CN106654304A - CuO/rGO composite material having efficient electrocatalysis oxygen reducing performance - Google Patents

Abstract

The invention relates to a CuO/rGO composite material with high-efficiency electrocatalytic oxygen reduction performance, belonging to the technical field of electrocatalytic materials. In the CuO/rGO composite material of the present invention, the nano-CuO particles are attached to the reduced graphene oxide sheet, the mass ratio of the nano-CuO to rGO is 100:3-5; the size of the nano-CuO particles is 6-10nm, and the reduced graphene oxide The sheet is a monolithic layer; it has electrocatalytic oxygen reduction performance. Compared with the existing oxygen reduction reaction catalyst, the cost of the CuO/rGO composite material of the present invention is obviously reduced; it is an oxygen reduction reaction catalyst with low price and excellent electrocatalytic oxygen reduction performance. The CuO/rGO composite material of the present invention uses copper salt, hydroxide and graphene oxide as raw materials, uses deionized water and absolute ethanol as solvents, and uses ethylene glycol as a dispersant and reducing agent. Synthesized by pot method. The raw materials are cheap and easy to obtain, the preparation operation is simple and easy, the post-treatment process is simple, the reaction parameters are easy to control, the process is short, and the energy consumption is low.

Description

A CuO/rGO composite material with high-efficiency electrocatalytic oxygen reduction performance

technical field

The invention relates to a CuO/rGO composite material with high-efficiency electrocatalytic oxygen reduction performance, belonging to the technical field of electrocatalytic materials.

Background technique

Today's society is in a stage of rapid development, and people's living standards are improving day by day, but there are also many problems, such as energy problems and environmental problems. In today's world, mastering energy is the greatest weapon for mastering development. However, my country's limited resources cannot meet people's unlimited needs for resources, especially the dependence on fossil fuels has led to the over-exploitation of petrochemical energy, the depletion of national reserves, and environmental pollution. And so on a series of questions. Batteries are a clean, safe, efficient, and pollution-free energy source that can replace fossil fuels to a certain extent. In 1839, Grove in England invented the fuel cell. After development and research, the fuel cell has made rapid progress in scientific research and commercial application in the past five years. The research on fuel cells in my country started in 1958, and entered the peak of fuel cell research in the 1970s. By the 21st century, the research and development of fuel cells in my country had made great progress. Although fuel cells have developed rapidly in recent years, compared with international developed countries, my country's fuel cell research is still relatively backward. In North America, Japan, Europe and other countries, fuel cell power generation is rapidly entering the stage of industrial scale application, and will become the fourth generation of power generation in the 21st century after thermal power, hydropower and nuclear power. Compared with valve-regulated lead-acid batteries, rechargeable nickel-cadmium batteries, and nickel-hydrogen batteries, fuel cells have high energy conversion efficiency and directly convert the chemical energy of fuel into electrical energy without the combustion process in the middle, so they are not affected by the Carnot cycle. limit. It can store and transfer electrical energy in the form of chemical energy, and it can be used in many fields in today's society; it can be used in military, power plant fields, motor vehicles, mobile devices, residents' homes and other fields.

For alkaline fuel cells, the oxygen reduction performance of cathode materials is a key technology restricting its development. Generally speaking, the electrochemical oxygen reduction reaction has different reaction mechanisms due to different electrode materials, surface properties, and solution pH values. Generally, it can be divided into two-electron reactions, direct four-electron reactions, and two-step two-electron (2+2) reaction processes. , is considered as an ideal oxygen reduction pathway because the four-electron reaction process can obtain more electric energy. Generally, the Pt/C catalyst prepared by loading Pt on a carbon material is the most commonly used electrocatalytic material. The carbon material used as a carrier generally includes ordinary carbon black, Vulan XC-72 carbon black, carbon nanotubes and multi-walled nanomaterials. carbon tube etc. However, because the carbon material is easily corroded, the noble metal attached to it falls off from the surface of the electrode or agglomerates into large particles, resulting in a decrease in the catalytic performance and stability of the catalytic material. Therefore, it is very necessary to find a stable non-carbon support to replace the carbon support material commonly used in catalysts under the working conditions of the fuel cell to improve the durability of the fuel cell.

