Preparation method and application of high-performance LaCo-LDH / NiPt / BVO photoelectrode film

Abstract

The invention belongs to the technical field of photoelectrochemistry, and particularly relates to a preparation method and application of a high-performance LaCo-LDH / NiPt / BVO photoelectrode film. Firstly, a BiOI nano array is prepared through an electro-deposition method, and then the BVO photoelectrode is prepared through high-temperature calcination. Dissolving nickel chloride hexahydrate, boric acid and chloroplatinic acid into deionized water, adding potassium chloride into the mixed solution to prepare NiPt electro-deposition liquid, and preparing the NiPt / BVO photoelectrode from the BVO photoelectrode in a three-electrode system through an electro-deposition method. Finally, cobalt nitrate hexahydrate, lanthanum nitrate hexahydrate and urea are dissolved in deionized water, a proper amount of ethyl alcohol is added to prepare a LaCo-LDH precursor solution, and the LaCo-LDH / NiPt / BVO photoelectrode thin film is prepared through a hydrothermal method. At the moment, the separation and injection efficiency of photon-generated carriers of the BVO is enhanced through the synergistic effect of the cocatalyst NiPt and the LaCo-LDH, so that the photoelectric property of the BVO photoelectrode is remarkably improved, and the BVO photoelectrode can be applied to photoelectrochemical water decomposition.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectrochemistry, and specifically relates to a preparation method and application of a high-performance LaCo-LDH / NiPt / BVO photoelectrode film. Background Art

[0002] The decline of fossil fuel reserves and the release of carbon dioxide and other greenhouse gases have exacerbated global warming, driving the growing demand for clean and sustainable energy and exploring alternative ways to reduce carbon footprints. Solar energy is currently the largest energy source on Earth, but its decentralized and intermittent nature remains a huge challenge to energy demand.

[0003] BVO has attracted attention due to its suitable band gap (about 2.4 eV), excellent energy band position, cheap synthetic raw materials and non-toxic properties. Theoretically, the theoretical photocurrent of BVO at 1.23 V (vs. RHE) is 7.5 mA / cm 2 , which can realize bias-free water splitting. However, the inherent disadvantages of the material are poor carrier transport capacity, high surface defect state density, and sluggish water oxidation reaction kinetics, which leads to serious carrier recombination. This makes it quite challenging to apply pure BVO photoanode in the field of photoelectrocatalysis. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a method for preparing a high-performance LaCo-LDH / NiPt / BVO photoelectrode film and its application. The method has the advantages of simple preparation method, convenient operation, and easy control of process conditions.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a high-performance LaCo-LDH / NiPt / BVO photoelectrode film comprises the following steps:

[0007] 1) dissolving bismuth nitrate pentahydrate and potassium iodide in deionized water with a pH of 1.7, stirring until fully dissolved, to obtain a solution A; dissolving p-benzoquinone in ethanol, stirring until fully dissolved, to obtain a solution B; and finally mixing the solution A with the solution B to obtain a BiOI electrodeposition solution;

[0008] 2) placing the cleaned FTO conductive glass in a BiOI electrodeposition solution to prepare a BiOI nanoarray by electrodeposition; dissolving vanadium acetylacetonate in a dimethyl sulfoxide solution to obtain a drop coating solution containing a vanadium source; dropping the drop coating solution containing a vanadium source onto the BiOI nanoarray, calcining at high temperature under air conditions, and finally immersing in a KOH solution to remove vanadium pentoxide produced during calcination to obtain a BVO photoelectrode film;

[0009] 3) dissolving nickel chloride hexahydrate, boric acid and chloroplatinic acid in deionized water, stirring until fully dissolved, and adding potassium chloride solution thereto to obtain a NiPt electrodeposition solution; electrodepositing the BVO photoelectrode film obtained in step 2) in the NiPt electrodeposition solution to obtain a NiPt / BVO photoelectrode film;

[0010] 4) Dissolving cobalt nitrate hexahydrate, lanthanum nitrate hexahydrate and urea in deionized water to obtain a precursor C solution, stirring until fully dissolved, and adding ethanol to the precursor C solution to obtain a precursor D solution; placing the NiPt / BVO photoelectrode film obtained in step 3) in the inner tank of a reactor with the conductive surface facing upward, adding the precursor D solution to the inner tank of the reactor, and finally obtaining a LaCo-LDH / NiPt / BVO photoelectrode film through a hydrothermal reaction.

[0011] Furthermore, in the above preparation method, in step 1), the molar ratio of Bi in bismuth nitrate pentahydrate to I in potassium iodide is 0.1:1.

