Preparation method and application of nickel cobalt oxide modified molybdenum doped bismuth vanadate composite photoanode

Abstract

The application discloses a preparation method of a nickel cobalt oxide modified molybdenum doped bismuth vanadate composite photoanode and application thereof, and belongs to the field of photoelectrochemical reaction engineering for decomposing water to produce hydrogen; the Mo-BiVO4 photoanode is obtained through a combination method of electrodeposition and calcination; a precursor solution containing bimetallic nickel and cobalt is prepared by using cobalt nitrate hexahydrate, nickel nitrate hexahydrate and boric acid; the Mo-BiVO4 photoanode is immersed in the precursor solution; a nickel cobalt oxide (NiCoO x ) cocatalyst is grown on the surface of the Mo-BiVO4 photoanode by using a light-assisted electrodeposition method; a NiCoO x cocatalyst modified Mo-BiVO4 composite photoanode is obtained; and the photocurrent density of the best NiCoO x cocatalyst modified Mo-BiVO4 composite photoanode is 5.2 times that of pure bismuth vanadate. The application has the advantages of simple operation, easily available raw materials, low economic cost and good stability.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode and application thereof, and belongs to the field of photoelectrochemical reaction engineering for water splitting. BACKGROUND

[0002] Bismuth vanadate (BiVO4) has a narrow band gap, good visible light absorption ability and remarkable stability, and is considered as a very promising photoelectrode material, which can be used in photoelectrochemical (PEC) systems. However, the photo-generated electron-hole pair of the BiVO4 photoanode has a high recombination rate, and the photoelectron conductivity is poor. Previous studies have also proposed that the basic problem of charge transfer in BiVO4 is that the conduction band is mainly composed of V3d orbits. The VO4 tetrahedron in BiVO4 is not connected to each other, so that the free electron can only jump between the VO4 tetrahedrons, resulting in low electron mobility. In order to solve these limitations, various strategies for improving the photoelectric performance of the BiVO4 photoanode have been developed, mainly through morphology control, element doping, and formation of heterojunctions.

[0003] Among them, doping BiVO4 with high-valence metal elements is an effective means to improve the carrier density and promote charge separation. Mo ions can be used as dopants to enhance the carrier density, as structure guides to promote one-dimensional nanostructures, and form effective charge transfer paths. Loading of the cocatalyst can significantly improve the activity of the surface sites, which not only retains the excellent properties of the photoanode surface, but also induces the generation of high-activity sites, providing sufficient space for the reactions occurring on the interface. The synergistic effect of the cocatalyst and bismuth vanadate can effectively accelerate the water oxidation kinetics, promote charge separation and transport, thereby significantly promoting the PEC water oxidation process and improving the water splitting activity.

[0004] However, so far, there has been no related report on using photo-assisted electrodeposition of nickel (Ni) and cobalt (Co) bimetallic oxide cocatalysts on the surface of a bismuth vanadate photoanode and performing photoelectrochemical reaction for water splitting. SUMMARY

[0005] The application aims to overcome some defects in the prior art, and provides a preparation method of a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode and application thereof. x The application loads a NiCoO

[0006] To achieve the above technical purposes, the technical solutions adopted by the application are as follows:

[0007] The application provides a preparation method of a nickel cobalt oxide modified molybdenum doped bismuth vanadate composite photoanode.

[0008] A molybdenum doped bismuth vanadate (Mo-BiVO4) film is prepared by using an electro-deposition combined calcination method, that is, a Mo-BiVO4 photoanode is obtained; a precursor solution containing bimetallic nickel (Ni) and cobalt (Co) is prepared, the Mo-BiVO4 photoanode is immersed into the precursor solution by using a three-electrode electrochemical system, and electro-deposition is carried out by linear scanning under light irradiation; after the electro-deposition is completed, the obtained material is washed and dried to obtain a NiCoO x / Mo-BiVO4 composite photoanode.

[0009] The preparation method of the precursor solution containing bimetallic nickel (Ni) and cobalt (Co) is as follows: Ni and Co sources are dissolved in a boric acid buffer solution, and stirring is continuously carried out until the Ni and Co sources are completely dissolved; potassium hydroxide (KOH) is added to adjust the pH value, and nitrogen is introduced for a certain period of time to prepare the precursor solution containing bimetallic nickel (Ni) and cobalt (Co).

