Ti@TiO2 Array@Cu x Pt Alloy Composite Electrode and Its Preparation and Application in Photoelectrocatalytic Reduction of NO3 - to Ammonia

Abstract

The present invention belongs to the field of photocatalytic ammonia production, and specifically discloses a Ti@TiO2 array@Cu x Pt alloy composite electrode and its preparation and application in photocatalytic NO3 ‑ reduction for ammonia production. Among them, the Ti@TiO2 array@Cu x Pt alloy composite electrode includes a Ti substrate, a TiO2 nanosheet array in-situ grown on the surface of the Ti substrate, and nano Cu x Pt alloy particles dispersed on the TiO2 nanosheet array; the TiO2 nanosheets in the TiO2 nanosheet array grow along the Z-axis direction of the Ti substrate; there is a heterojunction interface between the nano Cu x Pt alloy particles and the TiO2 nanosheet array. The self-supporting material of the present invention has excellent NH3 production activity, Faraday efficiency and stability.

Description

Technical Field

[0001] The present invention belongs to the field of photoelectrocatalytic electrodes, and particularly relates to the field of catalytic electrodes for the reduction of NO3 - (nitrate) to synthesize ammonia. Background Art

[0002] Ammonia (NH3), as an important industrial raw material, is widely used in the fields of fertilizer production, pharmaceuticals, and chemical manufacturing. However, the traditional Haber-Bosch process has problems such as high energy consumption and serious greenhouse gas emissions. The photoelectrocatalytic nitrate reduction (PEC-NO3 - RR) technology that couples solar energy driving with an electrocatalytic system, by photon injection to reduce the activation energy barrier of nitrogen intermediates and synergistically applying an external bias voltage to accelerate the reaction kinetics, has become an effective strategy to improve energy efficiency. However, the industrial development of the photocathode reduction of NO3 - to synthesize ammonia is restricted by the catalyst, mainly in the following four aspects: ① The photocathode catalytic materials generally have problems such as low light absorption efficiency, poor carrier mobility, and insufficient ammonia production rate; ② Traditional catalysts often use metal cocatalysts (such as Pd, Au, Ru) loaded on a substrate support material, and noble metal platinum particles are loaded on a carbon support. The reserves of noble metals are scarce and the price is expensive, resulting in a high overall cost of the catalyst; ③ In the actual operating environment of the photoelectrocatalytic reduction of NO3 - to synthesize ammonia, problems such as agglomeration, separation, dissolution of the alloy cocatalyst, and corrosion of the support occur, resulting in rapid decay of activity and low overall lifetime of the photocathode; ④ Currently, the photocathode catalyst used for the photoelectrocatalytic reduction of NO3 - to synthesize ammonia has low activity, resulting in a slow process of cathodic reduction of NO3 - Therefore, reducing the amount of noble metals used, reducing costs, and at the same time improving the activity of the catalyst are urgent needs in the field of photoelectrocatalytic reduction of NO3 - to synthesize ammonia.

[0003] There are also some existing technologies for the photoelectrocatalytic reduction of NO3 -Methods for synthesizing ammonia, for example, Chinese Patent Publication No. CN119530860A discloses a preparation method of a self-decomposing composite catalyst and its application in constructing a photoelectrochemical cell for ammonia production; the preparation method of the self-decomposing composite catalyst is to mix and dissolve copper acetate, cobalt acetate, and urea, and then place the treated titanium mesh in a reaction kettle. After hydrothermal treatment, a precursor material is obtained. During the calcination process in a muffle furnace, CuCo2O4 decomposes itself to produce CuO, forming an interface-free heterojunction, and obtaining an integrated electrode loaded with the catalyst for photocatalytic reduction of nitrate to ammonia. In addition, Chinese Patent Document No. CN118835273A discloses a preparation method of a Cu2O@NiFe2O4 / Ni integrated electrode and its application in ammonia synthesis. The preparation method includes using the ascorbic acid reduction method to prepare a Cu2O nanocube template, and then according to Pearson's acid-base theory, using sodium thiosulfate to etch the Cu2O cube. At the same time, using the alkaline environment generated by the etching to grow nickel-iron double hydroxide (NiFe-LDH) on the outer layer of the cube. Coating Cu2O@NiFe-LDH on Ni foam and annealing at 350 °C to obtain the Cu2O@NiFe2O4 / Ni integrated electrode. Another example is that Chinese Patent Document No. CN114411175A discloses a preparation method of an amorphous metal oxide-modified p-BiVO4 composite heterojunction. First, immerse a cleaned FTO glass sheet into a mixed aqueous solution of ammonium metavanadate and bismuth nitrate, and hydrothermally prepare an FTO sheet loaded with p-BiVO4; then mix X(OAc)2 and YCl2 according to a mass ratio of 2:1, and then mix with an ethylene glycol solution of sodium acetate, and stir evenly to obtain a metal salt solution; immerse the FTO sheet loaded with p-BiVO4 into the hydrothermally prepared amorphous metal oxide-modified p-BiVO4 composite heterojunction (A-M x O y / p-BiVO4), and after naturally cooling to room temperature, rinse it repeatedly with ethanol and dry it to obtain.

[0004] In summary, although there are some processes for photocatalytic reduction of nitrate to ammonia in the prior art, there is still a large room for improvement in the NH3 yield, Faraday efficiency, cost, and stability of the NH3 prepared by the existing processes. Summary of the Invention

[0005] Aiming at the problems of unsatisfactory NH3 yield, Faraday efficiency, and stability of the existing photocatalytic reduction of NO3 - for ammonia synthesis and relatively high cost, the first object of the present invention is to provide a Ti@TiO2 array@Cu x Pt alloy composite electrode, aiming to provide a composite electrode adapted to photocatalytic reduction of NO3 -A novel self-supporting electrode with the characteristics of ammonia synthesis, which improves its NH3 production, Faraday efficiency, stability, and reduces costs.