In 2015, the inventors of this case researched and prepared TiO2/rGO composite materials and TiO2/rGO composite materials doped with N and F. Experiments have shown that TiO2/rGO composites doped with N and F have electrocatalytic oxygen reduction reaction performance in alkaline solution and can be used as a catalyst for oxygen reduction reaction; while TiO2/rGO composites do not have electrocatalytic performance in alkaline solution Oxygen reduction reaction performance, can not be used as an oxygen reduction reaction catalyst. Although, compared with the Pt/C catalyst, the catalytic performance and stability of the TiO2/rGO composite material doped with N and F are significantly improved; the cost is also significantly reduced, and it can be used as one of the alternative materials for the Pt/C catalyst. But at this stage, there is still a lot of room for research on alternative materials for Pt/C catalysts, and many materials with low prices and great potential have not yet been discovered.

Contents of the invention

The purpose of the present invention is to provide a catalyst for oxygen reduction reaction with relatively low price.

Experimental studies have found that although the TiO ₂ /rGO composite material without N and F doping does not have the electrocatalytic oxygen reduction reaction performance, it cannot be used as an oxygen reduction reaction catalyst; however, the CuO/rGO composite material without N and F doping has the electrocatalytic performance. Catalytic oxygen reduction reaction performance, can be used as an oxygen reduction reaction catalyst.

Technical solutions

A CuO/rGO composite material, in which nano-CuO particles are attached to reduced graphene oxide sheets, and the mass ratio of nano-CuO to rGO is 100:3-5;

The size of nano CuO particles is 6-10nm;

The reduced graphene oxide sheet is a monolithic layer;

It has electrocatalytic oxygen reduction performance; in other words, it is a catalyst for oxygen reduction reaction.

The SEM test of the CuO/rGO composite material of the present invention shows that the nano-copper oxide particles are evenly attached to the surface of the reduced graphene oxide.

Cyclic voltammetry (CV) results show that the CuO/rGO composite material of the present invention has an initial oxidation potential of about -0.2 V for electrocatalytic oxygen reduction in an oxygen-saturated 0.1 M KOH solution, and the maximum oxygen reduction current can reach 10 On the order of ^-5 mA/cm ² ; it has high-efficiency electrocatalytic oxygen reduction performance.

The chronoamperometry test shows that after the electrochemical test of 16000s, the current density of the CuO/rGO composite material of the present invention is still as high as about 90% at the beginning, and has very good electrochemical stability, while the commercial Pt (20%)/C is only about 74% of the initial value.

Compared with the existing oxygen reduction reaction catalyst (Pt(20%)/C composite material, TiO2/rGO composite material doped with N and F), the cost of the CuO/rGO composite material of the present invention is significantly reduced; it is a Oxygen reduction reaction catalyst with low price and excellent electrocatalytic oxygen reduction performance.

The CuO/rGO composite material of the present invention uses copper salt, hydroxide and graphene oxide as raw materials, uses deionized water and absolute ethanol as solvents, and uses ethylene glycol as a dispersant and reducing agent. Synthesized by pot method. The copper salt refers to an inorganic salt that can provide copper ions and is soluble in water, such as copper chloride, copper sulfate, and copper nitrate. The hydroxide refers to an inorganic base that can provide hydroxide and is soluble in water, such as sodium hydroxide and potassium hydroxide.

During the above hydrothermal one-pot reaction, CuO nanoparticles were synthesized; and graphene oxide (GO) was reduced to reduced graphene oxide (rGO); meanwhile, nano-CuO was uniformly attached to the surface of reduced graphene oxide sheets A CuO/rGO composite material with high-efficiency electrocatalytic oxygen reduction performance was formed.

A kind of preparation method of above-mentioned CuO/rGO composite material, comprises the following steps:

After mixing copper salt, hydroxide, absolute ethanol, ethylene glycol, and deionized water, add graphene oxide, stir, and keep the temperature at 175-185°C for 24 hours;

The molar ratio of copper ion in copper salt to hydroxide in hydroxide is 1:4;

The mass ratio of graphene oxide to ethylene glycol is 1:200.

