A heteropoly acid and feohh co-doped alpha-fe2o3 photoanode and a preparation method thereof

Abstract

The application discloses a kind of heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode and preparation method thereof, comprising: after cleaning, tin oxide conductive glass is placed in precursor solution and is reacted, and the tin oxide electrode covered with β-FeOOH film is obtained;β-FeOOH film on tin oxide electrode is washed, and the washed tin oxide electrode is sequentially subjected to drying treatment, high-temperature annealing treatment, and α-Fe2O3 film photoanode is obtained;Heteropoly acid solution is dropped on the surface of α-Fe2O3 film photoanode, and α-Fe2O3 photoanode doped with heteropoly acid is obtained;FeOOH is deposited on the α-Fe2O3 photoanode doped with heteropoly acid, and α-Fe2O3 photoanode co-doped with heteropoly acid and FeOOH is obtained.The application can obtain more excellent photoelectrocatalytic performance by loading heteropoly acid and FeOOH as cocatalyst on the surface of α-Fe2O3 photoanode.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical technology, and in particular to an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH and its preparation method. Background Technology

[0002] Photoelectrocatalytic water splitting for hydrogen production, as a hydrogen production technology that couples light and electricity, has the advantages of being sustainable, clean, environmentally friendly, and energy-efficient, making it a promising method for hydrogen production. However, the solar-to-hydrogen conversion efficiency of this technology remains relatively low. Specifically, the water oxidation rate on the surface of the semiconductor photoanode is extremely slow, thus inhibiting the hydrogen evolution rate on the photocathode surface. Therefore, the performance of the photoanode material is a crucial factor determining the solar-to-hydrogen conversion efficiency of the photoelectrocatalytic hydrogen production system. Among various semiconductor photoanodes, metal oxide photoanodes have received widespread attention and experienced rapid development over the past few decades due to their excellent chemical stability and other advantages.

[0003] α-Fe2O3 has a suitable band gap, enabling it to absorb visible light below 600nm. It also boasts advantages such as abundant raw materials and high stability, making it one of the most promising metal oxide photoanode materials currently available.

[0004] However, α-Fe₂O₃ photoanodes suffer from drawbacks such as short diffusion distance of photogenerated holes, easy recombination of photogenerated electrons and holes, low oxidation kinetics, and poor conductivity. These drawbacks affect the photoelectric conversion efficiency of α-Fe₂O₃. Existing methods for preparing α-Fe₂O₃ photoanodes cannot effectively reduce the recombination of photogenerated electrons and holes, nor can they effectively improve the water oxidation capacity and conductivity of α-Fe₂O₃, resulting in poor photoelectrocatalytic performance of α-Fe₂O₃.

[0005] There is currently no effective solution to the above problems. Summary of the Invention

[0006] This specification provides an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH and its preparation method, in order to solve the problem that the existing technology cannot effectively reduce the recombination of photogenerated electrons and holes in α-Fe2O3, and cannot effectively improve the water oxidation capacity and conductivity of α-Fe2O3, thus resulting in poor photoelectrocatalytic performance of α-Fe2O3.

[0007] In one aspect, the embodiments of this specification provide a method for preparing α-Fe2O3 photoanodes co-doped with heteropolyacids and FeOOH, the method comprising the following steps:

[0008] The cleaned tin oxide conductive glass was placed in a pre-prepared precursor solution for reaction to obtain a tin oxide electrode covered with a β-FeOOH film;

[0009] The β-FeOOH film on the tin oxide electrode was rinsed and then dried and annealed at high temperature to obtain an α-Fe2O3 film photoanode.

[0010] A pre-prepared heteropolyacid solution was drop-coated onto the surface of an α-Fe2O3 thin film photoanode to obtain an α-Fe2O3 photoanode doped with heteropolyacid.

[0011] FeOOH was deposited on an α-Fe2O3 photoanode doped with heteropolyacid to obtain an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH.

[0012] In some embodiments, the precursor fluid is configured as follows:

[0013] A 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH of the aqueous solution was adjusted to 1-2. The adjusted aqueous solution was used as the precursor solution.

[0014] In some embodiments, the reaction temperature is set to 90°C to 100°C, and the reaction time is set to 4h to 6h.

