Preparation method of platinum-rhodium alloy for improving electro-catalytic hydrogenation activity and selectivity of phenol

Abstract

The invention belongs to the field of new materials and catalytic hydrogenation, and particularly provides a preparation method of a platinum-rhodium alloy for improving electro-catalytic hydrogenation activity and selectivity of phenol, and the platinum-rhodium alloy is prepared by introducing rhodium metal into a platinum-based structure with certain phenol hydrogenation activity and utilizing an electro-deposition process. Due to the fact that the hydrogen adsorption energy (-0.15 eV) on the surface of rhodium metal is higher than that of Pt (0 eV), HER kinetics is relatively slow so as to inhibit HER side reaction, meanwhile, alloying can further enhance adsorption of a substrate on the surface of the catalyst, and the utilization rate of active hydrogen in the electro-catalysis phenol hydrogenation process is increased.

Description

Technical Field

[0001] This invention belongs to the field of new materials and catalytic hydrogenation, and specifically provides a method for preparing a platinum-rhodium alloy for improving the activity and selectivity of electrocatalytic hydrogenation of phenol. Background Technology

[0002] Lignin, as the most carbon- and energy-rich component of biomass, holds immense promise for replacing fossil resources in the production of various high-value-added chemicals. However, the inherent chemical inertness of lignin-derived phenolic compounds severely inhibits the full utilization and value-added processing of lignin biomass. Phenol, as a fundamental building block of phenolic compounds, is primarily upgraded and converted through thermocatalytic hydrogenation (TCH), which often requires pressurized hydrogen (typically greater than 4 bar) and high operating temperatures (100-350℃). High energy consumption, high investment costs, and the use of "grey hydrogen" at the cost of significant CO2 emissions pose significant challenges to sustainable biomass upgrading. Electrocatalytic hydrogenation (ECH), utilizing green electricity from renewable energy sources (such as solar and wind power), is increasingly becoming a greener and more sustainable alternative strategy for upgrading lignin-derived phenolic compounds.

[0003] Platinum (Pt)-based metal catalysts have been extensively studied in the hydrogenation conversion of phenolic compounds using lignin as a model due to their low hydrogen evolution overpotential and excellent aromatic ring hydrogenation activity. However, the Faraday efficiency and product selectivity of Pt-catalyzed phenol hydrogenation remain unsatisfactory because pure Pt exhibits poor adsorption of phenolic substrates and is prone to vigorous HER side reactions. Alloying strategies can effectively regulate the adsorption / desorption behavior of reactants / intermediates / products on the catalyst by modulating the electronic structure and d-band centers of the metal, thereby improving ECH performance. Rhodium (Rh) has a higher hydrogen binding energy (-0.15 eV) than Pt (0 eV), resulting in relatively slow HER kinetics. Therefore, introducing Rh into Pt-based catalysts can modulate the surface hydrogen adsorption energy, suppress HER, and the synergistic effect of Pt and Rh can enhance substrate adsorption on the catalyst surface, improving the utilization rate of active hydrogen in ECH.

[0004] Existing methods for preparing platinum-rhodium alloys typically require various reducing agents and high-temperature reactions, resulting in complex processes and high costs. Electrodeposition, as a promising alternative for rapid synthesis at room temperature, is currently performed in organic electrolyte systems. However, the ionic conductivity of most organic solvents is far lower than that of water, and at the deposition potential, organic solvent molecules may undergo reduction or oxidative decomposition on the electrode surface, producing carbon, sulfur, nitrogen, and other fragments that co-deposit into the Pt alloy, severely contaminating the surface purity of the catalyst and poisoning active sites. Furthermore, commonly used polar aprotic solvents are expensive and highly toxic, leading to potential safety, environmental, and cost issues, and their application in the electrocatalytic hydrogenation of phenol is limited.

[0005] Therefore, it is of great significance to develop a green and controllable aqueous electrodeposition process to obtain a platinum-rhodium alloy that can improve the electrocatalytic hydrogenation activity and selectivity of phenol. Summary of the Invention

[0006] This invention addresses the numerous shortcomings of existing technologies by providing a method for preparing a platinum-rhodium alloy to improve the activity and selectivity of electrocatalytic hydrogenation of phenol. The method involves introducing rhodium metal into a platinum-based structure with certain phenol hydrogenation activity and then preparing the platinum-rhodium alloy using an electrodeposition process. Because the hydrogen adsorption energy on the rhodium metal surface (-0.15 eV) is higher than that of Pt (0 eV), the HER kinetics are relatively slow, thus suppressing HER side reactions. Simultaneously, alloying enhances the adsorption of the substrate on the catalyst surface, improving the utilization rate of active hydrogen during the electrocatalytic hydrogenation of phenol.

