Three-dimensional ordered pore structure integrated electrode and preparation method thereof

Abstract

The invention relates to the field of catalytic energy, and provides a three-dimensional ordered pore structure integrated electrode and a preparation method thereof.A narrow-band-gap semiconductor is arranged on the upper layer of a photoelectrode to absorb light with low energy, and a wide-band-gap semiconductor is arranged on the lower layer of the photoelectrode to absorb light with high energy, so that the photocatalytic reaction area and reaction active sites are increased, and the photocatalytic activity is improved. The separation of photo-induced electron-hole pairs and the utilization efficiency of solar energy are improved, the photoelectrocatalytic activity and stability are improved, and the material has excellent performance when being used as a catalyst for producing hydrogen by photoelectrocatalytic decomposition of water. The preparation method comprises the steps of metal pretreatment and preparation of the highly ordered array and three-dimensional structure heterojunction composite photoelectrocatalysis integrated electrode. The electrode overcomes the problems that a traditional powder catalyst is low in light utilization efficiency, difficult to fall off and recover, large in transfer resistance, complex in preparation process and not environmentally friendly, and has wide application prospects in the fields of efficient electro-catalytic decomposition of water, degradation of pollutants and hydrogen production.

Description

Technical Field

[0001] The present invention relates to the field of catalytic energy, and in particular to an integrated electrode with a three-dimensional ordered pore structure, a preparation method thereof, and an application thereof as a photoelectric catalyst. Background Art

[0002] Solar photoelectrochemistry (PEC) utilizes the inexhaustible energy of solar energy as an energy source. It is low-carbon, environmentally friendly, sustainable, and has broad development prospects. Currently, catalysts used in solar photoelectrocatalytic water splitting technology focus on materials such as TiO2, C3N4, sulfides, graphene, and metal-organic frameworks (MOFs). Among various photocatalyst materials, TiO2 has attracted widespread attention since its publication by Fuijishima and Honda (Nature, 1972, 238(5358): 37-38). As a traditional semiconductor photocatalyst, TiO2 possesses conductivity and a valence band suitable for redox reactions. However, its wide band gap (3.2 eV) and weak visible light response severely limit its application in photocatalysis.

[0003] Currently, with the continuous deepening of research on photoelectrocatalytic water splitting to produce hydrogen, electrode materials are developing in a diversified and multi-level direction. Perovskite oxides have a narrow band gap, can be excited by visible light, and are inexpensive, making them currently highly promising semiconductor photocatalytic materials. Lanthanum ferrite (LaFeO3), as a narrow-bandgap P-type semiconductor photocatalytic material (<2.3 eV) (Applied Surface Science, 2019, 471, 185-195), can respond well to visible light and has advantages that traditional TiO2 cannot match. Therefore, constructing a LaFeO3 / TiO2 binary heterojunction can fully utilize the valence band potential of LaFeO3 and TiO2, thereby improving the efficiency of solar light utilization.

[0004] Three-dimensional pore structure electrodes have advantages such as developed pore structure, large available specific surface area, and multiple reaction active sites. They are conducive to the transfer of reactants and charges, the storage of intermediate products, surface and interfacial reactions, and the alleviation of volume and internal stress changes during the cycle. They have broad application prospects in batteries, supercapacitors, photo / electrocatalysis and other fields.

[0005] The concept of this invention is to address the low light utilization efficiency of existing photocatalysts by combining narrow-bandgap and wide-bandgap semiconductors to form a heterojunction structure. The narrow-bandgap semiconductor is placed on the upper layer of the photoelectrode to absorb lower-energy light, while the wide-bandgap semiconductor is placed on the lower layer to absorb higher-energy light. This improves the utilization and stability of sunlight during the PEC water splitting hydrogen production process, while reducing internal stress and deformation in the electrode. Currently, there are no reports on the preparation of a LaFeO3 / TiO2 heterojunction photocatalytic integrated electrode with a three-dimensional ordered pore structure and its application in solar photocatalytic water splitting hydrogen production. Summary of the Invention