[0015] In some embodiments, the drying temperature of the drying process is set to 70°C to 90°C, and the drying time is set to 2 hours.

[0016] In some embodiments, the heteropolyacid solution includes at least one of the following: an ethanol solution of phosphomolybdic acid, an ethanol solution of phosphotungstic acid, or an ethanol solution of silicotungstic acid.

[0017] In some embodiments, after the pre-prepared heteropolyacid solution is drop-coated onto the α-Fe2O3 thin film photoanode, the method further includes:

[0018] After the α-Fe2O3 thin film photoanode was allowed to stand and dry, it was annealed at 120℃~150℃ for 2 hours to obtain the α-Fe2O3 photoanode doped with heteropolyacid.

[0019] In some embodiments, the deposition of FeOOH on an α-Fe₂O₃ photoanode doped with heteropolyacids includes:

[0020] The light source is shone onto the back of the α-Fe2O3 photoanode doped with heteropolyacid. The α-Fe2O3 photoanode doped with heteropolyacid is used as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and FeSO4 solution as the electrolyte solution. A first external voltage is applied to perform photodeposition.

[0021] After photodeposition, a second external voltage is applied for electrodeposition to obtain an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH.

[0022] In some embodiments, the light source is a xenon lamp with an AM 1.5G filter, the photodeposition time is set to 5 min to 30 min, the electrodeposition time is set to 1 min to 2 min, the first external voltage is 0.3 V to 0.4 V compared to the reference electrode, and the second external voltage is 1.0 V to 1.5 V compared to the reference electrode.

[0023] Secondly, the embodiments of this specification also provide α-Fe2O3 photoanodes co-doped with heteropolyacids and FeOOH, which are prepared by the above preparation method.

[0024] Thirdly, the α-Fe2O3 photoanode provided in the embodiments of this specification is used in photoelectrocatalytic water splitting for hydrogen production.

[0025] This specification provides an embodiment of an α-Fe₂O₃ photoanode co-doped with heteropolyacids and FeOOH, and its preparation method. First, cleaned tin oxide conductive glass is placed in a precursor solution for reaction to obtain a tin oxide electrode covered with a β-FeOOH film. The β-FeOOH film on the tin oxide electrode is then rinsed, and the rinsed tin oxide electrode is subsequently dried and annealed at high temperature to obtain an α-Fe₂O₃ film photoanode. Next, a heteropolyacid solution is drop-coated onto the surface of the α-Fe₂O₃ film photoanode to obtain an α-Fe₂O₃ photoanode doped with heteropolyacids. Finally, FeOOH is deposited on the α-Fe₂O₃ photoanode doped with heteropolyacids to obtain an α-Fe₂O₃ photoanode co-doped with heteropolyacids and FeOOH. This invention utilizes heteropolyacids and FeOOH as cocatalysts loaded on the surface of the α-Fe2O3 photoanode to effectively reduce the recombination of photogenerated electrons and holes in α-Fe2O3, improve the water oxidation capacity of α-Fe2O3, and enhance the conductivity of α-Fe2O3, thereby achieving superior photoelectrocatalytic performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:

[0027] Figure 1 A schematic flowchart illustrating a method for preparing α-Fe2O3 photoanodes co-doped with heteropolyacids and FeOOH, as provided in the embodiments of this specification;

[0028] Figure 2The images show SEM images of α-Fe2O3 / PMO / FeOOH in Example 1, α-Fe2O3 in Comparative Example 1, and α-Fe2O3 / PMO in Comparative Example 2. (a) is a top-view SEM image of α-Fe2O3 in Comparative Example 1, (d) is a cross-sectional SEM image of α-Fe2O3 in Comparative Example 1, (b) is a top-view SEM image of α-Fe2O3 / PMO in Comparative Example 2, (e) is a cross-sectional SEM image of α-Fe2O3 / PMO in Comparative Example 2, (c) is a top-view SEM image of the α-Fe2O3 / PMO / FeOOH photoanode in Example 1, and (f) is a cross-sectional SEM image of the α-Fe2O3 / PMO / FeOOH photoanode in Example 1.

[0029] Figure 3 The image shows the HRTEM images of the α-Fe2O3 / PMO / FeOOH photoanode in Example 1, where (a) and (b) are HRTEM images of the α-Fe2O3 / PMO / FeOOH photoanode at different shooting positions, respectively.

