photocatalytic water splitting to generate hydrogen gas as an energy carrier for all kind of energy requirement. In here photocatalyst absorb the photon energy and split the water molecule in to the hydrogen and oxygen by using reduction and oxidation half reaction known as redox reaction. So the ultimate product of this invention solve the big problem of the world by releasing the hydrogen molecules as an energy carrier. So as an energy carrier hydrogen gas employ enormous industrial applications are discuss herein below.
Internal combustion engine
Fossil fuel which used in combustion engine can replace by hydrogen gas to do the same thing but in high efficiency and hydrogen release more energy than fossil fuel (petrol, diesel etc.) and the product is the pure water of this reaction. No harmful gases.
2 H2 + 02 ® 2 H20 + energy
Hydrogen fuel cell.
Hydrogen fuel cell convert the hydrogen molecule in to the protons and release the electrons to produce the electric current for any purpose which can utilized electric current. Protons are travel through the proton exchange membrane and react with oxygen in order to make the water molecule. Hydrogen fuel cell can use for the electrical vehicle and can connect to the electrical grid for the electricity.
Steam power plant.
Combustion energy of hydrogen can use as a heat energy to produce the energy to water for make the steam for a steam power plant. Nuclear power plant.
Production of hydrogen bomb.
Production of liquid hydrogen or metal hydrogen.
Production of hydrogen balloon.
Production of hydrogen (in cylinder) for laboratory purpose.
Production of methane.
Production of hydrogen fill lighters.
Hydrogenation of carbon dioxide.
Production of hydrogenation water.
Claims
Claims :
01. A method to generate hydrogen by water splitting and/or for any other suitable oxidation and reduction process and/or any other photoactive methods from the photocatalyst by using modified Degussa P25 titanium dioxide nanoparticle from hydrothermal process, 4g and 6g of Degussa P25 titanium dioxide nanoparticle were dispersed in 21 ml and 31.5 ml of 10M (or above or below 10 M ) of sodium hydroxide aqueous solution by stirring and the mixtures were transferred into Teflon lined autoclave with capacity 28 ml and 42 ml respectively and Teflon autoclaves were kept at 170 °C for 24 hours in a furnace and the synthes ized titanium dioxide nanocomposite (~4g wet) was dispersed in approximately 40 ml of ethanol and sprayed onto the both sides of cleaned beer can and obtained a thin layer of titanium dioxide nanocomposite on the clean beer can(and/or red bull can or any other suitable metal and/or metal alloy). After that, it was kept at 420 °C for 3 hours in an oven. Also the synthesized titanium dioxide nanocomposite was mixed with various sizes and structures of cleaned beer can such as nanoparticle, microparticle, powder, dust, small pieces so on and mixture thereof and sintered at 420 °C for 3 hours in an oven. These synthesized titanium dioxide nanocomposite and various sizes of cleaned beer can metal and/or metal alloy were mixed with different ratios and followed the same treatment process. In this method photocatalyst absorb the light (photon) and charges (electron and hole) separate, one charge occupy in the metal and/or metal alloy and/or travel to the charge acceptor and accept the electron(s) by valance band of one or more nanostructures from electron donor(s) in order to ensure the reduction and oxidation process respectively. The said method comprising;
I. Titanium dioxide nanostructures absorb the different wave length of light and separated the charge particle.
II. Metal and/or metal alloy of beer can (and/or red bull can or any other suitable waste metal and/or metal alloy) contact with at least one or more
nanostmcture(s) and accept the electron and electron occupy in the metal and/or metal alloy and travel to the electron acceptor.
III. At least one or more electron(s) directly donate to the electron acceptor by one or more region of titanium dioxide nanostructures, in the water or aqueous solution.
IV. At least one or more region of titanium dioxide nanostructures accept the electron from the one or more hydroxyl group(s) or any other electron donor of the medium.
02. The method in claim 1, wherein said the different masses of Degussa P25 titanium dioxide nanoparticles can be disperse in the different volume of sodium hydroxide aqueous solution in order to obtain the different titanium dioxide nanostructures from the hydrothermal method.
03. The method in claim 1, wherein said the stirring time > 5 minutes.
04. The method in claim 1, wherein said the concentration of sodium hydroxide is > 10 m ld - 3 (10 M).
05. The method in claim 1, wherein said the temperature > H0 °C and the time > 10 hours , for the hydrothermal process.
06. The method in claim 1, wherein said the temperature > 100 °C and the time > 1 hour(s), for the sintering process.
07. The method in claim 1, wherein said the cleaned sheet and/or various structures and sizes of beer can or mixture thereof.
08. The method in claim 1, wherein said any solvent/chemical such as methanol, ethanol, water and further mixture thereof could be used to mix metal and/or metal alloy with titanium dioxide nanostructures.
09. The method in claim 1, wherein said at least one or more same titanium dioxide nanostructures comprise with at least two or more different metal atoms or same metal atoms of beer can.
10. The method in claim 1, wherein said at least two or more different titanium dioxide nanostructures comprise with at least two or more different metal atoms or same metal atoms of beer can.
11. The method in claim 1, wherein said at least one or more same titanium dioxide nanostructures comprise with at least one or more grains of beer can.
12. The method in claim 1, wherein said at least two or more different titanium dioxide nanostructures comprise with one or more grains of beer can.
13. The method in claim 1, wherein said there may be different Fermi energy levels of the same nanostructures and/or different nanostructures.
14. The method in claim 1, wherein said there may be different band gap or energy gap of the same titanium dioxide nanostructures and/or different titanium dioxide nanostructures.
15. The method in claim 1, wherein said the metal and/or metal alloy could be synthesized by combining different composition of elements and/or alloy thereof which included in beer cans.
16. The method in claim 1, wherein said the metal and/or metal alloy can be fabricated by choosing at least two or more elements and/or different composition and/or alloy thereof of the elements Al, Mg, Mn, Cu, Si Fe, Zn, Ga, V and Ti.
17. The method in claim 14, wherein said any element such as Pt, Pb, Au, Ag, Eu, Ge, Sr, Sb, Cd and Cr etc. and mixtures and/or alloy thereof can be combined.
18. The method in claim 13, wherein said any element of claim 14 and 15 and/or mixtures and/or alloy thereof can be mix with metal and/or metal alloy of beer cans.
19. The method in claim 1, wherein said the beer cans and/or red bull cans or any other suitable waste metal and/or metal alloy and/or mixture thereof.
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