A BiCu / Ti / TiO2 catalyst, its preparation method, and its application.

Abstract

The application discloses a BiCu / Ti / TiO2 catalyst as well as a preparation method and application, and belongs to the technical field of electrocatalytic materials and green synthesis; the BiCu bimetallic catalyst is in-situ grown on a pretreated Ti / TiO2 substrate through a hydrothermal reaction, electrochemical reduction and electrochemical deposition treatment in sequence; the obtained self-supporting BiCu / Ti / TiO2 catalyst is applied to an acidic electrolyte system containing KNO3 and glyoxylic acid as a working electrode to perform an electrocatalytic reduction reaction to synthesize glycine; the synergistic regulation effect of Bi and Cu effectively promotes the carbon-nitrogen coupling process in the reaction, and excellent glycine yield and faradic efficiency are obtained; meanwhile, the in-situ grown three-dimensional electrode structure effectively improves the problem that a traditional powder catalyst is easy to fall off, exhibits good catalytic stability, and provides a green and efficient new way for realizing resource utilization of nitrogen-containing wastewater.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials and green synthesis technology, specifically relating to a BiCu / Ti / TiO2 catalyst, its preparation method, and its application. Background Technology

[0002] Glycine, as an important basic chemical, has wide applications in medicine, food, and chemical industries. In recent years, electrocatalysis technology has been used to convert KNO3 (NO3) into glycine. - The co-reduction of glycine with glyoxylic acid to achieve C-N coupling has attracted much attention. Electrocatalysis technology not only provides a new pathway for the resource-based transformation of nitrogen-containing pollutants, but also effectively replaces traditional high-energy-consuming and high-polluting synthesis processes. It can greenly obtain high-value-added chemicals under mild conditions, and has extremely important environmental and economic value.

[0003] However, existing electrocatalysts still face many challenges in practical applications. The reaction pathway of KNO3 electroreduction is complex, with numerous intermediate products, making it difficult to further improve the selectivity and Faraday efficiency of the target product, glycine. Furthermore, traditional powdered catalysts are prone to detachment from the electrode surface or structural reconstruction under acidic conditions, leading to rapid catalyst deactivation and difficulty in maintaining long-term catalytic performance. To date, there are few reports on catalyst preparation techniques that combine high glycine yield and long-term structural stability in acidic systems; this invention aims to solve the above problems. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a method for preparing a BiCu / Ti / TiO2 catalyst and its application in the electrocatalytic synthesis of glycine. Specifically, it involves a method for preparing a BiCu bimetallic catalyst on a Ti / TiO2 substrate, the BiCu bimetallic catalyst itself, and its application in the electrocatalytic co-reduction of KNO3 and glyoxylic acid to synthesize glycine under acidic conditions. To achieve the above objective, this application proposes to utilize hydrothermal reaction and stepwise electrochemical reduction and deposition techniques to grow a BiCu bimetallic catalyst in situ on a pretreated Ti / TiO2 substrate and apply it in an acidic electrolyte system.

[0005] Specifically, to achieve the above objectives, the present invention is implemented through at least one of the following technical solutions.

[0006] According to a first aspect of the present invention, a method for preparing a BiCu / Ti / TiO2 catalyst is provided, comprising the following steps: (1) Obtaining a Ti / TiO2 substrate; (2) First, BiOCl precursor is grown on the Ti / TiO2 substrate by hydrothermal reaction, then electrochemically reduced to metallic Bi, and finally electrochemically deposited in a solution containing copper ions to obtain the BiCu / Ti / TiO2 catalyst.

[0007] In some embodiments, step (1) of obtaining the Ti / TiO2 substrate includes: washing the titanium substrate with water and alcohol, and then calcining it in an air atmosphere at 380-420°C for 2-6 hours.

[0008] In some embodiments, in step (2), the BiOCl precursor is a bismuth-containing compound; In some embodiments, in step (2), the temperature of the hydrothermal reaction is 160-200°C, and the holding time of the hydrothermal reaction is 18-24 hours.

[0009] In some embodiments, in step (2), the hydrothermal reaction is carried out in a reaction vessel lined with polytetrafluoroethylene.

