Integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode, its preparation method and application
By constructing a zinc oxide intermediate layer and a noble metal-modified nickel phosphide cocatalyst on a tungsten trioxide photoanode, a cocatalyst/heterogeneous structure is formed, which solves the problems of photogenerated carrier recombination and poor stability, and achieves efficient glycerol oxidation and high Faradaic efficiency photoelectrocatalytic effects.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2024-10-23
- Publication Date
- 2026-05-26
AI Technical Summary
Existing tungsten trioxide photoanodes suffer from severe recombination of photogenerated carriers, poor stability, and a wide variety of products during the photoelectrocatalytic oxidation of glycerol.
By constructing a nickel phosphide cocatalyst with zinc oxide as the intermediate layer and noble metal modification, an integrated structure of cocatalyst/heterogeneous structure/tungsten trioxide photoanode is formed, which suppresses photogenerated carrier recombination and improves the migration rate of photogenerated charge and the surface reaction rate.
It significantly improved the photoelectrocatalytic oxidation performance of glycerol, producing two products: glyceraldehyde and 1,3-dihydroxyacetone. The Faraday efficiency reached 82.9%, the photocurrent density reached 3.15 mA/cm2, and the stability was superior to that of the monomeric tungsten trioxide photoanode.
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Figure CN119352085B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of biomass conversion and photoelectrocatalysis technology, specifically relating to an integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode, its preparation method, and its application. Background Technology
[0002] Since the 1970s, the human economy has entered a stage of rapid development, and global carbon emissions have also increased year by year, leading to a continuous exacerbation of the greenhouse effect. In the face of increasingly serious climate change, countries around the world have introduced energy conservation and emission reduction plans to reduce carbon emissions.
[0003] Among numerous new energy sources, solar energy is favored due to its high energy density, wide applicability, and low cost. Photoelectrocatalysis is developed based on this advantage, representing a novel and widely applied catalytic method. Secondly, biomass is a low-carbon fuel, with its carbon originating from the atmosphere and returning to the atmosphere after a series of cycles. In 2004, the U.S. Department of Energy published a list of twelve biomass-based platform compounds. These compounds can all be converted from biomass such as lignocellulose and can be further transformed into high-value-added chemicals, possessing significant utilization potential. Glycerin is one of these twelve biomass-based platform compounds and is a byproduct of biodiesel production. Producing 1 kg of biodiesel yields 10% wt glycerin, resulting in overcapacity and low prices. However, it can be further converted into a series of high-value-added chemicals such as glyceraldehyde and 1,3-dihydroxyacetone, demonstrating significant utilization value.
[0004] Using photoelectrocatalysis for biomass conversion not only allows for milder reaction conditions and reduced energy consumption, but also transforms inexpensive biomass into high-value-added chemicals. This can replace the low-value oxygen at the anode of traditional photoelectrocatalytic water splitting, increasing the added value of the anode products while coupling with the cathode to produce hydrogen. This is an effective way to develop clean energy and fine chemicals.
[0005] Based on the principle of band structure, heterostructures can suppress the recombination of photogenerated carriers inside the photoelectrode and accelerate their migration rate; surface cocatalysts can improve the surface reaction rate and enhance the ability of photogenerated electrons or holes to react with chemical substances in the solution. Zhang Fuqin et al. constructed an integrated system of Bi / BiVO4 / WO3, in which BiVO4 and WO3 form a heterostructure, and Bi is used as a surface cocatalyst. Its selectivity for 1,3-dihydroxyacetone reaches 60% (Feng X., Feng X, Zhang F. Journal of Materials Chemistry A, 2023, 11(37): 20242-20253), but it still has the disadvantages of poor stability and a wide variety of products. Summary of the Invention
[0006] To improve the performance of glycerol oxidation via photoelectrocatalysis using tungsten trioxide photoanodes, this invention proposes an integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode, its preparation method, and applications. By constructing a heterogeneous structure and supporting a surface co-catalyst, the recombination of photogenerated carriers is suppressed, their migration rate is accelerated, and the lifetime of photogenerated charges is increased. Simultaneously, the energy barrier of the surface reaction is lowered, and the reaction stability is improved, thereby enhancing the performance of photoelectrocatalytic glycerol oxidation. In this invention, zinc oxide serves as an intermediate layer to suppress the recombination of photogenerated carriers; while noble metals possess good conductivity and catalytic activity. The noble metal-modified co-catalyst significantly reduces the surface energy barrier, improves surface reaction kinetics, and prolongs the lifetime of photogenerated charges. Furthermore, this system contains only two C3 products, glyceraldehyde and 1,3-dihydroxyacetone, offering a relatively limited variety and providing a feasible pathway for improving the high-value coupling of photoelectrocatalytic biomass to hydrogen production.