[0012] Furthermore, in the above preparation method, in step 1), the concentration of p-benzoquinone in the B solution is 0.23 mol / L.

[0013] Furthermore, in the above-mentioned preparation method, in step 2), the voltage of the electrodeposition process is -0.15 to -0.05 V vs. Ag / AgCl, and the time is 300-350 s.

[0014] Furthermore, in the above preparation method, in step 2), the concentration of vanadyl acetylacetonate in the drip coating solution containing the vanadium source is 0.4 mol / L.

[0015] Furthermore, in the above preparation method, in step 2), the concentration of the KOH solution is 0.5-1 mol / L, and the soaking time is 30-60 min.

[0016] Furthermore, in the above-mentioned preparation method, in step 2), the high-temperature calcination conditions are calcination at 400-550°C for 2-4h, and the heating rate is 1-10°C / min.

[0017] Furthermore, in the above preparation method, in step 3), the molar ratio of nickel chloride hexahydrate:boric acid:chloroplatinic acid is 2:2:0.03.

[0018] Furthermore, in the above preparation method, in step 3), the concentration of the potassium chloride solution is 0.5 mol / L.

[0019] Furthermore, in the above-mentioned preparation method, in step 3), the electrodeposition process has a voltage of -0.3 to -0.1 V vs. Ag / AgCl and a time of 30 to 60 s.

[0020] Furthermore, in the above preparation method, in step 4), the molar ratio of cobalt nitrate hexahydrate: lanthanum nitrate hexahydrate: urea is 1:0.1:10.

[0021] Furthermore, in the above preparation method, in step 4), the volume ratio of the precursor C solution to the added ethanol is 5:1.

[0022] Furthermore, in the above preparation method, in step 4), the temperature of the hydrothermal reaction is 100-140° C., and the time is 2-5 h.

[0023] Application of high-performance LaCo-LDH / NiPt / BVO photoelectrode film prepared by any of the preparation methods described above in photoelectrochemical water splitting.

[0024] The beneficial effects of the present invention are:

[0025] 1. The LaCo-LDH / NiPt / BVO photoelectrode film provided by the present invention, the loading of the co-catalyst NiPt and LaCo-LDH, synergistically improves the internal photogenerated carrier separation and transmission efficiency. At the same time, the outer layer loading of LaCo-LDH improves the serious recombination problem of surface carriers, thereby effectively improving the photoelectrochemical performance.

[0026] 2. The LaCo-LDH / NiPt / BVO photoelectrode film provided by the present invention has a preparation method with cheap and readily available raw materials, simple and convenient operation, provides new catalytic materials for the field of photoelectrocatalysis, alleviates the current energy shortage situation, and has good application prospects.

[0027] 3. The photocurrent density of the LaCo-LDH / NiPt / BVO photoelectrode film provided by the present invention is increased by 2.4 times compared with that of BVO.

[0028] 4. The present invention adopts the method of electrodeposition and hydrothermal to load the co-catalyst NiPt and LaCo-LDH on the outer layer of BVO, and improves the problem of poor carrier separation and transportation inside through the catalyst. At the same time, LaCo-LDH also improves the surface defects of BVO film and improves the kinetics of water oxidation reaction, thereby improving the serious surface carrier recombination problem and improving the photoelectrocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 XRD patterns of BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films prepared in Example 1.

[0030] Figure 2 This is a LSV comparison diagram of BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films prepared in Example 1.

[0031] Figure 3 is the η of the BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films prepared in Example 1 bulk Comparison chart.

[0032] Figure 4 is the η of the BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films prepared in Example 1 surface Comparison chart.

[0033] Figure 5 This is a photocurrent comparison diagram of BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films prepared in Example 1. DETAILED DESCRIPTION

[0034] Example 1 High-performance LaCo-LDH / NiPt / BVO photoelectrode film

[0035] (I) Preparation method

[0036] 1) Preparation of BVO photoelectrode film

[0037] First, 6.64g potassium iodide and 1.98g bismuth nitrate pentahydrate were dissolved in 100mL deionized water (a certain amount of dilute nitric acid was added to adjust the pH to 1.7) to obtain solution A. After that, 0.9946g of p-benzoquinone was weighed and dissolved in 40mL of anhydrous ethanol as solution B. Solution A and solution B were mixed and stirred thoroughly as BiOI electrodeposition solution. The electrodeposition process used a three-electrode system, in which platinum (Pt) foil was used as the counter electrode, FTO was used as the working electrode, and Ag / AgCl was used as the reference electrode. The working potential was set to -0.1V vs.Ag / AgCl, and the electrodeposition time was controlled at 5min to prepare the BiOI nanoarray. 0.1061g of acetylacetonato vanadium was weighed and dissolved in 1mL of dimethyl sulfoxide (DMSO) as a vanadium source solution. Then, 100μL of vanadium source solution was immediately added to each BiOI nanoarray sample. Subsequently, the sample with the vanadium source solution added was placed in a muffle furnace and kept at 450°C for 2 hours under air conditions, with a heating rate of 2°C / min. Finally, in order to remove the V2O5 remaining on the surface during calcination, the sample was immersed in a 1 mol / L KOH solution for 1 hour to obtain a BVO photoelectrode film.