[0010] In some embodiments, the PTFE-lined reactor is a PTFE-lined stainless steel reactor.

[0011] In some embodiments, the hydrothermal reaction in step (2) includes immersing the Ti / TiO2 substrate in a precursor fluid and heating it to 160-200°C for 18-24 hours.

[0012] In some embodiments, the precursor fluid is a mixed solution of Bi(NO3)3·5H2O and NH4Cl.

[0013] In some embodiments, the preparation of the precursor fluid includes: dissolving Bi(NO3)3·5H2O and NH4Cl in ethylene glycol, mixing them thoroughly, and obtaining the precursor fluid.

[0014] In some embodiments, the preparation of the precursor fluid includes: dissolving 1.5-1.7 mmol of Bi(NO3)3·5H2O and 3-5 mmol of NH4Cl in 40 mL of ethylene glycol, mixing well, and obtaining the precursor fluid.

[0015] In some embodiments, the preparation of the precursor fluid includes: dissolving 1.6 mmol of Bi(NO3)3·5H2O and 4 mmol of NH4Cl in 40 mL of ethylene glycol, mixing well, and obtaining the precursor fluid.

[0016] In some embodiments, in step (2), the electrochemical reduction is carried out in a sulfate solution.

[0017] In some embodiments, in step (2), the applied potential range for electrochemical reduction is -0.4 to -0.6 V vs. RHE, and the treatment time for electrochemical reduction is 50 to 70 minutes; the sulfate solution is a 0.08 to 0.12 mol / L Na2SO4 solution.

[0018] In some embodiments, in step (2), the solution containing copper ions is a sulfate solution containing copper ions.

[0019] In some embodiments, the sulfate solution containing copper ions is a mixed solution of Na2SO4 and CuSO4; in the mixed solution of Na2SO4 and CuSO4, the concentration of Na2SO4 is 0.1 mol / L and the concentration of CuSO4 is 0.001 mol / L; the applied potential for electrochemical deposition is -0.4 to -0.6 V vs. RHE, and the processing time for electrochemical deposition is 5 to 15 minutes.

[0020] In some embodiments, the electrochemical deposition is applied at a potential of -0.5V vs. RHE.

[0021] According to a second aspect of the present invention, the present invention provides a BiCu / Ti / TiO2 catalyst prepared by the above preparation method.

[0022] According to a third aspect of the present invention, the present invention provides the application of a BiCu / Ti / TiO2 catalyst in the electrosynthesis of glycine, the application comprising the following steps: Using a BiCu / Ti / TiO2 catalyst as the working electrode, an electrocatalytic reduction reaction was carried out in an acidic electrolyte containing KNO3 and glyoxylic acid to obtain glycine.

[0023] In some embodiments, the acidic electrolyte containing KNO3 and glyoxylic acid is a mixture obtained by mixing KNO3, glyoxylic acid, an inorganic acid, and water; the inorganic acid is sulfuric acid; and the concentration of the inorganic acid in the acidic electrolyte containing KNO3 and glyoxylic acid is 0.1~0.7 mol / L.

[0024] In some embodiments, in the acidic electrolyte containing KNO3 and glyoxylic acid, the concentration of KNO3 is 0.5~1.5 mol / L and the concentration of glyoxylic acid is 0.08~0.12 mol / L.

[0025] In some embodiments, the operating potential of the electrocatalytic reduction reaction is -0.5 to -0.7 V vs. RHE.

[0026] In some embodiments, the electrocatalytic reduction reaction is carried out in an H-type electrolytic cell separated by a proton exchange membrane, and a standard three-electrode system is used.