[0006] A second object of the present invention is to provide the Ti@TiO2 array@Cu x Preparation method of Pt alloy composite electrode.

[0007] A third object of the present invention is the Ti@TiO2 array@Cu x Pt alloy composite electrode in the photoelectrocatalytic reduction of NO3 - Application in ammonia synthesis.

[0008] A fourth object of the present invention is to provide a device comprising the Ti@TiO2 array@Cu x Pt alloy composite electrode.

[0009] There are different reaction principles in different photoelectrocatalytic fields, and different technical problems need to be overcome. For example, for the photoelectrocatalytic reduction of NO3 - For ammonia synthesis, compared with the electrocatalytic reduction of NO3 - Ammonia synthesis, photocatalytic reduction of NO3 - Ammonia synthesis, photoelectrocatalytic reduction of N2 to ammonia, electrocatalytic reduction of N2 to ammonia, photocatalytic reduction of N2 to ammonia and other types of ammonia synthesis systems have the advantages of fast electron transfer, low reaction energy consumption, strong substrate adsorption, etc.; however, the reaction catalyst is mainly a semiconductor material modified material, which has higher requirements for light absorption efficiency, carrier migration rate, overpotential, stability, Faraday efficiency, etc.; however, at present, semiconductor substrates, especially non-noble metals, still face relatively prominent problems such as insufficient light absorption and poor carrier mobility, making it difficult to meet the requirements of photoelectrochemical reduction of NO3 - Requirements for ammonia synthesis. Therefore, in order to reduce the noble metal cost of the electrode, the present invention attempts to provide an idea of reducing the electrode cost by introducing copper. However, in the early stage of research and development, it was found that simply anchoring a copper-based alloy on a semiconductor material is difficult to adapt to the reaction characteristics of photoelectrocatalytic reduction of NO3 - Ammonia synthesis, in the process of photoelectrocatalytic reduction of NO3 - Ammonia synthesis reaction, the alloy metal particles are prone to dissolution, growth, agglomeration and migration, resulting in a reduction in the active surface area, a decrease in activity, and poor stability, making it difficult to obtain the expected reaction effect. Aiming at the problems faced by copper-based materials in the photoelectrocatalytic reduction of NO3 - Ammonia synthesis, the present invention has conducted research and provided the following improvement solutions:

[0010] A Ti@TiO2 array@Cu x Pt alloy composite electrode, comprising a Ti substrate, a TiO2 nanosheet array grown in-situ on the surface of the Ti substrate, and nano-Cu dispersed on the TiO2 nanosheet arrayx Pt alloy particles;

[0011] In the TiO2 nanosheet array, the TiO2 nanosheets grow along the Z-axis direction of the Ti substrate;

[0012] The said nano-Cu x There is a heterojunction interface between the Pt alloy particles and the TiO2 nanosheet array;

[0013] nano-Cu x The particle size of the Pt alloy particles is 1 - 30 nm, and the weight ratio of Cu / Pt metal elements is 60 - 450:1;

[0014] The said Ti@TiO2 array@Cu x In the Pt alloy composite electrode, nano-Cu x The weight content of the Pt alloy particles is 35 - 45 Wt.%.

[0015] The present invention provides a brand-new self-supporting electrode, on which a TiO2 nanosheet array grows in-situ on a Ti substrate, and Cu with a high Cu ratio is dispersed on the TiO2 nanosheet array x Pt alloy particles. The self-supporting material described in the present invention can be adapted to the reaction characteristics of photocatalytic reduction of NO3 - for ammonia synthesis based on the combined synergy of material composition and morphology, improving the NH3 yield, Faraday efficiency, and stability. In addition, the material described in the present invention has a high Cu / Pt ratio and low cost.

[0016] In the present invention, the said Ti substrate is a Ti sheet (Ti foil), and its thickness can be 0.1 mm - 0.4 mm.

[0017] For the electrode described in the present invention, the special structure of the TiO2 nanosheet array substrate formed in-situ on the Ti surface and the Cu x Pt nanoparticles fused on its surface is the key to synergistically improving its catalytic activity and stability in photocatalytic reduction of NO3 - for ammonia synthesis. On this basis, further optimizing and controlling the composition and content of the TiO2 nanosheet array substrate size Cu x Pt nanoparticles can further improve the performance of the said material.

[0018] In the present invention, the said nano-Cu x In the Pt alloy particles, the weight ratio of Cu / Pt metal elements is 90 - 400:1; further, it can be 280 - 350:1. Research shows that at this preferred ratio, not only does it have an excellent Cu ratio and cost advantage, but it can also synergistically adapt to photocatalytic reduction of NO3 -The reaction characteristics of ammonia synthesis to improve NH3 yield, Faraday efficiency, and stability.

[0019] In the present invention, the TiO2 nanosheets in the TiO2 nanosheet array grow along the Z-axis direction of the Ti substrate (i.e., starting from the Ti substrate as the nucleation point and along its height direction), and the thickness of the TiO2 nanosheet array is 0.1 mm to 0.4 mm.

