A supported NiCrFeO4-PO x Catalysts, their preparation methods and applications

Abstract

This invention relates to the field of electrochemical materials technology, specifically disclosing a supported NiCrFeO4-PO4 material. x Catalysts, their preparation methods, and applications. This invention first grows NiCrFeO4 in situ on a conductive substrate via a hydrothermal reaction, then introduces phosphorus and oxygen species through constant-potential electrochemical treatment using hypophosphite as a phosphorus source, thus preparing supported NiCrFeO4-PO4. x This catalyst, through the synergistic effect of ternary metal sites and the electronic regulation of phosphorus and oxygen species, possesses excellent dual-function electrocatalytic performance for urea oxidation and hydrogen evolution. It exhibits fast reaction kinetics and low reaction overpotential. When used as both anode and cathode in a urea oxidation coupled hydrogen production system, it can achieve stable operation at high current density under low cell voltage, effectively reducing the energy consumption of the hydrogen production system. Furthermore, the active material is firmly bonded to the substrate and exhibits excellent long-term operational stability, showing broad industrial application prospects in clean hydrogen energy production and the resource utilization of urea-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of electrochemical materials technology, and more particularly to a supported NiCrFeO4-PO4 material. x Catalysts, their preparation methods, and applications. Background Technology

[0002] Hydrogen energy, as a clean and efficient secondary energy source, is an important carrier for building a new energy system. Electrolysis of water to produce hydrogen has become one of the core technological pathways for green hydrogen production due to its high product purity and environmentally friendly production process. However, in traditional water electrolysis systems, the oxygen evolution reaction at the anodic point is a four-electron transfer process with slow reaction kinetics, requiring a high overpotential to reach the target current density. This results in high overall energy consumption of the electrolysis system, becoming a key bottleneck restricting the large-scale application of hydrogen production through water electrolysis. To address this issue, coupled hydrogen production technology using urea oxidation to replace the oxygen evolution reaction at the anodic point has gradually become a research hotspot. The theoretical electrode potential of urea oxidation is significantly lower than that of the oxygen evolution reaction, which can greatly reduce the operating voltage of the electrolyzer and the energy consumption for hydrogen production. Simultaneously, it can treat urea-containing wastewater from industrial and domestic sources, combining pollutant treatment with energy production, and has promising application prospects.

[0003] In urea oxidation coupled with hydrogen production systems, the performance of the catalyst directly determines the system's energy utilization efficiency and operating cost. Its catalytic activity, long-term operational stability, and preparation cost are the core factors restricting the large-scale industrial application of this technology. Currently, platinum, ruthenium, and iridium-based noble metal catalytic materials exhibit outstanding urea oxidation catalytic performance. However, these materials are scarce and expensive, and are prone to surface oxidation and poisoning from reaction intermediates during long-term electrolysis, leading to continuous degradation of catalytic performance and hindering large-scale industrial applications. Therefore, developing low-cost, high-performance non-noble metal urea oxidation catalysts has become a key research direction in this field.

[0004] Transition metal oxides possess advantages such as tunable elemental composition, diverse valence states, and simple preparation processes. By constructing multi-metal composite oxide systems, they can effectively optimize catalytic reaction pathways and enhance catalytic activity through electronic interactions and synergistic effects between different metal sites, making them a class of catalytic materials with great development potential. However, these materials generally suffer from problems such as low intrinsic conductivity, insufficient number of surface active sites, and poor adsorption and conversion capabilities of reaction intermediates, resulting in unsatisfactory catalytic reaction kinetic rates and high overpotentials under high current density conditions, making them unsuitable for industrial-grade electrolytic hydrogen production.