[0007] Compared with existing technologies, the main inventive concept of this invention is to prepare a platinum-rhodium alloy using a simple and controllable electrodeposition process, and to use it as a catalyst for the hydrogenation of phenol. It can control the selectivity of the hydrogenation products simply by controlling the reaction current or applying a potential at room temperature and pressure. Compared with traditional thermocatalytic hydrogenation reactions, it has the advantages of milder reaction conditions, controllable cost, and sustainable production through coupling with renewable energy. The prepared platinum-rhodium alloy can be directly deposited on a carrier, thus avoiding the cumbersome coating process required by traditional methods, and the drawback of the introduction of binders affecting electrode conductivity.

[0008] The specific technical solution of the present invention is as follows: A method for preparing a platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol includes the following steps: (1) Pretreatment of conductive carbon substrate: The carbon substrate was pretreated with concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence. After drying, the modified carbon substrate was obtained for later use.

[0009] (2) Preparation of platinum-rhodium alloy precursor solution: H2PtCl6 and Rh(NO3)3 were uniformly mixed with Na2SO4 aqueous solution at a Pt / Rh molar ratio of 3:1-1:3. The mixture was then stirred in a magnetic stirrer, filtered, and set aside to obtain a platinum-rhodium alloy precursor solution.

[0010] (3) Preparation of platinum-rhodium alloy electrocatalyst: A modified carbon substrate was used as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode. Cyclic voltammetric electrodeposition was performed using the above precursor solution as the electrolyte. Finally, the obtained sample was rinsed with deionized water and dried with N2.

[0011] In step (1), the carbon substrate used is any one of carbon cloth, carbon paper, or carbon fiber paper; the area of ​​the carbon substrate is 1-5 cm². 2 .

[0012] In step (1), the carbon substrate is pretreated in concentrated nitric acid for 1-3 hours and the pretreatment temperature is 60-120℃; the nitric acid concentration is controlled at 40-60wt%.

[0013] In step (1), ultrasonic cleaning is performed in an ultrasonic cleaner with ethanol and deionized water in turn, and then the parts are dried for later use. The ultrasonic frequency is 40 kHz and the ultrasonic time is 20 min for each part.

[0014] In step (1), pretreating the carbon substrate with nitric acid can greatly enhance its hydrophilicity, allowing the originally hydrophobic carbon cloth to be completely wetted by water or electrolyte, ensuring sufficient contact between the electrode and the electrolyte; at the same time, it can also provide abundant active sites and binding sites, thereby promoting the subsequent loading of PtRh alloy. The subsequent ultrasonic cleaning can remove contaminants from the manufacturing and storage process, and can effectively remove some loose carbon particles or fragments that may be generated by concentrated nitric acid oxidation and not firmly bonded to the carbon fiber body, while neutralizing and removing residual acid.

[0015] In step (2), the total concentration of Pt and Rh ions in the precursor solution is 5-20 mmol / L and the molar ratio of Pt / Rh is 3:1-1:3; the concentration of the Na2SO4 aqueous solution is 0.5 mol / L and the total volume of the solution is 10-30 mL.

[0016] Furthermore, in step (2), the total ion concentration of Pt and Rh in the precursor solution is 10 mmol / L; the molar ratio of Pt / Rh is 1:3.

[0017] Furthermore, in step (3), the potential range of the cyclic voltammetric electrodeposition process is -0.5 to 1.7 V (vs. Ag / AgCl), the number of deposition cycles is 30 to 50 cycles, preferably 50 cycles, and the reaction is carried out at room temperature.

