Heteropolyacid and FeOOH co-doped alpha-Fe2O3 photo-anode and preparation method thereof

Abstract

The invention discloses a heteropoly acid and FeOOH co-doped alpha-Fe2O3 photo-anode and a preparation method thereof, and the preparation method comprises the following steps: placing cleaned tin oxide conductive glass in a precursor solution for reaction to obtain a tin oxide electrode covered with a beta-FeOOH film; washing the beta-FeOOH thin film on the tin oxide electrode, and sequentially carrying out drying treatment and high-temperature annealing treatment on the washed tin oxide electrode to obtain an alpha-Fe2O3 thin film photo-anode; a heteropoly acid solution is dispensed on the surface of the alpha-Fe2O3 thin film photo-anode, and a heteropoly acid doped alpha-Fe2O3 photo-anode is obtained; and FeOOH is deposited on the alpha-Fe2O3 photo-anode doped with the heteropoly acid, so that the alpha-Fe2O3 photo-anode co-doped with the heteropoly acid and the FeOOH is obtained. According to the invention, the heteropoly acid and the FeOOH are loaded on the surface of the alpha-Fe2O3 photo-anode to serve as cocatalysts, so that more excellent photoelectrocatalysis performance can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectrochemical technology, and in particular to an alpha-Fe2O3 photoanode co-doped with a heteropoly acid and FeOOH and a preparation method thereof. Background Art

[0002] Photoelectrocatalytic water splitting is a hydrogen production technology that couples light and electricity. It has the advantages of being sustainable, clean, environmentally friendly, and energy-saving. It is a promising way to produce hydrogen. However, the current solar-to-hydrogen conversion efficiency of this technology is still at a low level. Among them, the water oxidation rate on the surface of the semiconductor photoanode is extremely slow, which inhibits the hydrogen evolution rate on the surface of the photocathode. Therefore, the performance of the photoanode material is an important factor in determining the solar-to-hydrogen conversion efficiency of the photoelectrocatalytic hydrogen production system. Among the many semiconductor photoanodes, metal oxide photoanodes have received widespread attention and achieved rapid development in the past few decades due to their excellent chemical stability and other advantages.

[0003] α-Fe2O3 has a suitable band gap, can absorb visible light below 600nm, and has the advantages of abundant raw materials and high stability. It has become one of the most promising metal oxide photoanode materials.

[0004] However, the α-Fe2O3 photoanode has the disadvantages of short diffusion distance of photogenerated holes, easy recombination of photogenerated electrons and holes, low oxidation kinetics, and poor conductivity, which affect the photoelectric conversion efficiency of α-Fe2O3. The existing preparation methods of α-Fe2O3 photoanode cannot effectively reduce the recombination of photogenerated electrons and holes in α-Fe2O3, and cannot effectively improve the water oxidation ability and conductivity of α-Fe2O3, resulting in poor photoelectrocatalytic performance of α-Fe2O3.

[0005] To address the above problems, no effective solution has been proposed yet. Summary of the invention

[0006] The embodiments of this specification provide a heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode and a preparation method thereof to solve the problem that the prior art cannot effectively reduce the recombination of photogenerated electrons and holes in α-Fe2O3 and cannot effectively improve the water oxidation ability and conductivity of α-Fe2O3, thereby resulting in poor photoelectrocatalytic performance of α-Fe2O3.

[0007] In a first aspect, the present specification provides a method for preparing an α-Fe2O3 photoanode co-doped with a heteropoly acid and FeOOH, the method comprising the following steps:

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

[0009] Washing the β-FeOOH film on the tin oxide electrode and sequentially performing drying treatment and high-temperature annealing treatment on the washed tin oxide electrode to obtain an α-Fe2O3 film photoanode;

[0010] A pre-prepared heteropoly acid solution is drop-coated on the surface of the α-Fe2O3 thin film photoanode to obtain an α-Fe2O3 photoanode doped with heteropoly acid;

[0011] FeOOH is deposited on the α-Fe2O3 photoanode doped with heteropoly acid to obtain the α-Fe2O3 photoanode co-doped with heteropoly acid and FeOOH.

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

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

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

[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 comprises at least one of the following: an ethanol solution of phosphomolybdic acid, an ethanol solution of phosphotungstic acid, and an ethanol solution of silicotungstic acid.

[0017] In some embodiments, after drop coating the pre-configured heteropoly acid solution on the α-Fe2O3 thin film photoanode, the method further comprises:

[0018] The drop-coated α-Fe2O3 thin film photoanode was allowed to stand and dry, and then annealed at a temperature of 120°C to 150°C for 2h to obtain a heteropolyacid-doped α-Fe2O3 photoanode.