[0038] 2) Preparation of NiPt / BVO photoelectrode film

[0039] For NiPt deposition, 2.3769 g nickel chloride hexahydrate, 0.6183 g boric acid, and 0.0615 g chloroplatinic acid were dissolved in 50 mL deionized water, and then 1 mL potassium chloride solution (0.5 mol / L) was added to the solution. Electrochemical deposition was performed in a three-electrode cell with the BVO photoanode film as the working electrode, platinum foil as the counter electrode, and Ag / AgCl as the reference electrode. -0.1 V vs. Ag / AgCl was applied for 60 s to obtain the NiPt / BVO photoelectrode film.

[0040] 3) Preparation of LaCo-LDH / BVO photoelectrode film

[0041] 0.145515g of cobalt nitrate hexahydrate, 0.0216505g of lanthanum nitrate hexahydrate and 0.3003g of urea were dissolved in 50mL of deionized water, and then 10mL of ethanol was added dropwise to prepare a precursor solution. The BVO photoelectrode film was placed in a Teflon-lined autoclave with the conductive surface facing up, and the precursor solution was added to the autoclave and kept at 120°C for 3h. Finally, the LaCo-LDH / BVO photoelectrode film was rinsed and dried.

[0042] 4) Preparation of LaCo-LDH / NiPt / BVO photoelectrode film

[0043] Dissolve 0.145515g of cobalt nitrate hexahydrate, 0.0216505g of lanthanum nitrate hexahydrate and 0.3003g of urea in 50mL of deionized water, and then add 10mL of ethanol dropwise to prepare a precursor solution. Place the NiPt / BVO photoelectrode film with the conductive surface facing up in a Teflon-lined autoclave, add the precursor solution into the autoclave, and keep it at 120°C for 3h. Finally, rinse and dry to obtain the LaCo-LDH / NiPt / BVO photoelectrode film.

[0044] (II) Testing

[0045] Figure 1 XRD patterns of prepared BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films. Figure 1 It can be seen that BVO corresponds to the diffraction peak of SnO2 (FTO). The diffraction peaks of NiPt and LaCo-LDH do not appear because the NiPt and LaCo-LDH layers are too thin to be detected.

[0046] Example 2 Application

[0047] The BVO, NiPt / BVO, LaCo-LDH / BVO and LaCo-LDH / NiPt / BVO photoelectrode films prepared in Example 1 were subjected to LSV, η bulk , η surface And performance tests such as photocurrent.

[0048] All electrochemical experimental tests were conducted in a three-electrode electrochemical workstation (Princeton Applied Research 2273). The sample film was used as the working electrode, the platinum sheet was used as the counter electrode, the Ag / AgCl was used as the reference electrode, the electrolyte was 0.5 M potassium tetraborate tetrahydrate, and the sample light irradiation area was 1 cm 2 .

[0049] LSV test: The light source is a 300W xenon lamp, and the test results are as follows Figure 2 As shown in the figure, the photocurrent density of LaCo-LDH / NiPt / BVO photoelectrode film is much greater than that of BVO photoelectrode film, among which the photocurrent density of LaCo-LDH / NiPt / BVO photoelectrode is the highest. This improvement is due to the synergistic effect of the co-catalyst NiPt and LaCo-LDH, which improves the photoelectrochemical performance of BVO film.

[0050] η bulk Test: The light source is a 300W xenon lamp, and the test results are as follows Figure 3As shown in the figure, the charge separation efficiency of LaCo-LDH / NiPt / BVO photoelectrode film is much higher than that of BVO, indicating that the co-catalyst NiPt improves the transport of internal carriers. And the presence of LaCo-LDH further improves the separation and transport of internal carriers, thereby improving the performance of LaCo-LDH / NiPt / BVO photoelectrode film.