[0018] Carbon materials, as substrates, possess excellent chemical and electrochemical stability, thus providing a stable framework that is "never corroded" in harsh acidic reducing environments. At the same time, the carbon substrate itself exhibits excellent conductivity and charge transport capabilities, enabling the construction of a well-developed conductive network and a "highway system" with smooth mass transfer, ensuring the efficient transport of electrons, ions, and molecules. Based on this, the platinum-rhodium alloy catalyst prepared by deposition can achieve efficient and stable conversion of phenol, and it is effective when the molar ratio of Pt to Rh is changed within the range of 1:3 to 3:1. Specifically, it can improve the adsorption and activation of phenol on the catalyst surface, while weakening the interaction between the alloy and active hydrogen, and inhibiting the occurrence of competitive HER reaction. Thus, it exhibits better performance than pure Pt or pure Rh. In the catalytic hydrogenation reaction of phenol, it can simultaneously exhibit high Faradaic efficiency and cyclohexanol product selectivity. In addition, the catalyst with the Pt:Rh molar ratio of 1:3 has the best effect, which can take into account the characteristics of Pt (high cyclohexanol selectivity) and Rh (high Faradaic efficiency), and exhibit the best performance in the catalytic hydrogenation reaction of phenol (Faradaic efficiency of 93% and cyclohexanol selectivity of 73%).

[0019] The inventors further claim protection for the platinum-rhodium alloy catalyst prepared by the above preparation method, and the application of the platinum-rhodium alloy in the electrocatalytic hydrogenation process of phenol. Specifically, a PtRh alloy was prepared by a green and controllable aqueous electrodeposition process and deposited on a carbon substrate. The electrocatalytic hydrogenation performance of phenol in acidic aqueous solution was tested by chronopotentiometric method.

[0020] Compared with the prior art, the beneficial effects of the platinum-rhodium alloy catalyst provided by the present invention are reflected in: (1) The preparation process is simple and controllable at room temperature and pressure, and the prepared alloy has a uniform morphology and uniform particle size. The particle size can be controlled within the range of about 200 nm.

[0021] (2) The catalytic electrode prepared by this method can avoid the coating process required by traditional powder catalysts, and realize the integrated construction of catalyst and support at the nanoscale. It solves the three major bottlenecks of low physical adhesion, high interfacial contact resistance caused by the use of low-conductivity binders in the coating method, and poor mass transfer caused by the easy blockage of carbon substrate by binder and catalyst particles. Thus, it achieves a qualitative leap in catalytic activity, stability and precious metal utilization.

[0022] (3) This method uses an aqueous electrodeposition process with green and mild reaction conditions. The prepared alloy catalyst can be further used for the electrocatalytic hydrogenation of phenol in aqueous solution. Compared with the traditional thermal catalytic hydrogenation reaction, it has mild reaction conditions, controllable cost, and can achieve sustainable production by coupling with renewable energy, thereby reducing carbon emissions and helping to achieve the dual carbon target. Attached Figure Description

[0023] Figure 1 These are SEM and TEM images of the platinum-rhodium alloy deposited on a carbon substrate obtained in Example 1. Figure 2 This is a linear scan voltammetry comparison graph of Example 1 and Comparative Example 1. Figure 3 This is a comparison graph showing the hydrogenation performance of phenol after 3.5 h of reaction under different current density conditions for Example 1 and Comparative Example 1. Figure 4 Examples 1-3 and Comparative Examples 1 and 2 were tested at 5 mA / cm². 2 A comparison of the performance of catalytic hydrogenation of phenol under different current densities for 30 min. Figure 5 The graph shows a comparison of the hydrogenation performance of phenol in Examples 1, 4, and 5. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to embodiments, which will enable those skilled in the art to have a more comprehensive understanding of the present invention. The specific embodiments described below are for explanation only and are not intended to limit the scope of protection of the present invention.

[0025] In the following examples and comparative examples, when comparing the catalytic hydrogenation performance, linear sweep voltammetry was performed using a Bio-Logic VSP-300 multichannel electrochemical workstation system; test conditions: ambient temperature and pressure. The catalytic hydrogenation activity and selectivity were tested under different current density conditions to obtain information on the composition of the electrolysis products and Faradaic efficiency, among other properties.

[0026] Example 1: A method for preparing a platinum-rhodium alloy catalyst for improving the activity and selectivity of electrocatalytic hydrogenation of phenol, the specific steps of which are as follows: H₂PtCl₆ and Rh(NO₃)₃ were uniformly mixed with 0.5 M Na₂SO₄ aqueous solution at a Pt / Rh molar ratio of 1:3, resulting in a total volume of 30 mL. The total ion concentration of Pt and Rh in the precursor solution was fixed at 10 mmol / L (Pt concentration was 2.5 mmol / L and Rh concentration was 7.5 mmol / L). The mixture was then stirred at 600 rpm on a magnetic stirrer and filtered to remove insoluble impurities, yielding 30 mL of platinum-rhodium alloy precursor solution.