[0005] Therefore, developing efficient urea oxidation catalysts with simple preparation processes and excellent catalytic activity is of great practical significance for promoting the industrial application of urea oxidation coupled with hydrogen production technology. Summary of the Invention

[0006] To address the problems of low intrinsic conductivity, insufficient active sites, and slow reaction kinetics in existing transition metal oxide-based urea oxidation catalysts, this invention provides a supported NiCrFeO4-PO4 catalyst. x Catalysts, their preparation methods, and applications.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a supported NiCrFeO4-PO x The catalyst preparation method includes the following steps: S1 provides a conductive substrate; S2, soluble nickel salt, soluble chromium salt, soluble iron salt and triethanolamine are dissolved in water to obtain a mixed salt solution; the mixed salt solution and the conductive substrate are subjected to a hydrothermal reaction in a hydrothermal reactor to grow NiCrFeO4 in situ on the conductive substrate; S3, using a conductive substrate supported on NiCrFeO4 as the working electrode, a constant-potential electrochemical treatment was performed in an electrolyte containing hypophosphite solution to obtain a supported NiCrFeO4-PO4 substrate. x catalyst.

[0008] Compared with the prior art, the supported NiCrFeO4-PO provided by the present invention x The catalyst preparation method employs a two-step process combining hydrothermal in-situ growth and electrochemical phosphorus-oxygen modification to prepare a supported catalyst. A nickel-chromium-iron composite oxide is grown in situ on a conductive substrate via hydrothermal reaction, ensuring a tight bond between the catalytic active material and the substrate. This allows for the formation of a stable supported structure without the need for additional binders, effectively reducing the electrode interface contact resistance and preventing the loss of active material during long-term electrolysis, significantly improving the long-term operational stability of the electrode. Simultaneously, the synergistic effect among the multiple metal components provides abundant catalytic active sites, optimizing the adsorption and conversion pathways of intermediate products in the urea oxidation reaction. Combined with the gently introduced phosphorus and oxygen species during electrochemical treatment, the electronic structure and surface electronic states of the catalytic material can be further modulated, further enhancing the intrinsic conductivity and intrinsic catalytic activity of the active sites, effectively accelerating the kinetic rate of the urea oxidation reaction. When applied to a urea oxidation coupled hydrogen production system, this catalyst can achieve high current density operation at a low overpotential, significantly reducing the system energy consumption for electrolytic hydrogen production, demonstrating good potential for industrial application.

[0009] It should be noted that the nickel-chromium-iron composite oxide in the catalyst of this invention is a NiCrFeO4 crystal phase in which chromium partially replaces the iron sites in the spinel lattice, and phosphorus-oxygen species (PO) xBy incorporating amorphous doping into the NiCrFeO4 oxide system, the structural stability of the spinel phase and the synergistic effect of the multi-metal active sites are fully preserved. Furthermore, the introduction of phosphorus and oxygen species further optimizes the electronic structure of the catalytic material and the adsorption characteristics of reaction intermediates, thereby achieving a simultaneous improvement in catalytic activity and operational stability.

[0010] Furthermore, in S1, the conductive substrate is nickel foam.

[0011] In some specific embodiments of the present invention, the conductive substrate is pretreated before the hydrothermal reaction: the conductive substrate is first ultrasonically cleaned in hydrochloric acid solution, and then ultrasonically cleaned in anhydrous ethanol and deionized water.

[0012] Specifically, the concentration of the hydrochloric acid solution is 1~3 mol / L, and the ultrasonic cleaning time is 20 min~40 min.

[0013] Further, in S2, the soluble nickel salt is one or more of nickel nitrate, nickel chloride, or nickel sulfate; the soluble chromium salt is one or more of chromium nitrate, chromium sulfate, or chromium chloride; and the soluble iron salt is one or more of ferric nitrate, ferric chloride, or ferric sulfate.

[0014] Further, in S2, the molar ratio of the soluble nickel salt, soluble chromium salt, and soluble iron salt is (0.5~2):(0.075~0.1):(0.3~2).

[0015] Within this molar ratio range, nickel-chromium-iron composite oxides can form a stable spinel phase structure, fully leveraging the electronic synergistic effect among the three metal sites.

