Ti (at) TiO2 array (at) CuxPt alloy composite electrode, preparation thereof and application of Ti (at) TiO2 array (at) CuxPt alloy composite electrode in preparation of ammonia through photoelectrocatalysis NO3 <-> reduction

Abstract

The invention belongs to the field of photoelectrocatalysis ammonia production, and particularly discloses a Ti (at) TiO2 array (at) CuxPt alloy composite electrode, preparation of the Ti (at) TiO2 array (at) CuxPt alloy composite electrode and application of the Ti (at) TiO2 array (at) CuxPt alloy composite electrode to photoelectrocatalysis NO3 <-> reduction ammonia production, and the Ti (at) TiO2 array (at) CuxPt alloy composite electrode comprises a Ti substrate, a TiO2 nanosheet array growing on the surface of the Ti substrate in an in-situ mode and nano CuxPt alloy particles distributed on the TiO2 nanosheet array in a dispersed mode; tiO2 nanosheets in the TiO2 nanosheet array grow in the Z-axis direction of the Ti substrate; and a heterogeneous interface exists between the nano CuxPt alloy particles and the TiO2 nanosheet array. The self-supporting material provided by the 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 specifically relates to NO3 - The field of catalytic electrodes for the synthesis of ammonia by (nitrate) reduction. Background Art

[0002] Ammonia (NH3) is an important industrial raw material and is widely used in fertilizer production, pharmaceutical and chemical manufacturing. However, the traditional Haber-Bosch process has problems such as high energy consumption and serious greenhouse gas emissions. Photoelectrocatalytic nitrate reduction (PEC-NO3 - RR) technology, which reduces the activation energy barrier of nitrogen intermediates by photon injection and accelerates the reaction kinetics with external bias, has become an effective strategy to improve energy efficiency. - The industrial development of synthetic ammonia is restricted by catalysts, mainly in the following four aspects: ① Photocathode catalytic materials generally have problems such as low light absorption efficiency, poor carrier mobility, and insufficient ammonia yield; ② Traditional catalysts need to use more metal co-catalysts (such as Pd, Au, Ru) loaded on substrate support materials, and precious metal platinum particles loaded on carbon supports. The reserves of precious metals are scarce and expensive, resulting in high overall catalyst costs; ③ In the photocatalytic reduction of NO3 - Under the actual operation environment of synthetic ammonia, the alloy catalyst will agglomerate, separate, dissolve and the carrier will corrode, resulting in rapid activity decay and a low overall photocathode life; ④ At present, the photocatalytic reduction of NO3 - The low activity of the photocathode catalyst used in ammonia synthesis leads to the reduction of NO3 at the cathode - The process is slow. Therefore, reducing the amount of precious metals, reducing costs, and improving the activity of the catalyst is the key to photoelectrocatalytic reduction of NO3 - Urgent needs in the field of synthetic ammonia.

[0003] There are also some existing technologies for photocatalytic reduction of NO3 -A method for synthesizing ammonia. For example, Chinese patent publication number CN119530860A discloses a method for preparing a self-decomposing composite catalyst and its application in constructing a photoelectrochemical cell for ammonia production; the method for preparing the self-decomposing composite catalyst is to dissolve copper acetate, cobalt acetate and urea and place the mixture with a treated titanium mesh in a reactor, obtain a precursor material after hydrothermal treatment, and during calcination in a muffle furnace, CuCo2O4 decomposes itself to produce CuO, forming a heterojunction without an interface, and obtaining an integrated electrode loaded with a catalyst, which is used for photoelectrocatalytic nitrate reduction to produce ammonia. In addition, a Chinese patent document with publication number CN118835273A discloses a preparation method of a Cu2O@NiFe2O4 / Ni integrated electrode and its application in synthetic ammonia. The preparation method includes preparing a Cu2O nanocube template by an ascorbic acid reduction method, and then etching the Cu2O cube with sodium thiosulfate according to Pearson's acid-base theory, and growing nickel-iron double hydroxide (NiFe-LDH) on the outer layer of the cube by using the alkaline environment generated by etching, coating the Cu2O@NiFe-LDH on Ni foam and annealing at 350°C to obtain a Cu2O@NiFe2O4 / Ni integrated electrode. For another example, a Chinese patent document with publication number CN114411175A discloses a method for preparing an amorphous metal oxide modified p-BiVO4 composite heterojunction, firstly immersing a cleaned FTO glass sheet in a mixed aqueous solution of ammonium metavanadate and bismuth nitrate, and obtaining an FTO sheet loaded with p-BiVO4 after hydrothermal treatment; then mixing X(OAc)2 and YCl2 in a mass ratio of 2:1 and then mixing with an ethylene glycol solution of sodium acetate, stirring evenly to obtain a metal salt solution; immersing the FTO sheet loaded with p-BiVO4 in an amorphous metal oxide modified p-BiVO4 composite heterojunction (AM x O y / p-BiVO4), naturally cooled to room temperature, rinsed repeatedly with ethanol and air-dried.