[0030] Figure 4 Examples 1 (α-Fe₂O₃ / PMO / FeOOH), 2 (α-Fe₂O₃), and 3 (α-Fe₂O₃ / PMO) were subjected to AM 1.5G illumination (100 mW / cm²). 2 ) and linear sweep voltammetry (LSV) curves in the dark state;

[0031] Figure 5 The photo-hydrogen conversion efficiency (ABPE) graphs for Example 1 α-Fe2O3 / PMO / FeOOH, Comparative Example 1 α-Fe2O3, and Comparative Example 2 α-Fe2O3 / PMO are shown.

[0032] Figure 6 The external quantum efficiency (IPCE) plots are for Example 1 α-Fe2O3 / PMO / FeOOH, Comparative Example 1 α-Fe2O3, and Comparative Example 2 α-Fe2O3 / PMO.

[0033] Figure 7 Mott-Schottky curves of α-Fe₂O₃ / PMO / FeOOH in Example 1, α-Fe₂O₃ in Comparative Example 1, and α-Fe₂O₃ / PMO in Comparative Example 2 in 0.1 MkOH electrolyte;

[0034] Figure 8 Bulk charge separation efficiency (η) of Example 1 α-Fe2O3 / PMO / FeOOH, Comparative Example 1 α-Fe2O3, and Comparative Example 2 α-Fe2O3 / PMO. bulk ) and surface charge separation efficiency (η) surface), where (a) is the bulk charge separation efficiency (η) of α-Fe2O3, α-Fe2O3 / PMO and α-Fe2O3 / PMO / FeOOH. bulk (b) represents the surface charge separation efficiency (η) of α-Fe₂O₃, α-Fe₂O₃ / PMO, and α-Fe₂O₃ / PMO / FeOOH. surface ). Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0036] Please see Figure 1 As shown in the embodiments of this specification, a method for preparing an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH may include the following steps.

[0037] S101: The cleaned tin oxide conductive glass is placed in a pre-prepared precursor solution for reaction to obtain a tin oxide electrode covered with a β-FeOOH film;

[0038] S102: Rinse the β-FeOOH film on the tin oxide electrode and then dry and anneal the rinsed tin oxide electrode in sequence to obtain an α-Fe2O3 film photoanode;

[0039] S103: A pre-prepared heteropolyacid solution is drop-coated onto the surface of an α-Fe2O3 thin film photoanode to obtain an α-Fe2O3 photoanode doped with heteropolyacid;

[0040] S104: FeOOH is deposited on an α-Fe2O3 photoanode doped with heteropolyacid to obtain an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH.

[0041] Based on the above embodiments, heteropolyacids and FeOOH (iron hydroxyl oxide) can be loaded onto the surface of the α-Fe2O3 photoanode as cocatalysts, which effectively reduces the recombination of photogenerated electrons and holes in α-Fe2O3 and improves the water oxidation capacity of α-Fe2O3. The α-Fe2O3 photoanode co-doped with heteropolyacids and FeOOH has better photoelectrocatalytic performance.

[0042] In some embodiments, the precursor liquid in S101 above can be configured as follows:

[0043] A 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH of the aqueous solution was adjusted to 1-2. The adjusted aqueous solution was used as the precursor solution.

[0044] Specifically, 0.1M can be equal to 0.1 mol / L, where M is the molar concentration, also known as the concentration of substance, and its unit is mol / L, i.e., moles per liter. A 0.1M FeCl3·6H2O aqueous solution can be prepared first in a hydrothermal reactor, and then the pH of the 0.1M FeCl3·6H2O aqueous solution can be adjusted to 1-2 using hydrochloric acid to obtain the aforementioned precursor solution.

[0045] In some embodiments, the reaction temperature in S101 is set to 90°C to 100°C, and the reaction time is set to 4h to 6h.

[0046] Specifically, the cleaned tin oxide (FTO) conductive glass can be placed in the aforementioned precursor solution and reacted at 90℃~100℃ for 4h~6h to obtain a tin oxide (FTO) electrode covered with a β-FeOOH film. High-temperature resistant tape can be used to adhere the cleaned tin oxide (FTO) conductive glass to control the growth shape and location of α-Fe2O3.