[0027] Hydrophilic carbon paper measuring 2 cm × 2 cm was pretreated with 60 wt% concentrated nitric acid, and then subjected to ultrasonic treatment with ethanol and deionized water in sequence. The ultrasonic frequency was 40 kHz and the time was 20 min for each treatment. The paper was then dried for later use.

[0028] Using the modified carbon paper as the working electrode, a carbon rod as the counter electrode, Ag / AgCl as the reference electrode, and the precursor solution as the electrolyte, cyclic voltammetry was employed in the potential range of -0.5 to 1.7 V (vs. Ag / AgCl) at a rate of 100 mV·s. -1 Fifty cycles of voltammetric electrodeposition were performed at a scanning rate, followed by rinsing the working electrode three times with 50 mL of deionized water and drying it with N2 at room temperature. This resulted in uniformly loaded black gold nanoparticles on the carbon paper surface, with an alloy loading of 1.49 mg / cm³. 2 .

[0029] Using the aforementioned black gold nanoparticles loaded on carbon paper as a catalyst, the electrocatalytic hydrogenation of phenol was conducted in an H-type electrolyzer. The cathode chamber contained a 0.1 M H₂SO₄ solution with 10 mM phenol, and the anode chamber contained 12 mL of 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was performed using a chronopotentiometric method. The prepared catalyst was used as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The PtRh alloy was tested at 2.5, 5, 10, 15, and 20 mA / cm². 2 The selectivity, conversion, and Faradaic efficiency of catalytic hydrogenation of phenol under constant current density conditions were obtained. The liquid products after the reaction were qualitatively and quantitatively analyzed by GC-MS to investigate the Faradaic efficiency, selectivity of different hydrogenation products, and their yields during the phenol hydrogenation reaction. The results are as follows: Under various current density conditions, the electrocatalytic hydrogenation of phenol produces only cyclohexanone and cyclohexanol, with no other products; as the hydrogenation current density increases from 2.5 mA / cm², the product remains the same. 2 Increase to 5 mA / cm 2 The Faradaic efficiency of the electrocatalytic hydrogenation of phenol is significantly improved. However, when the current density is further increased, the Faradaic efficiency of the hydrogenation reaction is significantly reduced due to the intense competition for hydrogen evolution, and the yield and conversion of the hydrogenation product also decrease significantly. At lower current densities (e.g., 2.5 and 5 mA / cm²), the efficiency is significantly lower. 2 At a current density of 5 mA / cm², the hydrogenation product is mainly cyclohexanol, but at higher current densities, the selectivity for cyclohexanol decreases significantly, while the selectivity for cyclohexanone increases significantly. Therefore, at 5 mA / cm², the hydrogenation product is more selective. 2After 30 min of catalytic hydrogenation of phenol under optimal current density conditions, the hydrogenation Faraday efficiency can reach up to 93%. Moreover, the products of the electrocatalytic hydrogenation of phenol are only cyclohexanone and cyclohexanol, without any other products. The hydrogenation product is mainly cyclohexanol, but a small amount of cyclohexanone is still generated, and the selectivity of cyclohexanol product is 75%.

[0030] Example 2: A method for preparing a platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol, the specific steps of which are as follows: H₂PtCl₆ and Rh(NO₃)₃ were uniformly mixed with 0.5M Na₂SO₄ aqueous solution at a Pt / Rh molar ratio of 1:1, wherein the total ion concentration of Pt and Rh in the precursor solution was fixed at 10 mmol / L (Pt concentration was 5 mmol / L and Rh concentration was 5 mmol / L). The mixture was then stirred on a magnetic stirrer, filtered, and set aside to obtain 30 mL of platinum-rhodium alloy precursor solution.

[0031] 2 cm × 2 cm carbon paper was pretreated with 60 wt% concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence. The ultrasonic frequency was 40 kHz and the time was 20 min for each time. After that, it was dried and ready for use.

[0032] Using modified carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode, and the aforementioned precursor solution as the electrolyte, an electrolysis was performed at a rate of 100 mV·s within a potential range of -0.5 to 1.7 V (vs. Ag / AgCl). -1 Fifty cycles of voltammetric electrodeposition were performed at a scanning rate, followed by rinsing the electrode three times with 50 mL of deionized water and drying it with N2 at room temperature. This resulted in uniformly loaded black gold nanoparticles on the carbon paper surface, with a loading of 1.62 mg / cm³. 2 .