[0004] In summary, although there are some existing technologies for preparing ammonia by photoelectrocatalytic reduction of nitrates, there is still much room for improvement in the NH3 production, Faraday efficiency, cost and stability of the existing processes. Summary of the invention

[0005] For the existing photocatalytic reduction of NO3 - The first object of the present invention is to provide a Ti@TiO2 array@Cu x Pt alloy composite electrode is designed to provide a suitable photoelectrocatalytic reduction of NO3 -A new self-supporting electrode that improves the characteristics of synthetic ammonia and improves its NH3 production, Faradaic efficiency, stability, and reduces costs.

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

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

[0008] The fourth object of the present invention is to provide a method comprising the Ti@TiO2 array@Cu x Devices with Pt alloy composite electrodes.

[0009] Different photoelectrocatalytic fields have different reaction principles and need to overcome different technical problems. For example, for the photoelectrocatalytic reduction of NO3 - Compared with electrocatalytic reduction of NO3 - Synthetic ammonia, photocatalytic reduction of NO3 - Other types of ammonia synthesis systems such as synthetic ammonia, photoelectrocatalytic reduction of N2 synthetic ammonia, electrocatalytic reduction of N2 synthetic ammonia, photocatalytic reduction of N2 synthetic ammonia, etc. have the advantages of fast electron transfer, low reaction energy consumption, and strong substrate adsorption; however, the catalyst of this reaction is mainly a modified material of semiconductor materials, which has higher requirements for light absorption efficiency, carrier migration rate, overpotential, stability, and Faraday efficiency; however, at present, semiconductor substrates, especially non-precious metals, still face relatively prominent problems such as insufficient light absorption and poor carrier mobility, which makes it difficult to meet the photoelectrocatalytic reduction of NO3 - Therefore, in order to reduce the cost of precious metals in electrodes, the present invention attempts to provide a method of reducing electrode costs by introducing copper. However, it was found in the early stages of research and development that simply anchoring copper-based alloys on semiconductor materials is difficult to adapt to photoelectrocatalytic reduction of NO3 - Characteristics of ammonia synthesis reaction, photoelectrocatalytic reduction of NO3 - During the ammonia synthesis reaction, alloy metal particles are prone to dissolution, growth, agglomeration and migration, resulting in a reduction in active surface area, reduced activity, poor stability, and difficulty in achieving the expected reaction effect. - The problems faced in synthesizing ammonia, after research, the present invention provides the following improvement scheme:

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

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

[0012] The nano Cu x There is a heterogeneous interface between the Pt alloy particles and the TiO2 nanosheet arrays;

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

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

[0015] The present invention provides a new self-supporting electrode, which has a TiO2 nanosheet array grown in situ on a Ti substrate, and a Cu with a high Cu content dispersed on the TiO2 nanosheet array. x The self-supporting material of the present invention can be adapted to photoelectrocatalytic reduction of NO3 based on the combined synergy of material composition and morphology. - The reaction characteristics of synthetic ammonia improve NH3 production, Faraday efficiency, and stability. In addition, the material of the present invention has a high Cu / Pt ratio and low cost.