[0027] The beneficial effects of this invention are: The method provided in this invention successfully constructs a BiCu bimetallic catalyst based on a Ti / TiO2 substrate through a special pretreatment and stepwise electrochemical reduction and deposition process. This method has a relatively simple process flow and mild conditions. More importantly, when applied to the co-reduction reaction of KNO3 and glyoxylic acid under acidic conditions, the synergistic effect of Bi and Cu effectively promotes the carbon-nitrogen coupling process, resulting in excellent glycine Faradaic efficiency and yield. Simultaneously, when this BiCu / Ti / TiO2 catalyst is used as an electrode, its in-situ grown three-dimensional electrode structure significantly improves the technical problem of easy detachment of traditional powder catalysts, exhibiting high catalytic stability. This provides a promising approach for the high-value resource utilization of nitrogen-containing wastewater. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 These are scanning electron microscope (SEM) images of the products at each stage of the preparation process in Example 1 of this invention; wherein, (a) and (b) are BiOCl precursors generated by hydrothermal reaction, (c) and (d) are metal Bi / Ti / TiO2 catalysts obtained after electrochemical reduction, and (e) and (f) are BiCu / Ti / TiO2 catalysts obtained after electrochemical deposition of Cu; the scale bar of (a), (c), and (e) is 500 nm, and the scale bar of (b), (d), and (f) is 2.5 μm.

[0030] Figure 2 The X-ray diffraction (XRD) spectra of the single-metal Bi / Ti / TiO2 catalyst of Comparative Example 1 and the BiCu / Ti / TiO2 catalyst prepared in Example 1 are shown.

[0031] Figure 3 Linear sweep voltammetry curves of the BiCu / Ti / TiO2 catalyst prepared in Example 1 of this invention and the single metal Bi / Ti / TiO2 catalyst of Comparative Example 1 are shown. In the figure, the solid line (b) represents the BiCu / Ti / TiO2 catalyst and the dashed line (a) represents the comparative Bi / Ti / TiO2 catalyst.

[0032] Figure 4This is a comparison of the Faraday efficiency and yield performance of the single-metal Bi / Ti / TiO2 catalyst and the BiCu / Ti / TiO2 catalyst in the electrosynthesis of glycine under the same optimal acidic conditions, according to Comparative Example 1 of this invention. In the figure, the diagonally filled bars represent the glycine yield, and the horizontally filled bars represent the Faraday efficiency.

[0033] Figure 5 The figure shows the long-term stability test results of the BiCu / Ti / TiO2 catalyst prepared in Example 1 of this invention during the continuous electrocatalytic synthesis of glycine; in the figure, the diagonally filled bars represent the glycine yield, and the horizontally filled bars represent the Faraday efficiency.

[0034] Figure 6 The figures show the 1H NMR spectra of the product and the standard after electrolysis in Example 1 of this invention. In the figure, spectrum (a) is the 1H NMR spectrum of the product after electrolysis, and spectrum (b) is the 1H NMR spectrum of the standard containing 60mM glycine, 60mM glyoxylic acid and 60mM glycolic acid. Peak 1 is DMSO, peak 2 is glycine, peak 3 is glycolic acid, peak 4 is glyoxylic acid, and peak 5 is ammonium ion.

[0035] Figure 7 This is a performance comparison diagram of the catalysts prepared under different Cu electrodeposition times in Examples 1, 2 and 3 of the present invention; in the diagram, the diagonally filled bars represent glycine yield, and the horizontally filled bars represent Faraday efficiency.

[0036] Figure 8 The image shows the scanning electron microscope (SEM) morphology of the catalyst prepared under the condition of electrochemical deposition time of 5 minutes in Example 2 of the present invention; in the figure, (a) is the high magnification morphology image and (b) is the low magnification morphology image.

[0037] Figure 9 The image shows the scanning electron microscope (SEM) morphology of the catalyst prepared under the condition of electrochemical deposition time of 15 minutes in Example 3 of the present invention; in the image, (a) is a high-magnification morphology image and (b) is a low-magnification morphology image.

[0038] Figure 10 This is a comparison of the performance of the BiCu / Ti / TiO2 catalyst prepared in Example 1 of this invention in electrosynthesizing glycine in acidic electrolytes with different sulfuric acid concentrations; in the figure, the diagonally filled bars represent the glycine yield, and the horizontally filled bars represent the Faraday efficiency.

[0039] Figure 11 The graph shows a comparison of the performance of the BiCu / Ti / TiO2 catalyst prepared in Example 1 of this invention in the electrosynthesis of glycine at different working potentials. In the graph, the diagonally filled bars represent the glycine yield, and the horizontally filled bars represent the Faraday efficiency.

