CN102995053A - Method for preparing LaTiO2N high-efficiency photoelectrode material - Google Patents

Abstract

The method of preparing lanthanum titanate oxynitride high-efficiency photoelectrode material: using the solid state reaction method to prepare the precursor La ₂ Ti ₂ O ₇ of LaTiO ₂ N, according to the molar ratio of La and Ti of La ₂ Ti ₂ O ₇ Take La ₂ O ₃ and TiO ₂ ; mix them well and grind them thoroughly; calcinate the mixed raw materials at 800°C~1000°C for 6h~20h, then cool to room temperature, grind them and then calcinate them at 1100°C~1400°C 6h~20h; use electrophoretic deposition method to deposit LaTiO ₂ N particles on the conductive glass (FTO) substrate, and dry in the air to obtain the LaTiO ₂ N particle film; then drop TiCl on the prepared LaTiO ₂ N particle film ₄ methanol solution, and then heat-treat it at 300 ° C ~ 700 ° C for 10 minutes ~ 60 minutes under an ammonia atmosphere to obtain a LaTiO ₂ N photoelectrode.

Description

Method for preparing lanthanum titanate oxynitride high-efficiency photoelectrode material

technical field

The invention relates to a method for preparing lanthanum titanate oxynitride (LaTiO ₂ N) high-efficiency photoelectrode material.

Background technique

The world today is confronted with two major problems of energy shortage and environmental pollution, which restrict the sustainable development of human beings. The development of clean and renewable energy is a top priority. The energy that the sun irradiates on the earth in a year is nearly ten thousand times the total energy consumed by human beings in a year. From the perspective of long-term development, when mineral energy is facing depletion and the environment is seriously deteriorating, solar energy will definitely play an important role in the future energy structure because of its advantages such as cleanness, non-pollution, wide distribution, inexhaustibility, and inexhaustibility. character of. However, solar energy has disadvantages such as low energy density, strong dispersion, instability, and discontinuity, so that we still lack effective means for its high-efficiency, low-cost, and large-scale utilization. Photoelectrochemical cells can use solar energy to split water, convert low-energy-density solar energy into high-energy-density, easy-to-storage, and clean chemical hydrogen energy, and are expected to play an important role in solving energy problems, so they have attracted the attention of many countries. The key to using photoelectrochemical cells to split water to produce hydrogen is to find efficient and stable photoelectrode materials. So far, there are very few photoelectrode materials that can satisfy the two conditions of high efficiency and photostability at the same time. the

Lanthanum titanate oxynitride (LaTiO ₂ N) can absorb visible light up to 600nm [A.Kasahara, K.Nukumizu, G.Hitoki, JNKondo, M.Hara, H.Kobayashi, K.Domen, J.Phys.Chem. A, 106, 6750-6753 (2002)], the theoretical efficiency of solar energy conversion to hydrogen energy is as high as 16%, but the efficiency of actual solar energy conversion to hydrogen energy is very low.

Contents of the invention

The purpose of the present invention is to propose a method for preparing high-quality lanthanum titanate oxynitride (LaTiO ₂ N) high-efficiency photoelectrode material, so that the efficiency of LaTiO ₂ N solar energy conversion to hydrogen can be greatly improved, and the practical application of solar hydrogen production can be promoted .

The technical scheme of the present invention is a preparation method of high-efficiency photoelectrode material LaTiO ₂ N, comprising the following steps:

(1) The precursor La ₂ Ti ₂ O ₇ of LaTiO ₂ N was prepared by solid state reaction method, and La ₂ O ₃ and TiO ₂ were weighed according to the molar ratio of La and Ti of La ₂ Ti ₂ O ₇ ;

(2) Mix the raw materials weighed in step (1) evenly and grind them thoroughly;

(3) In the solid phase reaction method, the mixed raw materials are calcined at 800°C~1000°C for 6h~20h, then cooled to room temperature, ground and then calcined at 1100°C~1400°C for 10h;

(4) The product obtained in step (3) is cooled and crushed to obtain La ₂ Ti ₂ O ₇ particles;