[0007] To achieve the above objectives, the present invention adopts the following technical solution:
[0008] A method for preparing an integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode, the method comprising the following steps:
[0009] Step 1: Pre-treat the conductive substrate, and then prepare a tungsten trioxide photoanode on the conductive substrate.
[0010] Step 2: Zinc acetate, ethanolamine and anhydrous ethanol are mixed in a certain proportion and hydrothermally to obtain a zinc oxide precursor solution. This solution is then spin-coated onto the tungsten trioxide photoanode surface prepared in Step 1. Finally, the solution is annealed in air using a muffle furnace to obtain a zinc oxide / tungsten trioxide heterostructure.
[0011] Step 3: Sodium hypophosphite, precious metal hydrated chloride salt and nickel chloride hexahydrate are ground and mixed in a certain proportion. The mixture is then placed in a tube furnace and calcined under an argon atmosphere. The resulting solid product is cooled to room temperature and then washed, centrifuged and dried to obtain a precious metal modified nickel phosphide co-catalyst.
[0012] Step 4: Disperse the noble metal-modified nickel phosphide cocatalyst obtained in Step 3 in anhydrous ethanol and sonicate to obtain a suspension; spin-coat the obtained suspension onto the surface of the zinc oxide / tungsten trioxide heterostructure prepared in Step 2, and finally anneal in air to obtain the cocatalyst / heterostructure / tungsten trioxide photoanode integrated structure.
[0013] Furthermore, in step 1, the conductive substrate is fluorine-doped tin dioxide conductive glass or tin-doped indium oxide thin film.
[0014] Furthermore, the pretreatment process in step 1 is as follows: the conductive substrate is placed in deionized water, acetone and ethanol in sequence and ultrasonicated for 30-60 min respectively, then dried at 40-60℃ for 3-4 h, and finally treated in an ozone atmosphere for 10-40 min.
[0015] Further, in step 1, tungsten trioxide photoanodes are prepared using a hydrothermal method: 0.3–0.6 g of ammonium metatungstate and 3–6 mL of 6.25 M concentrated hydrochloric acid are added to every 30–60 mL of deionized water. After stirring for 10–20 min, 0.75–1.25 mL of hydrogen peroxide is added, and stirring is continued for 0.5–2 h to obtain a precursor solution. Subsequently, the pretreated conductive substrate is placed in a polytetrafluoroethylene-lined autoclave with the conductive side facing down. After adding 20–30 mL of the precursor solution, the substrate is hydrothermally heated at 140–180 °C for 3–5 h. After cooling to room temperature, the substrate is removed, and the solid impurities on the tungsten trioxide photoanode are cleaned with deionized water and ethanol. The substrate is then dried for 10–20 min and placed in a muffle furnace for annealing at 400–500 °C in air for 2–3 h to obtain the tungsten trioxide photoanode.
[0016] Further, step 2 specifically involves adding 40-80 μL of ethanolamine and 0.15-0.25 mol of zinc acetate to every 5-10 mL of ethanol. After mixing, the mixture is hydrothermally heated at 50-80 °C for 3-6 h to obtain a zinc oxide precursor solution. The obtained zinc oxide precursor solution is then spin-coated onto the tungsten trioxide photoanode from step 1 at a spin-coating speed of 1500-2000 rpm. The amount of spin-coated onto each 1 cm × 2 cm area photoanode is 0.2-0.4 mL. Afterward, the mixture is placed in a muffle furnace and annealed in air at a temperature of 350-500 °C for 10-40 min to obtain a zinc oxide / tungsten trioxide heterostructure.
