Bvo / FeNiOOH composite photo-anode, preparation method thereof and application of Bvo / FeNiOOH composite photo-anode in photoelectrocatalytic seawater oxidation

Abstract

This invention discloses a BVO / FeNiOOH composite photoanode, its preparation method, and its application in photoelectrocatalytic seawater oxidation. The photoanode is formed by in-situ growth of a FeNiOOH cocatalyst layer on the surface of bismuth vanadate (BVO) using photoelectrochemical deposition. The BVO / FeNiOOH composite photoanode provided by this invention, when used as a photoanode in a seawater system at a potential of 1.23 V vs. RHE, achieves a photocurrent density of 4.49 mA·cm⁻¹. ‑2 The chlorination faradaic efficiency was 95.4%. Within a 1-hour photoelectrolysis time, the concentration of hypochlorite ions generated per square centimeter of the composite photoanode reached 2.53 mmol·L⁻¹. ‑1 The BVO / FeNiOOH composite photoanode proposed in this invention has significant potential for photoelectrocatalytic generation of hypochlorite under practical conditions, using seawater as the electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials technology, and specifically relates to a BVO / FeNiOOH composite photoanode, its preparation method, and its application in photoelectrocatalytic seawater oxidation. Background Technology

[0002] The development of low-carbon, clean, and renewable new energy sources has become a core research direction for my country's energy structure transformation, ecological environmental protection, and high-quality social development. Solar energy possesses outstanding advantages such as unlimited reserves, wide distribution, and clean, pollution-free operation, making it a new type of renewable energy with great application potential.

[0003] Traditional chlor-alkali industry suffers from high energy consumption, high pollution, and high safety hazards. Current hypochlorous acid and hypochlorite disinfectants are generally prepared using chlor-alkali electrolysis, requiring the electrolysis of brine to generate chlorine gas, followed by a disproportionation reaction to synthesize the target product. This process is lengthy, carries extremely high risks associated with the storage and transportation of highly toxic chlorine gas, and consumes large amounts of fresh water, making it difficult to meet the requirements of low-carbon development. Photoelectrocatalysis technology offers a new solution to these challenges. Driven by the synergistic effect of light and electricity, this method can directly use seawater as a raw material to selectively oxidize chloride ions to hypochlorous acid under ambient temperature and pressure conditions, without requiring a free chlorine gas intermediate. Its core advantages are: 1) significantly reducing reaction energy consumption by utilizing renewable solar energy; 2) avoiding the generation and leakage risks of toxic chlorine gas, making the process greener and safer; 3) simplifying the process, allowing for direct one-step generation of hypochlorite ions. Therefore, developing a photoelectrocatalytic synthesis technology for hypochlorous acid is of great significance for promoting the low-carbon transformation of the chlor-alkali industry and the green production of disinfectants.

[0004] The photoelectrocatalytic oxidation of seawater to produce active chlorine (mainly hypochlorite) involves a competitive oxygen evolution reaction (OER) on the photoanode and resistance to severe chloride ion corrosion. Based on the needs of low-carbon energy transition and efficient utilization of marine resources, the development of chloride ion-resistant, highly active, and long-cycle-stable photoelectrocatalytic anode materials is crucial for developing low-carbon production pathways in chlor-alkali chemicals, supporting the green and low-carbon upgrading of the hydrogen energy industry, seawater resource utilization, and public disinfection water treatment sectors, and providing important theoretical basis and technical support for new energy technology innovation and the high-value utilization of marine resources. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a BVO / FeNiOOH composite photoanode, which, when used as the photoanode and seawater as the electrolyte, performs photoelectrocatalysis to generate hypochlorite ions. This provides important theoretical basis and technical support for new energy technology innovation and the high-value utilization of marine resources.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is: a BVO / FeNiOOH composite photoanode, which is formed by growing a FeNiOOH cocatalyst layer on the surface of bismuth vanadate (BVO) as a substrate by photoelectrochemical deposition.

[0007] A method for preparing a BVO / FeNiOOH composite photoanode, the method comprising: preparing FeSO4 6H2O and NiCl2 6H2O is dissolved in deionized water to form electroplating solution II; a three-electrode system is formed by using a bismuth vanadate (BVO) thin film / FTO electrode as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode; the three-electrode system is placed in electroplating solution II for photoelectrode deposition to form a BVO / FeNiOOH composite photoanode.