[0040] Figure 12 This is a comparison of the performance of the BiCu / Ti / TiO2 catalyst prepared in Example 1 of this invention in the electrosynthesis of glycine under different nitrate concentrations; in the figure, the diagonally filled bars represent the glycine yield, and the horizontally filled bars represent the Faraday efficiency.

[0041] Figure 13 The image shows the scanning electron microscope (SEM) morphology of the catalyst prepared in Comparative Example 2 of this invention with a CuSO4 concentration of 0.002 mol / L; in the image, (a) is the high-magnification morphology image and (b) is the low-magnification morphology image.

[0042] Figure 14 This is a comparison of the electrosynthesis performance of glycine by the catalyst prepared in Comparative Example 2 with a CuSO4 concentration of 0.002 mol / L and the BiCu / Ti / TiO2 catalyst prepared in Example 1. In the figure, the diagonally filled bars represent the glycine yield, and the horizontally filled bars represent the Faraday efficiency.

[0043] Figure 15 The images show a comparison of the macroscopic morphology of the electrodes of Example 1 and Comparative Example 3 before and after continuous electrocatalytic reduction reaction (glycine synthesis test); wherein: (a) is the morphology of the powder electrode of Comparative Example 3 prepared by the conventional drop coating method before the reaction; (b) is the morphology of the electrode of Comparative Example 3 after reacting for 10 h under -0.6V vs. RHE conditions, where severe detachment of the catalyst layer can be seen; (c) is the morphology of the electrode prepared by hydrothermal in-situ growth of Example 1 before the reaction; (d) is the morphology of the electrode of Example 1 after reacting for 10 h under the same conditions, where the catalyst layer is basically intact and there is no obvious detachment. Detailed Implementation

[0044] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0045] Example 1 The BiCu / Ti / TiO2 catalyst of this embodiment is prepared by the following steps: (1) After ultrasonically cleaning the titanium mesh with deionized water and anhydrous ethanol, the titanium mesh was placed in a muffle furnace and calcined in air at 400°C for 3 hours to obtain a Ti / TiO2 substrate with an oxide layer on the surface.

[0046] (2) Dissolve 1.6 mmol Bi(NO3)3·5H2O and 4 mmol NH4Cl in 40 mL of ethylene glycol and stir until homogeneous to obtain a precursor solution. Then, immerse the Ti / TiO2 substrate with an oxide layer on its surface into the precursor solution and perform a hydrothermal reaction at 180 °C for 20 hours. After the hydrothermal reaction is completed, remove the Ti / TiO2 substrate after the hydrothermal reaction, rinse it with deionized water and air dry it naturally to obtain an electrode with BiOCl precursor grown in situ (Ti / TiO2 substrate with BiOCl precursor grown).

[0047] (3) Electroreduction and deposition treatment: The electrode with BiOCl precursor prepared in step (2) was used as the working electrode, with a platinum sheet as the auxiliary electrode and Ag / AgCl as the reference electrode. At room temperature, it was first placed in a 0.1 mol / L Na2SO4 solution and electrochemically reduced for 60 minutes at a constant potential of -0.5 V vs. RHE to convert the BiOCl precursor into metallic bismuth, thus obtaining the electrochemically reduced metallic Bi / Ti / TiO2 catalyst. Subsequently, the electrochemically reduced metallic Bi / Ti / TiO2 catalyst was transferred as the deposition electrode to a sulfate solution containing copper ions (a mixed solution of Na2SO4 and CuSO4, with a Na2SO4 concentration of 0.1 mol / L and a CuSO4 concentration of 0.001 mol / L). Electrochemical deposition was performed for 10 minutes at a constant potential of -0.5 V vs. RHE to obtain the electrochemically deposited electrode. The electrode was repeatedly rinsed with deionized water and air-dried to obtain the BiCu / Ti / TiO2 catalyst.