[0010] Further, the Ni source includes Ni(NO3)2·6H2O or NiCl2·6H2O; and the Co source includes Co(NO3)2·6H2O or CoCl2·6H2O.

[0011] Further, the molar ratio of the metal nickel and cobalt in the precursor solution containing bimetallic nickel (Ni) and cobalt (Co) is 1-5:10.

[0012] Further, the concentration of the boric acid buffer solution is 0.5 M, the pH value adjusted by the KOH is 7-9, and the nitrogen is introduced for more than 30 minutes to ensure that other gases in the solution are exhausted.

[0013] In the three-electrode electrochemical system, the Mo-BiVO4 photoanode is used as a working electrode (WE), an Ag / AgCl electrode is used as a reference electrode (RE), and a platinum wire is used as a counter electrode (CE).

[0014] In the process of electro-deposition of the Mo-BiVO4 photoanode immersed in the precursor solution under light irradiation by linear scanning, the light source of the light irradiation is a 300 W xenon lamp, and the light intensity reaching the electrode is 100 mW / cm 2 .

[0015] Further, the linear scanning rate is 50 mV / s, the deposition voltage of the electro-deposition is-0.2-0.5 V, and the cycle is 2-4 times.

[0016] In the above method, the washing is carried out by using deionized water, and the drying condition in the oven is 60 DEG C drying for 12 h.

[0017] The application also provides the NiCoO x / Mo-BiVO4 composite photoanode prepared by the method.

[0018] The application also provides application of the photoanode prepared by the method in photoelectrocatalytic decomposition of water to produce hydrogen.

[0019] The application has the following beneficial effects:

[0020] At present, there are many studies on modification of the bismuth vanadate photoelectrode, including ion doping, composite cocatalyst, etc., but the NiCoO x / Mo-BiVO4 photoanode has not been reported.

[0021] The application composites nickel-cobalt bimetallic oxide (NiCoO x ) cocatalyst on the surface of molybdenum-doped bismuth vanadate (Mo-BiVO4) by the method of photo-assisted electrodeposition, and prepares a nickel-cobalt oxide / molybdenum-doped bismuth vanadate (NiCoO x / Mo-BiVO4) composite photoanode. The method of the application makes the Ni and Co in the NiCoO x cocatalyst synergistically act on each other, further enhances the conductivity of the Mo-BiVO4 surface, the nickel-cobalt oxide nanolayer has the effect of enhancing the surface charge separation efficiency, promoting the water oxidation capacity of the photoelectrode surface, improving the photoelectrocatalytic performance, enhancing the oxidation resistance of the electrode, slowing down the photo corrosion of the bismuth vanadate, and prolonging the working life of the electrode. x After PEC test, it is found that the NiCoO 2 / BiVO4 photoanode prepared by the method of the application exhibits a high photocurrent density of 5.3 mA / cm x under AM 1.5G illumination at 1.23 V (standard hydrogen electrode potential), which is 1.8 times as high as that of the original Mo-BiVO4 photoanode and 5.2 times as high as that of pure BiVO4. The NiCoO x / BiVO4 photoanode also exhibits a higher charge transfer efficiency, and has obvious advantages compared with the existing BiVO4-based photoelectrode for decomposition of water to produce hydrogen.

[0022] In the application, a nickel-cobalt oxide (NiCoO x ) cocatalyst is prepared by adjusting the Ni / Co ratio under photo-assisted electrodeposition using a Ni and Co bimetallic precursor solution, so as to improve the PEC performance of the molybdenum-doped bismuth vanadate. The method of the application has the advantages of adjustable metal molar ratio and simple composite mode, and the composite photoelectrode has obvious improvement in water decomposition activity compared with the pure molybdenum-doped bismuth vanadate photoelectrode.

[0023] The application loads the NiCoO xThe application discloses a preparation method of a Mo-BiVO4 composite light anode, and belongs to the technical field of photocatalysis. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 BiVO4, Mo-BiVO4 and NiCoO prepared in example 2 x XPS diffraction spectrum of the Mo-BiVO4 light anode sample, and the upper right corner of the drawing is the NiCoO x The Mo-BiVO4 light anode sample is shown in the drawing.