[0033] Using the aforementioned black gold nanoparticles loaded on the surface of carbon paper as a catalyst, the electrocatalytic hydrogenation experiment of phenol was carried out in an H-type electrolyzer. The cathode chamber contained a 0.1 M H₂SO₄ solution with 10 mM phenol, and the anode chamber contained 12 mL of a 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was carried out using a chronopotentiometric method, with the synthesized catalyst as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The specific reaction process was carried out according to the steps described in Example 1.

[0034] The reaction results are as follows: at 5 mA / cm 2After catalytic hydrogenation of phenol under the optimal current density conditions for 30 min, the hydrogenation Faraday efficiency was 83%, and the products of the electrocatalytic hydrogenation of phenol were only cyclohexanone and cyclohexanol, without any other products. The hydrogenation product was mainly cyclohexanol, but a small amount of cyclohexanone was still generated, and the selectivity of cyclohexanol product was 62%.

[0035] Example 3: A method for preparing a platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol, the specific steps of which are as follows: H₂PtCl₆ and Rh(NO₃)₃ were uniformly mixed with 0.5 M Na₂SO₄ aqueous solution at a Pt / Rh molar ratio of 3:1, with the total concentration of Pt and Rh in the precursor solution fixed at 10 mmol / L (Pt concentration of 7.5 mmol / L and Rh concentration of 2.5 mmol / L). The mixture was then stirred on a magnetic stirrer, filtered, and set aside to obtain 30 mL of platinum-rhodium alloy precursor solution.

[0036] 1cm×2cm carbon paper was pretreated with 45wt% concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence, followed by drying. The ultrasonic frequency was 40 kHz and the time was 20 min for each treatment. After drying, it was ready for use.

[0037] Using modified carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode, and the aforementioned precursor solution as the electrolyte, an electrolysis was performed at a rate of 100 mV·s within a potential range of -0.5 to 1.7 V (vs. Ag / AgCl). -1 Fifty cycles of voltammetric electrodeposition were performed at a scanning rate, followed by rinsing the electrode three times with 50 mL of deionized water and drying it with N2 at room temperature. This resulted in uniformly loaded black gold nanoparticles on the carbon paper surface, with a loading of 1.85 mg / cm³. 2 .

[0038] The electrocatalytic hydrogenation of phenol was conducted in an H-type electrolyzer, with the cathode chamber containing a 0.1 M H₂SO₄ solution of 10 mM phenol and the anode chamber containing 12 mL of a 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was carried out using a chronopotentiometric method, with the synthesized catalyst as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The specific reaction process followed the steps described in Example 1.

[0039] The reaction results are as follows: at 5 mA / cm 2After catalytic hydrogenation of phenol under the optimal current density conditions for 30 min, the hydrogenation Faraday efficiency was 71%, and the products of the electrocatalytic hydrogenation of phenol were only cyclohexanone and cyclohexanol, without any other products. The hydrogenation product was mainly cyclohexanol, but a small amount of cyclohexanone was still generated, and the selectivity of cyclohexanol product was 72%.

[0040] Example 4: A method for preparing a platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol, the specific steps of which are as follows: H2PtCl6 and Rh(NO3)3 were uniformly mixed with 0.5 M Na2SO4 aqueous solution at a Pt / Rh molar ratio of 1:3, with the total concentration of Pt and Rh in the precursor solution fixed at 5 mmol / L. The mixture was then stirred on a magnetic stirrer, filtered, and set aside to obtain 30 mL of platinum-rhodium alloy precursor solution.

[0041] Carbon paper measuring 2cm × 1.5cm was pretreated with 60wt% concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence, followed by drying. The ultrasonic frequency was 40 kHz, and the time was 20 min for each treatment. After drying, it was ready for use.

[0042] Using modified carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode, and the aforementioned precursor solution as the electrolyte, an electrolysis was performed at a rate of 100 mV·s within a potential range of -0.5 to 1.7 V (vs. Ag / AgCl). -1 Fifty cycles of voltammetric electrodeposition were performed at a scanning rate, followed by rinsing the electrode three times with 50 mL of deionized water and drying it with N2 at room temperature. This resulted in uniformly loaded black gold nanoparticles on the carbon paper surface, with a loading of 0.6 mg / cm³. 2 .