[0019] In some embodiments, the step of depositing FeOOH on the α-Fe2O3 photoanode doped with a heteropoly acid comprises:

[0020] The light source is irradiated to the back of the α-Fe2O3 photoanode doped with heteropoly acid, the α-Fe2O3 photoanode doped with heteropoly acid is used as the working electrode, Pt is used as the counter electrode, Ag / AgCl is used as the reference electrode, and FeSO4 solution is used as the electrolyte solution, and a first external voltage is applied to perform photodeposition;

[0021] After the photodeposition is completed, a second external voltage is applied to perform 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 light deposition time is set to 5 minutes to 30 minutes, the electro-deposition time is set to 1 minute to 2 minutes, the first external voltage is a 0.3V to 0.4V external voltage compared to the reference electrode, and the second external voltage is a 1.0V to 1.5V external voltage compared to the reference electrode.

[0023] In a second aspect, the embodiments of this specification also provide an α-Fe2O3 photoanode co-doped with a heteropoly acid and FeOOH, which is prepared by the above preparation method.

[0024] In a third aspect, the α-Fe2O3 photoanode provided in the embodiments of this specification is used in photoelectrocatalytic water decomposition to produce hydrogen.

[0025] The embodiments of this specification provide an α-Fe2O3 photoanode co-doped with a heteropoly acid and FeOOH and a preparation method thereof. First, the 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. Then, the β-FeOOH film on the tin oxide electrode is rinsed and the rinsed tin oxide electrode is dried and annealed at high temperature in sequence to obtain an α-Fe2O3 film photoanode. Then, a heteropoly acid solution is dripped on the surface of the α-Fe2O3 film photoanode to obtain an α-Fe2O3 photoanode doped with a heteropoly acid. Finally, FeOOH is deposited on the α-Fe2O3 photoanode doped with a heteropoly acid to obtain an α-Fe2O3 photoanode co-doped with a heteropoly acid and FeOOH. The present invention can effectively reduce the recombination of photogenerated electrons and holes in α-Fe2O3, improve the water oxidation ability of α-Fe2O3, and enhance the conductivity of α-Fe2O3 by loading heteropoly acid and FeOOH as co-catalysts on the surface of α-Fe2O3 photoanode, thereby obtaining more excellent photoelectrocatalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0027] Figure 1 A schematic flow chart of a method for preparing a heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode provided in an embodiment of this specification;

[0028] Figure 2The SEM images of α-Fe2O3 / PMO / FeOOH in Example 1, α-Fe2O3 in Comparative Example 1 and α-Fe2O3 / PMO in Comparative Example 2 are shown, wherein (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 HRTEM images of the α-Fe2O3 / PMO / FeOOH photoanode of Example 1, wherein (a) and (b) are HRTEM images of the α-Fe2O3 / PMO / FeOOH photoanode at different shooting positions, respectively;

[0030] Figure 4 The α-Fe2O3 / PMO / FeOOH of Example 1, Comparative Example 1, and α-Fe2O3 / PMO of Comparative Example 2 were illuminated with AM1.5G (100 mW / cm 2 ) and linear sweep voltammetry (LSV) curves in dark state;

[0031] Figure 5 The photohydrogen conversion efficiency (ABPE) diagram of Example 1 α-Fe2O3 / PMO / FeOOH, Comparative Example 1 α-Fe2O3 and Comparative Example 2 α-Fe2O3 / PMO;

[0032] Figure 6 The external quantum efficiency (IPCE) diagrams of Example 1 α-Fe2O3 / PMO / FeOOH, Comparative Example 1 α-Fe2O3 and Comparative Example 2 α-Fe2O3 / PMO;

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

[0034] Figure 8 The bulk charge separation efficiency (η) of α-Fe2O3 / PMO / FeOOH in Example 1, α-Fe2O3 in Comparative Example 1, and α-Fe2O3 / PMO in Comparative Example 2 is 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) is the surface charge separation efficiency (η) of α-Fe2O3, α-Fe2O3 / PMO and α-Fe2O3 / PMO / FeOOH surface ). DETAILED DESCRIPTION

[0035] In order 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 in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on the embodiments in this specification, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this specification.

[0036] See also Figure 1 As shown, a method for preparing a heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode provided in an embodiment of this specification may include the following steps.

