Hierarchical porous carbon supported nickel phosphide catalyst and application thereof in hydrogen production by electro-oxidative coupling of benzyl alcohol

Abstract

The application discloses a hierarchical porous carbon supported nickel phosphide catalyst and application thereof in hydrogen production through benzyl alcohol electro-oxidation coupling, and belongs to the technical field of benzyl alcohol electro-oxidation and catalysis. The application adopts basic zinc carbonate to assist in constructing a lignin-derived hierarchical porous carbon carrier, can significantly improve the pore structure and specific surface area of the carbon material, provides a favorable structural basis for dispersion of an active component and mass transfer of a reactant, solves the problems of insufficient specific surface area, imperfect pore structure, limited exposure of active sites and poor catalytic performance under high current density of existing nickel-based catalytic materials, and thus has a good application prospect and value in the technical field of benzyl alcohol electro-oxidation and catalysis.

Description

Technical Field

[0001] This invention belongs to the field of benzyl alcohol electro-oxidation and catalysis technology, specifically relating to a hierarchical porous carbon-supported nickel phosphide catalyst and its application in benzyl alcohol electro-oxidation coupled with hydrogen production. Background Technology

[0002] In alkaline electrolytic hydrogen production systems, the anode typically undergoes the oxygen evolution reaction (OER), and conventional anodes are often made of nickel or its alloys. Due to the slow kinetics of the OER, a high operating potential is usually required, resulting in high overall cell voltage and energy consumption. To lower the energy barrier of the anode reaction, replacing the OER with an organic small-molecule oxidation reaction has become an important technical route for reducing the energy consumption of electrolytic hydrogen production. Among these technologies, benzyl alcohol electrooxidation has attracted attention due to its low reaction potential and the ability to co-produce high-value-added oxidation products.

[0003] In existing technologies, to improve the conductivity, active component dispersion, and structural stability of nickel-based catalytic materials, nickel-based active components are typically loaded onto carbon supports. Lignin, due to its wide availability, high carbon content, and rich aromatic structures, can be used as a precursor for preparing carbon materials. After pyrolysis and carbonization, it forms a lignin-derived carbon support, which can then be further loaded or used to form nickel-based active components in situ, thereby constructing lignin-derived carbon-supported nickel-based catalytic materials.

[0004] However, while existing nickel-based catalytic materials supported by lignin-derived carbon have advantages such as low cost and good stability in alkaline media, they still have the following shortcomings: First, carbon materials obtained from the direct pyrolysis of lignin without pore structure regulation usually have a low specific surface area and underdeveloped pore structure, which is not conducive to the high dispersion loading of nickel-based active components and the exposure of active sites, nor is it conducive to electrolyte wetting and mass transport during the reaction process; Second, existing carbon-supported nickel-based catalytic materials exhibit significant polarization at high current densities, which is not conducive to reducing the operating voltage of the electrolyzer; Third, catalytic materials are prone to structural changes during long-term electro-oxidation, and if the support structure is not stable enough, it will further affect the catalytic activity and service life.

[0005] Therefore, there is an urgent need to provide a lignin-based nickel phosphide electrocatalyst material that combines hierarchical pore structure, high exposure of active sites, low charge transfer impedance, and good adaptability to high current density, in order to meet the requirements of catalytic activity, stability, and low energy consumption in the aromatic alcohol electro-oxidation coupled hydrogen production process. Summary of the Invention

[0006] This invention constructs a lignin-derived hierarchical porous carbon support with the assistance of basic zinc carbonate, and further loads it with nickel phosphide active components to form a composite catalytic material suitable for benzyl alcohol electro-oxidation coupled with cathode hydrogen evolution in alkaline systems.

[0007] The technical solution of the present invention is as follows: This invention provides a hierarchical porous carbon-supported nickel phosphide catalyst, prepared by the following method: (1) Preparation of lignin-derived hierarchical porous carbon support Lignin was mixed with pore-forming auxiliary components, calcined, and then the calcined product was acid-washed and dried to obtain lignin-derived hierarchical porous carbon support. (2) Preparation of composite materials with nickel precursors A lignin-derived hierarchical porous carbon support was mixed with a nickel source, placed in an organic solvent, impregnated, dried, and calcined to obtain a composite material loaded with a nickel precursor. (3) Preparation of hierarchical porous carbon-supported nickel phosphide catalyst The composite material with nickel precursor and phosphorus-containing reagent were placed in a reactor and subjected to gas-phase phosphating treatment to obtain a hierarchical porous carbon-supported nickel phosphide catalyst.