[0025] Figure 2 BiVO4, Mo-BiVO4 and NiCoO prepared in example 2 x SEM images of the Mo-BiVO4 light anode sample (a, d are pure BiVO4; b, e are Mo-BiVO4; c, f are NiCoO x / Mo-BiVO4)。

[0026] Figure 3 NiCoO prepared in example 2 x High-resolution transmission (HRTEM) images (a) and mapping element distribution images (b) of the Mo-BiVO4 composite light anode.

[0027] Figure 4 BiVO4, Mo-BiVO4 and NiCoO prepared in example 2 x J-V test graph of the Mo-BiVO4 composite light anode.

[0028] Figure 5 BiVO4, Mo-BiVO4 and NiCoO prepared in example 2 x J-V test graph of the Mo-BiVO4 composite light anode.

[0029] Figure 6 BiVO4, Mo-BiVO4 and NiCoO prepared in example 2 x Photoelectric impedance (PEIS) graph of the Mo-BiVO4 composite light anode. DETAILED DESCRIPTION

[0030] The application will be described in detail below with reference to the examples, so that those skilled in the art can better understand the application, but the application is not limited to the following examples.

[0031] The use of the terms "including", "comprising", "having", "containing", "involving", and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and should not be interpreted in an overly idealized or overly broad manner, unless expressly so defined herein.

[0032] In the examples, the preparation of BiOI and BiVO4 photoanodes is synthesized according to the method published by Professor Tae Woo Kim and Kyoung-Shin Choi in 2014 in Science (Nanoporous BiVO4 Photoanodes with Dual-Layer Oxygen Evolution Catalysts for Solar Water Splitting). Namely, the first step is to prepare BiOI photoanode by electrodeposition, and the second step is to prepare molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode by adding 1% mass fraction of Mo source (molybdenum acetylacetonate oxide) in V source (vanadium acetylacetonate oxide). Finally, the molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode is obtained. If no Mo source is added, and the V source is directly added to the surface of the BiOI photoelectrode and calcined, the pure bismuth vanadate (BiVO4) photoanode is obtained.

[0033] Specific method: first, BiOI is electrodeposited on FTO, at the same time, the DMF solution of molybdenum acetylacetonate oxide is added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution is 1% (mass fraction), then the mixed DMF solution is added to the surface of BiOI, and calcined at 450°C for 2 hours to obtain the molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0034] In the present application, the NiCoO x represents nickel-cobalt oxide.

[0035] Example 1: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0036] Step (1): deposit a bismuth iodine oxide (BiOI) film on the FTO conductive glass to obtain a BiOI photoanode.

[0037] Step (2): add the DMF solution of molybdenum acetylacetonate oxide to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution is 1% (mass fraction), then deposit the mixed DMF solution on the surface of BiOI, and calcine at 450°C for 2 hours to finally obtain the molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0038] Step (3): 0.01 mol Ni(NO3)2·6H2O, 0.1 mol Co(NO3)2·6H2O were dissolved in 80 mL of 0.5M boric acid buffer solution, after fully dissolved, KOH was added to adjust the pH value to 8.4, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, using a three-electrode electrochemical system, using the Mo-BiVO4 photoanode as the working electrode (WE), the Ag / AgCl electrode as the reference electrode (RE), and the platinum wire as the counter electrode (CE), under the irradiation of a 300W xenon lamp with an intensity of 100mV / cm 2 , the linear scan rate was 50mV / s, the deposition voltage was-0.2-0.5V for one cycle, and the cycle of this embodiment was 2 times.

[0039] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0040] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the method can be used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0041] Example 2: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0042] Step (1): Bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0043] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2 hours to finally obtain a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0044] Step (3): 0.01 mol mg Ni(NO3)2·6H2O, 0.1 mol Co(NO3)2·6H2O were dissolved in 80 mL of 0.5M boric acid buffer solution, after fully dissolved, KOH was added to adjust the pH value to 8.4, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, using a three-electrode electrochemical system, using the Mo-BiVO4 photoanode as the working electrode (WE), the Ag / AgCl electrode as the reference electrode (RE), and the platinum wire as the counter electrode (CE), under the irradiation of a 300W xenon lamp with an intensity of 100mV / cm 2 , the linear scan rate was 50mV / s, the deposition voltage was-0.2-0.5V for one cycle, and the cycle of the embodiment was 3 times.