[0016] Furthermore, in S2, the ratio of the soluble nickel salt to triethanolamine is (0.5~2) mmol: (0.1~1) mL.

[0017] Within this ratio range, triethanolamine can regulate the release rate of metal ions during hydrothermal processes through appropriate complexation, thereby controlling the nucleation and growth process of nickel-chromium-iron oxides, resulting in products with suitable crystallinity and uniform morphology, and avoiding problems such as particle agglomeration or uneven growth.

[0018] Furthermore, in S2, the ratio of the soluble nickel salt to water is (0.5~2) mmol: (30~40) mL.

[0019] Furthermore, in S2, the temperature of the hydrothermal reaction is 140℃~180℃, and the reaction time is 4h~10h.

[0020] Furthermore, in S3, the concentration of hypophosphite in the electrolyte is 0.5 mol / L to 2 mol / L.

[0021] Specifically, in S3, the hypophosphite is sodium hypophosphite.

[0022] Within this process parameter range, mild and controllable phosphorus and oxygen species modification of nickel-chromium-iron composite oxides can be achieved, effectively regulating the electronic structure and surface active site properties of the catalytic material. A suitable hypophosphite concentration can provide sufficient phosphorus source for the modification process, avoiding both insufficient phosphorus and oxygen species introduction and limited electronic regulation due to excessively low concentrations, and excessively high concentrations that could lead to over-phosphating and damage to the original phase structure.

[0023] Furthermore, in S3, the voltage of the constant potential electrochemical treatment is -3V to -1V (vs Ag / AgCl), and the treatment time is 600s to 1800s.

[0024] The aforementioned constant potential range and processing time are beneficial for the uniform doping distribution of phosphorus and oxygen species, while avoiding substrate corrosion and collapse and detachment of active material morphology caused by excessively negative potential or excessively long processing time. This effectively improves the intrinsic catalytic activity and operational stability of the catalyst while preserving the advantages of in-situ growth structure. In some specific embodiments of the present invention, the reference electrode in the constant potential electrochemical treatment is Ag / AgCl, and the counter electrode is a graphite electrode.

[0025] Secondly, the present invention also provides a supported NiCrFeO4-PO x The catalyst is a supported NiCrFeO4-PO4 catalyst as described in any of the above-mentioned embodiments. x The catalyst was prepared using the method described above.

[0026] The NiCrFeO4-PO prepared by this invention x The catalyst exhibits excellent bifunctional electrocatalytic performance in alkaline systems: when catalyzing the urea oxidation reaction, the current density reaches 100 mA / cm². 2 The corresponding reaction potential is only 1.35V; during the catalytic hydrogen evolution reaction, it reaches 100mA / cm. 2 The overpotential required for the current density is only 162.5 mV. In the assembled NiCrFeO4-PO x In the urea oxidation coupled hydrogen production process in an electrolytic cell, a cell voltage of only 1.45V is required to achieve 600mA / cm. 2 Its high current density exhibits outstanding electrocatalytic activity and energy efficiency advantages in the urea oxidation coupled hydrogen production process, and has broad application prospects in the field of clean hydrogen energy production.

[0027] Thirdly, the present invention also provides an electrode comprising the above-mentioned supported NiCrFeO4-PO x catalyst.

[0028] In this invention, the electrode is an integrated self-supporting electrode, meaning the catalytic material is directly constructed onto the surface of a conductive substrate via in-situ hydrothermal growth, rather than being coated with an external binder. This structure avoids the use of polymer binders, eliminating the embedding effect of binders on active sites, which is beneficial for fully utilizing the catalytic activity of the catalyst. Simultaneously, the in-situ grown catalyst forms a tight bond with the substrate, rather than a simple physical attachment, significantly reducing interfacial contact resistance and facilitating rapid electron transport from the active sites to the substrate current collector, thereby improving catalytic efficiency at high current densities.

[0029] Fourthly, the present invention also provides the above-mentioned supported NiCrFeO4-PO x Application of the catalyst or the electrode in electrocatalytic oxidation of urea coupled with hydrogen production.