[0020] The present invention also aims to provide the Ti@TiO2 array@Cu x Pt alloy composite electrode preparation method, but early research and development showed that synthesizing this material requires overcoming problems such as the difficulty in constructing the TiO2 nanosheet array, the difficulty in inducing the heterogeneous interface deposition and dispersed morphology of subsequent Cu x Pt alloy particles, and the easy peeling off, etc. In view of the problems faced in the preparation of this new material, the present invention provides the following solutions:

[0021] A method for preparing the Ti@TiO2 array@Cu x Pt alloy composite electrode, the steps include:

[0022] Step 1:

[0023] Place the Ti substrate in an alkaline solution and perform hydrothermal treatment at temperature T1, then subject the hydrothermal treatment product to acid solution ion exchange and then annealing treatment to obtain a Ti@TiO2 array with TiO2 nanosheets grown in-situ on the Ti substrate;

[0024] Among them, the concentration of the alkaline solute in the alkaline solution is 2 to 6 M; the temperature T1 is 150 to 200 °C; the holding time at temperature T1 is 6 to 12 h; the concentration of the acidic solute in the acid solution is 1 to 2 M; the annealing temperature is 300 to 500 °C;

[0025] Step 2:

[0026] Mix the Ti@TiO2 array with a mixed solution containing a Cu source, a Pt source, a base, ethylene glycol, and DMF, and perform solvothermal treatment at temperature T2 to obtain a Ti@TiO2 array@Cu x Pt alloy composite electrode deposited with nano-Cu x Pt alloy composite electrode;

[0027] In the mixed solution, the Cu source concentration is 3 to 15 mg / mL; the base concentration is 20 to 80 mg / mL; the temperature T2 is 140 to 180 °C; the holding time at temperature T2 is 6 to 10 h.

[0028] To address the challenges in preparing the materials of the present invention, the present invention subjects a Ti sheet and an alkaline solution to hydrothermal treatment, and further performs H + exchange and annealing; this helps to combine with subsequent solvothermal treatment and preparation parameters, and promotes the subsequent interfacial fusion growth of Cu x Pt on its surface, reduces problems such as material structure collapse, and improves the catalytic activity and stability of the prepared materials in the photocatalytic reduction of NO3 - to ammonia synthesis.

[0029] In the present invention, for the hydrothermal reaction, the concentration, temperature, and time of the alkaline solution, the concentration and time of the H + exchange acid, the temperature of annealing, and the combined control of the system, temperature, and time of solvothermal treatment help to synergistically optimize the thin layer, high dispersion, Z-direction growth morphology, and crystallinity of the TiO2 nanosheet array. This helps to combine with subsequent processes and further synergistically improve the interfacial fusion and composite of subsequent Cu x Pt, thereby improving its catalytic activity and stability in the photocatalytic reduction of NO3 - to ammonia synthesis.

[0030] In the present invention, in step 1, the alkaline solution is an aqueous solution of an alkaline solute, wherein the alkaline solute includes at least one of sodium hydroxide and potassium hydroxide. Preferably, the concentration of the alkaline solute in the alkaline solution is 3.5 - 4.5 M. Research in the present invention shows that at this preferred alkaline concentration, it helps to optimize the growth morphology and crystallinity of titanium dioxide nanosheets, and thus facilitates the subsequent interfacial fusion growth of the Cu x Pt alloy.

[0031] In the present invention, the temperature of the hydrothermal treatment is 160 - 180 °C. Preferably, the time of the hydrothermal treatment is 8.5 - 10.5 h. Research in the present invention shows that at this preferred temperature and time, it helps to optimize the thin layer Z-direction growth morphology and crystallinity of titanium dioxide nanosheets, and thus can serve as a nucleation center, such as the interfacial fusion growth of the Cu x Pt alloy.

[0032] In the present invention, in step 1, the acidic solute in the acid solution includes at least one of HCl, HNO3, and H2SO4. Preferably, the concentration of the acidic solute in the acid solution is 1.1 - 1.5 mol / L.

[0033] Preferably, the time for ion exchange of the hydrothermal treatment product in the acid solution is 30 - 60 min; more preferably 35 - 50 min.

[0034] In the present invention, the atmosphere in the annealing stage can be one of air, nitrogen, or argon.

[0035] Preferably, the annealing temperature is 400~500 °C, and further preferably 420~450 °C.

[0036] Preferably, the holding time at the annealing temperature is 1~5 h, and preferably 1.5~2.5 h.

[0037] In the present invention, under the described synthesis conditions, the required ultrathin TiO2 nanosheet arrays can be successfully obtained, which is beneficial for combination with subsequent processes and can serve as the nucleation centers for Cu x Pt, facilitating the preparation of the materials with the structure required by the present invention.

[0038] Preferably, the Ti@TiO2 arrays can be pre-electrochemically modified in an organic acid solution to obtain modified Ti@TiO2 arrays. The research of the present invention shows that innovatively electrochemically modifying in an organic acid solution can optimize the oxygen vacancies on its surface, which helps to further provide better nucleation sites for Cu x Pt, facilitating the obtaining of Cu x Pt ultrafine nanoparticles with highly dispersed distribution and a fused interface, which helps to improve its effect in the photoelectrocatalytic reduction of nitrate to ammonia.

[0039] The described organic acid solution includes, for example, an aqueous solution of at least one of formic acid and acetic acid. The concentration of the organic acid in the organic acid solution is 5~15 wt.%.

[0040] In the present invention, the process of electrochemical modification can be: placing the Ti@TiO2 arrays in an organic acid solution, using a pure Ti sheet as the counter electrode, and conducting electrochemical modification treatment by applying an electric current in a two-electrode system. Preferably, the current density of the electrochemical modification is 1~10 mA / cm -2 (further preferably 3~6 mA / cm -2 ), and the time of electrochemical modification can be 1~10 minutes (further preferably 3~6 min).