[0008] Furthermore, according to the feed-to-liquid ratio, FeSO4 6H2O: NiCl2 6H2O: Deionized water = (0.05 g - 0.07 g): (0.01 g - 0.02 g): (10 mL - 20 mL).

[0009] Furthermore, the photoelectrodeposition conditions are: under sunlight irradiation, a voltage of -0.2 V vs. Ag / AgCl is applied, and photoelectrodeposition is performed for 100 s - 500 s.

[0010] Further, the preparation method of the bismuth vanadate (BVO) thin film / FTO electrode includes: dispersing bismuth nitrate in an aqueous nitric acid solution with pH=1.7, adding potassium iodide to completely dissolve it, forming electroplating solution I; using FTO as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode to form a three-electrode system; placing the three-electrode system in electroplating solution I for electrodeposition to form a precursor film on the FTO surface; then adding acetylacetone vanadium oxide solution to the precursor film, placing it in a muffle furnace for calcination, cooling it to room temperature, immersing the obtained material in NaOH, rinsing it with deionized water to form a bismuth vanadate (BVO) thin film / FTO electrode.

[0011] Furthermore, according to the feed-liquid ratio, bismuth nitrate: potassium iodide: acetylacetone vanadium oxide = (0.9 g - 1.0 g): (3.0 g - 3.5 g): (20 μL - 30 μL).

[0012] Furthermore, the electrodeposition conditions are: deposition at -0.1 V vs. Ag / AgCl for 100 s - 500 s.

[0013] Furthermore, the calcination is performed at 400 ℃ - 500 ℃ for 2 h - 3 h.

[0014] The present invention provides the application of the BVO / FeNiOOH composite photoanode as a photoanode in the photoelectrocatalytic oxidation of seawater to generate hypochlorite.

[0015] Furthermore, the method includes: using a BVO / FeNiOOH composite photoanode as the photoanode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode to form a three-electrode system, using seawater as the electrolyte, and applying a voltage of 1.20 V vs RHE - 1.30 V vs RHE under illumination for photoelectrolysis for 1 h - 2 h.

[0016] The beneficial effects of this invention are: The BVO / FeNiOOH composite photoanode provided by this invention, when used as a photoanode in a seawater system at a potential of 1.23 V vs. RHE (relative to the reversible hydrogen electrode), achieves a photocurrent density of 4.49 mA·cm⁻¹. -2 The chlorination faradaic efficiency was 95.4%. Within a 1-hour photoelectrolysis time, the concentration of hypochlorite ions generated per square centimeter of the composite photoanode reached 2.53 mmol·L⁻¹. -1 The BVO / FeNiOOH composite photoanode proposed in this invention has significant potential for photoelectrocatalytic generation of hypochlorite under practical conditions, using seawater as the electrolyte. Attached Figure Description

[0017] Figure 1 These are transmission electron microscope (TEM) images of BVO and BVO / FeNiOOH prepared in Example 1.

[0018] Figure 2 The results are ICP test results for the BVO / FeNiOOH composite material prepared in Example 1.

[0019] Figure 3 This is the Fe 2p orbital curve on BVO / FeNiOOH prepared in Example 1.

[0020] Figure 4 The figures are LSV curves (a) and ABPE curves (b) for different photoanodes.

[0021] Figure 5 The absorbance of hypochlorite at different concentrations (a) and the standard curve between hypochlorite and absorbance (b) are shown.

[0022] Figure 6 This is a comparison of the Faraday efficiency of hypochlorite production on different photoanodes. Detailed Implementation

[0023] Example 1: BVO / FeNiOOH Composite Photoanode

[0024] (I) Preparation method

[0025] 1. Preparation of bismuth vanadate (BVO) thin film / FTO electrode

[0026] 0.97 g of bismuth nitrate was dispersed in 50 mL of nitric acid aqueous solution with pH=1.7, and 3.32 g of potassium iodide was added to completely dissolve it, forming electroplating solution I. A three-electrode system was constructed using FTO as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The three-electrode system was placed in electroplating solution I, and electrodeposition was performed for 300 s at -0.1 V vs. Ag / AgCl to form a precursor film on the FTO surface. Then, 25 μL of vanadium acetylacetonate solution was added to the precursor film, and the mixture was placed in a muffle furnace and calcined at 450 ℃ for 2 h. After naturally cooling to room temperature, the resulting material was immersed in 1M NaOH for 15 min, followed by rinsing with deionized water to form a bismuth vanadate (BVO) thin film / FTO electrode, which is the bismuth vanadate (BVO) electrode material.