[0048] Structural and morphological characterization: The products from each stage of the preparation process in this embodiment (Ti / TiO2 substrate with BiOCl precursor, electrochemically reduced metal Bi / Ti / TiO2 catalyst, and BiCu / Ti / TiO2 catalyst, respectively) were characterized by scanning electron microscopy (SEM). The results are shown in [link to SEM]. Figure 1 Following the hydrothermal reaction, lamellar BiOCl precursors were uniformly grown on the surface of the Ti / TiO2 substrate. Figure 1 (a) and (b)); after electrochemical reduction, the precursor is converted into metallic Bi ( Figure 1 (c) and (d)); after further electrochemical deposition of Cu, Cu nanoparticles can be observed dispersed on the surface of the Bi substrate, forming a BiCu bimetallic composite structure. Figure 1 (e) and (f)). X-ray diffraction (XRD) analyses were performed on the BiCu / Ti / TiO2 catalyst prepared in this embodiment and the single-metal Bi electrode in Comparative Example 1, respectively. The results are shown in [reference]. Figure 2Linear sweep voltammetry (LSV) tests were performed on the BiCu / Ti / TiO2 catalyst prepared in this embodiment and the single metal Bi electrode in Comparative Example 1. The BiCu composite electrode exhibited a higher current density than the single metal Bi electrode, indicating that the introduction of Cu effectively improved the electrocatalytic activity. (See the results below.) Figure 3 .

[0049] To verify the effectiveness of the BiCu / Ti / TiO2 catalyst prepared in this embodiment, it was used as a composite electrode for electrocatalytic reduction reaction (glycine synthesis test) to test its catalytic performance. Details are as follows.

[0050] Performance testing: The BiCu / Ti / TiO2 catalyst prepared in Example 1 (size 1cm × 2cm, with catalyst loaded on both sides, effective working area of ​​1.5cm² per single-sided surface) was tested. 2 Using a platinum sheet (1 cm × 1 cm) as the working electrode and an Ag / AgCl electrode filled with saturated KCl as the reference electrode, a standard three-electrode system was constructed in an H-type electrolytic cell separated by a Nafion 117 proton exchange membrane for electrolysis testing. The cathode chamber had a volume of 100 mL, and 50 mL of an acidic electrolyte (pH approximately 0, a mixture of KNO3, glyoxylic acid, inorganic acid, and water) containing 1 mol / L KNO3, 0.1 mol / L glyoxylic acid, and 0.5 mol / L H2SO4 was added. Electrolysis was performed at a constant working potential of -0.6 V vs. RHE, achieving a glycine Faradaic efficiency of 63.8% and a yield of 0.282 mmol / L. -1 cm -2 Performance degradation is less than 5% after 50 hours of continuous operation. See [link / reference] Figure 4 , Figure 5 .

[0051] The electrolysis products were subjected to proton nuclear magnetic resonance spectroscopy (NMR). 1 ¹H NMR analysis, by comparing with the chromatograms of standard samples containing glycine, glyoxylic acid, and glycolic acid, confirmed the formation of the target product glycine and the composition of other products. See the results below. Figure 6 .

[0052] Example 2 The only difference between the BiCu / Ti / TiO2 catalyst preparation method in this embodiment and that in Example 1 is that in step (3), the electrochemical deposition time in the sulfate solution containing copper ions (a mixed solution of Na2SO4 and CuSO4, with a Na2SO4 concentration of 0.1 mol / L and a CuSO4 concentration of 0.001 mol / L) is adjusted from 10 minutes to 5 minutes. All other operations and parameters are completely consistent with Example 1. Performance testing: Electrocatalytic reduction reaction was carried out according to the test conditions of Example 1. Due to the shorter electrochemical deposition time in this embodiment, the loading of Cu nanoparticles was insufficient, and the synergistic regulatory effect between the bimetals was weakened. The results showed that the carbon-nitrogen coupling efficiency of its catalytic conversion of KNO3 and glyoxylic acid decreased. The final glycine Faraday efficiency was 51.1%, and the yield was 0.204 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 7 The scanning electron microscope (SEM) morphology of the catalyst prepared in this embodiment is shown in [reference]. Figure 8 It can be seen that the coverage of Cu nanoparticles on the Ti / TiO2 substrate surface is significantly lower than that in Example 1 ( Figure 1 This is consistent with the causes of the aforementioned performance differences.