[0017] Furthermore, in step 3, the molar ratio of the noble metal hydrated chloride salt, nickel chloride hexahydrate, and sodium hypophosphite is (0.5-2):10:50, the calcination temperature is 200-400℃, and the time is 1-4h. The noble metal hydrated chloride salt is selected from one of tetrachloroauric acid trihydrate, chloroplatinic acid hexahydrate, and potassium chloride palladium chlorite.
[0018] Furthermore, in step 4, the mass concentration of the noble metal-modified nickel phosphide co-catalyst in the suspension is 1.0–5.0 mg / mL, the spin coating speed is 1000–1500 rpm, the spin coating amount on each 1 cm × 2 cm area photoanode is 0.1–0.5 mL, the annealing temperature is 100–160 °C, and the time is 1–4 h.
[0019] An integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode is prepared based on the above preparation method. The synthesized tungsten trioxide photoanode is a nanorod structure, zinc oxide is a thin layer structure covering the surface of tungsten trioxide, and the noble metal modified cocatalyst is nanoparticles uniformly dispersed on the surface of the heterostructure.
[0020] An application of an integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode is disclosed, which is used in the photoelectrocatalytic high-value coupling hydrogen production of glycerol. Specifically, the prepared integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode is used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode to form a standard three-electrode reaction system; the reaction electrolyte is a mixed aqueous solution of 0.5M sodium sulfate and 0.01-1M glycerol, under a simulated solar light source (300W xenon lamp, light intensity 100mW / cm²). 2 Under certain conditions, the photoelectrocatalytic oxidation of glycerol was carried out. The products at the anode were 1,3-dihydroxyacetone and glyceraldehyde, and the product at the cathode was hydrogen.
[0021] The principle of this invention lies in the fact that noble metals are widely used in thermocatalysis and electrocatalysis, but their application in photoelectrocatalysis is relatively limited. They possess good conductivity and catalytic activity, which can accelerate the migration of photogenerated carriers and improve surface reaction kinetics. In the photoelectrocatalytic glycerol oxidation system, when light irradiates the tungsten trioxide photoanode, it absorbs photons with energy equal to or greater than its band gap, causing the internal photogenerated carriers to separate into electrons and holes. Electrons migrate through the external circuit to the electrode surface to react and produce hydrogen gas, while holes react with glycerol adsorbed on the photoanode surface to produce glyceraldehyde and 1,3-dihydroxyacetone. However, for the tungsten trioxide photoanode itself, the recombination of electrons and holes is severe, resulting in only a small number of holes and electrons being able to undergo glycerol oxidation and hydrogen evolution reactions. In this invention, the integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide is used as the photoanode. The heterostructure of zinc oxide and tungsten trioxide can suppress the recombination of photogenerated carriers. The noble metal-modified cocatalyst can reduce the interfacial resistance between the heterostructure and the electrolyte, accelerate the migration of photogenerated holes, and improve the surface reaction rate, thus achieving excellent photoelectrocatalytic glycerol oxidation performance.
[0022] Compared with the prior art, the present invention has at least the following advantages:
[0023] (1) Due to the synergistic effect of the noble metal doped cocatalyst and the intermediate layer, the separation of photogenerated carriers was suppressed, the surface reaction energy barrier was lowered, the surface reaction kinetics were improved, and the rate of photogenerated holes and glycerol reaction was promoted. This enabled the integrated photoanode system to exhibit superior glycerol oxidation performance, with a photocurrent density of 3.15 mA / cm² at 1.23 V relative to the reversible hydrogen electrode. 2Furthermore, the incident photon-current conversion efficiency is increased to 57.4%, and it can operate stably for more than 50 hours. Its catalytic performance and stability are significantly better than those of the monomeric tungsten trioxide photoanode.
[0024] (2) For the glycerol oxidation reaction, the present invention produces only two C3 products: glyceraldehyde and 1,3-dihydroxyacetone, with a total Faradaic efficiency of up to 82.9%. Moreover, the integrated structure preparation method of the present invention has simple process conditions, which makes it easy to explore the preparation of large-scale electrodes in the future, and provides a feasible path for the high-value coupling of photoelectrocatalysis with biomass to produce hydrogen. Attached Figure Description
[0025] Figure 1 The X-ray diffraction (XRD) patterns of the tungsten trioxide photoanode, zinc oxide / tungsten trioxide heterostructure, and gold-modified nickel phosphide / zinc oxide / tungsten oxide photoanode integrated structure materials prepared in Example 1 are shown.