[0041] In the present invention, under the described hydrothermal conditions, TiO2 arrays that are ultrathin and conducive to inducing the growth of Cu x Pt alloy particles can be in-situ grown on the surface of the Ti substrate, and it helps to reduce the structural loss of the arrays during subsequent solvothermal treatment, which is beneficial for constructing the physicochemical structure suitable for the photoelectrocatalytic reduction of nitrate and for preparing materials with high ammonia production capacity, Faraday efficiency, and stability.

[0042] Preferably, in step 2, the Cu source is at least one of copper acetylacetonate, copper nitrate, and copper acetate.

[0043] Preferably, the Pt source is at least one of chloroplatinic acid and chloroplatinates.

[0044] Preferably, the base includes at least one of sodium hydroxide and potassium hydroxide.

[0045] In the mixed solution, the volume ratio of ethylene glycol to DMF is 1-3:2-4; further, it can be 1:1-2.

[0046] The Ti@TiO2 array is immersed in the mixed solution.

[0047] In the present invention, each component in the mixed solution can be ultrasonically treated for 0.5-2 h in advance, and then mechanically stirred for 10-20 h. After adding the titanium dioxide array, continue to stir for 10-20 h, and then perform subsequent solvothermal treatment.

[0048] In the present invention, further optimizing and controlling parameters such as the concentration of copper, the Cu / Pt ratio, and the concentration in the solvothermal system helps to further combine with the titanium dioxide array process, which is conducive to the nucleation of Cu x Pt on the surface of the array and construct a fusion interface, improving the performance of the prepared material in the photoreduction of nitrate to ammonia.

[0049] Preferably, the weight ratio of Cu / Pt metal elements is 90-400:1; further, it can be 280-350:1. Research shows that at the preferred ratio, the content of precious metals is very low. In addition, it can be combined with the process of the present invention synergistically, which helps to further enhance the performance of the prepared material in the photocatalytic reduction of nitrate.

[0050] Preferably, in the mixed solution, the concentration of the Cu source is 5-10 mg / mL; the concentration of the base is 30-40 mg / mL. At the preferred Cu concentration, base concentration and ratio, further combined with the induction of the titanium dioxide array, it can synergistically optimize the nucleation of Cu x Pt on the surface of the array and construct a fusion interface, improving the performance of the prepared material in the photoreduction of nitrate to ammonia.

[0051] Preferably in the present invention, after the solvothermal reaction is completed, the reaction vessel is directly quickly cooled with a cooling medium. Research in the present invention shows that adopting this rapid cooling process helps to further optimize the physical and chemical structure of other materials, making the prepared material more suitable for the photoreduction of nitrate to ammonia and obtaining better preparation effects.

[0052] In the present invention, the cooling medium can be water or an aqueous solution with a temperature below 30°C.

[0053] The present invention also provides an application of the Ti@TiO2 array@Cu x Pt alloy composite electrode, using it as a photocathode for photocatalytic reduction of NO3 -Ammonia synthesis.

[0054] In the application described in the present invention, except for the Ti@TiO2 array@Cu x Pt alloy composite electrode, other application methods can be well-known.

[0055] For example, the application steps described in the present invention are as follows: treatment is carried out using a three-electrode system, wherein the Ti@TiO2 array@Cu x Pt alloy composite electrode is used as the working electrode, Ag / AgCl is used as the reference electrode, and a Pt sheet is used as the counter electrode. Subsequently, photocatalytic electroreduction of nitrate to ammonia treatment is carried out under an electric field and light irradiation. The electrolyte can be an electrolyte containing nitrate (for example, an electrolyte containing at least one solute of sodium sulfate, potassium sulfate, potassium nitrate, and sodium nitrate), and the voltage during the photocatalytic nitrate electroreduction to ammonia process can be -0.1 to -0.8 V vs. RHE, and the light irradiation is sunlight, for example, a 300W Xe lamp.

[0056] The present invention also provides a device for photocatalytic reduction of NO3 - to synthesize ammonia, which includes a photocathode, and the photocathode is the Ti@TiO2 array@Cu x Pt alloy composite electrode described in the present invention or is prepared by the Ti@TiO2 array@Cu x Pt alloy composite electrode described in the present invention.

[0057] The device described in the present invention can be a Zn-NO3 battery.

[0058] Beneficial effects

[0059] 1) The present invention provides a novel Ti@TiO2 array@Cu x Pt alloy composite electrode, which can achieve synergy based on the combined control of composition and structure, and can improve the catalytic effect of the material in photocatalytic reduction of NO3 - to synthesize ammonia, and improve its catalytic activity, stability and other properties.

[0060] 2) The present invention also provides a preparation method of the Ti@TiO2 array@Cu x Pt alloy composite electrode. Through the combined control of the preparation method, the problems faced in the preparation of the material can be solved, and the thin-layer, Z-direction, and highly dispersed titanium dioxide nanosheet array can be successfully prepared. And innovatively, based on the titanium dioxide array with special physical and chemical characteristics as the nucleation center, the interfacial fusion nucleation of Cu x Pt alloy with an ultra-high Cu ratio can be successfully induced. In this way, the Cu xThe dispersion distribution of the Pt alloy reduces agglomeration, improves the exposure of active sites, and improves the stability of its interfacial fusion. The research of the present invention shows that the material prepared by the preparation method can be adapted to the photoelectrocatalytic reduction of NO3 - In terms of the application characteristics of ammonia synthesis, it can improve its synthesis effect. In addition, the method of the present invention can achieve batch preparation and is easy to industrialize. Description of the Drawings

[0061] Figure 1 Ti@TiO2 array@Cu prepared in Example 1 x Scanning electron microscopy image of the Pt alloy composite electrode.

[0062] Figure 2 Ti@TiO2 array@Cu prepared in Example 1 x High-resolution transmission electron microscopy image of the Pt alloy composite electrode.