[0047] In some embodiments, the drying temperature in the drying process of S102 is set to 70°C to 90°C, and the drying time is set to 2 hours.

[0048] Specifically, the β-FeOOH film on the tin oxide electrode can be rinsed and dried at 70℃~90℃ for 2h. Subsequently, it is placed in a tube furnace for high-temperature annealing treatment, with the annealing temperature maintained at 500℃~550℃ for 2h, and then maintained at 750℃ for 20min in an atmosphere of N2 or Ar, to obtain an α-Fe2O3 thin film photoanode.

[0049] In some embodiments, the heteropolyacid solution in S103 may include at least one of the following: an ethanol solution of phosphomolybdic acid (PMO), an ethanol solution of phosphotungstic acid (PTA), or an ethanol solution of silicotungstic acid (TSA).

[0050] In some embodiments, after the pre-prepared heteropolyacid solution is drop-coated onto the α-Fe2O3 thin film photoanode in step S103, the following may also be included:

[0051] After the α-Fe2O3 thin film photoanode was allowed to stand and dry, it was annealed at 120℃~150℃ for 2 hours to obtain the α-Fe2O3 photoanode doped with heteropolyacid.

[0052] Specifically, a 0.3 mol / L PMO ethanol solution, a 0.2 mol / L PTA ethanol solution, or a 0.3 mol / L TSA ethanol solution can be prepared. A certain amount of heteropolyacid solution is then measured and drop-coated onto the surface of an α-Fe₂O₃ thin-film photoanode. After allowing it to air dry, it is annealed at 120℃–150℃ for 2 hours to obtain an α-Fe₂O₃ photoanode doped with heteropolyacid. The concentration of the heteropolyacid solution can be 0.1 mol / L–0.5 mol / L, and the amount of heteropolyacid solution measured can be 2 μL–5 μL.

[0053] In some embodiments, the deposition of FeOOH on the α-Fe2O3 photoanode doped with heteropolyacid in S104 above may include:

[0054] The light source is shone onto the back of the α-Fe2O3 photoanode doped with heteropolyacid. The α-Fe2O3 photoanode doped with heteropolyacid is used as the working electrode, Pt is used as the counter electrode, and Ag / AgCl is used as the reference electrode. A first external voltage is applied to perform photodeposition.

[0055] After photodeposition, a second external voltage is applied for electrodeposition to obtain an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH.

[0056] In some embodiments, the light source is a xenon lamp with an AM 1.5G filter, the photodeposition time is set to 5 min to 30 min, the electrodeposition time is set to 1 min to 2 min, the first external voltage is 0.3 V to 0.4 V compared to the reference electrode, and the second external voltage is 1.0 V to 1.5 V compared to the reference electrode.

[0057] Specifically, a 0.1 mol / L FeSO4 solution can be prepared, and the solution can be purged with N2 to remove oxygen. FeOOH is then deposited on an α-Fe2O3 photoanode doped with heteropolyacids using photodeposition. The photodeposition light source is a xenon lamp equipped with an AM 1.5G filter, illuminating the back of the photoanode at an intensity of 1–5 mW / cm². 2The reaction employed a conventional three-electrode system, using an α-Fe₂O₃ photoanode doped with heteropolyacids (e.g., α-Fe₂O₃ / PMO) as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. An oxygen-removed FeSO₄ solution was used as the electrolyte. An external voltage of 0.3–0.4 V vs. Ag / AgCl (the first external voltage) was applied for photodeposition for 5–30 min. After photodeposition, an external voltage of 1.0–1.5 V vs. Ag / AgCl (the second external voltage) was applied for electrodeposition for 1–2 min, yielding an α-Fe₂O₃ photoanode co-doped with heteropolyacids and FeOOH.

[0058] In some embodiments, the α-Fe2O3 photoanode co-doped with the heteropolyacid and FeOOH is prepared by the above preparation method.

[0059] In some embodiments, the α-Fe2O3 photoanode co-doped with the above-mentioned heteropolyacid and FeOOH is used in photoelectrocatalytic water splitting for hydrogen production.

[0060] Specifically, α-Fe2O3 photoanodes co-doped with heteropolyacids and FeOOH can be used as co-catalysts for photoelectrochemical water splitting.