[0053] Example 3 The preparation method of the BiCu / Ti / TiO2 catalyst in this embodiment differs from that in Example 1 only in that: in step (3), the electrochemical deposition time in the sulfate solution containing copper ions (a mixed solution of Na2SO4 and CuSO4, with a Na2SO4 concentration of 0.1 mol / L and a CuSO4 concentration of 0.001 mol / L) is adjusted from 10 minutes to 15 minutes. All other operations and parameters are completely consistent with those in Example 1. Performance test: The electrocatalytic reduction reaction was carried out according to the test conditions of Example 1. Due to the excessively long electrochemical deposition time in this embodiment, excessive Cu deposition occurred. The excessively thick Cu layer may significantly obscure the Bi active sites at the bottom layer, and the contact interface and synergistic effect between the two may be destroyed. The results show that the final glycine Faraday efficiency is 45.3%, and the yield is 0.213 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 7 The scanning electron microscope (SEM) morphology of the catalyst prepared in this embodiment is shown in [reference]. Figure 9 It can be seen that the excessive deposition and significant agglomeration of Cu nanoparticles on the Ti / TiO2 substrate surface are consistent with the causes of the aforementioned performance differences.

[0054] Example 4 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the sulfuric acid concentration of the acidic electrolyte in the electrocatalytic reduction reaction was adjusted from 0.5 mol / L to 0.1 mol / L; all other test conditions were identical to those in Example 1. Due to the low acidity of the electrolyte system, insufficient proton supply affected the proton-coupled electron transfer step in the nitrate reduction process, leading to hindered conversion kinetics of the target product. The results showed that the final glycine obtained had a Faraday efficiency of 26.7% and a yield of 0.040 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 10 .

[0055] Example 5 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the sulfuric acid concentration of the acidic electrolyte in the electrocatalytic reduction reaction was adjusted from 0.5 mol / L to 0.3 mol / L; all other test conditions were identical to those in Example 1. The results show that while moderately increasing the acidity helps the reaction proceed, the optimal proton concentration was not reached, and the final glycine Faraday efficiency was 47.2%, with a yield of 0.237 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 10 .

[0056] Example 6 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the sulfuric acid concentration of the acidic electrolyte in the electrocatalytic reduction reaction was adjusted from 0.5 mol / L to 0.7 mol / L; all other test conditions were identical to those in Example 1. Due to the excessively high acidity of the system, the hydrogen evolution side reaction on the cathode surface may be aggravated, resulting in strong electron competition with the nitrate reduction reaction and a decrease in glycine production performance. The results show that the final glycine obtained has a Faraday efficiency of 25.7% and a yield of 0.218 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 10 .

[0057] Example 7 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the constant working potential in the electrocatalytic reduction reaction was adjusted from -0.6V vs. RHE to -0.5V vs. RHE; all other test conditions were identical to those in Example 1. Due to the more positive applied reduction potential, the overall electrochemical driving force of the reaction is relatively weak, which is presumably likely to slow down the electron transfer rate, thereby limiting the kinetics of nitrate reduction and subsequent carbon-nitrogen coupling to some extent. The results show that the final glycine obtained has a Faradaic efficiency of 54.6% and a yield of 0.170 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 11 .

[0058] Example 8 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the constant working potential in the electrocatalytic reduction reaction was adjusted from -0.6V vs. RHE to -0.7V vs. RHE; all other test conditions were identical to those in Example 1. Due to the excessively negative applied reduction potential, it is speculated that this may have exacerbated the hydrogen evolution side reaction on the electrode surface, leading to the consumption of some electrons by the water reduction side reaction, thereby reducing the electron utilization rate of the target carbon-nitrogen coupling reaction. The results show that the final glycine obtained has a Faraday efficiency of 56.7% and a yield of 0.245 mmol / h. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 11 .

[0059] Example 9 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the concentration of KNO3 in the acidic electrolyte during the electrocatalytic reduction reaction was adjusted from 1 mol / L to 0.5 mol / L; all other test conditions were identical to those in Example 1. Due to the low concentration of the substrate nitrate, it is speculated that this may have led to insufficient local reactant supply on the catalyst surface, limiting the formation rate of the key nitrogen-containing intermediate and thus affecting the final glycine synthesis efficiency. The results show that the final glycine obtained has a Faradaic efficiency of 49.8% and a yield of 0.163 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 12 .