(5) Heat-treat La ₂ Ti ₂ O ₇ prepared in step (4) at 600°C~1000°C for 15 hours in NH ₃ atmosphere to obtain LaTiO ₂ N particles;

(6) Deposit the LaTiO ₂ N particles prepared in step (5) on conductive glass by electrophoretic deposition, and dry in air to prepare a LaTiO ₂ N particle film;

(7) Drop TiCl ₄ methanol solution on the LaTiO ₂ N particle film prepared in step (6), and then heat-treat it at 300°C~700°C for 10 minutes to 60 minutes under an ammonia atmosphere to obtain a LaTiO ₂ N photoelectric pole.

(8) Co ₃ O ₄ electrocatalyst is supported on the surface of the LaTiO ₂ N photoelectrode prepared in step (7), so that the prepared LaTiO ₂ N photoelectrode has high efficiency of solar energy conversion to hydrogen energy. The specific process of supporting Co ₃ O ₄ electrocatalyst is as follows: NaOH solution is dripped into the aqueous solution of Co ²⁺ to form Co(OH) ₂ colloid, and then the LaTiO ₂ N photoelectrode is immersed in the colloid for 10 minutes to 120 minutes ; Take out the LaTiO ₂ N photoelectrode, rinse the LaTiO ₂ N photoelectrode with water, and finally sinter at 200°C~400°C for 1h to obtain the Co ₃ O ₄ surface modified LaTiO ₂ N photoelectrode.

Step (6) Electrophoresis deposition step: Electrophoresis uses iodine acetone solution as the electrolyte, and the LaTiO ₂ N particle material is suspended in the electrolyte; both the anode and the cathode are made of conductive glass, the cathode and the anode are parallel, and the cathode and the anode are 2/3 Part of the conductive glass is immersed in iodine-acetone solution, and the LaTiO ₂ N particles suspended in the electrolyte are deposited on the conductive glass of the cathode by direct current with a voltage of 10V~40V to obtain a LaTiO ₂ N photoelectrode.

The beneficial effects of the present invention are: the lanthanum titanate oxynitride (LaTiO ₂ N) high-efficiency photoelectrode material prepared by this method greatly improves the efficiency of LaTiO ₂ N solar energy conversion to hydrogen energy, and under simulated sunlight (AM 1.5G , 100mW cm ^-2 ) with a photocurrent exceeding 4.2mA/cm ² (bias voltage 1.5V), corresponding to a solar-to-hydrogen energy conversion efficiency of 5.2%.

Description of drawings

Figure 1 is the X-ray diffraction pattern of LaTiO ₂ N prepared under different conditions;

Figure 2 is the optical absorption spectrum of LaTiO ₂ N prepared under different conditions;

Figure 3 shows the quantum conversion efficiency of the LaTiO ₂ N photoelectrode under different bias voltages;

Figure 4 is an electron micrograph of the LaTiO ₂ N photoelectrode;

Fig. 5 is a graph of the photocurrent of the LaTiO ₂ N photoelectrode under simulated sunlight.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings. the

The preparation method of high-efficiency photoelectrode material LaTiO ₂ N comprises the following steps:

(1) The precursor La ₂ Ti ₂ O ₇ of LaTiO ₂ N was prepared by solid state reaction method, and La ₂ O ₃ and TiO ₂ were weighed according to the molar ratio of La and Ti of La ₂ Ti ₂ O ₇ ;

(2) Mix the above raw materials evenly and grind them thoroughly; grind them until the particle size is mainly distributed between 1 micron and 4 microns;

(3) In the solid phase reaction method, the mixed raw materials are calcined at 800°C, 900 or 1000°C for 6h, 10h, 12h, 20h, and calcined under ordinary air conditions, or under weak vacuum conditions Calcined, then cooled to room temperature. Carry out the second step of grinding, and the second step of grinding is also until the particle size is mainly distributed in 1 micron to 4 microns; after grinding, it is calcined at 1100°C, 1250°C or 1400°C for 10h. The sample sintered at 1250°C has the best crystallinity;