[0063] Figure 3 Ti@TiO2 array@Cu prepared in Example 1 x Linear sweep voltammetry (LSV) comparison chart of the Pt alloy composite electrode (labeled CuPt / TiO2) prepared in Example 1, the TiO2 nanosheet array of Comparative Example 8 (labeled TiO2), the Cu@TiO2 nanosheet array prepared in Comparative Example 5 (labeled Cu / TiO2), and the Pt@TiO2 nanosheet array prepared in Comparative Example 6 (labeled Pt / TiO2) in the reaction system.

[0064] Figure 4 Ti@TiO2 array@Cu prepared in Example 1 x Incident photon-to-current conversion efficiency (IPCE) comparison chart of the Pt alloy composite electrode (labeled CuPt / TiO2) prepared in Example 1, the TiO2 nanosheet array of Comparative Example 8 (labeled TiO2), the Cu@TiO2 nanosheet array prepared in Comparative Example 5 (labeled Cu / TiO2), and the Pt@TiO2 nanosheet array prepared in Comparative Example 6 (labeled Pt / TiO2).

[0065] Figure 5 Ti@TiO2 array@Cu prepared in Example 1 x NH3 production rate comparison chart of the Pt alloy composite electrode (labeled CuPt / TiO2) prepared in Example 1, the TiO2 nanosheet array of Comparative Example 8 (labeled TiO2), the Cu@TiO2 nanosheet array prepared in Comparative Example 5 (labeled Cu / TiO2), and the Pt@TiO2 nanosheet array prepared in Comparative Example 6 (labeled Pt / TiO2) in the reaction system.

[0066] Figure 6 Ti@TiO2 array@Cu prepared in Example 1 xComparison chart of Faraday efficiency among Pt alloy composite electrodes (labeled as CuPt / TiO2), TiO2 nanosheet arrays of Comparative Example 8 (labeled as TiO2), Cu@TiO2 nanosheet arrays prepared in Comparative Example 5 (labeled as Cu / TiO2), and Pt@TiO2 nanosheet arrays prepared in Comparative Example 6 (labeled as Pt / TiO2).

[0067] Figure 7 For Cu prepared in Example 1 x NH3 production rate and Faraday efficiency diagram of the Cu

[0068] Figure 8 For Cu prepared in Example 1 x Voltage stability diagram of the Zn-NO3 battery assembled with the Cu

[0069] Figure 9 For Cu prepared in Example 1 x Power supply time diagram of the Zn-NO3 battery assembled with the Cu Specific embodiments

[0070] The following specific embodiments are intended to further illustrate the content of the present invention in detail, rather than further limiting the protection scope of the claims of the present invention.

[0071] The reagents involved in the following examples are commercial reagent products directly purchased from the market if not otherwise specified.

[0072] Example 1

[0073] Step 1: Preparation of TiO2 nanosheet arrays:

[0074] A titanium sheet with a size of 2.5 cm × 2 cm and a thickness of 0.5 mm was successively ultrasonically cleaned in deionized water, hydrochloric acid, acetone, and absolute ethanol for 20 min. After cleaning, the titanium mesh was placed in an 80 °C oven and dried for 20 min. Subsequently, 4.8 g of sodium hydroxide was weighed and dissolved in 30 mL of water, stirred for 10 min, and ultrasonically treated for 15 min to obtain solution A. The dried titanium sheet was vertically inserted into solution A, transferred to a 50-ml polytetrafluoroethylene container, and hydrothermally treated at 170 - 180 °C (labeled as T1) for 10 ± 0.5 hours. After cooling to room temperature, it was successively washed 4 times with deionized water and 4 times with absolute ethanol, and then immersed in 20 mL of 1.2 mol / L HCl for H +Exchange for 45 min. After the exchange, wash it successively 4 times with deionized water and 4 times with absolute ethanol. After the washing is completed, place the titanium mesh in an oven at 80 °C for drying for 20 min. Finally, put the material into a muffle furnace for high-temperature annealing. The annealing temperature is 420 - 450 °C, the annealing time is 2 h, and the heating rate is 5 °C / min. After cooling to room temperature, TiO2 nanosheet arrays (Ti@TiO2; also simply referred to as TiO2 in the test drawings of the present invention) are obtained.

[0075] Step 2. Modification

[0076] Place the TiO2 nanosheet arrays obtained in Step 1 in a 10% formic acid solution, use a pure Ti sheet as the counter electrode, and react at a current density of 5 mA / cm -2 for 5 minutes in a two-electrode system to obtain modified Ti@TiO2.

[0077] Step 3. Growth of CuPt alloy particles on TiO2 nanosheet arrays:

[0078] Weigh 100 mg of copper acetylacetonate as the precursor, measure H2PtCl6 (15 mg mL -1 , with a Cu / Pt element weight ratio of 320:1), 6 mL of ethylene glycol, 9 mL of DMF. After mixing, add 500 mg of potassium hydroxide, ultrasonic for 1 h and then stir for 16 h. Then vertically immerse the modified TiO2 nanosheet arrays in Step 2 in the above mixed solution (the area of the TiO2 nanosheet arrays is 2.5 cm 2 ), continue to stir for 11 - 12 h, then heat it to 170 ± 10 °C (marked as T2) and keep it for reaction (solvothermal) for 8 h. Then take out the reaction vessel and rapidly cool it to room temperature with tap water at 10 - 20 °C. The obtained product is washed successively 4 times with deionized water, and finally the CuPt alloy@TiO2 nanosheet array photocathode composite catalytic material (also simply referred to as CuPt@TiO2 or CuPt / TiO2) is obtained. The SEM image of the material is shown in Figure 1 , and it can be seen from the results that Cu x Pt alloy nanoparticles are evenly distributed on the TiO2 nanosheet arrays. The high-resolution transmission electron microscope image is shown in Figure 2 , and it can be seen from the results that the lattice fringe spacing of the nanosheet arrays is 0.352 nm, and the lattice fringe spacing of the nanoparticles is 0.219 nm, indicating that Cu and Pt form an alloy and anatase TiO2 is synthesized.