[0026] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the gold-modified nickel phosphide cocatalyst prepared in Example 1.
[0027] Figure 3 This is a scanning electron microscope (SEM) image of the nanorod-shaped tungsten trioxide photoanode prepared in Example 1.
[0028] Figure 4 This is a scanning electron microscope (SEM) image of the zinc oxide / tungsten trioxide heterostructure prepared in Example 1.
[0029] Figure 5 This is a scanning electron microscope (SEM) image of the gold-modified nickel phosphide cocatalyst prepared in Example 1.
[0030] Figure 6 This is a scanning electron microscope (SEM) image of the gold-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode integrated structure prepared in Example 1.
[0031] Figure 7 Linear scan voltammogram (LSV) of the tungsten trioxide photoanode, zinc oxide / tungsten trioxide heterostructure, and gold-modified nickel phosphide / zinc oxide / tungsten oxide photoanode integrated structure prepared in Example 1 in sodium sulfate electrolyte containing glycerol.
[0032] Figure 8 Linear scan voltammograms (LSVs) of the photoanodes prepared in Example 1 and Comparative Example 1 in sodium sulfate electrolyte containing glycerol.
[0033] Figure 9The figure shows the product distribution of photoelectrocatalytic glycerol oxidation using the gold-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode integrated structure prepared in Example 1. In the figure, the bar chart represents the production rate and the dotted line chart represents the Faraday efficiency. Detailed Implementation
[0034] Example 1
[0035] A method for preparing an integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode includes the following steps:
[0036] Step 1: A 2cm × 3cm fluorine-doped tin dioxide conductive glass (FTO) was ultrasonically treated in deionized water, acetone, and anhydrous ethanol for 45 min each time, followed by drying in an oven at 60°C for 3 h. After drying, it was treated under ozone conditions for 20 min. A tungsten trioxide photoanode was then prepared on the FTO using a hydrothermal method. Specifically: 0.6 g of ammonium metatungstate was added to 60 mL of deionized water, followed by 6 mL of 6.25 M concentrated hydrochloric acid. After stirring for 20 min, 1.25 mL of hydrogen peroxide was added, and the mixture was stirred for another 2 h to obtain a tungsten trioxide precursor solution. The treated FTO was then placed face down in a polytetrafluoroethylene-lined reactor, and 30 mL of the tungsten trioxide precursor solution was added. The reactor was then placed in an oven and hydrothermally heated at 180 °C for 5 h. After the reaction was complete and the reactor cooled to room temperature, it was removed and cleaned with deionized water and ethanol to remove solid impurities from the photoanode. After drying for 10 min, the photoanode was placed in a muffle furnace and calcined at 500 °C for 3 h in air to obtain nanorod-shaped tungsten trioxide photoanodes. Figure 3 The image shows a scanning electron microscope (SEM) image of the tungsten trioxide photoanode, which reveals that the synthesized tungsten trioxide photoanode has a nanorod-like structure.
[0037] Step 2: Prepare the zinc oxide precursor solution using a hydrothermal method. Specifically, mix 5 mL of ethanol, 40 μL of ethanolamine, and 0.25 mol of zinc acetate uniformly, and hydrothermally heat at 50 °C for 3 h to obtain the zinc oxide precursor solution. Spin-coat the zinc oxide precursor solution onto the tungsten trioxide photoanode prepared in Step 1, with a coating amount of 0.4 mL and a spin speed of 1500 rpm. Then, anneal in a muffle furnace at 350 °C in air for 10 min to obtain a zinc oxide / tungsten trioxide heterostructure. Figure 4 This is a scanning electron microscope (SEM) image of a zinc oxide / tungsten trioxide heterostructure.