[0027] 2. Preparation of BVO / FeNiOOH composite photoanode

[0028] Weigh out 0.062 g of FeSO4 6H2O and 0.017 g NiCl2 6H₂O was dissolved in 15 mL of deionized water to form electroplating solution II. A three-electrode system was constructed using a bismuth vanadate (BVO) thin film / FTO electrode as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The three-electrode system was placed in electroplating solution II, and under AM 1.5 G simulated sunlight irradiation, a voltage of -0.2 V vs. Ag / AgCl was applied, and photoelectrodeposition was performed for 300 s to form a BVO / FeNiOOH composite photoanode.

[0029] (ii) Characterization

[0030] Figure 1 Transmission electron microscopy (TEM) images of BVO and BVO / FeNiOOH. (From...) Figure 1 As can be seen from the comparative analysis of the transmission electron microscopy (TEM) characterization results for BVO and BVO / FeNiOOH, the FeNiOOH cocatalyst layer exhibits a uniform and continuous distribution on the BVO surface, with a clear interface between it and the BVO substrate. This interface characteristic indicates that FeNiOOH forms a robust growth structure on the BVO surface, rather than being a simple physical adhesion. Furthermore, this continuous and uniform growth pattern significantly increases the electrochemical reaction active sites of the composite photoanode, thereby enhancing its photoelectrocatalytic performance.

[0031] To further confirm the presence and composition of FeNiOOH on the BVO surface, inductively coupled plasma (ICP) testing was performed on the BVO / FeNiOOH sample. The test results are as follows: Figure 2 .Depend on Figure 2 It can be seen that the Fe content on the electrode is 3315.79%. g·L -1 The Ni content is 363.77%. g·L -1 The elemental ratio of Fe to Ni on the electrode is close to 9:1. This result clearly confirms the presence of Fe and Ni species on BVO.

[0032] Since the Ni content is extremely low, it indicates that Fe is the main co-catalytic active site. Therefore, X-ray photoelectron spectroscopy (XPS) was performed on the Fe element on BVO / FeNiOOH, and the results are as follows. Figure 3 .Depend on Figure 3 It can be observed that the energy spectrum curve of the Fe 2p orbital is consistent with the standard energy spectrum curve of Fe2O3, thus confirming that Fe mainly exists in the +3 valence state in the composite material.

[0033] Example 2 BVO / FeNiOOH composite photoanode

[0034] The preparation method is as follows: 1. Preparation of bismuth vanadate (BVO) thin film / FTO electrode Same as Example 1.

[0035] 2. Preparation of BVO / FeNiOOH composite photoanode

[0036] Weigh out 0.062 g of FeSO4 6H2O and 0.017 g NiCl2 6H₂O was dissolved in 15 mL of deionized water to form electroplating solution II. A three-electrode system was constructed using a bismuth vanadate (BVO) thin film / FTO electrode as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The three-electrode system was placed in electroplating solution II, and under AM 1.5 G simulated sunlight irradiation, a voltage of -0.2 V vs. Ag / AgCl was applied, and photoelectrodeposition was performed for 100 s to form a BVO / FeNiOOH composite photoanode.

[0037] Example 3 BVO / FeNiOOH composite photoanode

[0038] The preparation method is as follows: 1. Preparation of bismuth vanadate (BVO) thin film / FTO electrode Same as Example 1.