[0008] In the above technical solution, in step (1), the lignin is at least one of dealkalized lignin, alkali lignin, enzymatically hydrolyzed lignin, and organic solvent lignin.

[0009] In the above technical solution, in step (1), the pore-forming auxiliary component is at least one of basic zinc carbonate and basic calcium carbonate.

[0010] In the above technical solution, in step (1), the mass ratio of lignin to pore-forming auxiliary components is 1:(0.5~2).

[0011] In the above technical solution, in step (1), the calcination conditions are: calcination at 850~1000℃ for 1~4h under an inert gas atmosphere; the pickling conditions are: pickling in acid solution for 6~24h at a solid-liquid mass ratio of 1:(20~40).

[0012] In the above technical solution, in step (2), the nickel source is at least one of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate or their hydrates, preferably nickel nitrate hexahydrate.

[0013] In the above technical solution, in step (2), the organic solvent is at least one of ethanol, methanol, and isopropanol, preferably ethanol.

[0014] In the above technical solution, in step (2), the mass ratio of the lignin-derived hierarchical porous carbon support to the nickel source is (0.3~0.5):1.

[0015] In the above technical solution, in step (2), the conditions for impregnation are: impregnation in an organic solvent for 1-4 hours; the conditions for calcination are: calcination at 350-450°C for 1-4 hours under an inert gas atmosphere.

[0016] In the above technical solution, in step (3), the phosphorus-containing reagent is at least one of sodium hypophosphite monohydrate, sodium hypophosphite, and ammonium hypophosphite, preferably sodium hypophosphite monohydrate.

[0017] In the above technical solution, in step (3), the mass ratio of the composite material loaded with nickel precursor to the phosphorus-containing reagent is 1:(20~60).

[0018] In the above technical solution, the conditions for the gas phase phosphating treatment in step (3) are: calcination at 250~350℃ for 0.5~3h in an inert gas atmosphere.

[0019] This invention provides the application of the above-mentioned hierarchical porous carbon-supported nickel phosphide catalyst in benzyl alcohol electro-oxidation coupled hydrogen production.

[0020] This invention provides a method for producing hydrogen from benzyl alcohol via electro-oxidation coupling, comprising the following steps: A hierarchical porous carbon-supported nickel phosphide catalyst was used as the anode catalyst and Pt / C as the cathode catalyst. The anode and cathode were fabricated on a conductive substrate to construct a dual-electrode electrolysis system. Electrolysis was carried out in a system containing an alkaline electrolyte and a benzyl alcohol substrate to achieve cathode hydrogen production.

[0021] In the above-mentioned benzyl alcohol electro-oxidation coupled hydrogen production method, the conductive substrate is at least one of nickel foam, carbon paper, carbon cloth, and titanium mesh; the electrolyte is a KOH aqueous solution with a concentration of 0.5~2 mol / L; and the concentration of benzyl alcohol is 0.05~0.5 mol / L.

[0022] The beneficial effects of this invention are as follows: This invention employs basic zinc carbonate to assist in the construction of a lignin-derived hierarchical porous carbon support, which can significantly improve the pore structure and specific surface area of ​​the carbon material, providing a favorable structural basis for the dispersion of active components and the mass transfer of reactants. It solves the problems of insufficient specific surface area, imperfect pore structure, limited exposure of active sites, and poor catalytic performance under high current density in existing nickel-based catalytic materials, thus showing good application prospects and value in the field of benzyl alcohol electro-oxidation and catalytic technology.

[0023] This invention significantly enhances the electro-oxidation activity of benzyl alcohol by loading nickel phosphide active components onto a hierarchical porous carbon support. The prepared catalyst material can effectively reduce the operating voltage of the electrolyzer in a two-electrode system, achieving low-energy hydrogen production and exhibiting good long-term operational stability. Attached Figure Description

[0024] Figure 1 The figures show nitrogen adsorption-desorption isotherms for HPLC-NiP and LC-NiP; where (a) is HPLC-NiP and (b) is LC-NiP.