[0079] Electrochemical detection

[0080] Take the prepared Ti@TiO2 array@Cu of 1.25×2 cm xThe Pt alloy composite electrode was used to test its photoelectrochemical performance with an electrochemical workstation. Among them, a saturated Ag / AgCl electrode was used as the reference electrode, a platinum sheet was used as the counter electrode, 0.1 M Na2SO4 and 0.1 M NaNO3 were used as the electrolytes, the scanning rate was 0.005 V / s, the voltage was -0.6 V vs. RHE, and the catalyst activity was measured under a neutral environment irradiated by a 300W Xe lamp.

[0081] Assembly of Zn-NO3 battery:

[0082] A 5 cm × 5 cm × 6 cm two-chamber fuel cell reactor device was used. Among them, a 1.25 × 1.25 cm 2 high-purity zinc sheet was used as the positive electrode, and a 1.25 × 1.25 cm 2 Ti@TiO2 array@Cu x Pt alloy composite electrode was used as the negative electrode. The positive and negative electrode chambers were separated by a Nafion117 proton exchange membrane. Among them, the positive electrode electrolyte was 30 mL of 1 M KOH, and the negative electrode electrolyte was 30 mL of 0.5 M K2SO4 and 0.5 M KNO3. The electrolytes in the positive and negative electrode chambers were circulated through a peristaltic pump respectively, and the peristaltic speed of the peristaltic pump was 40 r / min. After the positive and negative electrodes of the battery were respectively contacted with the positive and negative electrodes in the timer battery box, the battery power supply test was carried out.

[0083] The LSV diagram of the material can be seen in Figure 3 . The IPCE diagram can be seen in Figure 4 ; The NH3 yield diagram can be seen in Figure 5 ; The Faraday efficiency test can be seen in Figure 6 . It shows that the material described in the present invention has a good effect on photocatalytic reduction of nitrate to ammonia.

[0084] In addition, the cycle diagram of the NH3 yield and Faraday efficiency of the material can be seen in Figure 7 . It can be seen from the results that the NH3 yield of Cu x Pt@TiO2 only decreased by 0.96 mg h after 10 cycles -1 , and the Faraday efficiency only decreased by 5.61%, indicating high stability.

[0085] Example 2

[0086] Compared with Example 1, the difference is only that step two is not carried out, but the TiO2 nanosheets prepared in step one are directly subjected to the treatment of step three, and other operations and parameters are the same as those in Example 1.

[0087] Example 3

[0088] Compared with Example 1, the only difference is that in Step 3, the mass ratio of Pt to Cu is changed to: Cu:Pt = 91:1, and the total weight of Pt and Cu metal elements, as well as other operations and parameters, are the same as those in Example 1.

[0089] Example 4

[0090] Compared with Example 1, the only difference is that in Step 3, the mass ratio of Pt to Cu is changed to: Cu:Pt = 60:1, and the total weight of Pt and Cu metal elements, as well as other operations and parameters, are the same as those in Example 1.

[0091] Example 5

[0092] Compared with Example 1, the only difference is that in Step 3, the total weight of Pt and Cu metal elements is doubled, and the mass ratio and other operations and parameters are the same as those in Example 1.

[0093] Example 6

[0094] Compared with Example 1, the only difference is that in Step 3, the addition amount of KOH is doubled (that is, the mass of KOH in Solution B is 1 g), and other operations and parameters are the same as those in Example 1.

[0095] Example 7

[0096] Compared with Example 1, the only difference is that after the reaction in Step 3 ends, the heat source is turned off and natural cooling is carried out until room temperature, instead of rapid cooling, and the total weight of Pt and Cu metal elements, the mass ratio, and other operations and parameters are the same as those in Example 1.

[0097] Comparative Example 1

[0098] Compared with Example 1, the only difference is that in Step 1, the hydrothermal reaction time is 15 h, and other operations and parameters are the same as those in Example 1.

[0099] Comparative Example 2

[0100] Compared with Example 1, the only difference is that in Step 1, the addition amount of NaOH is doubled (that is, the mass of NaOH in Solution A is 9.6 g), and other operations and parameters are the same as those in Example 1.

[0101] Comparative Example 3

[0102] Compared with Example 1, the only difference is that the material obtained after hydrothermal treatment in Step 1 is not subjected to acid treatment for proton exchange, and the total weight of Pt and Cu metal elements, as well as other operations and parameters, are the same as those in Example 1.

[0103] Comparative Example 4

[0104] Compared with Example 1, the difference is only that in Step 2, the TiO2 nanosheet array obtained in Step 1 is placed in a 10% sulfuric acid solution, and a pure Ti sheet is used as the counter electrode, and the reaction is carried out at a current density of 5 mA / cm -2 for 5 minutes in a two-electrode system, and other operations and parameters are the same as those in Example 1.

[0105] Comparative Example 5

[0106] Compared with Example 1, the difference is only that in Step 3, no Pt source is added, and the remaining Cu element and the total weight of Cu and Pt elements in Cu x Pt are the same as those in Example 1, and other operations and parameters are the same as those in Example 1. The material finally prepared in this comparative example is also labeled as Cu / TiO2 (or labeled as Cu@TiO2 or Cu / TiO2).