[0030] Fifthly, the present invention also provides a method for electrocatalytic oxidation of urea coupled with hydrogen production, comprising the following steps: using a two-electrode system, with the supported NiCrFeO4-PO4... x The catalyst serves as both the anode and cathode, and is placed in an alkaline electrolyte containing urea to carry out an electrocatalytic oxidation of urea coupled with hydrogen production.

[0031] The catalyst system provided by this invention exhibits the synergistic effect of multiple metal cations, as well as PO. x The modification effectively regulates the electron density of active sites, and the catalyst exhibits excellent adsorption, activation, and dissociation capabilities for urea molecules, enabling efficient urea oxidation at relatively low anodic potentials. Therefore, the supported NiCrFeO4-PO4 of this invention... x The catalyst and its integrated electrode have broad application prospects in the field of electrocatalytic oxidation of urea coupled with hydrogen production, and are suitable for various forms of electrochemical devices such as alkaline electrolyzers, urea fuel cells, and urea-containing wastewater treatment coupled with hydrogen production devices.

[0032] In summary, this invention discloses a supported NiCrFeO4-PO4 x The catalyst, its preparation method, and its application involve first growing NiCrFeO4 in situ on a conductive substrate via a hydrothermal reaction, and then introducing phosphorus-oxygen species (PO4) through potentiostatic electrochemical treatment using hypophosphite as the phosphorus source. x ), to prepare supported NiCrFeO4-PO xThis catalyst, through the synergistic effect of ternary metal sites and the electronic regulation of phosphorus and oxygen species, possesses excellent dual-function electrocatalytic performance for urea oxidation and hydrogen evolution. It exhibits fast reaction kinetics and low reaction overpotential. When used as both anode and cathode in a urea oxidation coupled hydrogen production system, it can achieve stable operation at high current density under low cell voltage, effectively reducing the energy consumption of the hydrogen production system. Furthermore, the active material is firmly bonded to the substrate and exhibits excellent long-term operational stability, showing broad industrial application prospects in clean hydrogen energy production and the resource utilization of urea-containing wastewater. Attached Figure Description

[0033] Figure 1 This is a scanning electron microscope image of the NiCrFeO4-POx catalyst prepared in Example 1 of the present invention; Figure 2 The XRD pattern of the NiCrFeO4-POx catalyst prepared in Example 1 of this invention; Figure 3 This is a high-resolution XPS P 2p image of the NiCrFeO4-POx catalyst prepared in Example 1 of this invention; Figure 4 The NiCrFeO4-PO prepared in Example 1 of this invention x Catalyst and NiCrFeO4-PO in Comparative Examples 1 and 2 x and NiCrFeO4-PO x Linear sweep voltammetry curve of the hydrogen evolution reaction of the catalyst in 1 mol / L potassium hydroxide solution; Figure 5 The NiCrFeO4-PO prepared in Example 1 of this invention x Linear sweep voltammetry curves of the catalyst in the oxygen evolution reaction in 1 mol / L potassium hydroxide solution and the urea oxidation reaction in solutions containing 0.5 mol / L urea and 1 mol / L potassium hydroxide. Figure 6 The NiCrFeO4-PO prepared in Example 1 of this invention x Polarization curves of the catalyst in the hydrogen evolution + urea oxidation system and the traditional hydrogen evolution + oxygen evolution system; Figure 7 The NiCrFeO4-PO prepared in Example 1 of this invention x Catalyst and NiFeO4-PO in Comparative Examples 1 and 2 x and NiCrO4-PO x Linear sweep voltammetry curve of urea oxidation reaction in 1 mol / L potassium hydroxide solution containing 0.5 mol / L urea. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] To better illustrate the present invention, further examples are provided below.