[0037] S101: placing the cleaned tin oxide conductive glass in a pre-configured precursor solution for reaction to obtain a tin oxide electrode covered with a β-FeOOH film;

[0038] S102: washing the β-FeOOH film on the tin oxide electrode and sequentially performing a drying process and a high-temperature annealing process on the washed tin oxide electrode to obtain an α-Fe2O3 film photoanode;

[0039] S103: drop-coating a pre-configured heteropoly acid solution on the surface of the α-Fe2O3 thin film photoanode to obtain an α-Fe2O3 photoanode doped with heteropoly acid;

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

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

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

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

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

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

[0046] Specifically, the cleaned tin oxide (FTO) conductive glass can be placed in the above-mentioned precursor solution and reacted at 90°C to 100°C for 4h to 6h to obtain a tin oxide (FTO) electrode covered with a β-FeOOH film. The cleaned tin oxide (FTO) conductive glass can be pasted with a high temperature resistant tape to control the growth shape and location of α-Fe2O3.

[0047] In some embodiments, the drying temperature of the drying process in 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 washed and dried at 70°C to 90°C for 2 hours. Subsequently, it is placed in a tube furnace for high-temperature annealing treatment, the annealing temperature is maintained at 500°C to 550°C for 2 hours, and then maintained at 750°C for 20 minutes, the atmosphere is N2 or Ar, and the α-Fe2O3 thin film photoanode is obtained.

[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), and an ethanol solution of silicotungstic acid (TSA).

[0050] In some embodiments, after the α-Fe2O3 thin film photoanode is drop-coated with a pre-configured heteropoly acid solution in S103, the following steps may also be performed:

[0051] The drop-coated α-Fe2O3 thin film photoanode was allowed to stand and dry, and then annealed at a temperature of 120°C to 150°C for 2h to obtain a heteropolyacid-doped α-Fe2O3 photoanode.

[0052] Specifically, a PMO ethanol solution with a concentration of 0.3 mol / L, a PTA ethanol solution with a concentration of 0.2 mol / L, or a TSA ethanol solution with a concentration of 0.3 mol / L can be prepared, and then a certain amount of heteropoly acid solution can be measured and dripped on the surface of the α-Fe2O3 film photoanode, and then dried at 120°C to 150°C for 2 hours to obtain an α-Fe2O3 photoanode doped with heteropoly acid. The concentration of the heteropoly acid solution can be 0.1 mol / L to 0.5 mol / L, and the amount of the heteropoly acid solution measured can be 2 μL to 5 μL.

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

[0054] The light source is irradiated to the back of the heteropoly acid-doped α-Fe2O3 photoanode, the heteropoly acid-doped α-Fe2O3 photoanode is used as the working electrode, Pt is used as the counter electrode, and Ag / AgCl is used as the reference electrode, and a first external voltage is applied to perform photodeposition;

[0055] After the photodeposition is completed, a second external voltage is applied to perform electrodeposition to obtain an α-Fe2O3 photoanode co-doped with heteropoly acid and FeOOH.

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

[0057] Specifically, a FeSO4 solution with a concentration of 0.1 mol / L can be prepared, and the solution can be purged with N2 to remove oxygen. FeOOH is deposited on the α-Fe2O3 photoanode doped with heteropolyacid by photo / electrodeposition. The light source for photodeposition is a xenon lamp equipped with an AM 1.5G filter, and the light source irradiates the back of the photoanode with a light intensity of 1 to 5 mW / cm 2The reaction adopts a traditional three-electrode system, with a heteropoly acid-doped α-Fe2O3 photoanode (such as α-Fe2O3 / PMO) as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and a FeSO4 solution that has been deoxygenated as the electrolyte solution. An external voltage of 0.3-0.4V vs.Ag / AgCl (the first external voltage) is applied, and the photodeposition time is 5min-30min. After the photodeposition is completed, an external voltage of 1.0-1.5V vs.Ag / AgCl (the second external voltage) is applied for electrodeposition, and the electrodeposition time is 1min-2min to obtain an α-Fe2O3 photoanode co-doped with heteropoly acid and FeOOH.

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

[0059] In some embodiments, the above-mentioned heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode is used in photoelectrocatalytic water decomposition to produce hydrogen.

[0060] Specifically, the heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode can be used as a co-catalyst for photoelectrocatalytic water decomposition.