[0043] The electrocatalytic hydrogenation of phenol was conducted in an H-type electrolyzer, with the cathode chamber containing a 0.1 M H₂SO₄ solution of 10 mM phenol and the anode chamber containing 12 mL of a 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was carried out using a chronopotentiometric method, with the synthesized catalyst as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The specific reaction process followed the steps described in Example 1.

[0044] The reaction results are as follows: at 5 mA / cm 2 After catalytic hydrogenation of phenol under the optimal current density conditions for 30 min, the hydrogenation Faraday efficiency was 72%, and the products of the electrocatalytic hydrogenation of phenol were only cyclohexanone and cyclohexanol, without any other products. The hydrogenation product was mainly cyclohexanol, but a small amount of cyclohexanone was still generated, and the selectivity of cyclohexanol product was 60%.

[0045] Example 5: A method for preparing a platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol, the specific steps of which are as follows: H2PtCl6 and Rh(NO3)3 were uniformly mixed with 0.5 M Na2SO4 aqueous solution at a Pt / Rh molar ratio of 1:3, with the total concentration of Pt and Rh in the precursor solution fixed at 20 mmol / L. The mixture was then stirred on a magnetic stirrer, filtered, and set aside to obtain 30 mL of platinum-rhodium alloy precursor solution.

[0046] Carbon paper measuring 2 cm × 2.5 cm was pretreated with 50 wt% concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence, followed by drying. The ultrasonic frequency was 40 kHz, and the time was 20 min for each treatment. After drying, it was ready for use.

[0047] Using modified carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode, and the aforementioned precursor solution as the electrolyte, an electrolysis was performed at a rate of 100 mV·s within a potential range of -0.5 to 1.7 V (vs. Ag / AgCl). -1 Fifty cycles of voltammetric electrodeposition were performed at a scanning rate, followed by rinsing the electrode three times with 50 mL of deionized water and drying it with N2 at room temperature. This resulted in uniformly loaded black gold nanoparticles on the carbon paper surface, with a loading of 2.9 mg / cm³. 2 .

[0048] The electrocatalytic hydrogenation of phenol was conducted in an H-type electrolyzer, with the cathode chamber containing a 0.1 M H₂SO₄ solution of 10 mM phenol and the anode chamber containing 12 mL of a 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was carried out using a chronopotentiometric method, with the synthesized catalyst as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The specific reaction process followed the steps described in Example 1.

[0049] The reaction results are as follows: at 5 mA / cm 2 After catalytic hydrogenation of phenol under the optimal current density conditions for 30 min, the hydrogenation Faraday efficiency was 70%, and the products of the electrocatalytic hydrogenation of phenol were only cyclohexanone and cyclohexanol, without any other products. The hydrogenation product was mainly cyclohexanol, but a small amount of cyclohexanone was still generated, and the selectivity of cyclohexanol product was 58%.

[0050] Comparative Example 1 Mix 10 mmol / L H2PtCl6 with 0.5 M Na2SO4 aqueous solution evenly, then stir on a magnetic stirrer, filter and set aside to obtain 30 mL of precursor solution.

[0051] 2 cm × 2 cm carbon paper was pretreated with 60 wt% concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence, followed by drying. The ultrasonic frequency was 40 kHz and the time was 20 min for each treatment. After drying, it was ready for use.

[0052] Using modified carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode, and the aforementioned precursor solution as the electrolyte, an electrolysis reaction was performed at a rate of 100 mV·s within a potential range of -0.5 to 1.7 V (vs. Ag / AgCl). -1 The scanning rate was used to perform 50 cycles of voltammetric electrodeposition, and the final sample was prepared with a Pt particle loading of 1.5 mg / cm³. 2 Left and right. Finally, rinse the electrode with deionized water and dry it with N2.

[0053] The electrocatalytic hydrogenation of phenol was conducted in an H-type electrolyzer, with the cathode chamber containing a 0.1 M H₂SO₄ solution of 10 mM phenol and the anode chamber containing 12 mL of a 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was carried out using a chronopotentiometric method, with the synthesized catalyst as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The specific reaction process followed the steps described in Example 1.