[0060] Example 10 The preparation method of BiCu / Ti / TiO2 in this embodiment is completely consistent with that in Example 1. The only difference in performance testing compared to Example 1 is that the KNO3 concentration of the acidic electrolyte in the electrolysis test was adjusted from 1 mol / L to 1.5 mol / L; all other test conditions were identical to those in Example 1. Due to the excessively high nitrate concentration in the system, it is speculated that this may lead to competitive over-adsorption of nitrate and its reduction intermediates at the active sites on the catalyst surface, which to some extent hinders the effective activation of the other substrate (glyoxylic acid), thus disrupting the optimal carbon-nitrogen coupling equilibrium. The results show that the final glycine obtained has a Faraday efficiency of 38.5% and a yield of 0.188 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 12 .

[0061] Comparative Example 1 This comparative example aims to verify the key synergistic regulatory role of Cu in the carbon-nitrogen coupling and subsequent hydrogenation process, and provides a catalyst (a single-metal Bi / Ti / TiO2 pure bismuth electrode). Its preparation method differs from Example 1 in that: in step (3), after electrochemical reduction at a constant potential of -0.5V vs. RHE for 60 minutes in 0.1 mol / L Na2SO4 solution, the electrochemically reduced Bi / Ti / TiO2 catalyst is directly removed, washed, and dried, omitting the subsequent electrochemical deposition step in a sulfate solution containing copper ions, ultimately yielding only a single-metal Bi / Ti / TiO2 pure bismuth electrode. Performance testing: The single-metal Bi / Ti / TiO2 pure bismuth electrode was subjected to an electrocatalytic reduction reaction (glycine synthesis test) under the same acidic conditions as in Example 1. The results show that, due to the lack of synergistic electronic modulation by Cu, the single-metal Bi site's ability to further hydrogenate and reduce the key carbon-nitrogen coupling intermediate (i.e., the C=N bond) is significantly limited. This caused the reaction process to be blocked in the final step, resulting in a final glycine Faraday efficiency of 38.7% and a yield of 0.184 mmol / L. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 4 The scanning electron microscope (SEM) morphology of the catalyst (a single-metal Bi / Ti / TiO2 pure bismuth electrode) prepared in this comparative example is shown in [reference]. Figure 1 This is consistent with the causes of the aforementioned performance differences.

[0062] Comparative Example 2 The preparation method of the BiCu / Ti / TiO2 catalyst in this comparative example differs from that in Example 1 only in that: in step (3), the concentration of CuSO4 in the sulfate solution containing copper ions (a mixed solution of Na2SO4 and CuSO4) is adjusted from 0.001 mol / L to 0.002 mol / L. All other operations and parameters are completely consistent with Example 1. Performance testing: Electrocatalytic reduction reaction (glycine synthesis test) was carried out according to the performance test conditions of Example 1. Due to the Cu in the deposition solution... 2+ With increasing concentration, Cu during electrochemical deposition... 2+ The significantly increased flux led to excessive Cu deposition and aggregation on the Bi surface, forming a densely packed granular layer that heavily encapsulated the underlying Bi. This morphological change significantly reduced the effective exposed area of ​​Bi active sites, limiting the ability of nitrate to efficiently activate and generate key nitrogen-containing intermediates. Furthermore, it disrupted the co-exposure and synergy between Bi and Cu at the catalytic interface, making the tandem catalytic mechanism between the Bi and Cu bimetals difficult to function. Simultaneously, the increased Cu exposure ratio exacerbated the hydrogen evolution side reaction under acidic conditions. The final glycine obtained had a Faraday efficiency of 50.9% and a yield of 0.224 mmol / h. -1 cm -2 All are lower than in Example 1, see [link / reference] Figure 14 The scanning electron microscope (SEM) morphology of the catalyst prepared in this comparative example is shown in [reference]. Figure 13 This is consistent with the causes of the aforementioned performance differences.