[0061] By loading heteropoly acid and FeOOH as co-catalysts on the surface of α-Fe2O3 photoanode, the recombination of photogenerated electrons and holes in α-Fe2O3 is reduced, and the water oxidation ability of α-Fe2O3 is improved. The constructed heteropoly acid and FeOOH co-doped α-Fe2O3 photoanode (such as: α-Fe2O3 / phosphomolybdic acid (PMO) / FeOOH photoanode) has better photoelectrocatalytic performance. At 1.23V vs. RHE, the photocurrent density is 1.81mA / cm 2 , which is about 3 times the photocurrent density of α-Fe2O3. RHE is the abbreviation of Reversible Hydrogen Electrode, V is the unit of voltage, volt, and vs. may mean "relative to" or "comparison".

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

[0063] Example 1

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

[0065] In the second step, a 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH was adjusted to 1.5 with hydrochloric acid as a precursor solution for the hydrothermal reaction. The pasted FTO glass was placed in the precursor solution and reacted at 90°C for 5h to obtain a tin oxide (FTO) electrode covered with a β-FeOOH film.

[0066] In the third step, the β-FeOOH film on the tin oxide (FTO) electrode was rinsed and dried at 70°C for 2h. Subsequently, it was placed in a tube furnace for high-temperature annealing treatment, the annealing temperature was maintained at 520°C for 2h, and then maintained at 750°C for 20min in an Ar atmosphere to obtain an α-Fe2O3 thin film photoanode.

[0067] The fourth step is to prepare an ethanol solution of phosphomolybdic acid (PMO) with a concentration of 0.3 mol / L, measure 3 μL of PMO solution, and drop it on the surface of the α-Fe2O3 thin film photoanode, let it stand to dry, and then anneal it at 150°C for 3 hours to obtain a PMO-doped α-Fe2O3 photoanode (α-Fe2O3 / PMO photoanode).

[0068] The fifth step is to prepare a FeSO4 solution with a concentration of 0.1 mol / L and purge the solution with N2 to remove O2. FeOOH is deposited on the α-Fe2O3 / PMO photoanode using the photo / electrodeposition method. The light source for the photodeposition is a xenon lamp equipped with an AM 1.5G filter, and the light source is irradiated to the back of the photoanode with a light intensity of 2mW / cm 2 The reaction adopts the traditional three-electrode system, with α-Fe2O3 / PMO as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and the FeSO4 solution with oxygen removed as the electrolyte solution. An external voltage of 0.35V vs.Ag / AgCl is applied, and the photodeposition time is 20min. After the photodeposition is completed, an external voltage of 1.2V vs.Ag / AgCl is applied for electrodeposition, and the electrodeposition time is 1.5min to obtain a PMO and FeOOH co-doped α-Fe2O3 photoanode (such as: α-Fe2O3 / PMO / FeOOH photoanode).

[0069] Comparative Example 1

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

[0071] In the second step, a 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH was adjusted to 1.5 with hydrochloric acid as a precursor solution for the hydrothermal reaction. The pasted FTO glass was placed in the precursor solution and reacted at 90°C for 5h to obtain an FTO electrode covered with a β-FeOOH film.

[0072] In the third step, the β-FeOOH film on the tin oxide (FTO) electrode was rinsed and dried at 70°C for 2h. Subsequently, it was placed in a tube furnace for high-temperature annealing treatment, the annealing temperature was maintained at 520°C for 2h, and then maintained at 750°C for 20min in an Ar atmosphere to obtain an α-Fe2O3 thin film photoanode.

[0073] Comparative Example 2

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

[0075] In the second step, a 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH was adjusted to 1.5 with hydrochloric acid as a precursor solution for the hydrothermal reaction. The pasted FTO glass was placed in the precursor solution and reacted at 90°C for 5h to obtain an FTO electrode covered with a β-FeOOH film.

[0076] In the third step, the β-FeOOH film on the tin oxide (FTO) electrode was rinsed and dried at 70°C for 2h. Subsequently, it was placed in a tube furnace for high-temperature annealing treatment, the annealing temperature was maintained at 520°C for 2h, and then maintained at 750°C for 20min in an Ar atmosphere to obtain an α-Fe2O3 thin film photoanode.

[0077] The fourth step is to prepare an ethanol solution of PMO with a concentration of 0.3 mol / L, measure 3 μL of PMO solution, and drop it on the surface of the α-Fe2O3 photoanode, let it stand to dry, and then anneal it at 150°C for 3 hours to obtain a PMO-doped α-Fe2O3 photoanode (α-Fe2O3 / PMO photoanode).