[0006] The purpose of the present invention is to provide a LaFeO3 / TiO2 heterojunction photocatalytic integrated electrode with a three-dimensional ordered pore structure, a preparation method thereof, and an application as a photoelectrocatalyst in water decomposition and hydrogen production. The present invention aims to solve the problems of low light utilization efficiency, weak binding force between heterojunctions, easy detachment of catalysts, difficulty in recycling powder catalysts, complex and environmentally unfriendly preparation processes in existing photoelectrocatalysts, increase the effective photocatalytic reaction area and reaction active sites, strengthen the transmission and separation and utilization of photogenerated electron-hole pairs, enhance the photoelectrocatalytic activity and stability of the catalyst, and improve light utilization efficiency. The electrode is binder-free and not easy to fall off, which facilitates catalyst recycling.

[0007] In a first aspect, an embodiment of the present invention provides an integrated electrode with a three-dimensional ordered pore structure, comprising: The electrode consists of an array and particles; the particles cover the surface of the array.

[0008] Optionally, the array is formed directly on the metal substrate, and the particles are formed directly on the array without the need for a binder.

[0009] In a second aspect, an embodiment of the present invention provides a method for preparing an integrated electrode with a three-dimensional ordered pore structure, comprising: Step 1: Pretreatment of titanium sheet cutting the titanium sheet into a suitable size, cleaning and vacuum drying the sheet to obtain a pretreated titanium sheet; Step 2: Prepare TiO2 array tubes Anodic oxidation was carried out using a pretreated titanium sheet as the anode, graphite as the cathode, and an aqueous solution containing NH4F and ethylene glycol as the electrolyte. After cleaning, heat treatment was performed to obtain a highly ordered TiO2 array grown on the Ti substrate; Step 3: Prepare a three-dimensional ordered pore structure LaFeO3 / TiO2 integrated electrode using a TiO2 array grown on Ti as the cathode, graphite as the anode, and an aqueous solution containing FeCl2, La(NO3)3 and KNO3 as the electrolyte to electrochemically synthesize particles; After cleaning and vacuum drying, a LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered pore structure is obtained by heat treatment.

[0010] Optionally, in step 2 of the method for preparing an integrated electrode with a three-dimensional ordered pore structure, the mass fraction of NH4F is 0.4-0.6%, the volume concentration of ethylene glycol is 90-98%, the anodizing voltage is 20-50 V, the anodizing treatment time is 10-30 min, and the electrolyte temperature is 25-50°C.

[0011] Optionally, in step 2 of the method for preparing an integrated electrode with a three-dimensional ordered pore structure, the heat treatment temperature is 400-600° C., and the heat treatment time is 1-3 hours.

[0012] Optionally, in step three of the method for preparing an integrated electrode with a three-dimensional ordered pore structure, the concentration of FeCl2 in the electrolyte is 0.005-0.025 mol / L, the concentration of La(NO3)3 is 0.005-0.025 mol / L, the concentration of KNO3 is 0.05-0.25 mol / L, the voltage of the electrochemically synthesized particles is 1.0-2.5 V, the time for the electrochemical synthesis of particles is 20-50 s, and the electrolyte temperature is maintained at 20-50°C.

[0013] Optionally, in step three of the method for preparing an integrated electrode with a three-dimensional ordered pore structure, the heat treatment temperature is 400-600° C., and the heat treatment time is 1-3 h.

[0014] Optionally, the integrated electrode is prepared by any of the above methods, and the three-dimensional ordered pore structure LaFeO3 / TiO2 integrated electrode includes: a TiO2 array formed on a Ti substrate and LaFeO3 particles on the surface or inside the TiO2 array; the LaFeO3 is formed by an in-situ reaction of iron-containing lanthanum raw materials directly on the surface or inside the porous three-dimensional substrate to form a LaFeO3 / TiO2 binary heterojunction without the need for an adhesive.

[0015] In a third aspect, the present invention provides the application of the above-mentioned LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered heterojunction pore structure in photoelectrocatalysis, which has high hydrogen production activity when used as a photoelectrode in solar PEC water decomposition to produce hydrogen.