[0054] The reaction results are as follows: at 5 mA / cm 2 Under optimal current density conditions, the catalytic hydrogenation of phenol yielded a high cyclohexanol product after 30 min, with no other products formed. Although its selectivity for catalytic hydrogenation of phenol to cyclohexanol was high, approaching 100%, its hydrogenation Faraday efficiency was the lowest among all samples, at only 63%, due to intense competition from the hydrogen evolution side reaction. Figure 4 (As shown).

[0055] When the hydrogenation time of phenol is further extended to 3.5 h, so that the amount of electricity passing through the electrolyzer is theoretically just enough to completely convert phenol into cyclohexanol, although the content of cyclohexanone in the product is very low, the hydrogenation Faraday efficiency will further decrease to 38% (e.g., Figure 3 As shown in the figure); it can be seen that changing the hydrogen addition current density does not significantly improve the Faraday efficiency of Comparative Example 1.

[0056] Comparative Example 2 Mix 10 mmol / L Rh(NO3)3 with 0.5 M Na2SO4 aqueous solution evenly, then stir on a magnetic stirrer, filter and set aside to obtain 30 mL of precursor solution.

[0057] 2 cm × 2 cm carbon paper was pretreated with 60 wt% concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence, followed by drying. The ultrasonic frequency was 40 kHz and the time was 20 min for each treatment. After drying, it was ready for use.

[0058] Using modified carbon paper as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode, and the aforementioned precursor solution as the electrolyte, an electrolysis reaction was performed at a rate of 100 mV·s within a potential range of -0.5 to 1.7 V (vs. Ag / AgCl). -1 The scanning rate was used to perform 50 cycles of voltammetric electrodeposition, and the final sample was prepared with the Rh particle loading maintained at 1.5 mg / cm³. 2 Left and right. Finally, rinse the electrode with deionized water and dry it with N2.

[0059] The electrocatalytic hydrogenation of phenol was conducted in an H-type electrolyzer, with the cathode chamber containing a 0.1 M H₂SO₄ solution of 10 mM phenol and the anode chamber containing 12 mL of a 0.1 M H₂SO₄ solution. The electrocatalytic hydrogenation reaction was carried out using a chronopotentiometric method, with the synthesized catalyst as the working electrode, a graphite rod as the counter electrode, and Hg / Hg₂SO₄ as the reference electrode. The specific reaction process followed the steps described in Example 1.

[0060] The reaction results are as follows: at 5 mA / cm 2 Under the optimal current density conditions, the catalytic hydrogenation of phenol produced only cyclohexanone and cyclohexanol for 30 min, with no other products generated. Although the Faraday efficiency of catalytic hydrogen evolution reaction of phenol can be maintained at close to 80% due to the weak activity of Rh catalysis, the selectivity of catalytic hydrogenation of phenol to cyclohexanol is the lowest among all samples, at only 52%, due to its poor catalytic hydrogenation reaction activity.

[0061] Comparative Example 3 Ni as reported in the prior art x @MoO 2-x / C catalyst, as Comparative Example 3, was tested in an acidic environment of 0.1 M H2SO4 according to the steps described in Example 1. The results showed that Ni x @MoO 2-x The products of catalytic hydrogenation of phenol by / C are only cyclohexanone and cyclohexanol, with no other products generated; the hydrogenation product is mainly cyclohexanol, but a small amount of cyclohexanone is still generated; in addition, although the selectivity of its cyclohexanol product can be comparable to that of the above embodiments, its Faraday efficiency for catalytic hydrogenation of phenol is only 50% lower than that of the embodiments in this patent.

[0062] Experimental Example The platinum-rhodium alloy catalyst obtained in Example 1 was characterized by SEM and HRTEM, as follows: Figure 1 As shown, the alloy morphology consists of uniformly and densely grown nanoparticles on the surface of carbon cloth. HRTEM characterization shows clear lattice stripes with a lattice spacing of 0.221 nm, which is between Pt (0.226 nm) and Rh (0.219 nm), corresponding to the (111) crystal plane of the alloy.

[0063] Subsequently, the catalysts prepared in Example 1 and Comparative Example 1 were used as catalysts for the electrocatalytic hydrogenation of phenol, and their hydrogenation performance was compared. Figure 2 The figure represents the linear sweep voltammetry curves of the catalyst in a perchloric acid solution (0.1 M) with or without 10 mM phenol. It can be seen that, compared with Comparative Example 1, the LSV curve of the alloy catalyst in Example 1 shows a more significant increase in current density after the addition of phenol, which fully demonstrates that the alloy has superior phenol hydrogenation activity.