[0038] Step 3: Gold-modified nickel phosphide cocatalyst was prepared using a phosphating method. Tetrachloroauric acid trihydrate, nickel chloride hexahydrate, and sodium hypophosphite in a molar ratio of 1:10:50 were thoroughly mixed and ground until homogeneous. The ground solid was then calcined in an argon furnace at 250°C for 2 hours. After the reaction was complete and the mixture was cooled to room temperature, the solid powder was washed with deionized water and anhydrous ethanol, centrifuged, and dried to obtain the gold-modified nickel phosphide cocatalyst. Figure 5 The image shows a scanning electron microscope (SEM) image of the prepared gold-modified nickel phosphide cocatalyst. Figure 2 The XRD images of the catalyst showed that the synthesized Au (PDF#04-0784) was an elemental substance, and the (111), (201), and (210) crystal planes of Ni2P (PDF#03-0953) were located at 40.80°, 44.60°, and 47.31°, respectively.
[0039] Step 4: The gold-modified nickel phosphide co-catalyst powder prepared in Step 3 is dispersed in anhydrous ethanol at a concentration of 3 mg / mL and spin-coated onto the zinc oxide / tungsten trioxide photoanode prepared in Step 2. The spin-coating amount is 0.4 mL, and the spin speed is 1200 rpm. The resulting structure is then annealed in a muffle furnace at 120°C for 2 hours in air to obtain the integrated structure of the gold-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode. Figure 6 The scanning electron microscope (SEM) image of the prepared gold-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode shows that the co-catalyst is uniformly dispersed in nanoparticles on the surface of the heterostructure.
[0040] Example 2
[0041] Step 1: A 1cm × 2cm tin-doped indium oxide (ITO) film was sequentially placed in deionized water, acetone, and ethanol and sonicated for 30 min. It was then dried in an oven at 50℃ for 3.5 h, followed by ozone treatment for 10 min. Tungsten trioxide photoanodes were then prepared on the ITO using a hydrothermal method. Specifically: 0.4g ammonium metatungstate was added to 30mL of deionized water, followed by 4mL of 6.25M concentrated hydrochloric acid. After stirring for 10 min, 1mL of hydrogen peroxide was added, and the mixture was stirred for another 30 min to obtain a tungsten trioxide precursor solution. The treated ITO was then placed face down in a polytetrafluoroethylene-lined autoclave, and 20mL of the precursor solution was added. The autoclave was then placed in an oven and hydrothermally heated at 140℃ for 3 h. After the reaction was complete and the autoclave cooled to room temperature, it was removed and cleaned of solid impurities with deionized water and ethanol. The autoclave was dried for 15 min and then calcined in a muffle furnace at 400℃ for 2 h in air to obtain the tungsten trioxide photoanode.
[0042] Step 2: Prepare the zinc oxide precursor solution using a hydrothermal method. Specifically, mix 10 mL of ethanol, 60 μL of ethanolamine, and 0.15 mol of zinc acetate uniformly, and hydrothermally heat at 70 °C for 4 h to obtain the zinc oxide precursor solution. Spin-coat the zinc oxide precursor solution onto the tungsten trioxide photoanode prepared in Step 1, with a coating amount of 0.2 mL and a spin speed of 1700 rpm. Then, anneal in a muffle furnace at 400 °C for 20 min under air conditions to obtain a zinc oxide / tungsten trioxide heterostructure.
[0043] Step 3: Palladium-modified nickel phosphide cocatalyst is prepared by phosphating. Potassium chloride palladiumate, nickel chloride hexahydrate and sodium hypophosphite in a molar ratio of 0.5:10:50 are thoroughly mixed and ground evenly. The ground solid is placed in an argon furnace and calcined at 200°C for 1 hour. After the reaction is completed and cooled to room temperature, the solid powder is washed with deionized water and anhydrous ethanol, centrifuged and dried to obtain palladium-modified nickel phosphide cocatalyst.
[0044] Step 4: The palladium-modified nickel phosphide co-catalyst powder prepared in Step 3 is dispersed in anhydrous ethanol at a concentration of 1 mg / mL and spin-coated onto the zinc oxide / tungsten trioxide photoanode prepared in Step 2. The spin-coating amount is 0.1 mL and the spin speed is 1000 rpm. Then, it is placed in a muffle furnace and annealed at 100°C for 4 h under air conditions to obtain the integrated structure of palladium-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode.