[0016] The three-dimensional ordered pore structure integrated electrode is different from the existing array or powder catalysts. Anodization is first used to form an array tube on a metal substrate, and then the catalyst is deposited on the surface of the array tube to form a three-dimensional ordered pore structure integrated electrode. In the three-dimensional ordered pore structure integrated electrode, different catalysts form a heterojunction and the binding force is significantly enhanced compared with the existing technology. Different wavelengths of light can be used to increase the effective photocatalytic reaction area and reaction active sites, strengthen the transmission and separation and utilization of photogenerated electron-hole pairs, enhance the photoelectrocatalytic activity and stability of the catalyst, and improve the light utilization efficiency. The electrode has no binder and is not easy to fall off, which facilitates the recycling of the catalyst.

[0017] The three-dimensional ordered pore structure integrated electrode is based on titanium metal, and has high strength, good conductivity and toughness, and good corrosion resistance, which can overcome the application limitations of traditional granular catalysts. By using the anodizing method, TiO2 nano-array tubes with a highly ordered surface and a three-dimensional pore structure can be prepared, which greatly increases the loading area of the base material and enhances ion and charge transfer.

[0018] In the described integrated electrode with a three-dimensional ordered pore structure, narrow-bandgap LaFeO₃ particles are distributed on the surface of a wide-bandgap TiO₂ array tube, forming a LaFeO₃ / TiO₂ heterojunction composite photoelectrocatalytic electrode. The LaFeO₃ enhances the electrode's photoelectrocatalytic performance, increasing photoresponse and photocurrent. Furthermore, under an applied electric field, it enables rapid and effective separation of photogenerated electrons and holes, improving the electrode's hydrogen production efficiency and pollutant treatment efficiency. This makes it widely applicable for the PEC synergistic degradation of organic pollutants and the co-production of hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 Schematic diagram of the prepared integrated electrode with three-dimensional ordered pore structure.

[0021] Figure 2 The response current-voltage curves of the LaFeO3 / TiO2 integrated electrode and the TiO2 electrode prepared in Example 1 of the present invention under simulated sunlight irradiation conditions; Figure 3 The response current-voltage curves of the LaFeO3 / TiO2 integrated electrode prepared in Example 1 of the present invention under dark light and simulated sunlight irradiation conditions respectively; Figure 4This is the response current-time curve of the LaFeO3 / TiO2 integrated electrode prepared in Example 1 of the present invention under alternating light and dark conditions. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0023] This embodiment provides an integrated electrode with a three-dimensional ordered pore structure, a preparation method thereof, and an application thereof as a catalyst in photoelectrocatalytic water decomposition to produce hydrogen. The preparation method comprises the following steps: Example 1

[0024] Titanium sheets were cut to appropriate sizes and polished to a smooth surface. The polished sheets were then ultrasonically treated with acetone, ethanol, and deionized water to clean the surface grease. The degreased sheets were then dried in a vacuum oven to obtain pretreated titanium sheets. A two-electrode system was constructed using the pretreated titanium sheet as the anode and high-purity graphite as the cathode. Anodization was performed under a DC power supply using an electrolyte solution containing 0.5% (mass fraction) NH4F and 98% (volume fraction) ethylene glycol in water. Electrolysis was performed at 50 V DC for 20 minutes, with the electrolyte temperature maintained at 25°C. The sample titanium sheet obtained after anodization treatment was cleaned and vacuum-dried, and then calcined in a muffle furnace at 450°C for 3 hours to obtain a TiO2 array with a three-dimensional ordered structure; further, 0.01 mol / L La(NO3)3·6H2O, 0.01 mol / L FeCl2·4H2O and 0.1 mol / L KNO3 aqueous solution were used as the coating solution, and the reaction was carried out at a constant potential of 1.7 V with a DC power supply for 20 seconds. The iron lanthanum precursor was deposited on the surface of the TiO2 array by electrochemical co-deposition of La(OH)3 and Fe(OH)2. After electrodeposition, the mixed metal hydroxide was calcined in air at 500°C for 3 hours to obtain a LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered pore structure, as shown in the schematic diagram. Figure 1 shown.