[0107] Comparative Example 6

[0108] Compared with Example 1, the difference is only that in Step 3, no Cu source is added, and the remaining Pt element and the total weight of Cu and Pt elements in Cu x Pt are the same as those in Example 1, and other operations and parameters are the same as those in Example 1. The material finally prepared in this comparative example is also labeled as Pt / TiO2 (or labeled as Pt@TiO2 or Pt / TiO2).

[0109] Comparative Example 7

[0110] Compared with Example 1, the difference is only that the preparation steps of the TiO2 nanosheet array in Steps 1 and 2 are not carried out. Instead, commercial TiO2 (P25) is used to replace the prepared TiO2 nanosheet array, and it is used to replace the TiO2 nanosheet array in Step 3, and the treatment in Step 3 is carried out, and other operations and parameters are the same as those in Example 1.

[0111] Comparative Example 8

[0112] Compared with Example 1, the difference is only that the reactions in Steps 2 and 3 are not carried out, and the modified TiO2 nanosheet array prepared in Step 1 is directly used for the reaction, and other operations and parameters are the same as those in Example 1.

[0113] Comparative Example 9

[0114] Compared with Example 1, the difference is only that the reactions in Steps 1 and 2 are not carried out. In Step 3, carbon paper is used to replace the titanium dioxide array to prepare Cu x Pt alloy for the reaction, and other operations and parameters are the same as those in Example 1.

[0115] Comparative Example 10

[0116] Compared with Example 1, the only difference is that after adding the copper source and platinum source in Step 3, instead of adding DMF, KOH, and ethylene glycol, 5 mL of 0.1 M NaBH4 solution is added. The total weight, mass ratio of Pt and Cu metal elements, and other operations and parameters are the same as those in Example 1.

[0117] The catalysts prepared in each example and each comparative example were listed in Table 1 according to the electrochemical test and subsequent calculation results of Example 1.

[0118] Table 1 NH3 production and Faraday efficiency of each catalyst (voltage is -0.6 V vs. RHE, light intensity is 300W Xe lamp)

[0119]

[0120] In summary, through the examples and comparative examples, it can be seen that by hydrothermally treating the Ti sheet and alkaline solution, and further performing H + exchange and annealing; this helps to combine with subsequent solvothermal treatment and preparation parameters, and promotes the subsequent in-situ growth and interfacial fusion of Cu x Pt on its surface, reduces problems such as material structure collapse, and improves the catalytic activity and stability of the prepared material in the photocatalytic reduction of NO3 - to ammonia.

[0121] For example, through Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, it can be seen that by using the preferred titanium dioxide nanorod array preparation process described in the present invention, the morphology and crystallinity of the array can be optimized, which is beneficial for creating good physical and chemical conditions for the subsequent in-situ growth of Cu x Pt, and is conducive to the dispersion and interfacial fusion growth of subsequent Cu x Pt.

[0122] Through Example 1 and Comparative Example 4, it can be seen that using the organic acid electrochemical modification described in the present invention cannot achieve the expected effect and is not conducive to the subsequent in-situ growth of Cu x Pt.

[0123] By comparing Example 1 with Comparative Example 5 and Comparative Example 6, it can be seen that using the Cu-Pt composite described in the present invention and controlling a high Cu ratio is beneficial for the catalytic activity and stability in the photocatalytic reduction of NO3 - to ammonia.

[0124] Through Example 1 and Comparative Example 7, Comparative Example 8, and Comparative Example 9, it can be seen that the titanium dioxide nanosheet array prepared by the process described in the present invention is beneficial for providing good physical and chemical conditions for the subsequent growth of Cu x Pt, and helps the dispersion and interfacial fusion growth of Cu x Pt.

[0125] From Examples 1 and Comparative Example 10, it can be seen that using the DMF, KOH, and ethylene glycol system described in the present invention is conducive to combining with the titanium dioxide support and synergistically inducing the interfacial fusion and dispersion growth of Cu x Pt.

[0126] In addition, from Examples 1 and 2, it can be seen that performing the electrochemical modification treatment on the titanium dioxide nanosheet array described in the present invention helps to improve the in-situ growth and interfacial fusion distribution of Cu x Pt, and helps to further improve its ammonia production and Faraday efficiency.

[0127] From Examples 1, 3, and 4, it can be seen that using the high Cu ratio described in the present invention can not only significantly reduce the amount of Pt used, but also unexpectedly obtain better ammonia production and Faraday efficiency.

[0128] From Examples 1 and 7, it can be seen that rapidly cooling the solvothermal system helps to further optimize the physical and chemical characteristics of the material and helps to further improve the ammonia production and Faraday efficiency of the material.

[0129] The specific embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A Ti@TiO2 array@Cu x Pt alloy composite electrode, characterized in that It includes a Ti substrate, a TiO2 nanosheet array grown in-situ on the surface of the Ti substrate, and nano-Cu x x Pt alloy particles; The TiO₂ nanosheets in the TiO₂ nanosheet array grow along the Z-axis direction of the Ti substrate; The described nano-Cu x There is a heterojunction interface between the Pt alloy particles and the TiO2 nanosheet array; Nano-Cu x The particle size of the Pt alloy is 1-30 nm, and the weight ratio of the Cu / Pt metal elements is 60-450:1; The Ti@TiO2 array@Cu described above x In the Pt alloy composite electrode, the nano-Cu x The weight content of the Pt alloy particles is 35-45 Wt.%. The described Ti@TiO2 array@Cu x The preparation steps of the Pt alloy composite electrode include: Step 1: Place the Ti substrate in an alkaline solution and perform hydrothermal treatment at temperature T1. Then, subject the hydrothermal treatment product to acid solution ion exchange in advance and subsequently perform annealing treatment to obtain a Ti@TiO₂ array with TiO₂ nanosheet array grown in-situ on the Ti substrate; Among them, the concentration of the alkaline solute in the alkaline solution is 2 - 6 M; the temperature T1 is 150 - 200 °C; the heat preservation time at temperature T1 is 6 - 12 h; the concentration of the acidic solute in the acid solution is 1 - 2 M; the annealing temperature is 300 - 500 °C; Step 2: Mix the Ti@TiO2 array with a mixed solution containing a Cu source, a Pt source, a base, ethylene glycol, and DMF, and perform solvothermal treatment at temperature T2 to obtain a Ti@TiO2 array@Cu x Pt alloy particle-deposited Ti@TiO2 array@Cu x Pt alloy composite electrode; In the mixed solution, the concentration of the Cu source is 3 - 15 mg / mL; the concentration of the base is 20 - 80 mg / mL; the temperature T2 is 140 - 180 °C; the heat preservation time at temperature T2 is 6 - 10 h.