[0016] In the present invention, the Ti substrate is a Ti sheet (Ti foil), and the thickness thereof may be 0.1 mm to 0.4 mm.

[0017] The electrode of the present invention comprises a TiO2 nanosheet array substrate formed in situ on the Ti surface and a Cu nanosheet fused on the surface interface. x The special structure of Pt nanoparticles is a synergistic improvement in their photoelectrocatalytic reduction of NO3 - The key to the catalytic activity and stability in the synthesis of ammonia is to further study the Cu substrate size of TiO2 nanosheet arrays. x Optimizing and controlling the composition and content of Pt nanoparticles can further improve the performance of the material.

[0018] In the present invention, the 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. Studies have shown that this preferred ratio not only has an excellent Cu ratio and excellent cost advantage, but also can synergistically adapt to the photocatalytic reduction of NO3 -The reaction characteristics of synthetic ammonia improve NH3 production, 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 (that is, with the Ti substrate as the nucleation starting point and along its height direction), wherein 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 The preparation method of Pt alloy composite electrode, but the early stage of research and development showed that the synthesis of this material needs to overcome the difficulty of constructing TiO2 nanosheet arrays and the difficulty of inducing subsequent Cu x The heterogeneous interface deposition and dispersion morphology of Pt alloy particles, as well as easy peeling, etc., in view of the problems faced by the preparation of this new material, the present invention provides the following solutions:

[0021] A Ti@TiO2 array@Cu x The preparation method of the Pt alloy composite electrode comprises the following steps:

[0022] Step 1:

[0023] The Ti substrate is placed in an alkaline solution and subjected to a hydrothermal treatment at a temperature T1, and the hydrothermal treatment product is pre-treated with an acid solution ion exchange and then annealed to obtain a Ti@TiO2 array having an in-situ TiO2 nanosheet array grown on the Ti substrate;

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

[0025] Step 2:

[0026] The Ti@TiO2 array is mixed with a mixed solution containing a Cu source, a Pt source, an alkali, ethylene glycol and DMF, and subjected to a solvent thermal treatment at a temperature T2 to obtain a Ti@TiO2 array with nano Cu deposited on the Ti@TiO2 array. x Ti@TiO2 arrays@Cu of Pt alloy particles x Pt alloy composite electrode;

[0027] In the mixed solution, the concentration of Cu source is 3-15 mg / mL; the concentration of alkali is 20-80 mg / mL; the temperature T2 is 140-180°C; and the insulation time at temperature T2 is 6-10 hours.

[0028] In view of the difficulty in preparing the material described in the present invention, the present invention comprises Ti sheets and alkali solution for hydrothermal treatment, and further H + exchange and annealing; this helps to combine with subsequent solvent thermal treatment and preparation parameters, and promotes the subsequent Cu x Pt grows at its surface interface, reducing the structural collapse of the material and improving the photocatalytic reduction of NO3 - Catalytic activity and stability in ammonia synthesis.

[0029] In the present invention, the concentration, temperature and time of the hydrothermal reaction are as follows: + The concentration and time of the exchange acid, the annealing temperature, the solvothermal system, the temperature and the time are combined to help optimize the thin layer, high dispersion, Z-direction growth morphology and crystallinity of the TiO2 nanosheet array, which helps to combine with the subsequent process and further improve the subsequent Cu x The interfacial fusion of Pt improves its photocatalytic reduction of NO3 - Catalytic activity and stability in ammonia synthesis.

[0030] In the present invention, in step 1, the alkali 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 alkali solution is 3.5-4.5 M. The present invention shows that the preferred alkali concentration helps to optimize the growth morphology and crystallinity of titanium dioxide nanosheets, thereby facilitating the subsequent Cu x Pt alloy interface fusion growth.