[0045] Example 3
[0046] Step 1: A 1cm × 2cm piece of ITO was sequentially placed in deionized water, acetone, and ethanol and sonicated for 60 min. It was then dried in an oven at 40℃ for 4 h, followed by ozone treatment for 40 min. Tungsten trioxide photoanodes were then prepared on the ITO using a hydrothermal method. Specifically: 0.3g of ammonium metatungstate was added to 50mL of deionized water, followed by 3mL of 6.25M concentrated hydrochloric acid. After stirring for 15 min, 0.75mL of hydrogen peroxide was added, and the mixture was stirred for another 1 h to obtain a tungsten trioxide precursor solution. The treated ITO was then placed face down in a polytetrafluoroethylene-lined autoclave, and 25mL of the precursor solution was added. The autoclave was then placed in an oven and hydrothermally heated at 170℃ for 4 h. After the reaction was complete and the autoclave cooled to room temperature, it was removed and cleaned of solid impurities with deionized water and ethanol. The autoclave was dried for 20 min and then calcined in a muffle furnace at 450℃ for 2.5 h in air to obtain the tungsten trioxide photoanode.
[0047] Step 2: A zinc oxide precursor solution was prepared using a hydrothermal method. Specifically, 7 mL of ethanol, 80 μL of ethanolamine, and 0.2 mol of zinc acetate were uniformly mixed and hydrothermally heated at 80 °C for 6 h to obtain the zinc oxide precursor solution. The zinc oxide precursor solution was then spin-coated onto the tungsten trioxide photoanode prepared in Step 1, with a coating amount of 0.4 mL and a spin speed of 2000 rpm. The resulting structure was then annealed in a muffle furnace at 500 °C for 40 min under air conditions to obtain a zinc oxide / tungsten trioxide heterostructure.
[0048] Step 3: Prepare platinum-modified nickel phosphide cocatalyst by phosphating. Mix chloroplatinic acid hexahydrate, nickel chloride hexahydrate and sodium hypophosphite in a molar ratio of 2:10:50 thoroughly and grind evenly. Place the ground solid in an argon furnace and calcine at 400°C for 4 hours. After the reaction is completed and cooled to room temperature, wash the solid powder with deionized water and anhydrous ethanol, centrifuge and dry to obtain platinum-modified nickel phosphide cocatalyst.
[0049] Step 4: The platinum-modified nickel phosphide co-catalyst powder prepared in Step 3 is dispersed in anhydrous ethanol at a concentration of 5 mg / mL and spin-coated onto the zinc oxide / tungsten trioxide photoanode prepared in Step 2. The spin-coating amount is 0.5 mL, the spin speed is 1500 rpm, and then the mixture is annealed in a muffle furnace at 160 °C for 1 h under air conditions to obtain the platinum-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode system.
[0050] Comparative Example 1
[0051] After preparing the zinc oxide / tungsten trioxide heterostructure according to steps 1 and 2 in Example 1, the nickel phosphide / zinc oxide / tungsten trioxide photoanode system was prepared according to the following steps:
[0052] Step 3: Prepare nickel phosphide co-catalyst by phosphating. Mix nickel chloride hexahydrate and sodium hypophosphite in a molar ratio of 1:5 thoroughly and grind evenly. Place the ground solid in an argon furnace and calcine at 250°C for 2 hours. After the reaction is completed and cooled to room temperature, wash the solid powder with deionized water and anhydrous ethanol, centrifuge and dry to obtain nickel phosphide co-catalyst.
[0053] Step 4: Disperse the nickel phosphide co-catalyst powder prepared in Step 3 in anhydrous ethanol at a concentration of 3 mg / mL, spin-coat it onto the prepared zinc oxide / tungsten trioxide photoanode at a spin coating amount of 0.4 mL and a spin speed of 1200 rpm, and then anneal it in a muffle furnace at 120 °C for 2 h under air conditions to obtain the nickel phosphide / zinc oxide / tungsten trioxide photoanode system.