[0045] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0046] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the application is used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0047] Example 3: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0048] Step (1): Bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0049] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2h to finally obtain a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0050] Step (3): 0.01 mol of Ni(NO3)2·6H2O and 0.1 mol of Co(NO3)2·6H2O were dissolved in 80 mL of 0.5M boric acid buffer solution, after being dissolved thoroughly, KOH was added to adjust the pH value to 8.4, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, and a three-electrode electrochemical system was used, taking the Mo-BiVO4 photoanode as a working electrode (WE), an Ag / AgCl electrode as a reference electrode (RE), and a platinum wire as a counter electrode (CE), under the irradiation of a 300W xenon lamp with an intensity of 100mV / cm 2 , the linear scan rate was 50mV / s, the deposition voltage was-0.2-0.5V for one cycle, and the cycle of the embodiment was 4 times.

[0051] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0052] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the method can be used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0053] Example 4: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0054] Step (1): A bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0055] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2h to finally obtain a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0056] Step (3): 0.01 mol of Ni(NO3)2·6H2O and 0.1 mol of Co(NO3)2·6H2O were dissolved in 80 mL of 0.5 M boric acid buffer solution, after being dissolved thoroughly, KOH was added to adjust the pH value to 7, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, and a three-electrode electrochemical system was used, taking the Mo-BiVO4 photoanode as a working electrode (WE), an Ag / AgCl electrode as a reference electrode (RE), and a platinum wire as a counter electrode (CE), and a 300 W xenon lamp was used to irradiate at an intensity of 100 mV / cm 2 , and electrodeposition was carried out at a linear scan rate of 50 mV / s and a deposition voltage of-0.2-0.5 V for one cycle, and the cycle of the embodiment was 3 times.

[0057] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60 DEG C for 12 h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0058] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the method can be used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0059] Example 5: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0060] Step (1): A bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0061] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), and then the mixed DMF solution was deposited on the surface of the BiOI, and calcination was carried out at 450 DEG C for 2 h to finally obtain a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0062] Step (3): 0.01 mol of Ni(NO3)2·6H2O and 0.1 mol of Co(NO3)2·6H2O were dissolved in 80 mL of 0.5 M boric acid buffer solution, after being fully dissolved, KOH was added to adjust the pH value to 9, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, and a three-electrode electrochemical system was used, with the Mo-BiVO4 photoanode as the working electrode (WE), the Ag / AgCl electrode as the reference electrode (RE), and the platinum wire as the counter electrode (CE), under the irradiation of a 300 W xenon lamp with an intensity of 100 mV / cm 2 , the linear scan rate was 50 mV / s, the deposition voltage was-0.2-0.5 V for one cycle, and the cycle of this embodiment was 3 times.

[0063] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12 h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0064] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the method has the advantages of high hydrogen production rate, high stability, and low cost.

[0065] Example 6: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0066] Step (1): A bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0067] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2 hours to finally obtain a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0068] Step (3): 0.02 mol of Ni(NO3)2·6H2O and 0.1 mol of Co(NO3)2·6H2O were dissolved in 80 mL of 0.5 M boric acid buffer solution, after being dissolved thoroughly, KOH was added to adjust the pH value to 8.4, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, and a three-electrode electrochemical system was used, taking the Mo-BiVO4 photoanode as a working electrode (WE), an Ag / AgCl electrode as a reference electrode (RE), and a platinum wire as a counter electrode (CE), and a 300 W xenon lamp was irradiated at an intensity of 100 mW / cm 2 , and electrodeposition was carried out at a linear scan rate of 50 mV / s and a deposition voltage of-0.2-0.5 V for one cycle, and the cycle of the present embodiment was 3 times.

[0069] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12 h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0070] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the present application is used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0071] Example 7: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0072] Step (1): A bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0073] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), and then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2 hours to finally obtain a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode.