[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. The present invention shows that the preferred temperature and time are helpful to optimize the thin layer Z-direction growth morphology and crystallinity of the titanium dioxide nanosheets, so that it can be used as a nucleation center, such as Cu x Pt alloy interface fusion growth.

[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 ion exchange time of the hydrothermal treatment product in the acid solution is 30 to 60 minutes; more preferably, it is 35 to 50 minutes.

[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 may further be 420-450°C.

[0036] Preferably, the holding time at the annealing temperature is 1 to 5 hours, preferably 1.5 to 2.5 hours.

[0037] In the present invention, under the synthetic conditions, the desired ultrathin TiO2 nanosheet array can be successfully obtained, which is conducive to the combination with subsequent processes and can be used as Cu x The Pt nucleation center is beneficial for preparing the material with the required structure of the present invention.

[0038] Preferably, the Ti@TiO2 array can be electrochemically modified in an organic acid solution in advance to obtain a modified Ti@TiO2 array. The present invention shows that the innovative electrochemical modification in an organic acid solution can optimize the oxygen vacancies on its surface, which helps to further x Pt provides better nucleation sites, which is conducive to obtaining Cu with highly dispersed distribution and fusion interface. x Pt ultrafine nanoparticles, which helps to improve its performance in the photoelectrocatalytic reduction of nitrate to ammonia.

[0039] The 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 electrochemical modification process can be: placing the Ti@TiO2 array in an organic acid solution, using a pure Ti sheet as a counter electrode, and conducting electrochemical modification in the two-electrode system. Preferably, the current density of the electrochemical modification is 1-10 mA / cm -2 (It can be further 3~6mA / cm -2 ), the time of electrochemical modification can be 1 to 10 minutes (further can be 3 to 6 min).

[0041] In the present invention, under the hydrothermal conditions, an ultra-thin Cu layer can be grown in situ on the surface of the Ti substrate and is conducive to inducing x The TiO2 array of Pt alloy particles helps to reduce the structural loss of the array caused by subsequent solvent thermal treatment, which is conducive to constructing a physicochemical structure suitable for nitrate photoelectrocatalytic reduction and 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 chloroplatinate.

[0044] Preferably, the alkali 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 pre-ultrasonicated for 0.5 to 2 hours, and then mechanically stirred for 10 to 20 hours. After the titanium dioxide array is added, stirring is continued for 10 to 20 hours, and then subsequent solvent thermal treatment is performed.

[0048] In the present invention, the concentration of copper, Cu / Pt ratio, concentration and other parameters in the solvent thermal system are further optimized and controlled, which is helpful to further combine with the titanium dioxide array process and further facilitate Cu x Pt nucleates on the array surface and constructs a fusion interface, improving the effect of the prepared material in the photoelectric reduction of nitrate to produce ammonia.

[0049] Preferably, the weight ratio of Cu / Pt metal elements is 90-400:1; further, it can be 280-350:1. Studies have shown that under the preferred ratio, the precious metal content is very low. In addition, it can be combined with the process of the present invention to further enhance the effect of the prepared material in nitrate photoelectrocatalysis.

[0050] Preferably, in the mixed solution, the concentration of Cu source is 5-10 mg / mL; the concentration of alkali is 30-40 mg / mL. Under the preferred Cu concentration, alkali concentration and ratio, the induction effect of the titanium dioxide array can be further combined to synergistically optimize the Cu x Pt nucleates on the array surface and constructs a fusion interface, improving the effect of the prepared material in the photoelectric reduction of nitrate to produce ammonia.

[0051] Preferably, after the solvent thermal reaction is completed, the reaction vessel is directly cooled rapidly using a cooling medium. The present invention shows that the rapid cooling process is helpful to further optimize the physical and chemical structure of the prepared material, making the prepared material more suitable for nitrate photoelectric reduction to produce ammonia, and obtaining a better preparation effect.

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

[0053] The present invention also provides a Ti@TiO2 array@Cu x Application of Pt alloy composite electrode as photocathode for photoelectrocatalytic reduction of NO3 -Synthetic ammonia.