(4) The product obtained in step (3) is cooled and ground to obtain La ₂ Ti ₂ O ₇ particles; ground until the particles are mainly distributed in a particle size of 1 micron to 4 microns; (more than 85% of the mass);

(5) Heat-treat La ₂ Ti ₂ O ₇ prepared in step (4) in NH ₃ atmosphere at 600°C, 700°C, 850°C, 950°C, 1000°C for 15 hours to obtain LaTiO ₂ N particles, ammonia gas The flow rate is 20ml/min~1000ml/min, the results show that the performance of the sample synthesized at 950°C (200ml/min, 15h) is the best;

(6) The LaTiO ₂ N particles synthesized in step (5) were deposited on conductive glass by electrophoretic deposition method, and dried in air to prepare a LaTiO ₂ N particle film. The specific process of the electrophoretic deposition method is that ^the electrolyte uses an iodine-containing acetone solution (the solvent acetone is 50ml; the solute iodine is 10mg), and 40mg LaTiO ₂ N is suspended in the electrolyte; the anode and the cathode are both conductive. Glass (F-doped SnO ₂ ), the cathode and anode are parallel, the conductive glass part of the cathode and anode 2/3 is immersed in the acetone solution of iodine, and the LaTiO ₂ N particles suspended in the electrolyte are separated by direct current with a voltage of 10V, 30V or 40V Deposit the conductive glass on the cathode (deposition time is 2 min) to obtain the LaTiO ₂ N photoelectrode.

(7) TiCl ₄ methanol solution was dropped on the LaTiO ₂ N particle film prepared in step (6), and it was heat-treated at 500°C for 30 minutes under an ammonia atmosphere (500ml/min) to obtain a LaTiO ₂ N photoelectric film with interconnected particles. pole.

(8) Co ₃ O ₄ electrocatalyst is supported on the surface of the LaTiO ₂ N photoelectrode prepared in step (7), so that the prepared LaTiO ₂ N photoelectrode has high efficiency of solar energy conversion to hydrogen energy. The specific process of supporting Co ₃ O ₄ electrocatalyst is as follows: use NaOH solution to drop into the aqueous solution containing Co ²⁺ to form Co(OH) ₂ colloid, and then immerse the LaTiO ₂ N photoelectrode in this colloid for 10 minutes; then take it out LaTiO ₂ N photoelectrode, wash the LaTiO ₂ N photoelectrode with water, and finally sinter at 300°C for 1h to obtain Co ₃ O ₄ surface modified LaTiO ₂ N photoelectrode.

Figure 1 is the X-ray diffraction pattern of La ₂ Ti ₂ O ₇ prepared by solid-state sintering method (1250°C) and LaTiO ₂ N sample treated in ammonia atmosphere (950°C, 200ml/min). It can be seen from the X-ray diffraction patterns that the synthesized La ₂ Ti ₂ O ₇ and LaTiO ₂ N samples are all pure phases, and no impurity phases appear.

Figure 2 shows the optical absorption spectrum of LaTiO ₂ N samples obtained by treating La ₂ Ti ₂ O ₇ prepared by solid-state sintering method (1250°C) under ammonia atmosphere (950°C, 200ml/min). The light absorption edge of LaTiO ₂ N sample reaches 600nm, and there is obvious tailing after 600nm, which may be from the light absorption of Ti ³⁺ defects.

Figure 3 shows the _{LaTiO 2} N (LTON SSR 1250) samples prepared by solid-state sintering (1250°C ₎ treated in ammonia atmosphere (950°C, 200ml/ _min ) at different Photoaction spectrum under bias voltage (quantum efficiency IPCE versus wavelength curve). Under 1.23V bias (reversible hydrogen electrode), the quantum efficiency of LaTiO ₂ N loaded with Co ₃ O ₄ catalyst in the range of 380nm~560nm reaches about 25%.

Figure 4 shows the morphology of LaTiO ₂ N samples obtained by treating La ₂ Ti ₂ O ₇ prepared by solid-state sintering method (1250°C) under ammonia atmosphere (950°C, 200ml/min). The inset is the selected area diffraction pattern of LaTiO ₂ N. It can be seen that LaTiO ₂ N has good crystallinity, and the particles present a single crystal diffraction pattern.