[0074] Step (3): 0.03 mol of Ni(NO3)2·6H2O and 0.1 mol of Co(NO3)2·6H2O were dissolved in 80 mL of 0.5 M boric acid buffer solution, after being dissolved thoroughly, KOH was added to adjust the pH value to 8.4, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, and a three-electrode electrochemical system was used, taking the Mo-BiVO4 photoanode as a working electrode (WE), an Ag / AgCl electrode as a reference electrode (RE), and a platinum wire as a counter electrode (CE), and a 300 W xenon lamp was irradiated at an intensity of 100 mW / cm 2 , and electrodeposition was carried out at a linear scan rate of 50 mV / s and a deposition voltage of-0.2-0.5 V for one cycle, and the cycle of the present embodiment was 3 times.

[0075] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12 h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0076] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the present application is used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0077] Example 8: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0078] Step (1): A bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0079] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), and then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2 hours, and finally a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode was obtained.

[0080] Step (3): 0.04 mol of Ni(NO3)2·6H2O and 0.1 mol of Co(NO3)2·6H2O were dissolved in 80 mL of 0.5 M boric acid buffer solution, after being dissolved thoroughly, KOH was added to adjust the pH value to 8.4, and N2 was bubbled for 30 min to remove dissolved oxygen in the solution to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, and a three-electrode electrochemical system was used, taking the Mo-BiVO4 photoanode as a working electrode (WE), an Ag / AgCl electrode as a reference electrode (RE), and a platinum wire as a counter electrode (CE), and a 300 W xenon lamp was irradiated at an intensity of 100 mW / cm 2 , and electrodeposition was carried out at a linear scan rate of 50 mV / s and a deposition voltage of-0.2-0.5 V for one cycle, and the cycle of the present embodiment was 3 times.

[0081] After the deposition was completed, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12 h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0082] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the present application is used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0083] Example 9: Preparation of NiCoO x / Mo-BiVO4 composite photoanode

[0084] Step (1): A bismuth oxyiodide (BiOI) thin film was deposited on FTO conductive glass to obtain a BiOI photoanode.

[0085] Step (2): The DMF solution of molybdenum acetylacetonate oxide was added to the N,N-dimethylformamide (DMF) solution of vanadium acetylacetonate oxide, so that the concentration of the mixed DMF solution was 1% (mass fraction), and then the mixed DMF solution was deposited on the surface of BiOI, and calcination was carried out at 450℃ for 2 hours, and finally a molybdenum-doped bismuth vanadate (Mo-BiVO4) photoanode was obtained.

[0086] Step (3): 0.05 mol Ni(NO3)2.6H2O, 0.1 mol Co(NO3)2.6H2O were dissolved in 80 mL 0.5M boric acid buffer solution, after fully dissolved, KOH was added to adjust the pH value to 8.4, N2 was bubbled to remove dissolved oxygen in the solution for 30 min to obtain a precursor solution. The Mo-BiVO4 photoanode obtained in step (2) was immersed in the obtained precursor solution and stirred, using a three-electrode electrochemical system, Mo-BiVO4 photoanode as the working electrode (WE), Ag / AgCl electrode as the reference electrode (RE), platinum wire as the counter electrode (CE), under the irradiation of a 300W xenon lamp with an intensity of 100mV / cm 2 , the linear scan rate was 50mV / s, the deposition voltage was-0.2-0.5V for one cycle, and the cycle of the embodiment was 3 times.

[0087] After the deposition, the photoelectrode was washed with deionized water and dried in an oven at 60℃ for 12h to obtain a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode (denoted as NiCoO x / Mo-BiVO4 composite photoanode).

[0088] The NiCoO x / Mo-BiVO4 composite photoanode obtained by the application can be used for photoelectrocatalytic reaction to decompose water to produce hydrogen.

[0089] Phase testing:

[0090] The bismuth vanadate (BiVO4), molybdenum-doped bismuth vanadate (Mo-BiVO4) and the NiCoO x / Mo-BiVO4 composite photoanode sample prepared in Example 2 were tested by X-ray energy spectrum diffractometer, and the XPS diffraction chart as shown in Figure 1 was obtained. It is shown in the chart that the three samples all have peaks of elements O, V and Bi, and in the enlarged chart of the NiCoO x / Mo-BiVO4 photoanode sample, peaks of Ni and Co appear, proving that the NiCoO x co-catalyst is on the surface of the Mo-BiVO4 photoanode.