[0078] See also Figure 2 As shown in (a), (b), (c), (d), (e) and (f), the comparative example 1 α-Fe2O3 presents a dispersed nanorod structure, and the nanorod structure of the embodiment 1 α-Fe2O3 / PMO / FeOOH and the comparative example 2 α-Fe2O3 / PMO is more compact, which is beneficial to increase the contact area with the electrolyte and improve the interfacial charge transfer efficiency. Wherein, SEM is a scanning electron microscope, and the pixel size of the SEM image is 200nm.

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

[0080] See also 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 -4 mW / cm 2 , 1.48×10 -3 mW / cm 2 and 2.28×10 - 3 mW / cm 2 The current density of the three photoanodes in the dark state is very small, and the water electrolysis performance is weak. The photocurrent density of α-Fe2O3, α-Fe2O3 / PMO and α-Fe2O3 / PMO / FeOOH under illumination is 0.63mW / cm 2 , 1.12mW / cm 2 and 1.81mW / cm 2 Compared with α-Fe2O3 and α-Fe2O3 / PMO, α-Fe2O3 / PMO / FeOOH exhibits a larger photocurrent density, indicating that it has the most excellent photoelectrocatalytic water splitting performance.

[0081] See also 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-to-hydrogen conversion efficiencies ABPE were 0.07%, 0.11% and 0.18% respectively.

[0082] See also Figure 6 As shown, at 320nm~620nm, α-Fe2O3 / PMO / FeOOH has the best external quantum efficiency, indicating that it has the highest photon absorption efficiency.

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

[0084] See also Figure 8 As shown in (a) and (b) in Figure 2, compared with α-Fe2O3 and α-Fe2O3 / PMO, α-Fe2O3 / PMO / FeOOH has a higher bulk charge separation efficiency η bulk and surface charge separation efficiency η surface Since the higher photocurrent density comes from the full utilization of photogenerated holes, it shows 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 heteropoly acid solution is an ethanol solution of phosphotungstic acid (PTA), the steps of the above-mentioned method for preparing an α-Fe2O3 photoanode co-doped with heteropoly acid and FeOOH are as follows:

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

[0087] In the second step, a 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH was adjusted to 1.5 with hydrochloric acid as a precursor solution for the hydrothermal reaction. The pasted FTO glass was placed in the precursor solution and reacted at 90°C for 5h to obtain an FTO electrode covered with a β-FeOOH film.

[0088] In the third step, the β-FeOOH film on the tin oxide (FTO) electrode was rinsed and dried at 70°C for 2h. Subsequently, it was placed in a tube furnace for high-temperature annealing treatment, the annealing temperature was maintained at 520°C for 2h, and then maintained at 750°C for 20min in an Ar atmosphere to obtain an α-Fe2O3 thin film photoanode.

[0089] The fourth step is to prepare an ethanol solution of phosphotungstic acid (PTA) with a concentration of 0.2 mol / L, measure 3 μL of PTA solution, and drop it on the surface of the α-Fe2O3 photoanode, let it stand to dry, and then anneal it at 120°C for 3 hours to obtain a PTA-doped α-Fe2O3 photoanode (such as: α-Fe2O3 / PTA photoanode).

[0090] The fifth step is to prepare a FeSO4 solution with a concentration of 0.1 mol / L and purge the solution with N2 to remove O2. FeOOH is deposited on the α-Fe2O3 / PTA photoanode using the photo / electrodeposition method. The light source for the photodeposition is a xenon lamp equipped with an AM 1.5G filter, and the light source is irradiated to the back of the photoanode with a light intensity of 2mW / cm2 The reaction adopts the traditional three-electrode system, with α-Fe2O3 / PTA as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and the FeSO4 solution with oxygen removed as the electrolyte solution. An external voltage of 0.35V vs.Ag / AgCl is applied, and the photodeposition time is 30min. After the photodeposition is completed, an external voltage of 1.2V vs.Ag / AgCl is applied for electrodeposition, and the electrodeposition time is 1.0min to obtain a PTA and FeOOH co-doped α-Fe2O3 photoanode (such as: α-Fe2O3 / PTA / FeOOH photoanode).

[0091] In this example 2, the RHE Under bias, 1.75mW / cm 2 The photocurrent density.

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

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

[0094] In the second step, a 0.1M FeCl3·6H2O aqueous solution was prepared in a hydrothermal reactor, and the pH was adjusted to 1.5 with hydrochloric acid as a precursor solution for the hydrothermal reaction. The pasted FTO glass was placed in the precursor solution and reacted at 90°C for 5h to obtain an FTO electrode covered with a β-FeOOH film.