[0051] η surface Test: The light source is a 300W xenon lamp, and the test results are as follows Figure 4 As shown in the figure, the surface injection efficiency of LaCo-LDH / NiPt / BVO photoelectrode film is much higher than that of BVO, indicating that the loading of co-catalyst NiPt effectively improves the recombination problem of surface electron holes and improves the surface injection efficiency. At the same time, after LaCo-LDH loading, the surface recombination problem is further improved by improving the OER reaction and accelerating the surface injection efficiency. Thus, the performance of LaCo-LDH / NiPt / BVO photoelectrode film is improved.

[0052] Photocurrent test: The light source is a 300W xenon lamp, the bias voltage is 1.23V vs. RHE, and the measured results are as follows Figure 5 As shown in the figure, the photocurrent density of the LaCo-LDH / NiPt / BVO photoelectrode film is much greater than that of BVO, indicating that the synergistic effect of the co-catalyst NiPt and LaCo-LDH increases the photocurrent density. At the same time, the presence of LaCo-LDH can further improve the surface carrier recombination problem and improve the stability of the photoelectrode.

Claims

1. A method for preparing a high-performance LaCo-LDH / NiPt / BVO photoelectrode film, characterized in that: The steps include: 1) dissolving bismuth nitrate pentahydrate and potassium iodide in deionized water with a pH of 1.7, stirring until fully dissolved, to obtain a solution A; dissolving p-benzoquinone in ethanol, stirring until fully dissolved, to obtain a solution B; and finally mixing the solution A with the solution B to obtain a BiOI electrodeposition solution; 2) placing the cleaned FTO conductive glass in a BiOI electrodeposition solution to prepare a BiOI nanoarray by electrodeposition; Dissolving vanadyl acetylacetonate in a dimethyl sulfoxide solution to obtain a drop coating solution containing a vanadium source; The drop coating solution containing vanadium source is dripped onto the BiOI nanoarray, calcined at high temperature under air conditions, and finally immersed in KOH solution to remove vanadium pentoxide produced during calcination to obtain a BVO photoelectrode film; 3) dissolving nickel chloride hexahydrate, boric acid and chloroplatinic acid in deionized water, stirring until fully dissolved, and adding potassium chloride solution thereto to obtain a NiPt electrodeposition solution; electrodepositing the BVO photoelectrode film obtained in step 2) in the NiPt electrodeposition solution to obtain a NiPt / BVO photoelectrode film; 4) Dissolving cobalt nitrate hexahydrate, lanthanum nitrate hexahydrate and urea in deionized water to obtain a precursor C solution, stirring until fully dissolved, and adding ethanol to the precursor C solution to obtain a precursor D solution; placing the NiPt / BVO photoelectrode film obtained in step 3) in the inner tank of a reactor with the conductive surface facing upward, adding the precursor D solution to the inner tank of the reactor, and finally obtaining a LaCo-LDH / NiPt / BVO photoelectrode film through a hydrothermal reaction.

2. The preparation method according to claim 1, characterized in that: In step 1), the molar ratio of Bi in bismuth nitrate pentahydrate to I in potassium iodide is 0.1:1; and the concentration of p-benzoquinone in solution B is 0.23 mol / L.

3. The preparation method according to claim 1, characterized in that: In step 2), the voltage of the electrodeposition process is -0.15 to -0.05 V vs. Ag / AgCl, and the time is 300 to 350 seconds.

4. The preparation method according to claim 1, characterized in that: In step 2), in the drip coating solution containing the vanadium source, the concentration of vanadyl acetylacetonate is 0.4 mol / L; the concentration of the KOH solution is 0.5-1 mol / L, and the immersion time is 30-60 min.

5. The preparation method according to claim 1, characterized in that: In step 2), the high temperature calcination conditions are calcination at 400-550°C for 2-4h and a heating rate of 1-10°C / min.

6. The preparation method according to claim 1, characterized in that: In step 3), the molar ratio of nickel chloride hexahydrate: boric acid: chloroplatinic acid is 2:2:0.03; the concentration of the potassium chloride solution is 0.5 mol / L.

7. The preparation method according to claim 1, characterized in that: In step 3), the electrodeposition process has a voltage of -0.3 to -0.1 V vs. Ag / AgCl and a time of 30 to 60 s.

8. The preparation method according to claim 1, characterized in that: In step 4), the molar ratio of cobalt nitrate hexahydrate: lanthanum nitrate hexahydrate: urea = 1:0.1:10; the volume ratio of the precursor C solution to the added ethanol is 5:

1.

9. The preparation method according to claim 1, characterized in that: In step 4), the temperature of the hydrothermal reaction is 100-140° C. and the time is 2-5 hours.

10. Application of the high-performance LaCo-LDH / NiPt / BVO photoelectrode film prepared by the preparation method according to any one of claims 1 to 10 in photoelectrochemical water splitting.

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