[0036] Example 1 This embodiment provides a supported NiCrFeO4-PO x The catalyst is prepared by the following steps: S1. Add nickel foam (1.0cm*1.0cm) to 2mol / L hydrochloric acid solution and ultrasonically clean for 30min. Then ultrasonically clean in anhydrous ethanol and deionized water for 30min in sequence. S2, 0.5 mmol nickel nitrate hexahydrate, 0.075 mmol chromium nitrate nonahydrate, 0.3 mmol ferric nitrate nonahydrate and 0.1 mL triethanolamine were added to 35 mL deionized water and dissolved. The mixed salt solution and the pretreated nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated to 160 °C for hydrothermal reaction for 6 h. After the reaction was completed, the nickel foam was taken out, washed with deionized water and anhydrous ethanol, and dried under vacuum to obtain nickel foam loaded with NiCrFeO4. S3, using NiCrFeO4-supported nickel foam as the working electrode, graphite as the counter electrode, and Ag / AgCl as the reference electrode, was subjected to potentiostatic electrochemical treatment in a 0.5 mol / L sodium hypophosphite solution at a voltage of -1 V for 1800 s. After treatment, it was washed with deionized water and dried to obtain the supported NiCrFeO4-PO4. x catalyst.

[0037] Example 2 This embodiment provides a supported NiCrFeO4-PO x The catalyst is prepared by the following steps: S1. Add nickel foam (2.0cm*2.0cm) to 3mol / L hydrochloric acid solution and ultrasonically clean for 20min. Then ultrasonically clean in anhydrous ethanol and deionized water for 20min in sequence. S2, 2 mmol nickel nitrate hexahydrate, 0.1 mmol chromium nitrate nonahydrate, 2 mmol ferric nitrate nonahydrate and 1 mL triethanolamine were added to 40 mL deionized water. After dissolving, the mixed salt solution and the pretreated nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene. The mixture was heated to 140 °C and hydrothermally reacted for 10 h. After the reaction was completed, the nickel foam was removed, washed with deionized water and anhydrous ethanol, and vacuum dried to obtain nickel foam loaded with NiCrFeO4. S3, using NiCrFeO4-supported nickel foam as the working electrode, graphite as the counter electrode, and Ag / AgCl as the reference electrode, was subjected to constant potential electrochemical treatment in a 2 mol / L sodium hypophosphite solution at a voltage of -3V for 600 s. After treatment, the sample was washed with deionized water and dried to obtain the supported NiCrFeO4-PO4. x catalyst.

[0038] Example 3 This embodiment provides a supported NiCrFeO4-PO x The catalyst is prepared by the following steps: S1. Add nickel foam (1.0cm*2.0cm) to 1mol / L hydrochloric acid solution and ultrasonically clean for 40min. Then ultrasonically clean in anhydrous ethanol and deionized water for 40min in sequence. S2, 1 mmol nickel nitrate hexahydrate, 0.083 mmol chromium nitrate nonahydrate, 1 mmol ferric nitrate nonahydrate and 0.5 mL triethanolamine were added to 30 mL deionized water and dissolved. The mixed salt solution and the pretreated nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated to 180 °C for hydrothermal reaction for 4 h. After the reaction was completed, the nickel foam was taken out, washed with deionized water and anhydrous ethanol, and dried under vacuum to obtain nickel foam loaded with NiCrFeO4. S3, using NiCrFeO4-supported nickel foam as the working electrode, graphite as the counter electrode, and Ag / AgCl as the reference electrode, was subjected to potentiostatic electrochemical treatment in a 1.5 mol / L sodium hypophosphite solution at a voltage of -2 V for 1200 s. After treatment, it was washed with deionized water and dried to obtain the supported NiCrFeO4-PO4. x catalyst.