[0063] Comparative Example 3 This comparative example provides a control electrode for the electrocatalytic synthesis of glycine, differing from Example 1 only in that it is prepared using a traditional powder drop-coating method instead of an in-situ growth method. Specifically, the preparation method is as follows: After growing a BiCu catalyst layer in situ on a Ti / TiO2 substrate according to the method in Example 1, the catalyst layer is completely scraped off the substrate to obtain BiCu catalyst powder with the same composition as in Example 1. The obtained BiCu catalyst powder is dispersed in 1 mL of anhydrous ethanol, and 50 μL of a 5% (w / w) Nafion solution is added. The mixture is ultrasonically mixed to form a catalyst slurry, which is then drop-coated onto the surface of a Ti / TiO2 substrate of the same size as in Example 1 and allowed to dry naturally to form a film. Performance testing: Electrocatalytic reduction reaction (glycine synthesis test) was conducted under the same constant potential and acidic electrolyte system as in Example 1. Because the powder catalyst prepared by the traditional drop-coating method is only physically attached to the electrode surface by a polymer binder, its bonding force with the conductive substrate is weak. During the vigorous electrolysis process under acidic conditions, the formation and escape of local microbubbles may occur, making the catalyst layer highly susceptible to delamination due to interfacial stress. Results showed that after 10 hours of continuous reaction, the catalyst layer on the comparative electrode surface suffered severe detachment; in contrast, the BiCu catalyst layer in Example 1, firmly grown in situ on the Ti / TiO2 substrate, remained largely intact with no significant detachment. This demonstrates that the in-situ growth strategy employed in this invention has significant advantages in improving electrode mechanical stability and extending cycle life. (See [link to previous section]). Figure 15 .

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a BiCu / Ti / TiO2 catalyst, characterized in that, Includes the following steps: (1) Obtaining a Ti / TiO2 substrate; (2) First, BiOCl precursor is grown on the Ti / TiO2 substrate by hydrothermal reaction, then electrochemically reduced to metallic Bi, and finally electrochemically deposited in a solution containing copper ions to obtain the BiCu / Ti / TiO2 catalyst. In step (1), obtaining the Ti / TiO2 substrate includes: washing the titanium substrate with water and alcohol, then calcining it in an air atmosphere at 380-420°C for 2-6 hours; In step (2), the solution containing copper ions is a sulfate solution containing copper ions; The sulfate solution containing copper ions is a mixed solution of Na2SO4 and CuSO4; in the mixed solution of Na2SO4 and CuSO4, the concentration of Na2SO4 is 0.1 mol / L and the concentration of CuSO4 is 0.001 mol / L; the applied potential for electrochemical deposition is -0.4 to -0.6 V vs. RHE; and the processing time for electrochemical deposition is 10 to 15 minutes.

2. The method for preparing a BiCu / Ti / TiO2 catalyst according to claim 1, characterized in that, In step (2), the temperature of the hydrothermal reaction is 160-200℃, and the holding time of the hydrothermal reaction is 18-24 hours.

3. The method for preparing a BiCu / Ti / TiO2 catalyst according to claim 1, characterized in that, In step (2), the electrochemical reduction is carried out in a sulfate solution.

4. The method for preparing a BiCu / Ti / TiO2 catalyst according to claim 3, characterized in that, In step (2), the applied potential range for electrochemical reduction is -0.4 to -0.6 V vs. RHE, and the treatment time for electrochemical reduction is 50 to 70 minutes; the sulfate solution is a 0.08 to 0.12 mol / L Na2SO4 solution.

5. A BiCu / Ti / TiO2 catalyst, characterized in that, The catalyst was prepared using the method described in any one of claims 1-4.

6. The application of the BiCu / Ti / TiO2 catalyst as described in claim 5 in the electrosynthesis of glycine, characterized in that, Includes the following steps: Using a BiCu / Ti / TiO2 catalyst as the working electrode, an electrocatalytic reduction reaction was carried out in an acidic electrolyte containing KNO3 and glyoxylic acid to obtain glycine.

7. The application of the BiCu / Ti / TiO2 catalyst according to claim 6 in the electrosynthesis of glycine, characterized in that, The acidic electrolyte containing KNO3 and glyoxylic acid is a mixture obtained by mixing KNO3, glyoxylic acid, an inorganic acid, and water; the inorganic acid is sulfuric acid; and the concentration of the inorganic acid in the acidic electrolyte containing KNO3 and glyoxylic acid is 0.1~0.7 mol / L.

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