2. The Ti@TiO2 array@Cu x Pt alloy composite electrode, characterized in that The nanoscale Cu x in the Pt alloy particles has a weight ratio of Cu to Pt metal elements of 90 to 400:1; The Ti substrate is a Ti sheet with a thickness of 0.1 mm - 0.4 mm; The thickness of the TiO₂ nanosheet array is 1 - 5 nm.

3. Preparation method of the Ti@TiO2 array@Cu x Pt alloy composite electrode, characterized in that the steps Including: Step 1: Place the Ti substrate in an alkaline solution and perform hydrothermal treatment at temperature T1. Then, subject the hydrothermal treatment product to acid solution ion exchange in advance and subsequently perform annealing treatment to obtain a Ti@TiO₂ array with TiO₂ nanosheet array grown in-situ on the Ti substrate; Among them, the concentration of the alkaline solute in the alkaline solution is 2 - 6 M; the temperature T1 is 150 - 200 °C; the heat preservation time at temperature T1 is 6 - 12 h; the concentration of the acidic solute in the acid solution is 1 - 2 M; the annealing temperature is 300 - 500 °C; Step 2: Mix the Ti@TiO2 array with a mixed solution containing a Cu source, a Pt source, a base, ethylene glycol, and DMF, and perform solvothermal treatment at temperature T2 to obtain a Ti@TiO2 array@Cu x Pt alloy particle-deposited Ti@TiO2 array@Cu x Pt alloy composite electrode; In the mixed solution, the concentration of the Cu source is 3 - 15 mg / mL; the concentration of the base is 20 - 80 mg / mL; the temperature T2 is 140 - 180 °C; the heat preservation time at temperature T2 is 6 - 10 h.

4. The Ti@TiO2 array@Cu x Preparation method of the Pt alloy composite electrode, characterized in that In Step 1, the alkaline solution is an aqueous solution of an alkaline solute, among which the alkaline solute includes at least one of sodium hydroxide and potassium hydroxide; The concentration of the alkaline solute in the alkaline solution is 3.5 - 4.5 M; The temperature of the hydrothermal treatment is 160 - 180 °C; The time of the hydrothermal treatment is 8.5 - 10.5 h; The acidic solute in the acid solution includes at least one of HCl, HNO₃, and H₂SO₄; The time for ion exchange of the hydrothermal treatment product in the acid solution is 30 - 60 min; The annealing temperature is 400 - 500 °C; The heat preservation time at the annealing temperature is 1 - 5 h.

5. The preparation method of the Ti@TiO2 array@Cu x Pt alloy composite electrode according to claim 3, characterized in that, In Step 1, the Ti@TiO₂ array is pre-electrochemically modified in an organic acid solution to obtain a modified Ti@TiO₂ array. ​​​ 6. The preparation method of the Ti@TiO2 array@Cu x Pt alloy composite electrode as claimed in claim 3, characterized in that, x In Step 2, the Cu source is at least one of copper acetylacetonate, copper nitrate, and copper acetate; The Pt source is at least one of chloroplatinic acid and chloroplatinate; The base includes at least one of sodium hydroxide and potassium hydroxide; The weight ratio of Cu / Pt metal elements is 90 - 400:1; In the mixed solution, the volume ratio of ethylene glycol to DMF is 1 - 3:2 - 4; In the mixed solution, the concentration of the Cu source is 5 - 10 mg / mL; the concentration of the base is 30 - 40 mg / mL.

7. The preparation method of the Ti@TiO2 array@Cu x Pt alloy composite electrode according to claim 3, characterized in that, x In Step 2, after the solvothermal reaction is completed, the reaction vessel is directly subjected to rapid cooling treatment using a cooling medium.

8. The Ti@TiO2 array@Cu according to any one of claims 1 to 2 x Pt alloy composite electrode or the Ti@TiO2 array@Cu prepared by the preparation method according to any one of claims 3 to 7 x Application of the Pt alloy composite electrode, characterized in that Use it as a photocathode for photocatalytic reduction of NO3 - to synthesize ammonia.

9. A device for photocatalytic reduction of NO3 - to synthesize ammonia, comprising a photo - cathode, characterized in that, The photocathode is the Ti@TiO2 array@Cu described in any one of claims 1 to 2 x Pt alloy composite electrode, or the Ti@TiO2 array@Cu prepared by the preparation method described in any one of claims 3 to 7 x Pt alloy composite electrode, or the Ti@TiO2 array@Cu x Pt alloy composite electrode is prepared.

10. The device for photocatalytic reduction of NO3 to synthesize ammonia as claimed in claim 9, wherein, - The device described is a Zn-NO3 battery.

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