[0025] Figure 2 The images are scanning electron microscope images of HPLC-NiP and LC-NiP; where (a) and (b) are LC-NiP, and (c) and (d) are HPLC-NiP.

[0026] Figure 3 This is a transmission electron microscope image of HPLC-NiP.

[0027] Figure 4 X-ray diffraction patterns of HPLC-NiP, LC-NiP, and HPLC-NiO are shown.

[0028] Figure 5 This is a constant current continuous electrolysis test for HPLC-NiP. Detailed Implementation

[0029] The alkali-free lignin used in the following embodiments of the present invention is from Shanghai Maclean Biochemical Technology Co., Ltd.

[0030] Other materials used in this invention, unless otherwise stated, are commercially available. Other terms used in this invention, unless otherwise specified, generally have the meanings commonly understood by those skilled in the art. The invention is further described in detail below with reference to specific embodiments and data. The following embodiments are merely illustrative and not intended to limit the scope of the invention in any way. Example 1

[0031] The steps for preparing a hierarchical porous carbon-supported nickel phosphide electrocatalyst (HPLC-NiP) are as follows: Alkali-degraded lignin and basic zinc carbonate were mixed at a 1:1 mass ratio and thoroughly ground to obtain a homogeneous mixture. This mixture was placed in a tube furnace, and nitrogen gas was introduced at a flow rate of 80 mL / min. Under nitrogen atmosphere, the temperature was increased to 950 °C at a rate of 5 °C / min and held for 2 h. After cooling to room temperature, the resulting sample was acid-washed in 1 M hydrochloric acid solution at a solid-liquid mass ratio of 1:30 for 12 h, and then dried at 80 °C to obtain a lignin-derived hierarchical porous carbon support (HPLC).

[0032] 500 mg of HPLC and 1163 mg of nickel nitrate hexahydrate were added to 30 mL of anhydrous ethanol for impregnation, and the mixture was stirred continuously for 2 h. After impregnation, the sample was dried in an oven at 80 ℃. After drying, the sample was re-ground and placed in a tube furnace. Nitrogen gas was introduced at a flow rate of 80 mL / min, and the temperature was increased to 400 ℃ at a rate of 5 ℃ / min under nitrogen atmosphere, and held at this temperature for 2 h to obtain HPLC-NiO.

[0033] Four g of sodium hypophosphite monohydrate and 0.1 g of HPLC-NiO were placed in two separate crucibles and then placed together in a tube furnace. Nitrogen gas was introduced at a flow rate of 50 mL / min, and the temperature was increased to 300 °C at a rate of 2 °C / min under nitrogen atmosphere, and held at this temperature for 1 h for gas-phase phosphating treatment. After cooling to room temperature, the sample was removed and ground to obtain HPLC-NiP.

[0034] Comparative Example 1 This comparative example prepared a nickel phosphide electrocatalyst (LC-NiP). The preparation method was basically the same as that in Example 1, except that basic zinc carbonate was not added when preparing the carbon support. The other conditions were the same as in Example 1, and LC-NiP was finally obtained.

[0035] Comparative Example 2 This comparative example prepared a nickel-based electrocatalyst (HPLC-NiO). The preparation method was basically the same as that in Example 1, except that the phosphating step was omitted, while the other conditions remained the same as in Example 1.

[0036] I. Structural Characterization The catalysts obtained in the above implementation cases were characterized in terms of pore structure, morphology, and phase structure. The characterization results are as follows.

[0037] 1. Pore structure characterization The pore structures of the HPLC-NiP described in Example 1 and the LC-NiP described in Comparative Example 1 were characterized using nitrogen adsorption-desorption testing. Before testing, the samples were degassed at 150 °C for 24 h. The total specific surface area of ​​the samples was calculated using the BET method, and the mesoporous / macroporous specific surface area and total pore volume were calculated based on the relevant pore structure analysis results.