[0054] Figure 1The images show the XRD patterns of the tungsten trioxide photoanode, zinc oxide / tungsten trioxide heterostructure, and gold-modified nickel phosphide / zinc oxide / tungsten oxide photoanode integrated structure prepared in Example 1. Testing revealed that the synthesized tungsten trioxide photoanode is a monoclinic phase (PDF#72-0677). Besides the characteristic peaks belonging to tin oxide (FTO, PDF#41-1445), three distinct characteristic peaks at 2θ of 23.11°, 23.58°, and 24.35° are attributed to the (002), (020), and (200) crystal planes, respectively. With the addition of the intermediate layer and co-catalyst, its XRD pattern showed almost no change, which we believe is due to the low loading. Although XRD cannot show the loading of various layers, combined with… Figure 3-6 The successful synthesis of the integrated photoanode system has been demonstrated.
[0055] Figure 7 This is a linear sweep voltammogram of the tungsten trioxide photoanode, zinc oxide / tungsten trioxide heterostructure, and gold-modified nickel phosphide / zinc oxide / tungsten oxide photoanode integrated structure prepared in Example 1 in a sodium sulfate electrolyte containing glycerol. As can be seen from the figure, the photocurrent density of the gold-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode integrated structure is 3.15 mA / cm² relative to the reversible hydrogen electrode at 1.23 V. 2 It is higher than the 2.08 mA / cm² of tungsten trioxide. 2 And 2.26 mA / cm of zinc oxide / tungsten trioxide 2 This indicates that the co-catalyst reduces surface resistance and improves the performance of glycerol oxidation. Figure 8 The linear sweep voltammetry plots of the gold-modified nickel phosphide / zinc oxide / tungsten oxide photoanode integrated structure prepared in Example 1 and the nickel phosphide / zinc oxide / tungsten trioxide photoanode system prepared in the comparative example in sodium sulfate electrolyte containing glycerol show that the photocurrent density of nickel phosphide / zinc oxide / tungsten trioxide at 1.23 V relative to the reversible hydrogen electrode is only 2.52 mA / cm². 2 This is because noble metal doping improves the conductivity of the cocatalyst. Furthermore, noble metals are also part of the active center and their activity is higher than that of nickel phosphide. Therefore, the addition of noble metals further reduces surface resistance, improves surface reaction kinetics, accelerates charge transport efficiency, and enhances the activity of photoelectrocatalytic glycerol oxidation.
[0056] Figure 9 The gold-modified nickel phosphide / zinc oxide / tungsten trioxide photoanode integrated structure prepared in Example 1 was tested under simulated solar light (300W xenon lamp, light intensity 100mW / cm²). 2 The photoelectrocatalytic oxidation of glycerol was carried out under simulated solar light conditions (300W xenon lamp, light intensity 100mW / cm²). The products were then analyzed by high-performance liquid chromatography (HPLC). 2Under the conditions of 0.8 V relative to the reversible hydrogen electrode and 1 M glycerol, after 2 h of reaction, the integrated photoanode produced almost no products for the glycerol oxidation reaction other than 1,3-dihydroxyacetone and glyceraldehyde, achieving a total Faradaic efficiency of 82.9% and a glycerol consumption rate of 191.4 mmol / (m²). 2 h). Furthermore, as the voltage increases, its overall Faraday efficiency continuously decreases, indicating that the closer the voltage is to the theoretical potential for oxygen production, the more competitive it becomes in water oxidation. However, even with increased voltage, glycerol oxidation still dominates in this system.
[0057] The embodiments described above are merely illustrative of implementation methods of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.
Claims
1. An application of an integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode, characterized in that, The aforementioned integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode is applied to the high-value coupling of photoelectrocatalytic glycerol for hydrogen production; In the integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode, the synthesized tungsten trioxide photoanode is a nanorod structure, zinc oxide is a thin layer structure covering the surface of tungsten trioxide, and the noble metal modified cocatalyst is nanoparticles uniformly dispersed on the surface of heterostructure. The integrated structure of cocatalyst / heterogeneous structure / tungsten trioxide photoanode was prepared by the following method: first, zinc oxide / tungsten trioxide heterostructure was synthesized; second, a nickel phosphide cocatalyst modified with noble metal was synthesized by phosphating; and finally, it was loaded onto the surface of the heterostructure to successfully construct the integrated system of cocatalyst / heterogeneous structure / photoanode.
2. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 1, characterized in that, A standard three-electrode reaction system was formed using an integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode. The reaction electrolyte was a mixed aqueous solution of 0.5M sodium sulfate and 0.01~1M glycerol. The photoelectrocatalytic oxidation of glycerol was carried out under simulated solar light conditions.
3. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 1, characterized in that, The integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode was prepared by the following method: Step 1: Pre-treat the conductive substrate and prepare a tungsten trioxide photoanode on the conductive substrate; Step 2: Synthesize zinc oxide / tungsten trioxide heterostructures on a conductive substrate by spin coating and calcination; Zinc acetate, ethanolamine and anhydrous ethanol were mixed in a certain proportion and hydrothermally to obtain a zinc oxide precursor solution, which was then spin-coated onto the surface of the tungsten trioxide photoanode prepared in step 1 and annealed in air to obtain a zinc oxide / tungsten trioxide heterostructure. Step 3: Sodium hypophosphite, precious metal hydrated chloride and nickel chloride hexahydrate are ground and mixed in a certain proportion. The mixture is placed in a tube furnace and calcined under an argon atmosphere. The obtained solid product is cooled to room temperature and then washed, centrifuged and dried to obtain a precious metal modified nickel phosphide co-catalyst. Step 4: Disperse the noble metal-modified nickel phosphide cocatalyst obtained in Step 3 in anhydrous ethanol and sonicate to obtain a suspension; spin-coat the obtained suspension onto the surface of the zinc oxide / tungsten trioxide heterostructure prepared in Step 2, and finally anneal in air to obtain the cocatalyst / heterostructure / tungsten trioxide photoanode integrated structure.
4. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 3, characterized in that, In step 1, the conductive substrate is fluorine-doped tin dioxide conductive glass or tin-doped indium oxide thin film; in step 3, the noble metal hydrated chloride salt is selected from one of tetrachloroauric acid trihydrate, chloroplatinic acid hexahydrate, and potassium chloride palladium chlorite.
5. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 3, characterized in that, In step 1, a tungsten trioxide photoanode is prepared on a conductive substrate using a hydrothermal method, specifically as follows: Add 0.3-0.6 g of ammonium metatungstate and 3-6 mL of 6.25 M concentrated hydrochloric acid to every 30-60 mL of deionized water, stir well, then add 0.75-1.25 mL of hydrogen peroxide, and continue stirring for 0.5-2 h to obtain the precursor solution. The pretreated conductive substrate was then placed in a polytetrafluoroethylene-lined autoclave with the conductive side facing down. After adding 20-30 mL of precursor solution, the substrate was hydrothermally heated at 140-180 °C for 3-5 h. After cooling to room temperature, the substrate was removed, cleaned, and dried. It was then placed in a muffle furnace and annealed at 400-500 °C in air for 2-3 h to obtain a tungsten trioxide photoanode.
6. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 3, characterized in that, Step 2 specifically includes: Add 40-80 μL of ethanolamine and 0.15-0.25 mol of zinc acetate to every 5-10 mL of ethanol. After mixing, hydrothermally heat at 50-80 °C for 3-6 h to obtain a zinc oxide precursor solution. Spin-coat the zinc oxide precursor solution onto the tungsten trioxide photoanode prepared in step 1, with a spin-coating amount of 0.2-0.4 mL per 1 cm × 2 cm area photoanode. Then place it in a muffle furnace for air annealing at a temperature of 350-500 °C for 10-40 min to obtain a zinc oxide / tungsten trioxide heterostructure.
7. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 3, characterized in that, In step 3, the molar ratio of precious metal hydrated chloride, nickel chloride hexahydrate, and sodium hypophosphite is (0.5~2):10:50, the calcination temperature is 200~400℃, and the time is 1~4h.
8. The application of the integrated structure of co-catalyst / heterogeneous structure / tungsten trioxide photoanode according to claim 3, characterized in that, In step 4, the mass concentration of the noble metal-modified nickel phosphide co-catalyst in the suspension is 1.0~5.0 mg / mL, the spin-coating amount on the photoanode is 0.1~0.5 mL per 1 cm × 2 cm area, the annealing temperature is 100~160℃, and the time is 1~4 h.