In the above preparation method,

1. While the hydroxide is used as the reactant, the pH of the solution is adjusted; therefore, the molar ratio of the copper ion in the copper salt to the hydroxide in the hydroxide is limited to 1:4, and the hydroxide is excessive; at this time, the reaction The pH of the system is about 10;

2. Deionized water and absolute ethanol are used as solvents to ensure the uniform dispersion and mixing of various components in the medium; those skilled in the art can adjust their dosage according to specific operations; deionized water and absolute ethanol are used to ensure that the particles are fully dissolved and mixed Melt, its dosage can be slightly adjusted without affecting the product morphology and particle state;

3. Ethylene glycol is used as a dispersant and reducing agent, in order to obtain CuO particles with uniform particles, and at the same time reduce graphene oxide to reduced graphene oxide; therefore, compared with graphene oxide, the amount of ethylene glycol is greatly excessive.

The above preparation method specifically includes adding copper salt, hydroxide, deionized water, absolute ethanol, and ethylene glycol into a 100ml small beaker, stirring until a blue clear solution is formed, adding graphene oxide, stirring evenly, and setting the temperature at 175 React at a constant temperature of -185°C for 24 hours, and cool to room temperature after the reaction;

In the above method, after the above reaction is completed, the product is washed several times with absolute ethanol, and then the product is washed several times with double distilled water, and then distilled under reduced pressure; a black powdery CuO/rGO composite material is obtained.

In the above preparation method, preferably, the constant temperature condition is 180° C. for 24 hours. If the temperature is too low or too high, CuO crystals cannot be formed; if the reaction time is too short, CuO cannot be generated.

In the present invention, the rGO refers to reduced graphene oxide.

In the present invention, 0.1 M KOH solution refers to a KOH solution with a concentration of 0.1 mol/L.

Beneficial effect

1. In the CuO/rGO composite material of the present invention, the nano-CuO is granular, not flake-like, nor needle-shaped; it is uniformly attached to the reduced graphene oxide sheet;

2. Although the CuO/rGO composite material of the present invention is not doped, it has high-efficiency electrocatalytic oxygen reduction performance and very good electrochemical stability;

3. Compared with the existing oxygen reduction reaction catalyst, the cost of the CuO/rGO composite material of the present invention is significantly reduced;

4. The liquid phase system is prepared by one-step feeding and one-pot reaction method, and the reaction is carried out under constant temperature heating conditions; the raw materials are cheap and easy to obtain, the preparation operation is simple and easy, the post-treatment process is simple, the reaction parameters are easy to control, and the process is short. Low energy consumption.

Description of drawings

Fig. 1 is the scanning electron microscope (SEM) collection of illustrative plates of the nanometer CuO that comparative example 1 prepares;

Fig. 2 is the scanning electron microscope (SEM) atlas of CuO/rGO composite material;

Fig. 3 Scanning electron microscope (SEM) pattern of TiO2/rGO composite;

Fig. 4 is at room temperature, the cyclic voltammetry curves of the nano-CuO prepared in Comparative Example 2, the rGO prepared in Comparative Example 1, and the CuO/rGO composite in an oxygen-saturated 0.1 M KOH solution; among the figures, according to the initial potential, From top to bottom, the cyclic voltammetry curves of rGO, CuO, and CuO/rGO composite materials in turn; it shows that the electrocatalytic oxygen reduction performance of the composite material is better than that of the two single materials, and rGO plays a role in enhancing the conductivity of the material. ;

Figure 5 is the cyclic voltammetry curve of TiO2/rGO composite in oxygen-saturated 0.1 M KOH solution at room temperature;

Figure 6 shows the cyclic voltammetry curves of CuO/rGO composites in oxygen-saturated 0.1 M KOH solution at different scan rates at room temperature; in the figure, according to the initial potential, from top to bottom, the scan rates are 5, 10, 20, 50mV/s; the figure shows that the peak current density of the material increases with the increase of the scan rate, which proves that the electrocatalytic oxygen reduction reaction is controlled by diffusion;

Figure 7 is the time-current curves of CuO/rGO and Pt/C composites; this figure shows that the final current of CuO/rGO composites is about 92% of the initial current after 16000 seconds of cycling, and the commercial Pt/C C is about 74%, so the stability of the CuO/rGO composite is better.

detailed description

Example 1

In a 100 mL small beaker, while stirring with a magnetic stirrer, add 40 mL of deionized water, slowly add CuCl ₂ 2H ₂ O 1.71 g (0.01 mol), NaOH 1.60 g (0.04 mol), stir for 5 min, and form a light blue To a homogeneous liquid, add 10mL of absolute ethanol, 5mL of ethylene glycol and 4mL of 6g/L graphene oxide and stir the solution fully (about 10 min), transfer the reaction solution into a 100 ml autoclave, heat to 180°C, Take it out after 24 hours at constant temperature, wash the product three times with absolute ethanol, then wash three times with double distilled water, put it in a vacuum distillation device for 20 min at 50°C, and obtain a black powdery solid, which is a high-efficiency electrolytic product. CuO/rGO composites with catalytic oxygen reduction performance. It was detected that the mass ratio of CuO and rGO in the CuO/rGO composite was about 100:3.