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

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

[0056] The present invention also provides a photoelectrocatalytic reduction of NO3 - A device for synthesizing ammonia, comprising a photocathode, wherein the photocathode is the Ti@TiO2 array@Cu x Pt alloy composite electrode or the Ti@TiO2 array@Cu x Pt alloy composite electrode was prepared.

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

[0058] Beneficial Effects

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

[0060] 2) The present invention also provides the Ti@TiO2 array@Cu x The preparation method of the Pt alloy composite electrode can solve the problems faced by the material preparation through the joint control of the preparation method, and can successfully prepare the thin layer, Z-direction, highly dispersed titanium dioxide nanosheet array, and innovatively use the titanium dioxide array with special physical and chemical characteristics as the nucleation center to successfully induce the Cu with ultra-high Cu ratio. x The interface fusion nucleation of Pt alloy can improve the Cu xThe dispersed distribution of Pt alloy reduces agglomeration, improves active site exposure, and improves its interface fusion stability. The present invention shows that the material prepared by the preparation method can be adapted to the photoelectrocatalytic reduction of NO3 - The application characteristics of synthetic ammonia can improve its synthesis effect. In addition, the method described in the present invention can realize batch preparation and is easy to realize industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Ti@TiO2 array@Cu prepared in Example 1 x Scanning electron microscope image of 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 LSV comparison diagram of Pt alloy composite electrode (marked as CuPt / TiO2), TiO2 nanosheet array of Comparative Example 8 (marked as TiO2), Cu@TiO2 nanosheet array prepared in Comparative Example 5 (marked as Cu / TiO2), and Pt@TiO2 nanosheet array prepared in Comparative Example 6 (marked as Pt / TiO2) in the reaction system.

[0064] Figure 4 The Ti@TiO2 array@Cu prepared in Example 1 x IPCE comparison chart of Pt alloy composite electrode (marked as CuPt / TiO2), TiO2 nanosheet array of Comparative Example 8 (marked as TiO2), Cu@TiO2 nanosheet array prepared in Comparative Example 5 (marked as Cu / TiO2), and Pt@TiO2 nanosheet array prepared in Comparative Example 6 (marked as Pt / TiO2).

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

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

[0067] Figure 7 The Cu prepared in Example 1 x NH3 yield and Faraday efficiency of Pt alloy@TiO2 nanosheet array photocathode catalyst after 10 cycles.

[0068] Figure 8 The Cu prepared in Example 1 x Voltage stability diagram of Zn-NO3 battery assembled with Pt alloy@TiO2 nanosheet array photocathode catalyst;

[0069] Fig. 9 The Cu prepared in Example 1 x Power supply time diagram of Zn-NO3 battery assembled with Pt alloy@TiO2 nanosheet array photocathode catalyst. DETAILED DESCRIPTION

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

[0071] The reagents involved in the following examples, unless otherwise specified, are commercial reagents purchased directly from the market.

[0072] Example 1

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

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

[0075] Step 2: Modification

[0076] The TiO2 nanosheet array obtained in step 1 was placed in a 10% formic acid solution, with a pure Ti sheet as the counter electrode, and the two-electrode system was charged at 5 mA / cm -2 The modified Ti@TiO2 was obtained by reacting at a current density of 5 min.

[0077] Step 3: TiO2 nanosheet array growth CuPt alloy particles:

[0078] Weigh 100 mg of the precursor copper acetylacetonate and H2PtCl6 (15 mg mL -1 , Cu / Pt element weight ratio is 320:1), 6mL ethylene glycol, 9mL DMF, after mixing, add 500mg potassium hydroxide, ultrasonicate for 1h and stir for 16h, then immerse the modified TiO2 nanosheet array in the above mixture vertically (the area of ​​the TiO2 nanosheet array is 2.5 cm 2 ), continue stirring for 11-12 hours, then heat it to 170±10℃ (marked as T2) and keep it warm for 8 hours (solvent heat), then take out the reaction container and use 10-20℃ tap water to quickly cool it to room temperature. The obtained product is washed with deionized water 4 times in sequence, and finally the CuPt alloy @TiO2 nanosheet array photocathode composite catalytic material (also referred to as CuPt@TiO2 or CuPt / TiO2) is obtained. The SEM image of the material is shown in Figure 1 , the results show that Cu x Pt alloy nanoparticles are evenly distributed on the TiO2 nanosheet array. High-resolution transmission electron microscopy image is shown in Figure 2 The results show that the lattice fringe spacing of the nanosheet array 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 phase TiO2 is synthesized.