[0091] The BiVO4, Mo-BiVO4 and the NiCoO x / Mo-BiVO4 composite photoanode sample prepared in Example 2 were tested by scanning electron microscope, and the SEM image as shown in Figure 2 was obtained. From the chart, it is seen that the NiCoO x co-catalyst is not obvious, so other tests are needed to verify the existence of the NiCoO x co-catalyst.

[0092] The sample of Example 2 was taken, and the sample on the surface of the electrode was scraped off with a blade to obtain a powder sample, and then high-resolution transmission electron microscopy (HRTEM) test was performed. Figure 3 The results show that the molybdenum-doped bismuth vanadate (Mo-BiVO4) has good crystallinity on the 011 and 110 crystal planes, and the lattice stripe spacing is 0.476 and 0.466 nm, and the nickel-cobalt oxide is in an amorphous state. In addition, it can be clearly seen from the element distribution map that the nickel-cobalt oxide (NiCoO x ) is uniformly distributed on the surface of the Mo-BiVO4.

[0093] In summary, the above results show that the method of the present application successfully prepares a nickel-cobalt oxide modified molybdenum-doped bismuth vanadate composite photoanode, and the nickel-cobalt oxide (NiCoO x ) is uniformly distributed on the surface of the Mo-BiVO4.

[0094] Further, the composite photoanode prepared by the method of the present application is tested:

[0095] Photoelectric performance test:

[0096] In the present application, the NiCoOx / Mo-BiVO4 photoanode is prepared by electrodeposition without light assistance, and compared with the NiCoOx / Mo-BiVO4 photoanode prepared by the method of the present application with light assistance, the photoelectrochemical test performance of the photoanode prepared without light assistance is lower than that of the photoanode prepared by the method of the present application.

[0097] All the photoelectrochemical test results are measured by using an electrochemical workstation (CHI 614) in a three-electrode system using the prepared sample as a working electrode (WE), an Ag / AgCl electrode as a reference electrode (RE), and a platinum wire as a counter electrode (CE), and all the electrolytes are 0.5M borate buffer solution with a pH value of 9.5 unless otherwise specified. A xenon lamp source with a rated power of 300W and a light intensity of 100mW / cm 2 is used to simulate sunlight.

[0098] The effect of the photoanode of the present application on the photoelectrochemical decomposition of water to produce hydrogen is reflected in the photocurrent density, and under the same test conditions, the higher the photocurrent density, the better the hydrogen production effect, as shown in Figure 4 In this embodiment, linear voltammetry (LSV) is used to test the J-V of pure bismuth vanadate (BiVO4 photoanode), molybdenum-doped bismuth vanadate (Mo-BiVO4), and the samples of Examples 1 to 3, and the voltage range is -0.6-0.8 (vs.Ag / AgCl), and the scan rate is 50mV / s. The results are shown in Figure 4 At a bias of 1.23V (vs.RHE), the pure BiVO4 (denoted as BiVO4 in the figure), Example 1 (denoted as NiCoOx / Mo-BiVO4-2), Example 2 (denoted as NiCoO in the figure) x / Mo-BiVO4-3) and Example 3 (denoted as NiCoO in the figure) x The photocurrent density corresponding to the sample with / Mo-BiVO4-4 was 1.02 mA / cm. 2 3.87 mA / cm 2 5.30mA / cm 2 and 4.22mA / cm 2 That is, the sample in Example 2 had the highest photocurrent density.

[0099] Figure 5 In the figure, the photocurrent density corresponding to Mo-BiVO4 is 2.91 mA / cm². 2 In contrast, Mo-doped and NiCoO-supported... x Bismuth vanadate after co-catalysis (sample of Example 2, denoted as NiCoO) x The photocurrent density of / Mo-BiVO4 was significantly improved, and the effect of the number of electrodeposition cycles on NiCoO was also clearly observed. x The photocurrent density of the Mo-BiVO4 composite photoanode is significantly affected. The sample with three electrodeposition cycles exhibits the highest photocurrent density, which is 5.2 times that of pure bismuth vanadate and 1.8 times that of Mo-BiVO4. Currently, photocurrent density is a key metric for the effectiveness of photoelectrochemical water splitting for hydrogen production, as it is directly proportional to the amount of hydrogen produced; higher photocurrent density results in greater hydrogen production. The photoelectrode prepared by the method of this invention demonstrates a significantly outstanding effect in photoelectrochemical catalytic water splitting for hydrogen production.