[0095] In the third step, the β-FeOOH film on the tin oxide (FTO) electrode was rinsed and dried at 70°C for 2h. Subsequently, it was placed in a tube furnace for high-temperature annealing treatment, the annealing temperature was maintained at 520°C for 2h, and then maintained at 750°C for 20min in an Ar atmosphere to obtain an α-Fe2O3 thin film photoanode.

[0096] The fourth step is to prepare an ethanol solution of silicotungstic acid (TSA) with a concentration of 0.3 mol / L, measure 5 μL of TSA solution, and drop it on the surface of the α-Fe2O3 photoanode, let it stand to dry, and then anneal it at 150°C for 4 hours to obtain a TSA-doped α-Fe2O3 photoanode (such as: α-Fe2O3 / TSA photoanode).

[0097] The fifth step is to prepare a FeSO4 solution with a concentration of 0.1 mol / L and purge the solution with N2 to remove O2. FeOOH is deposited on the α-Fe2O3 / TSA photoanode using a photo / electrodeposition method. The light source for the photodeposition is a xenon lamp equipped with an AM 1.5G filter, and the light source is irradiated to the back of the photoanode with a light intensity of 2mW / cm 2 The reaction adopts the traditional three-electrode system, with α-Fe2O3 / TSA as the working electrode, Pt as the counter electrode, Ag / AgCl as the reference electrode, and the FeSO4 solution with oxygen removed as the electrolyte solution. An external voltage of 0.35V vs.Ag / AgCl is applied, and the photodeposition time is 25min. After the photodeposition is completed, an external voltage of 1.2V vs.Ag / AgCl is applied for electrodeposition, and the electrodeposition time is 2min to obtain a TSA and FeOOH co-doped α-Fe2O3 photoanode (such as: α-Fe2O3 / TSA / FeOOH photoanode).

[0098] In this example 3, the RHE Under bias, 1.69mW / cm 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a heteropolyacid and FeOOH co-doped α-Fe2O3 photoanode, characterized in that: include: The cleaned tin oxide conductive glass is placed in a pre-configured precursor solution for reaction to obtain a tin oxide electrode covered with a β-FeOOH film; Washing the β-FeOOH film on the tin oxide electrode and sequentially performing drying treatment and high-temperature annealing treatment on the washed tin oxide electrode to obtain an α-Fe2O3 film photoanode; A pre-prepared heteropoly acid solution is drop-coated on the surface of the α-Fe2O3 thin film photoanode to obtain an α-Fe2O3 photoanode doped with heteropoly acid; FeOOH is deposited on the α-Fe2O3 photoanode doped with heteropoly acid to obtain the α-Fe2O3 photoanode co-doped with heteropoly acid and FeOOH.

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

3. The method according to claim 1, characterized in that The reaction temperature of the reaction is set to 90° C. to 100° C., and the reaction time is set to 4 h to 6 h.

4. The method according to claim 1, characterized in that: The drying temperature of the drying process is set to 70° C. to 90° C., and the drying time is set to 2 hours.

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

6. The method according to claim 1, characterized in that After the α-Fe2O3 thin film photoanode is drop-coated with a pre-configured heteropoly acid solution, the method further comprises: The drop-coated α-Fe2O3 thin film photoanode was allowed to stand and dry, and then annealed at a temperature of 120°C to 150°C for 2h to obtain a heteropolyacid-doped α-Fe2O3 photoanode.

7. The method according to claim 1, characterized in that The method of depositing FeOOH on the α-Fe2O3 photoanode doped with heteropoly acid comprises: The light source is irradiated to the back of the α-Fe2O3 photoanode doped with heteropoly acid, the α-Fe2O3 photoanode doped with heteropoly acid is used as the working electrode, Pt is used as the counter electrode, Ag / AgCl is used as the reference electrode, and FeSO4 solution is used as the electrolyte solution, and a first external voltage is applied to perform photodeposition; After the photodeposition is completed, a second external voltage is applied to perform 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 light deposition time is set to 5 minutes to 30 minutes, the electro-deposition time is set to 1 minute to 2 minutes, the first external voltage is a 0.3V to 0.4V external voltage compared to the reference electrode, and the second external voltage is a 1.0V to 1.5V external voltage compared to the reference electrode.

9. An α-Fe2O3 photoanode co-doped with a heteropoly acid and FeOOH, prepared by the preparation method according to any one of claims 1 to 8.

10. The α-Fe2O3 photoanode according to claim 9, characterized in that: The α-Fe2O3 photoanode is used in photoelectrocatalytic water decomposition to produce hydrogen.

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