[0061] By loading heteropolyacids and FeOOH as cocatalysts onto the surface of α-Fe₂O₃ photoanodes, the recombination of photogenerated electrons and holes in α-Fe₂O₃ was reduced, thereby improving the water oxidation capacity of α-Fe₂O₃. The constructed α-Fe₂O₃ photoanodes co-doped with heteropolyacids and FeOOH (e.g., α-Fe₂O₃ / phosphomolybdic acid (PMO) / FeOOH photoanodes) exhibit superior photoelectrocatalytic performance, with a photocurrent density of 1.81 mA / cm² at 1.23 V vs. RHE. 2 It is approximately three times the photocurrent density of α-Fe₂O₃. Here, RHE is an abbreviation for Reversible Hydrogen Electrode, V is the unit of voltage (volt), and vs. may mean "relative to" or "compared to".

[0062] In a specific implementation scenario, when the heteropolyacid solution is an ethanol solution of phosphomolybdic acid (PMO), the steps of the above-described method for preparing α-Fe2O3 photoanodes co-doped with heteropolyacid and FeOOH are as follows:

[0063] Example 1

[0064] The first step is to use high-temperature resistant tape to adhere the cleaned tin oxide (FTO) conductive glass to control the growth shape and location of α-Fe2O3;

[0065] The second step involves preparing a 0.1M FeCl3·6H2O aqueous solution in a hydrothermal reactor and adjusting the pH to 1.5 using hydrochloric acid as a precursor solution for the hydrothermal reaction. The bonded FTO glass is then placed in the precursor solution and reacted at 90℃ for 5 hours to obtain a tin oxide (FTO) electrode covered with a β-FeOOH film.

[0066] The third step involves rinsing the β-FeOOH film on the tin oxide (FTO) electrode and drying it at 70°C for 2 hours. Subsequently, it is placed in a tube furnace for high-temperature annealing at 520°C for 2 hours, followed by 750°C for 20 minutes in an Ar atmosphere to obtain the α-Fe2O3 thin film photoanode.

[0067] The fourth step involves preparing an ethanol solution of phosphomolybdic acid (PMO) with a concentration of 0.3 mol / L. 3 μL of the PMO solution is then drop-coated onto the surface of the α-Fe₂O₃ thin-film photoanode, allowed to stand and dry, and subsequently annealed at 150 °C for 3 h to obtain a PMO-doped α-Fe₂O₃ photoanode (α-Fe₂O₃ / PMO photoanode).

[0068] Fifth, a 0.1 mol / L FeSO4 solution was prepared and purged with N2 to remove O2. FeOOH was then deposited on the α-Fe2O3 / PMO photoanode using photodeposition. The photodeposition light source was a xenon lamp equipped with an AM 1.5G filter, illuminating the back of the photoanode at an intensity of 2 mW / cm². 2 The reaction employed a traditional three-electrode system, using α-Fe₂O₃ / PMO as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. An oxygen-removed FeSO₄ solution was used as the electrolyte. An external voltage of 0.35V vs. Ag / AgCl was applied, and the photodeposition time was 20 min. After photodeposition, an external voltage of 1.2V vs. Ag / AgCl was applied for electrodeposition for 1.5 min, yielding a PMO and FeOOH co-doped α-Fe₂O₃ photoanode (e.g., α-Fe₂O₃ / PMO / FeOOH photoanode).

[0069] Comparative Example 1

[0070] The first step is to use high-temperature resistant tape to adhere the cleaned tin oxide (FTO) conductive glass to control the growth shape and location of α-Fe2O3;

[0071] The second step involves preparing a 0.1M FeCl3·6H2O aqueous solution in a hydrothermal reactor and adjusting the pH to 1.5 using hydrochloric acid as a precursor solution for the hydrothermal reaction. The bonded FTO glass is then placed in the precursor solution and reacted at 90℃ for 5 hours to obtain an FTO electrode covered with a β-FeOOH film.

[0072] The third step involves rinsing the β-FeOOH film on the tin oxide (FTO) electrode and drying it at 70°C for 2 hours. Subsequently, it is placed in a tube furnace for high-temperature annealing at 520°C for 2 hours, followed by 750°C for 20 minutes in an Ar atmosphere to obtain the α-Fe2O3 thin film photoanode.