After SEM characterization (as shown in Figure 2), the nano-CuO is granular and uniformly attached to the surface of the rGO sheet; the results of cyclic voltammetry (CV) show that the CuO/rGO composite is stable in oxygen-saturated 0.1 M KOH In the solution, it has high electrocatalytic oxygen reduction performance, and the initial oxidation potential is about -0.2V; the time current method (i-t) shows that after 16000s of electrochemical experiments, the current density of the CuO/rGO composite material is the initial About 91% of the time.

Example 2

In a small 100 mL beaker, while stirring with a magnetic stirrer, add 40 mL of deionized water, slowly add CuCl ₂ 2H ₂ O 0.01 mol, NaOH 0.04 mol, stir for 5 min to form a light blue uniform liquid, add absolute ethanol 10mL, 5mL of ethylene glycol, and 8.3mL of 6g/L graphene oxide, fully stir the solution (about 10 min), transfer the reaction solution into a 100 ml autoclave, heat to 180°C, and take it out after 24 hours at constant temperature. The product was washed three times with absolute ethanol, then washed three times with twice distilled water, put into a vacuum distillation device and distilled under reduced pressure for 20 min at 50°C to obtain a black powdery solid, which is CuO with high-efficiency electrocatalytic oxygen reduction performance. /rGO composites. It was detected that the mass ratio of CuO and rGO in the CuO/rGO composite was about 100:5.

After SEM characterization (as shown in Figure 2), the nano-CuO is granular and uniformly attached to the surface of the rGO sheet; the results of cyclic voltammetry (CV) show that the CuO/rGO composite is stable in oxygen-saturated 0.1 M KOH In the solution, it has high electrocatalytic oxygen reduction performance, and the initial oxidation potential is about -0.2 V; the time current method (i-t) shows that after 16000s of electrochemical experiments, the current density of the CuO/rGO composite material is the initial About 92% of the time.

Example 3

In a small 100 mL beaker, while stirring with a magnetic stirrer, add 40 mL of deionized water, slowly add CuCl ₂ 2H ₂ O 0.01 mol, NaOH 0.04 mol, stir for 5 min to form a light blue uniform liquid, add absolute ethanol 10mL, 5mL of ethylene glycol, and 6.7 mL of 6g/L graphene oxide, fully stir the solution (about 10 min), transfer the reaction solution into a 100 ml autoclave, heat to 180°C, keep the temperature for 24 hours and take it out. The product was washed three times with absolute ethanol, then washed three times with twice distilled water, put into a vacuum distillation device and distilled under reduced pressure for 20 min at 50°C to obtain a black powdery solid, which is CuO with high-efficiency electrocatalytic oxygen reduction performance. /rGO composites. It was detected that the mass ratio of CuO and rGO in the CuO/rGO composite was about 100:4.

After SEM characterization (as shown in Figure 2), the nano-CuO is granular and uniformly attached to the surface of the rGO sheet; the results of cyclic voltammetry (CV) show that the CuO/rGO composite is stable in oxygen-saturated 0.1 M KOH In the solution, it has high electrocatalytic oxygen reduction performance, and the initial oxidation potential is about -0.2V; the time current method (i-t) shows that after 16000s of electrochemical experiments, the current density of the CuO/rGO composite material is the initial About 92% of the time.

Comparative example 1

In a small 100 mL beaker, while stirring with a magnetic stirrer, add 40 mL of deionized water, slowly add CuCl ₂ 2H ₂ O 0.01 mol, NaOH 0.04 mol, stir for 5 min to form a light blue uniform liquid, add 10 mL of ethanol and ethylene glycol 5mL, fully stir the solution (about 10 min), transfer the reaction solution into a 100 ml autoclave, heat to 180°C, take it out after constant temperature for 24 hours, wash the product three times with absolute ethanol, and then wash with two After washing with sub-distilled water three times, put it into a vacuum distillation device and conduct vacuum distillation at 50°C for 20 min to obtain a black powdery solid, nano-CuO particles.