[0100] The number of electrodeposition cycles directly determines the loading of nickel-cobalt oxide on molybdenum-doped bismuth vanadate. When the number of electrodeposition cycles is less than 3, it may be NiCoO. x The low content of co-catalyst leads to NiCoO x The effect of catalytic assistance is not obvious; when the number of electrodeposition cycles is greater than 3, it may be due to NiCoO. x A high content of cocatalyst leads to a reduction in active sites on Mo-BiVO4, resulting in a decrease in performance.

[0101] Figure 6 Pure BiVO4, Mo-BiVO4, and the sample from Example 2 were subjected to photoimpedance testing (PEIS). Figure 6 As shown, the smaller the radius of the curve for the sample in Example 2, the faster the carrier transfer rate is compared to pure BiVO4 and Mo-BiVO4. These results indicate that the NiCoO on the Mo-BiVO4 surface... xThe presence of the semiconductor material is conducive to carrier separation, thereby improving the overall performance of the PEC, can inhibit the photogenerated electron / hole recombination, solves the problem of high photogenerated electron-hole pair recombination rate of the current bismuth vanadate photoanode.

[0102] The above examples describe the basic principles and main features of the present application and the advantages of the present application, the present application is not limited to the details of the above examples, and the present application can be realized in other specific forms without departing from the spirit or essential characteristics of the present application. The described examples are exemplary, not restrictive.

Claims

1. A method for preparing a nickel cobalt oxide modified molybdenum doped bismuth vanadate composite photoanode, characterized in that, The method comprises: A Mo-BiVO4 photoanode is prepared by electrodepositing combined with calcination; a precursor solution containing bimetallic Ni and Co is prepared, the Mo-BiVO4 photoanode is immersed in the precursor solution by using a three-electrode electrochemical system, and then electrodepositing is carried out by linear scanning under light irradiation; after the electrodepositing, the obtained material is washed and dried to obtain a NiCoO x / Mo-BiVO4 composite photoanode; the preparation method of the precursor solution containing bimetallic Ni and Co is as follows: Ni and Co sources are dissolved in a boric acid buffer solution, and stirring is continuously carried out until complete dissolution; KOH is added to adjust the pH, and nitrogen is introduced for a certain time to prepare the precursor solution containing bimetallic Ni and Co; the content ratio of Ni and Co in the precursor solution containing bimetallic Ni and Co is 1-5:10 in terms of molar ratio; the rate of linear scanning is 50 mV / s, the voltage of electrodepositing is-0.2 V to 0.5 V, and the cycle is 2-4 times.

2. The method of claim 1, wherein, The Ni source comprises Ni(NO3)2·6H2O or NiCl2·6H2O; and the Co source comprises Co(NO3)2·6H2O or CoCl2·6H2O.

3. The method of claim 1, wherein, The concentration of the boric acid buffer solution is 0.5 M, the pH value is adjusted to 7-9 by KOH, and nitrogen is introduced for more than 30 minutes to ensure that other gases in the solution are exhausted.

4. The method of claim 1, wherein, In the three-electrode electrochemical system, Mo-BiVO4 photoanode is used as the working electrode, Ag / AgCl electrode is used as the reference electrode, and platinum wire is used as the counter electrode; the light source of the light irradiation is a 300 W xenon lamp, and the light intensity reaching the electrode is 100 mW / cm 2 .

5. The method of claim 1, wherein, The drying condition is 60 DEG C for 12 h.

6. The NiCoO4 / Mo-BiVO4 composite photoanode prepared by the method of any one of claims 1-5. x / Mo-BiVO4 composite photoanode.

7. The NiCoO x / Mo-BiVO4 composite photoanode prepared by the method of any one of claims 1-5, or the NiCoO x / Mo-BiVO4 composite photoanode of claim 6 in the photoelectrocatalytic decomposition of water to produce hydrogen.

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