[0039] 2. Preparation of BVO / FeNiOOH composite photoanode

[0040] Weigh out 0.062 g of FeSO4 6H2O and 0.017 g NiCl2 6H₂O was dissolved in 15 mL of deionized water to form electroplating solution II. A three-electrode system was constructed using a bismuth vanadate (BVO) thin film / FTO electrode as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. The three-electrode system was placed in electroplating solution II, and under AM 1.5 G simulated sunlight irradiation, a voltage of -0.2 V vs. Ag / AgCl was applied, and photoelectrodeposition was performed for 500 s to form a BVO / FeNiOOH composite photoanode.

[0041] Example 4: Application of BVO / FeNiOOH composite photoanode as photoanode in the photoelectrocatalytic oxidation of seawater to hypochlorite.

[0042] (I) Construction of a photoelectrocatalytic seawater system: A three-electrode system was constructed using BVO or BVO / FeNiOOH as the photoanode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode. 0.5 M NaCl was used as simulated seawater (SSW). Photolysis was performed for 1 h under AM 1.5G illumination with a voltage of 1.23 V vsRHE.

[0043] (II) Test of photoelectrocatalytic seawater oxidation

[0044] Linear sweep voltammetric cycling tests were performed on BVO and BVO / FeNiOOH (photoelectrodeposition for 300 s) under AM 1.5G illumination. The results are as follows: Figure 4 a. From Figure 4 Linear sweep voltammetry (LSV) curves for a single BVO photoanode revealed a photocurrent density of only 1.48 mA·cm⁻¹ at 1.23 V vs. RHE. -2 The BVO / FeNiOOH (photoelectrodeposition 300 s) composite photoanode achieved a photocurrent density of 4.49 mA·cm⁻¹ at 1.23 V vs. RHE. -2 This indicates that BVO alone cannot effectively participate in the photoelectro-chlorination reaction.

[0045] The photoelectrodeposition process was optimized. Table 1 shows the design and systematic investigation of the effects of different metal-modified materials as photoanodes and the photoelectrodeposition time on the photoelectrocatalytic performance of the photoanodes. The test results are shown in Table 1. Table 1 shows that at 1.23 V vs. RHE, the photocurrent density of BVO / FeOOH is 3.90 mA·cm⁻¹.-2 The photocurrent density of BVO / NiOOH is 3.43 mA·cm⁻¹. -2 The photocurrent density of BVO / FeNiOOH (photoelectrodeposition for 300 s) can reach 4.49 mA·cm⁻¹. -2 This study confirmed that the BVO / FeNiOOH composite photoanode with iron-nickel bimetallic synergistic modification exhibits superior photoelectrocatalytic activity compared to single-metal modification. Building upon this, the effect of photoelectrodeposition time on electrode performance was further investigated. Experimental results showed that when the photoelectrodeposition time was 300 s, the prepared BVO / FeNiOOH composite photoanode achieved the optimal photoelectric response performance at 1.23 V vs. RHE, with a photocurrent density reaching 4.49 mA·cm⁻¹. -2 This indicates that the loading of FeNiOOH effectively enhances the activity of the chlorination reaction.

[0046] Table 1. Comparison of photocurrent density of different photoanodes under 1.23 V vs. RHE conditions.

[0047]

[0048] Meanwhile, based on formula (1), the applied bias photoelectric conversion efficiency (ABPE) curves of different bismuth vanadate-based composite photoanodes were plotted, and the results are as follows: Figure 4 b. Figure 4 Figure b shows that the ABPE of the BVO / FeNiOOH composite photoanode reaches 1.23%, significantly higher than that of the BVO photoanode (0.16%). This significant difference fully demonstrates that the BVO / FeNiOOH composite photoanode possesses excellent photoelectric conversion efficiency.

[0049] In summary, the introduction of FeNiOOH not only increases the photocurrent density but also optimizes the overall photoelectric conversion performance, thus further verifying the technical advantages of the BVO / FeNiOOH composite photoanode in the photoelectrocatalytic chlorination reaction.

[0050] (ii) Products of chlorination oxidation (ClO) - Determination of )

[0051] First, a series of hypochlorite standard solutions with gradient concentrations were prepared. The DPD colorimetric method was used to develop the colorimetric reaction of each standard solution. The absorbance of the colorimetric system was measured at a wavelength of 553 nm, and the peak absorbance was recorded. The results are as follows: Figure 5 a.