[0025] The prepared three-dimensional ordered pore structure LaFeO3 / TiO2 integrated electrode was applied as a catalyst in the photoelectrocatalytic water splitting hydrogen production system. The specific photoelectrocatalytic performance test included: using a dual-chamber photoelectrochemical cell, and a perfluorocarboxylic acid / sulfonic acid composite ion exchange membrane (Nafion membrane) to divide the photoelectrochemical cell into two chambers: a cathode chamber and an anode chamber. The cathode chamber and the anode chamber were filled with 0.5 mol / L H2SO4 and 1 mol / L NaOH electrolytes, respectively; using a standard three-electrode test system, the prepared LaFeO3 / TiO2 integrated electrode was used as the photoanode (working electrode), a saturated calomel electrode (SCE) was used as the reference electrode, and a Pt electrode was used as the counter electrode; using a 350 W spherical xenon lamp to simulate sunlight light source, and using a Princeton Applied Research VersaSATA3 electrochemical workstation in the United States, the photoelectrochemical performance of the LaFeO3 / TiO2 integrated electrode prepared under simulated sunlight conditions was measured, including linear voltammetry (IV) curves and current-time (It) curves, as shown in Figure 2. Figure 1 、 Figure 2 and Figure 3 As shown, the performance of the prepared LaFeO3 / TiO2 integrated electrode is significantly higher than that of a single TiO2 array tube. Example 2

[0026] Titanium sheets were cut to appropriate sizes and polished to a smooth surface. The polished sheets were ultrasonically degreased with acetone, ethanol, and deionized water, respectively, and dried in an inert gas stream to obtain pretreated titanium sheets. A two-electrode system was constructed using the pretreated titanium sheet as the anode and graphite as the cathode. Anodization was performed under a DC power supply using an electrolyte containing 0.4% (mass fraction) NH4F and 90% (volume fraction) ethylene glycol in water. Electrolysis was performed at 30 V DC for 30 minutes, with the electrolyte temperature maintained at 35°C. The titanium sample obtained after anodization was cleaned and vacuum-dried, and then calcined in a muffle furnace at 450°C for 2 hours to obtain a TiO2 array with a three-dimensional ordered structure. Furthermore, an iron-lanthanum precursor was deposited on the TiO2 array surface via electrochemical co-deposition of La(OH)3 and Fe(OH)2. The coating solution was an aqueous solution of 0.005 mol / L La(NO3)3·6H2O, 0.005 mol / L FeCl2·4H2O, and 0.08 mol / L KNO3, and the coating was performed under a DC power supply at a constant potential of 2.5 V for 30 s. After electrodeposition, the mixed metal hydroxide film was calcined in air at 400°C for 2 hours to obtain a LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered pore structure. Example 3

[0027] Titanium sheets were cut to appropriate size and polished to a smooth surface. The polished sheets were ultrasonically degreased with acetone, ethanol, and deionized water, respectively, and dried in an inert atmosphere to obtain pretreated titanium sheets. A two-electrode system was constructed with the pretreated titanium sheet as the anode and graphite as the cathode. Anodization was performed under a DC power supply using an electrolyte containing 0.6% (mass fraction) NH₄F and 93% (volume fraction) ethylene glycol in water at 20 V DC for 10 minutes, with the electrolyte temperature maintained at 46°C. The resulting titanium sheet was cleaned and vacuum-dried, and then calcined in a muffle furnace at 600°C for one hour to obtain a three-dimensional ordered TiO₂ array. Furthermore, an iron-lanthanum precursor was deposited on the TiO2 array surface via electrochemical co-deposition of La(OH)3 and Fe(OH)2. The coating was performed using an aqueous solution of 0.025 mol / L La(NO3)3·6H2O, 0.025 mol / L FeCl2·4H2O, and 0.25 mol / L KNO3 at a constant potential of 1.0 V using a DC power supply for 50 s. After electrodeposition, the mixed metal hydroxide film was calcined in air at 600°C for 1 hour to obtain a LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered pore structure. Example 4