After SEM (as shown in Figure 1), the nano-CuO particles grow in the shape of needles, and the particles are uniform. The results of cyclic voltammetry (CV) show that the nano-CuO has electrocatalytic oxygen reduction performance in an oxygen-saturated 0.1 M KOH solution. The initial oxidation potential is around -0.2V.

Comparative example 2

In a small 100 mL beaker, while stirring with a magnetic stirrer, add 40 mL of deionized water, slowly add 1.60 g of NaOH, add 10 mL of ethanol, 5 mL of ethylene glycol, and 4 mL of 6 g/L graphene oxide to fully stir the solution (about 10 min), transfer the reaction solution into a 100ml autoclave, heat to 180°C, take it out after 24 hours at a constant temperature, wash the product three times with absolute ethanol, then wash three times with twice distilled water, put it into the vacuum distillation After vacuum distillation at 50 °C for 20 min in the device, a black powdery solid was obtained, which was the lamellar rGO material. Cyclic voltammetry (CV) results showed that the sheet-like rGO material had no electrocatalytic oxygen reduction performance in oxygen-saturated 0.1 M KOH solution.

Comparative example 3

In a 50mL small beaker, while stirring with a magnetic stirrer, add 10.00mL of absolute ethanol and 3.00mL of ethylene glycol, slowly add 10.00mL of tetrabutyl titanate as a raw material, stir for 5 min, a light yellow transparent liquid is formed, add graphite oxide 4 mL (6 g/L), stirred until the solution was clear (about 5 min), and finally 16.00 mL of 6 mol/L hydrochloric acid was added dropwise. After fully stirring, the reaction solution was transferred to a 100 mL autoclave and heated to 200 ℃, take it out after constant temperature for 10 hours, wash the product three times with absolute ethanol, and then wash three times with twice distilled water, put it in a vacuum distillation device and distill under reduced pressure for 20 minutes at 50 ℃ to obtain a black powdery solid.

After SEM characterization (as shown in Figure 3), nano-titanium dioxide particles are uniformly attached to the surface of rGO, and the results of cyclic voltammetry (CV) show that (as shown in Figure 5), the composite material in oxygen-saturated 0.1 M KOH solution , does not possess electrocatalytic oxygen reduction performance.

Claims (7)

1. a kind of CuO/rGO composites, it is characterised in that nanometer CuO particle is attached on redox graphene lamella, is received The mass ratio of rice CuO and rGO is 100：3-5；

The size of nanometer CuO particle is 6-10nm

Redox graphene piece is monolithic layer.

2. CuO/rGO composites according to claim 1, it is characterised in that possess electrocatalytic oxidation reducing property.

3. CuO/rGO composites according to claim 1 and 2, it is characterised in that be with mantoquita, hydroxide and oxygen Graphite alkene is raw material, with deionized water and absolute ethyl alcohol as solvent, with ethylene glycol as dispersant and reducing agent, using hydro-thermal one Pot method synthesis.

4. the preparation method of CuO/rGO composites described in a kind of claim 1,2 or 3, comprises the following steps：

After mantoquita, hydroxide, absolute ethyl alcohol, ethylene glycol, deionized water mixing, graphene oxide, stirring, 175-185 are added Constant temperature 24h at DEG C；

Copper ion and mol ratio hydroxy in hydroxide are 1 in mantoquita：4；

Graphene oxide is 1 with the mass ratio of ethylene glycol:200.

5. preparation method according to claim 4, it is characterised in that by mantoquita, hydroxide, deionized water, anhydrous second Alcohol, ethylene glycol are added in 100 ml small beakers, are stirred to blue settled solution is formed, and graphene oxide are added, after stirring In 175-185 DEG C of isothermal reaction 24h, reaction is cooled to room temperature after terminating；.

6. preparation method according to claim 6, it is characterised in that reaction terminates rear product absolute ethanol washing for several times With redistilled water product is washed for several times again afterwards, then vacuum distillation；Obtain black powder CuO/rGO composites.

7. the preparation method according to claim 4,5 or 6, it is characterised in that constant temperature is 180 DEG C, 24h.