[0052] like Figure 5In step b, a linear regression was performed with hypochlorite concentration as the independent variable and peak absorbance as the dependent variable to establish a standard working curve for hypochlorite concentration-absorbance. The linear regression equation was obtained as y = 487.26x - 0.0001, and the correlation coefficient Rb was [value missing]. 2 The linear correlation can reach 0.999, showing good linearity. This clarifies the quantitative response relationship between hypochlorite concentration and absorbance, providing a reliable calibration basis and analytical foundation for the subsequent quantitative detection of target products.

[0053] Based on the hypochlorite concentration-absorbance standard working curve, the Faradaic efficiencies of the two photoanodic electrocatalytic oxidation processes for chloride ions to hypochlorite were further calculated and measured, and the results are as follows: Figure 6 .Depend on Figure 6 Test results show that the BVO / FeNiOOH composite photoanode exhibits a chloride oxidation Faradaic efficiency of up to 95.4%, significantly higher than that of the pure BVO photoanode. This fully demonstrates that FeNiOOH surface modification can effectively enhance the photoanode's chloride ion oxidation performance, achieving efficient and directional hypochlorite generation. Furthermore, calculations show that within a 1-hour photoelectrolysis time, the concentration of hypochlorite catalyzed by the composite photoanode can reach 2.53 mmol·L⁻¹. -1 .

Claims

1. A BVO / FeNiOOH composite photoanode, characterized in that, It is a BVO / FeNiOOH composite photoanode formed by growing a FeNiOOH cocatalyst layer on the surface of bismuth vanadate (BVO) as a substrate through photoelectrophotodeposition.

2. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 1, characterized in that, The preparation method includes: taking FeSO4 6H2O and NiCl2 6H2O is dissolved in deionized water to form electroplating solution II; a three-electrode system is formed by using a bismuth vanadate BVO thin film / FTO electrode as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode; the three-electrode system is placed in electroplating solution II for photoelectrode deposition to form a BVO / FeNiOOH composite photoanode.

3. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 2, characterized in that, According to the feed-liquid ratio, FeSO4 6H2O: NiCl2 6H2O: Deionized water = (0.05 g - 0.07 g): (0.01 g - 0.02 g): (10 mL - 20 mL).

4. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 2, characterized in that, The photoelectrodeposition conditions are as follows: under sunlight irradiation, a voltage of -0.2 V vs. Ag / AgCl is applied, and photoelectrodeposition is performed for 100 s - 500 s.

5. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 2, characterized in that, The preparation method of the bismuth vanadate BVO thin film / FTO electrode includes: dispersing bismuth nitrate in a nitric acid aqueous solution with pH=1.7, adding potassium iodide to completely dissolve it, forming electroplating solution I; using FTO as the working electrode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode to form a three-electrode system; placing the three-electrode system in electroplating solution I for electrodeposition to form a precursor film on the FTO surface; then adding acetylacetone vanadium oxide solution to the precursor film, placing it in a muffle furnace for calcination, cooling it to room temperature, immersing the obtained material in NaOH, rinsing it with deionized water, and forming the bismuth vanadate BVO thin film / FTO electrode.

6. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 5, characterized in that, According to the feed-to-liquid ratio, bismuth nitrate: potassium iodide: acetylacetone vanadium oxide = (0.9 g - 1.0 g): (3.0 g - 3.5 g): (20 μL - 30 μL).

7. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 5, characterized in that, The electrodeposition conditions are: deposition at -0.1 V vs. Ag / AgCl for 100 s - 500 s.

8. The method for preparing a BVO / FeNiOOH composite photoanode according to claim 5, characterized in that, The calcination is performed at 400 ℃ - 500 ℃ for 2 h - 3 h.

9. The application of the BVO / FeNiOOH composite photoanode as described in claim 1 as a photoanode in the photoelectrocatalytic oxidation of seawater to generate hypochlorite.

10. The application according to claim 9, characterized in that, The method includes: using a BVO / FeNiOOH composite photoanode as the photoanode, saturated Ag / AgCl as the reference electrode, and platinum wire as the counter electrode to form a three-electrode system, using seawater as the electrolyte, and applying a voltage of 1.20 V vs RHE - 1.30 V vs RHE under illumination for photoelectrolysis for 1 h - 2 h.

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