_Figure 5 shows the LaTiO _{2 N} samples prepared by solid-state sintering (1250°C) under simulated sunlight ( _AM Photocurrent (solid line; dotted line indicates dark current) at 1.5G, 100mW cm ^-2 ). Under simulated sunlight (AM 1.5G, 100mW cm ^-2 ), the photocurrent exceeds 4.2mA cm ^-2 (with a bias voltage of 1.5V), corresponding to a solar-to-hydrogen efficiency of 5.2%.

Claims (4)

1. prepare the method for lanthanium titanate oxynitride efficiency light electrode material, it is characterized in that comprising the steps:

(1) utilize solid reaction process to prepare LaTiO ₂The presoma La of N ₂Ti ₂O ₇, according to La ₂Ti ₂O ₇La and the molar weight proportioning of Ti take by weighing La ₂O ₃And TiO ₂

(2) raw material that step (1) is taken by weighing mixes and fully grinds;

(3) in the solid reaction process, with the raw material of mixing 800 ° of C ~ 1000 ° C calcining 6h ~ 20h, then be cooled to room temperature, ° C calcining 6h ~ 20h 1100 ° of C ~ 1400 again after the grinding;

(4) grind after the product cooling that step (3) is obtained, namely get La ₂Ti ₂O ₇Particle;

(5) La that step (4) is prepared ₂Ti ₂O ₇Powder is at NH ₃600 ° of C ~ 1000 ° C thermal treatment 10h ~ 30h obtain LaTiO in the atmosphere ₂The N particle.

(6) utilize electrophoretic deposition with the LaTiO of step (5) preparation ₂The N particle deposition at air drying, can obtain LaTiO on conductive glass (FTO) substrate ₂The N membrana granulosa;

(7) LaTiO for preparing in step (6) ₂Splash into TiCl on the N membrana granulosa ₄Methanol solution then with lower 300 ° of C-700 ° of C thermal treatments of its ammonia atmosphere 10 minutes ~ 60 minutes, has obtained the connect LaTiO of (Necking) of Particle Phase ₂The N optoelectronic pole.

(8) LaTiO for preparing in step (7) ₂The N optoelectronic pole supports Co on the surface ₃O ₄Eelctro-catalyst is so that the LaTiO of preparation ₂The N optoelectronic pole has high-efficiency solar converts hydrogen energy efficiency.

2. the method for preparing lanthanium titanate oxynitride efficiency light electrode material according to claim 1 is characterized in that being ground to and is distributed in 1 micron ~ 4 microns particle diameter.

3. the method for preparing lanthanium titanate oxynitride efficiency light electrode material according to claim 1 is characterized in that the electrophoretic deposition step of step (6); Electrolytic solution adopts the acetone soln of iodine during electrophoresis, with LaTiO ₂The N particulate material is suspended in this electrolytic solution; Anode and negative electrode all adopt conductive glass, and negative electrode is parallel with anode, and the conductive glass of negative electrode and anode 2/3 partly immerses the acetone soln of iodine, and adopting voltage is that the direct current of 10V ~ 40V is with the LaTiO that suspends in the electrolytic solution ₂The N particle deposition obtains LaTiO at the conductive glass of negative electrode ₂The N optoelectronic pole.

4. the method for preparing lanthanium titanate oxynitride efficiency light electrode material according to claim 1 is characterized in that at LaTiO ₂The N optoelectronic pole supports Co on the surface ₃O ₄Eelctro-catalyst; Support Co ₃O ₄The concrete technology of eelctro-catalyst is: NaOH solution is splashed into contain Co ²⁺The aqueous solution, form Co (OH) ₂Colloid is then with LaTiO ₂The N optoelectronic pole immerses this colloid, floods 10 minutes ~ 120 minutes; Take out again LaTiO ₂The N optoelectronic pole, water flushing LaTiO ₂The N optoelectronic pole, the last ° C sintering 1h 200 ° of C ~ 400 is with Co ₃O ₄Be supported on LaTiO ₂N optoelectronic pole surface.

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