[0073] Comparative Example 2

[0074] The first step is to use high-temperature resistant tape to adhere the cleaned tin oxide (FTO) conductive glass to control the growth shape and location of α-Fe2O3;

[0075] The second step involves preparing a 0.1M FeCl3·6H2O aqueous solution in a hydrothermal reactor and adjusting the pH to 1.5 using hydrochloric acid as a precursor solution for the hydrothermal reaction. The bonded FTO glass is then placed in the precursor solution and reacted at 90℃ for 5 hours to obtain an FTO electrode covered with a β-FeOOH film.

[0076] The third step involves rinsing the β-FeOOH film on the tin oxide (FTO) electrode and drying it at 70°C for 2 hours. Subsequently, it is placed in a tube furnace for high-temperature annealing at 520°C for 2 hours, followed by 750°C for 20 minutes in an Ar atmosphere to obtain the α-Fe2O3 thin film photoanode.

[0077] The fourth step involves preparing an ethanol solution of PMO with a concentration of 0.3 mol / L, measuring 3 μL of the PMO solution, drop-coating it onto the surface of the α-Fe2O3 photoanode, allowing it to stand and dry, and then annealing it at 150℃ for 3 hours to obtain the PMO-doped α-Fe2O3 photoanode (α-Fe2O3 / PMO photoanode).

[0078] See Figure 2 As shown in (a), (b), (c), (d), (e), and (f), Comparative Example 1 α-Fe₂O₃ exhibits a loose nanorod structure, while the nanorod structures of Example 1 α-Fe₂O₃ / PMO / FeOOH and Comparative Example 2 α-Fe₂O₃ / PMO are more compact. This is beneficial for increasing the contact area with the electrolyte and improving the interfacial charge transfer efficiency. SEM images were obtained using scanning electron microscopy, with a pixel size of 200 nm.

[0079] See Figure 3As shown in (a) and (b), lattice spacings of 0.26 nm and 0.149 nm correspond to the (104) and (112) crystal planes of α-Fe₂O₃, respectively, and lattice spacing of 0.151 nm corresponds to the (210) crystal plane of γ-FeOOH. PMO (phosphomolybdic acid) exists in the form of an ultrathin amorphous nanolayer. HRTEM is a high-resolution transmission electron microscope; the pixel size of the HRTEM image is 5 nm. Figure 3 The combination of (a) and (b) in the figure proves that the prepared photoanode is an α-Fe2O3 / PMO / FeOOH composite material.

[0080] See Figure 4 As shown, in 0.1M KOH electrolyte, 1.23V RHE Under bias, the current densities of α-Fe₂O₃, α-Fe₂O₃ / PMO, and α-Fe₂O₃ / PMO / FeOOH in the dark state are 7.11 × 10⁻⁶. -4 mW / cm 2 1.48×10 -3 mW / cm 2 and 2.28×10 - 3 mW / cm 2 The three photoanodes exhibited very low current densities in the dark, resulting in weak water electrolysis performance. Under illumination, the photocurrent densities of α-Fe₂O₃, α-Fe₂O₃ / PMO, and α-Fe₂O₃ / PMO / FeOOH were 0.63 mW / cm². 2 1.12mW / cm 2 and 1.81mW / cm 2 Compared with α-Fe2O3 and α-Fe2O3 / PMO, α-Fe2O3 / PMO / FeOOH exhibits a higher photocurrent density, indicating that it has the best photoelectrochemical water splitting performance.

[0081] See Figure 5 As shown, α-Fe₂O₃, α-Fe₂O₃ / PMO, and α-Fe₂O₃ / PMO / FeOOH in 0.1M KOH solution at 1.08V RHE The photo-hydrogen conversion efficiencies (ABPE) were 0.07%, 0.11%, and 0.18%, respectively.

[0082] See Figure 6 As shown, α-Fe2O3 / PMO / FeOOH exhibits the best external quantum efficiency in the range of 320nm to 620nm, indicating that it has the highest photon absorption efficiency.

[0083] See Figure 7As shown, the curve corresponding to α-Fe2O3 / PMO / FeOOH has the lowest slope, indicating that it has the highest carrier concentration, which helps to obtain the best photoelectrocatalytic performance.