[0039] Comparative Example 1 This comparative example provides a supported NiFeO4-PO4 x The catalyst is prepared by the following steps: S1. Add nickel foam (1.0cm*1.0cm) to 2mol / L hydrochloric acid solution and ultrasonically clean for 30min. Then ultrasonically clean in anhydrous ethanol and deionized water for 30min in sequence. S2, 0.5 mmol nickel nitrate hexahydrate, 0.3 mmol ferric nitrate nonahydrate and 0.1 mL triethanolamine were added to 35 mL deionized water and dissolved. The mixed salt solution and the pretreated nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated to 160 °C for hydrothermal reaction for 6 h. After the reaction was completed, the nickel foam was taken out, washed with deionized water and anhydrous ethanol, and dried under vacuum to obtain nickel foam loaded with NiFeO4. S3, using NiFeO4-supported nickel foam as the working electrode, graphite as the counter electrode, and Ag / AgCl as the reference electrode, was subjected to constant potential electrochemical treatment in a 0.5 mol / L sodium hypophosphite solution at a voltage of -1 V for 1800 s. After treatment, it was washed with deionized water and dried to obtain supported NiFeO4-PO4. x catalyst.

[0040] Comparative Example 2 This comparative example provides a supported NiCrO4-PO x The catalyst is prepared by the following steps: S1. Add nickel foam (1.0cm*1.0cm) to 2mol / L hydrochloric acid solution and ultrasonically clean for 30min. Then ultrasonically clean in anhydrous ethanol and deionized water for 30min in sequence. S2, 0.5 mmol nickel nitrate hexahydrate, 0.075 mmol chromium nitrate nonahydrate and 0.1 mL triethanolamine were added to 35 mL deionized water and dissolved. The mixed salt solution and the pretreated nickel foam were transferred to a high-pressure reactor lined with polytetrafluoroethylene and heated to 160 °C for hydrothermal reaction for 6 h. After the reaction was completed, the nickel foam was taken out, washed with deionized water and anhydrous ethanol, and dried under vacuum to obtain nickel foam loaded with NiCrO4. S3, using NiCrO4-supported nickel foam as the working electrode, graphite as the counter electrode, and Ag / AgCl as the reference electrode, underwent potentiostatic electrochemical treatment in a 0.5 mol / L sodium hypophosphite solution at a voltage of -1 V for 1800 s. After treatment, the sample was washed with deionized water and dried to obtain supported NiCrO4-PO4. x catalyst.

[0041] Material characterization Figure 1 The supported NiCrFeO4-PO prepared in Example 1 of this invention x Scanning electron microscope (SEM) image of the catalyst. As shown in the image, the surface of the nickel foam substrate is completely covered by nanoparticles of catalytically active material, with the active particles forming a rich, rough, protruding structure on the substrate surface. This structure effectively increases the electrochemically active specific surface area of ​​the catalyst, exposes more catalytically active sites, and provides favorable channels for electrolyte diffusion and charge transport, thus contributing to improving the kinetic rate of the catalytic reaction.

[0042] Figure 2 The NiCrFeO4-PO prepared in Example 1 of this invention xX-ray diffraction (XRD) pattern of the catalyst. As shown in the figure, the main phase of the catalyst is a spinel-type NiCrFeO4 crystal phase. In the crystal lattice, Ni exists as divalent ions, while Fe and Cr exist as trivalent ions. Cr partially replaces Fe sites in the spinel lattice, forming a chromium-doped modified nickel ferrite spinel oxide structure.

[0043] Figure 3 The NiCrFeO4-PO prepared in Example 1 of this invention x High-resolution X-ray photoelectron spectroscopy (HPS) of the catalyst at the 2p phase. As shown in the figure, a characteristic peak exists at 133.92 eV, corresponding to the characteristic signal of the PO bond, confirming the successful formation of a phosphorus-oxygen bond structure in the catalytic material, with phosphorus as the dominant element in the PO bond. x Doping species into the NiCrFeO4 oxide system can regulate the electronic structure of the oxide matrix.