[0064] Figure 3 The figure represents the changes in the composition of the phenol hydrogenation products and their Faradaic efficiency after 3.5 h of reaction under different current densities for the catalysts of Example 1 and Comparative Example 1. As can be seen from the figure, at 5 mA / cm², the efficiency of the catalysts in the hydrogenation process of phenol varies. 2 Under the current density conditions, the reaction was carried out for 3.5 h, so that the amount of electricity passing through the electrolyzer was theoretically just enough to completely convert phenol into cyclohexanol. The Faradaic efficiency of the platinum-rhodium alloy catalyzing the hydrogenation of phenol obtained in Example 1 can reach as high as 83%, and the main product in the hydrogenation reaction is cyclohexanol. In contrast, the Faradaic efficiency and selectivity of the cyclohexanol product of Comparative Example 1 catalyzing the hydrogenation of phenol under the same test conditions are relatively low. Moreover, when the current density of the hydrogenation reaction is changed, the performance of Example 1 is still better than that of Comparative Example 1.

[0065] Figure 4 Examples 1, 2, and 3, and Comparative Examples 1 and 2, were tested at 5 mA / cm². 2 A comparison of the performance of catalytic hydrogenation of phenol under optimal current density conditions for 30 min. Figure 5 The graph shows a comparison of the hydrogenation performance of phenol in Examples 1, 4, and 5. It can be seen that Example 1 of this application has the best effect.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol, characterized in that, Includes the following steps: (1) Pretreatment of conductive carbon substrate: The carbon substrate was pretreated with concentrated nitric acid, and then ultrasonically treated with ethanol and deionized water in sequence, followed by drying to obtain the modified carbon substrate. (2) Preparation of platinum-rhodium alloy precursor solution: H2PtCl6 and Rh(NO3)3 were mixed with Na2SO4 aqueous solution at a Pt / Rh molar ratio of 3:1-1:

3. The mixture was then stirred in a magnetic stirrer, filtered, and set aside to obtain a platinum-rhodium alloy precursor solution. (3) Preparation of platinum-rhodium alloy electrocatalyst: A modified carbon substrate was used as the working electrode, a carbon rod as the counter electrode, and Ag / AgCl as the reference electrode. Cyclic voltammetric electrodeposition was performed using a platinum-rhodium alloy precursor solution as the electrolyte. Finally, the obtained sample was rinsed with deionized water and dried with N2.

2. The method for preparing the platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol according to claim 1, characterized in that, In step (1), the carbon substrate used is any one of carbon cloth, carbon paper, or carbon fiber paper; the area of ​​the carbon substrate is 1-5 cm². 2 .

3. The method for preparing the platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol according to claim 1 or 2, characterized in that, In step (1), the carbon substrate is pretreated in concentrated nitric acid for 1-3 h at a temperature of 60-120 °C and the nitric acid concentration is controlled at 40-60 wt%.

4. The method for preparing the platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol according to claim 1 or 2, characterized in that, In step (1), ultrasonic cleaning is performed in an ultrasonic cleaner with ethanol and deionized water in turn, and then the water is dried for later use; the ultrasonic frequency is 40 kHz and the ultrasonic time is 20 min for each.

5. The method for preparing the platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol according to claim 1, characterized in that, In step (2), the total concentration of Pt and Rh ions in the precursor solution is 5-20 mmol / L; the concentration of the Na2SO4 aqueous solution is 0.5 mol / L, and the total volume of the solution is 10-30 mL.

6. The method for preparing the platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol according to claim 1 or 5, characterized in that, In step (2), the total ion concentration of Pt and Rh in the precursor solution is 10 mmol / L; the molar ratio of Pt and Rh is 1:

3.

7. The method for preparing the platinum-rhodium alloy for improving the electrocatalytic hydrogenation activity and selectivity of phenol according to claim 1, characterized in that, In step (3), the potential range of the cyclic voltammetric electrodeposition process is -0.5 to 1.7 V, the number of deposition cycles is 30 to 50, and the reaction is carried out at room temperature.

8. A platinum-rhodium alloy obtained by the preparation method of claim 1 for improving the electrocatalytic hydrogenation activity and selectivity of phenol.

9. The application of the platinum-rhodium alloy according to claim 9 in the electrocatalytic hydrogenation process of phenol.

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