[0084] See Figure 8 As shown in (a) and (b), α-Fe2O3 / PMO / FeOOH exhibits a higher bulk charge separation efficiency η compared to α-Fe2O3 and α-Fe2O3 / PMO. bulk and surface charge separation efficiency η surface The high photocurrent density stems from the full utilization of photogenerated holes, indicating that the loading of PMO and FeOOH effectively improves the oxygen evolution kinetics on the α-Fe2O3 surface.

[0085] In a specific implementation scenario, when the heteropolyacid solution is an ethanol solution of phosphotungstic acid (PTA), the steps of the above-described method for preparing α-Fe2O3 photoanodes co-doped with heteropolyacid and FeOOH are as follows:

[0086] The first step is to use high-temperature resistant tape to adhere the cleaned tin oxide (FTO) conductive glass to control the growth shape and location of α-Fe2O3;

[0087] The second step involves preparing a 0.1M FeCl3·6H2O aqueous solution in a hydrothermal reactor and adjusting the pH to 1.5 using hydrochloric acid as a precursor solution for the hydrothermal reaction. The bonded FTO glass is then placed in the precursor solution and reacted at 90℃ for 5 hours to obtain an FTO electrode covered with a β-FeOOH film.

[0088] The third step involves rinsing the β-FeOOH film on the tin oxide (FTO) electrode and drying it at 70°C for 2 hours. Subsequently, it is placed in a tube furnace for high-temperature annealing at 520°C for 2 hours, followed by 750°C for 20 minutes in an Ar atmosphere to obtain the α-Fe2O3 thin film photoanode.

[0089] The fourth step involves preparing an ethanol solution of phosphotungstic acid (PTA) with a concentration of 0.2 mol / L. 3 μL of the PTA solution is then drop-coated onto the surface of the α-Fe₂O₃ photoanode, allowed to stand and dry, and subsequently annealed at 120°C for 3 hours to obtain a PTA-doped α-Fe₂O₃ photoanode (e.g., α-Fe₂O₃ / PTA photoanode).

[0090] Fifth, a 0.1 mol / L FeSO4 solution was prepared and purged with N2 to remove O2. FeOOH was then deposited on the α-Fe2O3 / PTA photoanode using photodeposition. The photodeposition light source was a xenon lamp equipped with an AM 1.5G filter, illuminating the back of the photoanode at an intensity of 2 mW / cm².2 The reaction employed a traditional three-electrode system, using α-Fe₂O₃ / PTA as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. A deoxygenated FeSO₄ solution was used as the electrolyte. An external voltage of 0.35V vs. Ag / AgCl was applied, and the photodeposition time was 30 min. After photodeposition, an external voltage of 1.2V vs. Ag / AgCl was applied for electrodeposition for 1.0 min, yielding a PTA and FeOOH co-doped α-Fe₂O₃ photoanode (e.g., α-Fe₂O₃ / PTA / FeOOH photoanode).

[0091] In Example 2, the electrolyte was 0.1M KOH at 1.23V. RHE Under bias voltage, 1.75 mW / cm² was obtained. 2 The photocurrent density.

[0092] In a specific implementation scenario, when the heteropolyacid solution is an ethanol solution of silicotungstic acid (TSA), the steps of the above-described method for preparing α-Fe2O3 photoanodes co-doped with heteropolyacid and FeOOH are as follows:

[0093] The first step is to use high-temperature resistant tape to adhere the cleaned tin oxide (FTO) conductive glass to control the growth shape and location of α-Fe2O3;

[0094] The second step involves preparing a 0.1M FeCl3·6H2O aqueous solution in a hydrothermal reactor and adjusting the pH to 1.5 using hydrochloric acid as a precursor solution for the hydrothermal reaction. The bonded FTO glass is then placed in the precursor solution and reacted at 90℃ for 5 hours to obtain an FTO electrode covered with a β-FeOOH film.

[0095] The third step involves rinsing the β-FeOOH film on the tin oxide (FTO) electrode and drying it at 70°C for 2 hours. Subsequently, it is placed in a tube furnace for high-temperature annealing at 520°C for 2 hours, followed by 750°C for 20 minutes in an Ar atmosphere to obtain the α-Fe2O3 thin film photoanode.

[0096] The fourth step involves preparing an ethanol solution of 0.3 mol / L silicotungstic acid (TSA), measuring 5 μL of the TSA solution, drop-coating it onto the surface of the α-Fe2O3 photoanode, allowing it to stand and dry, and then annealing it at 150℃ for 4 hours to obtain a TSA-doped α-Fe2O3 photoanode (e.g., α-Fe2O3 / TSA photoanode).