[0079] Electrochemical detection

[0080] Take the 1.25×2cm Ti@TiO2 array@Cu xThe photoelectrochemical performance of the Pt alloy composite electrode was tested using an electrochemical workstation, with saturated Ag / AgCl as the reference electrode, platinum sheet as the counter electrode, 0.1 M Na2SO4 and 0.1 M NaNO3 as the electrolyte, a scan rate of 0.005 V / s, a voltage of -0.6 V vs. RHE, and the catalyst activity in a neutral environment irradiated by a 300W Xe lamp.

[0081] Zn-NO3 battery assembly:

[0082] A 5 cm × 5 cm × 6 cm dual-chamber fuel cell reactor device was used, in which a 1.25 × 1.25 cm 2 As the positive electrode, a high-purity zinc sheet of 1.25×1.25cm 2 Ti@TiO2 array@Cu x The Pt alloy composite electrode is used as the negative electrode. The positive and negative electrode chambers are separated by Nafion117 proton exchange membrane. Among them, the positive electrode electrolyte is 30mL 1M KOH, and the negative electrode electrolyte is 30mL0.5 K2SO4 and 0.5 M KNO3. The electrolytes in the positive and negative electrode chambers are circulated by a circulating peristaltic pump, and the peristaltic pump peristaltic speed is 40r / min. After the positive and negative electrodes of the battery are respectively contacted with the positive and negative electrodes in the timer battery box, the battery power supply test is carried out.

[0083] The LSV diagram of the material is shown in Figure 3 IPCE diagram Figure 4 ; NH3 yield diagram see Figure 5 ; Faraday efficiency test see Figure 6 It shows that the material of the present invention has a good effect of photoelectric reduction of nitrate to produce ammonia.

[0084] In addition, the NH3 yield and Faraday efficiency diagrams of the materials are shown in the cycle diagram. Figure 7 The results show that Cu x After 10 cycles of Pt@TiO2, the NH3 yield decreased by only 0.96 mg h -1 , the Faraday efficiency only decreased by 5.61%, indicating high stability.

[0085] Example 2

[0086] Compared with Example 1, the only difference is that step 2 is not performed, and the TiO2 nanosheets obtained in step 1 are directly processed in step 3. Other operations and parameters are the same as in Example 1.

[0087] Example 3

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

[0089] Example 4

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

[0093] Example 6

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

[0095] Example 7

[0096] Compared with Example 1, the only difference is that after the reaction in step 3 is completed, the heat source is turned off and the reaction is naturally cooled to room temperature instead of rapid cooling. The total weight, mass ratio and other operations and parameters of Pt and Cu metal elements 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 hours, and the other operations and parameters are the same as in Example 1.

[0099] Comparative Example 2

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

[0103] Comparative Example 4

[0104] Compared with Example 1, the only difference is 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 a counter electrode. -2 The reaction was carried out for 5 minutes at a current density of , and other operations and parameters were the same as those in Example 1.

[0105] Comparative Example 5

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

[0107] Comparative Example 6

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

[0109] Comparative Example 7

[0110] Compared with Example 1, the only difference is that the preparation steps of the TiO2 nanosheet array in steps one and two are not performed. Instead, commercial TiO2 (P25) is used to replace the TiO2 nanosheet array prepared therein, and it is used to replace the TiO2 nanosheet array in step three, and the treatment of step three is performed. Other operations and parameters are the same as in Example 1.