[0044] Application examples The electrocatalytic performance tests of the catalysts in the embodiments and comparative examples of this invention were all conducted on a Chenhua 760E electrochemical workstation. Specifically, the urea oxidation reaction and hydrogen evolution reaction single-electrode performance tests were performed using a standard three-electrode system: with a supported NiCrFeO4-PO4 electrode. x The catalyst was used directly as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Linear sweep voltammetry was performed in a 1 mol / L potassium hydroxide solution and a mixed solution of 1 mol / L potassium hydroxide containing 0.5 mol / L urea. The performance of the system for hydrogen production coupled with water electrolysis and urea oxidation was tested using a two-electrode system with a supported NiCrFeO4-PO4 electrode. x The catalyst is used as both the anode and cathode in the electrolytic cell assembly.

[0045] All potentials collected during the test were expressed by formula E. RHE =E Ag / AgCl +0.197 +0.059 × pH is converted to the reversible hydrogen electrode (RHE) potential.

[0046] Figure 4 Linear sweep voltammetry curves are shown for the catalytic hydrogen evolution reaction of the catalysts prepared in Example 1, Comparative Examples 1 and 2. The hydrogen evolution reaction was tested in a 1 mol / L potassium hydroxide solution. The curves show that NiCrFeO4-PO x Catalytic hydrogen evolution reaction at 100 mA / cm 2 The overpotential required for the current density is only 162.5 mV, while NiFeO4-PO x With NiCrO4-PO xAchieving the same current density requires 319.7 mV and 271.6 mV respectively. This indicates that NiCrFeO4-PO x The catalyst exhibits excellent hydrogen evolution catalytic performance in alkaline systems.

[0047] Figure 5 NiCrFeO4-PO prepared in Example 1 x Linear sweep voltammetry curves of the catalyst catalyzing the oxygen evolution reaction (OER) and urea oxidation reaction were obtained. The OER test was conducted in a 1 mol / L potassium hydroxide solution, and the urea oxidation test was conducted in a 1 mol / L potassium hydroxide solution containing 0.5 mol / L urea. The curves show that the potential for urea oxidation catalyzed by this catalyst is significantly lower than that for the OER, reaching 300 mA / cm². 2 At a current density of 1.56V (vs RHE), the potential corresponding to the oxygen evolution reaction is 1.56V (vs RHE), while the urea oxidation reaction only requires 1.37V (vs RHE) to achieve the same current density. This indicates that replacing the anodic oxygen evolution reaction with urea oxidation can effectively reduce the anodic reaction potential and reduce the energy consumption of the electrolysis system.

[0048] Figure 6 NiCrFeO4-PO prepared according to Example 1 x The catalyst was used as both the anode and cathode to construct dual-electrode polarization curves for a total water splitting system and a urea oxidation coupled hydrogen production system, respectively. The electrolyte for the total water splitting (HER&OER) system was a 1 mol / L potassium hydroxide solution, while the electrolyte for the urea oxidation coupled hydrogen production (HER&UOR) system was a mixed solution of 1 mol / L potassium hydroxide containing 0.5 mol / L urea.

[0049] As shown in the figure, the operating cell voltage of the urea oxidation coupled hydrogen production system is significantly lower than that of the traditional total water splitting system: the current density reaches 200 mA / cm². 2 At that time, the cell voltage of the urea oxidation coupled hydrogen production system was only 1.43V, while the total water splitting system required 1.79V; when the current density increased to 600mA / cm 2 At the same time, the urea oxidation coupled hydrogen production system requires only a cell voltage of 1.45V, far lower than the 1.92V required by the total water splitting system. This result indicates that replacing the anode oxygen evolution reaction with the urea oxidation reaction to construct a coupled hydrogen production system can significantly reduce the operating voltage of the electrolysis process and substantially reduce hydrogen production energy consumption, making it a highly efficient and energy-saving hydrogen production method.