[0097] Fifth, a 0.1 mol / L FeSO4 solution was prepared and purged with N2 to remove O2. FeOOH was then deposited on the α-Fe2O3 / TSA photoanode using photodeposition. The photodeposition light source was a xenon lamp equipped with an AM 1.5G filter, illuminating the back of the photoanode at an intensity of 2 mW / cm². 2 The reaction employed a traditional three-electrode system, using α-Fe₂O₃ / TSA as the working electrode, Pt as the counter electrode, and Ag / AgCl as the reference electrode. An oxygen-removed FeSO₄ solution was used as the electrolyte. An external voltage of 0.35V vs. Ag / AgCl was applied, and the photodeposition time was 25 min. After photodeposition, an external voltage of 1.2V vs. Ag / AgCl was applied for electrodeposition for 2 min, yielding a TSA and FeOOH co-doped α-Fe₂O₃ photoanode (e.g., α-Fe₂O₃ / TSA / FeOOH photoanode).

[0098] In Example 3, the electrolyte was 0.1M KOH at 1.23V. RHE Under bias voltage, 1.69 mW / cm² was obtained. 2 The photocurrent density.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an α-Fe₂O₃ photoanode co-doped with heteropolyacid and FeOOH, characterized in that, include: The cleaned tin oxide conductive glass was placed in a pre-prepared precursor solution for reaction to obtain a tin oxide electrode covered with a β-FeOOH film; The β-FeOOH film on the tin oxide electrode was rinsed and then dried and annealed at high temperature to obtain an α-Fe2O3 film photoanode. A pre-prepared heteropolyacid solution was drop-coated onto the surface of an α-Fe2O3 thin film photoanode to obtain an α-Fe2O3 photoanode doped with heteropolyacid. FeOOH was deposited on an α-Fe2O3 photoanode doped with heteropolyacid to obtain an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH.

2. The method according to claim 1, characterized in that, The precursor solution is prepared in the following manner: A 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH of the aqueous solution was adjusted to 1-2. The adjusted aqueous solution was used as the precursor solution.

3. The method according to claim 1, characterized in that, The reaction temperature was set to 90℃~100℃, and the reaction time was set to 4h~6h.

4. The method according to claim 1, characterized in that, The drying temperature for the drying process is set to 70℃~90℃, and the drying time is set to 2h.

5. The method according to claim 1, characterized in that, The heteropolyacid solution includes at least one of the following: an ethanol solution of phosphomolybdic acid, an ethanol solution of phosphotungstic acid, or an ethanol solution of silicotungstic acid.

6. The method according to claim 1, characterized in that, After the pre-prepared heteropolyacid solution is drop-coated onto the α-Fe2O3 thin film photoanode, the process further includes: After the α-Fe2O3 thin film photoanode was allowed to stand and dry, it was annealed at 120℃~150℃ for 2 hours to obtain the α-Fe2O3 photoanode doped with heteropolyacid.

7. The method according to claim 1, characterized in that, The deposition of FeOOH on an α-Fe2O3 photoanode doped with heteropolyacids includes: The light source is shone onto the back of the α-Fe2O3 photoanode doped with heteropolyacid. The α-Fe2O3 photoanode doped with heteropolyacid is used as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and FeSO4 solution as the electrolyte solution. A first external voltage is applied to perform photodeposition. After photodeposition, a second external voltage is applied for electrodeposition to obtain an α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH.

8. The method according to claim 7, characterized in that, The light source is a xenon lamp with an AM 1.5G filter. The photodeposition time is set to 5 min to 30 min, the electrodeposition time is set to 1 min to 2 min, the first external voltage is 0.3 V to 0.4 V compared to the reference electrode, and the second external voltage is 1.0 V to 1.5 V compared to the reference electrode.

9. An α-Fe2O3 photoanode co-doped with heteropolyacid and FeOOH, prepared by any one of the preparation methods of claims 1-8.

10. The α-Fe₂O₃ photoanode according to claim 9, characterized in that, The α-Fe2O3 photoanode is used in photoelectrocatalytic water splitting for hydrogen production.

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