[0111] Comparative Example 8

[0112] Compared with Example 1, the only difference is that the reactions in steps 2 and 3 are not performed, and the modified TiO2 nanosheet array prepared in step 1 is directly used for the reaction. Other operations and parameters are the same as in Example 1.

[0113] Comparative Example 9

[0114] Compared with Example 1, the only difference is that the reactions in steps 1 and 2 are not performed, and in step 3, carbon paper is used to replace the titanium dioxide array to prepare Cu x Pt alloy was used for the reaction, and other operations and parameters were the same as in Example 1.

[0115] Comparative Example 10

[0116] Compared with Example 1, the only difference is that after adding the copper source and the platinum source in step 3, DMF, KOH and ethylene glycol are not added, but 5 mL of 0.1 M NaBH4 solution is added instead, and the total weight, mass ratio of Pt and Cu metal elements and other operations and parameters are the same as in Example 1.

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

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

[0119]

[0120] In summary, it can be seen from the embodiments and comparative examples that the Ti sheet and the alkali solution are subjected to hydrothermal treatment and further subjected to H + exchange and annealing; this helps to combine with subsequent solvent thermal treatment and preparation parameters, and promotes the subsequent Cu x Pt grows at its surface interface, reducing the structural collapse of the material and improving the photocatalytic reduction of NO3 - Catalytic activity and stability in ammonia synthesis.

[0121] For example, it can be seen from Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 that the preferred titanium dioxide nanoarray preparation process of the present invention can optimize the morphology and crystallinity of the array, which is beneficial for the subsequent Cu x The in-situ growth of Pt creates favorable physical and chemical conditions, which is beneficial to the subsequent Cu x Pt diffusion and interface fusion growth.

[0122] It can be seen from Example 1 and Comparative Example 4 that the organic acid electrochemical modification of the present invention cannot achieve the expected effect, which is not conducive to the subsequent Cu x In situ growth of Pt.

[0123] By comparing Example 1 with Comparative Examples 5 and 6, it can be seen that the Cu-Pt composite of the present invention is used and the high Cu ratio is controlled, which is beneficial to the photoelectrocatalytic reduction of NO3 - Catalytic activity and stability in ammonia synthesis.

[0124] It can be seen from Example 1 and Comparative Examples 7, 8 and 9 that the titanium dioxide nanosheet array prepared by the process of the present invention is beneficial for the subsequent Cu x Pt provides good physical and chemical conditions for the growth of Cu x Pt diffusion and interface fusion growth.

[0125] It can be seen from Example 1 and Comparative Example 10 that the DMF, KOH and ethylene glycol system of the present invention is beneficial to combine with the titanium dioxide carrier to synergistically induce Cu x The interface fusion and diffusion growth of Pt.

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

[0127] It can be seen from Examples 1, 3 and 4 that 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] It can be seen from Example 1 and Example 7 that rapid cooling of the solvent thermal system helps to further optimize the physicochemical characteristics of the material and helps to further improve the ammonia production and Faraday efficiency of the material.

[0129] The above describes the specific implementation of the present invention. However, the present invention is not limited to the above implementation. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A Ti@TiO2 array@Cu x The Pt alloy composite electrode is characterized by: The invention comprises a Ti substrate, a TiO2 nanosheet array in situ grown on the surface of the Ti substrate, and nano-Cu dispersed on the TiO2 nanosheet array. x Pt alloy particles; The TiO2 nanosheets in the TiO2 nanosheet array grow along the Z-axis direction of the Ti substrate; The nano Cu x There is a heterogeneous interface between the Pt alloy particles and the TiO2 nanosheet arrays; Nano Cu x The particle size of the Pt alloy particles is 1-30 nm, wherein the weight ratio of Cu / Pt metal elements is 60-450:1; The Ti@TiO2 array@Cu x In the Pt alloy composite electrode, nano Cu x The weight content of the Pt alloy particles is 35~45Wt.%.