[0050] Figure 7 The linear sweep voltammetric curves of the urea oxidation reaction of the catalysts prepared in Example 1, Comparative Examples 1 and 2 in a 1 mol / L potassium hydroxide solution containing 0.5 mol / L urea are shown in the figure. As can be seen from the figure, the NiCrFeO4-PO4 catalyst of Example 1… xThe catalyst exhibited optimal catalytic activity for urea oxidation: the current density reached 100 mA / cm². 2 At that time, NiCrFeO4-PO x The corresponding reaction potential is only 1.35V, while NiFeO4-PO x With NiCrO4-PO x Achieving the same current density requires 1.51V and 1.49V, respectively. This result confirms that the co-doping of Cr and Fe elements can optimize the electronic structure and reaction intermediate adsorption characteristics of the catalytic material through the synergistic effect between multiple metal sites, effectively accelerating the urea oxidation reaction kinetics, reducing the reaction overpotential, and improving the performance of the ternary NiCrFeO4-PO4 catalyst. x It possesses catalytic performance far superior to that of binary oxide systems.

[0051] 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 or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A supported NiCrFeO4-PO x A method for preparing a catalyst, characterized in that, Includes the following steps: S1 provides a conductive substrate; S2, soluble nickel salt, soluble chromium salt, soluble iron salt and triethanolamine are dissolved in water to obtain a mixed salt solution; the mixed salt solution and the conductive substrate are subjected to a hydrothermal reaction in a hydrothermal reactor to grow NiCrFeO4 in situ on the conductive substrate; S3, using a conductive substrate supported on NiCrFeO4 as the working electrode, a constant-potential electrochemical treatment was performed in an electrolyte containing hypophosphite solution to obtain supported NiCrFeO4-PO4. x catalyst.

2. The supported NiCrFeO4-PO4 as described in claim 1 x A method for preparing a catalyst, characterized in that, In S1, the conductive substrate is nickel foam.

3. The supported NiCrFeO4-PO4 as described in claim 1 x A method for preparing a catalyst, characterized in that, In S2, the soluble nickel salt is one or more of nickel nitrate, nickel chloride, or nickel sulfate; the soluble chromium salt is one or more of chromium nitrate, chromium sulfate, or chromium chloride; and the soluble iron salt is one or more of ferric nitrate, ferric chloride, or ferric sulfate.

4. The supported NiCrFeO4-PO4 as described in claim 1 x A method for preparing a catalyst, characterized in that, In S2, the molar ratio of the soluble nickel salt, soluble chromium salt, and soluble iron salt is (0.5~2):(0.075~0.1):(0.3~2); and / or In S2, the ratio of the soluble nickel salt to triethanolamine is (0.5~2) mmol:(0.1~1) mL; and / or In S2, the ratio of the soluble nickel salt to water is (0.5~2) mmol: (30~40) mL.

5. The supported NiCrFeO4-PO4 as described in claim 1 or 4 x A method for preparing a catalyst, characterized in that, In S2, the temperature of the hydrothermal reaction is 140℃~180℃, and the reaction time is 4h~10h.

6. The supported NiCrFeO4-PO4 as described in claim 1 x A method for preparing a catalyst, characterized in that, In S3, the concentration of hypophosphite in the electrolyte is 0.5 mol / L to 2 mol / L; the voltage of the constant potential electrochemical treatment is -3V to -1V (vs Ag / AgCl), and the treatment time is 600s to 1800s.

7. A supported NiCrFeO4-PO x Catalyst, characterized in that, The supported NiCrFeO4-PO according to any one of claims 1 to 6 x The catalyst was prepared using the same method.

8. An electrode, characterized in that, Including the supported NiCrFeO4-PO as described in claim 7 x catalyst.

9. The supported NiCrFeO4-PO4 according to claim 7 x Application of the catalyst or the electrode of claim 8 in electrocatalytic oxidation of urea coupled with hydrogen production.

10. A method for electrocatalytic oxidation of urea coupled with hydrogen production, characterized in that, The steps include: employing a two-electrode system, with the supported NiCrFeO4-PO4... x The catalyst serves as both the anode and cathode, and is placed in an alkaline electrolyte containing urea to carry out an electrocatalytic oxidation of urea coupled with hydrogen production.

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