[0028] Titanium sheets were cut to appropriate size and polished to a smooth surface. The polished sheets were ultrasonically degreased with acetone, ethanol, and deionized water, respectively, and dried in an inert atmosphere to obtain pretreated titanium sheets. A two-electrode system was constructed with the pretreated titanium sheet as the anode and graphite as the cathode. Anodization was performed under a DC power supply using an electrolyte containing 0.6% (mass fraction) NH₄F and 96% (volume fraction) ethylene glycol in water at 40 V DC for 15 minutes, with the electrolyte temperature maintained at 50°C. The resulting anodized titanium sheet was cleaned and vacuum-dried, and then calcined in a muffle furnace at 400°C for 2.6 hours to obtain a three-dimensional ordered TiO₂ array. Furthermore, an iron-lanthanum precursor was deposited on the TiO2 array surface via electrochemical co-deposition of La(OH)3 and Fe(OH)2. Deposition was performed using an aqueous solution of 0.007 mol / L La(NO3)3·6H2O, 0.007 mol / L FeCl2·4H2O, and 0.11 mol / L KNO3 as the coating solution, under a DC power supply at a constant potential of 2.0 V for 40 s. After electrodeposition, the mixed metal hydroxide film was calcined in air at 460°C for 1.5 hours to obtain a LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered pore structure.

Claims

1. A three-dimensional ordered pore structure integrated electrode and its preparation method, characterized in that: include: The electrodes consist of arrays and particles; The particles cover the surface of the array.

2. The three-dimensional ordered pore structure integrated electrode and preparation method thereof according to claim 1, characterized in that: The array is directly formed on the metal substrate, and the particles are directly formed on the array without the need for a binder.

3. The three-dimensional ordered pore structure integrated electrode and the preparation method thereof according to claims 1 and 2, characterized in that: include: Step 1: Pretreatment of titanium sheet cutting the titanium sheet into a suitable size, cleaning and vacuum drying the sheet to obtain a pretreated titanium sheet; Step 2: Prepare TiO2 array tubes Anodic oxidation was carried out using a pretreated titanium sheet as the anode, graphite as the cathode, and an aqueous solution containing NH4F and ethylene glycol as the electrolyte. After cleaning, heat treatment was performed to obtain a highly ordered TiO2 array grown on the Ti substrate; Step 3: Preparation of three-dimensional ordered pore structure LaFeO3 / TiO2 integrated electrode The particles were electrochemically synthesized using a TiO2 array grown on Ti as the cathode, graphite as the anode, and an aqueous solution containing FeCl2, La(NO3)3, and KNO3 as the electrolyte. After cleaning and vacuum drying, a LaFeO3 / TiO2 integrated electrode with a three-dimensional ordered pore structure is obtained by heat treatment.

4. The three-dimensional ordered pore structure integrated electrode and the preparation method thereof according to claim 3, characterized in that: In the step 2, the mass fraction of NH4F is 0.4-0.6%, the volume concentration of ethylene glycol is 90-98%, the voltage of the anodizing is 20-50V, the treatment time of the anodizing is 10-30min, and the temperature of the electrolyte is 25-50°C.

5. The three-dimensional ordered pore structure integrated electrode and the preparation method thereof according to claim 3, characterized in that: In the step 2, the heat treatment temperature is 400-600° C., and the heat treatment time is 1-3 hours.

6. The three-dimensional ordered pore structure integrated electrode and the preparation method thereof according to claim 3, characterized in that: In the step three, the concentration of FeCl2 in the electrolyte is 0.005-0.025 mol / L, the concentration of La(NO3)3 is 0.005-0.025 mol / L, the concentration of KNO3 is 0.05-0.25 mol / L, the voltage of the electrochemically synthesized particles is 1.0-2.5 V, the time of the electrochemically synthesized particles is 20-50 s, and the electrolyte temperature is maintained at 20-50°C.

7. The three-dimensional ordered pore structure integrated electrode and the preparation method thereof according to claim 3, characterized in that: In the step 3, the heat treatment temperature is 400-600° C., and the heat treatment time is 1-3 h.

8. A three-dimensional ordered pore structure integrated electrode and its preparation method, characterized by: The integrated electrode is prepared according to any one of the methods of claims 1 to 7, and the LaFeO3 particles of the prepared three-dimensional ordered pore structure LaFeO3 / TiO2 integrated electrode are deposited on the surface or inside the TiO2 array.

9. A three-dimensional ordered pore structure integrated electrode and its preparation method, characterized by: The synthesized particles can form a film on the surface of the array.

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