2. The Ti@TiO2 array@Cu as claimed in claim 1 x The Pt alloy composite electrode is characterized by: The nano Cu x In the Pt alloy particles, the weight ratio of Cu / Pt metal elements is 90~400:1; The Ti substrate is a Ti sheet with a thickness of 0.1 mm to 0.4 mm; The thickness of the TiO2 nanosheet array is 1~5 nm.

3. A Ti@TiO2 array@Cu according to claim 1 or 2 x The preparation method of Pt alloy composite electrode is characterized by the following steps: include: Step 1: The Ti substrate is placed in an alkaline solution and subjected to a hydrothermal treatment at a temperature T1, and the hydrothermal treatment product is pre-treated with an acid solution ion exchange and then annealed to obtain a Ti@TiO2 array having an in-situ TiO2 nanosheet array grown on the Ti substrate; The concentration of the alkaline solute in the alkali solution is 2-6M; the temperature T1 is 150-200°C; the holding time at the temperature T1 is 6-12h; the concentration of the acidic solute in the acid solution is 1-2M; the annealing temperature is 300-500°C; Step 2: The Ti@TiO2 array is mixed with a mixed solution containing a Cu source, a Pt source, an alkali, ethylene glycol and DMF, and subjected to a solvent thermal treatment at a temperature T2 to obtain a Ti@TiO2 array with nano Cu deposited on the Ti@TiO2 array. x Ti@TiO2 arrays@Cu of Pt alloy particles x Pt alloy composite electrode; In the mixed solution, the concentration of Cu source is 3-15 mg / mL; the concentration of alkali is 20-80 mg / mL; the temperature T2 is 140-180 °C; and the insulation time at temperature T2 is 6-10 h.

4. The Ti@TiO2 array@Cu as claimed in claim 3 x The method for preparing a Pt alloy composite electrode is characterized in that: In step 1, the alkali solution is an aqueous solution of an alkaline solute, wherein the alkaline solute includes at least one of sodium hydroxide and potassium hydroxide; The concentration of alkaline solute in the alkali solution is 3.5~4.5M; The temperature of the hydrothermal treatment is 160~180℃; The hydrothermal treatment time 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; Annealing temperature is 400~500℃; The holding time at the annealing temperature is 1 to 5 hours.

5. The Ti@TiO2 array@Cu as claimed in claim 3 x The method for preparing a Pt alloy composite electrode is characterized in that: In step 1, the Ti@TiO2 array is electrochemically modified in an organic acid solution in advance to obtain a modified Ti@TiO2 array.

6. The Ti@TiO2 array@Cu as claimed in claim 3 x The method for preparing a Pt alloy composite electrode is characterized in that: 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 alkali includes at least one of sodium hydroxide and potassium hydroxide; The Cu / Pt metal element weight ratio 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 Cu source is 5-10 mg / mL; the concentration of alkali is 30-40 mg / mL.

7. The Ti@TiO2 array@Cu as claimed in claim 3 x The method for preparing a Pt alloy composite electrode is characterized in that: In step 2, after the solvent thermal reaction is completed, the reaction container is directly cooled rapidly using a cooling medium.

8. A Ti@TiO2 array@Cu according to any one of claims 1 to 2 x Pt alloy composite electrode or Ti@TiO2 array@Cu prepared by the preparation method according to any one of claims 3 to 7 x The application of Pt alloy composite electrode is characterized by: Use it as a photocathode for photoelectrocatalytic reduction of NO3 - Synthetic ammonia.

9. A photoelectrocatalytic reduction of NO3 - A device for synthesizing ammonia, comprising a photocathode, characterized in that The photocathode is the Ti@TiO2 array@Cu x Pt alloy composite electrode, or Ti@TiO2 array@Cu prepared by the preparation method according to any one of claims 3 to 7 x Pt alloy composite electrode, or through the Ti@TiO2 array@Cu x Pt alloy composite electrode was prepared.

10. Photoelectrocatalytic reduction of NO3 as claimed in claim 9 - A device for synthesizing ammonia, characterized in that The device is a Zn-NO3 battery.

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