[0038] Test results are as follows Figure 1 As shown: Both HPLC-NiP and LC-NiP exhibited type IV adsorption-desorption isotherms. Specifically, the adsorption capacity increased sharply when P / P0 < 0.05, indicating the presence of micropores in the sample; a significant hysteresis loop was observed in the range of 0.4 < P / P0 < 0.9, indicating the presence of mesoporous structures; and the adsorption capacity increased again when P / P0 > 0.9, indicating the presence of macroporous structures. These results demonstrate that both HPLC-NiP and LC-NiP possess a hierarchical pore structure characterized by the coexistence of micropores, mesopores, and macropores.

[0039] The hierarchical pore structure is primarily formed during the carbon support preparation process, where lignin undergoes high-temperature carbonization to form a carbon skeleton, and the corresponding pore structure is retained during subsequent acid washing. For LC-NiP, although basic zinc carbonate is not added during carbon support preparation, lignin still undergoes volatilization and structural rearrangement during high-temperature pyrolysis, resulting in a certain number of micropores. This is accompanied by skeleton shrinkage and interparticle accumulation, forming mesopores and macropores. Therefore, the resulting material still exhibits hierarchical pore structure characteristics. For HPLC-NiP, the participation of basic zinc carbonate in the carbon support preparation process further facilitates the formation of abundant pore structures, resulting in a more developed hierarchical pore structure in the final material.

[0040] Furthermore, the total specific surface area of ​​HPLC-NiP is 615.4 m². 2 / g, the mesoporous / macroporous specific surface area is 208.33m². 2 / g, total pore volume is 0.69 cm³ 3 / g; while the total specific surface area, mesoporous / macroporous specific surface area, and total pore volume of LC-NiP are 35.34 m² / g; 2 / g、28.27 m 2 / g and 0.18 cm 3 / g. Therefore, although both HPLC-NiP and LC-NiP exhibit hierarchical pore structures, HPLC-NiP demonstrates a significantly more developed pore structure, exhibiting a higher specific surface area, larger pore volume, and a richer variety of usable mesoporous / macroporous structures. This difference is primarily attributed to the introduction of basic zinc carbonate. During heating, basic zinc carbonate decomposes, forming zinc-based species and releasing gases, which helps reduce the compaction and shrinkage of the carbon skeleton and promotes pore structure formation. Subsequent acid washing removes these substances, preserving more pore structures in situ, resulting in a higher specific surface area, larger pore volume, and a richer variety of usable mesoporous / macroporous structures. In contrast, LC-NiP mainly relies on spontaneous pore formation during lignin pyrolysis, thus its pore structure development is significantly lower than that of HPLC-NiP.

[0041] The above results demonstrate that the HPLC-NiP of Example 1 can provide more exposed active sites, and is more conducive to electrolyte wetting, diffusion of reactants and intermediates, and timely escape of gases during the reaction, thus providing a favorable structural basis for its excellent electrocatalytic performance.

[0042] 2. Morphological and structural characterization The morphology of HPLC-NiP from Example 1 and LC-NiP from Comparative Example 1 was characterized using scanning electron microscopy. The characterization results are as follows: Figure 2 As shown: like Figure 2As shown in (a) and (b), LC-NiP exhibits a dense, blocky structure with a relatively compact surface, and no clearly open, interconnected three-dimensional pore framework was observed; while... Figure 2 As shown in (c) and (d), HPLC-NiP forms a three-dimensional network structure constructed from stacked nanosheets, with interconnected macroporous channels inside.

[0043] Furthermore, the HPLC-NiP from Example 1 was characterized using transmission electron microscopy. The characterization results are as follows: Figure 3 As shown, HPLC-NiP contains metal particles with a diameter of approximately 15 nm, and these metal particles are relatively uniformly dispersed on the surface of the carbon matrix.

[0044] Based on the above pore structure characterization results, although both HPLC-NiP and LC-NiP exhibit hierarchical pore structures, scanning electron microscopy reveals that LC-NiP remains relatively dense overall, indicating poorer pore openness and connectivity. In contrast, HPLC-NiP not only possesses a higher specific surface area and pore volume but also forms a more favorable three-dimensional network framework and interconnected macroporous channels for mass transport. Furthermore, the active components in HPLC-NiP are better dispersed, which improves the utilization rate of active sites and promotes interfacial reactions, thus demonstrating a more significant structural advantage.

[0045] 3. Characterization of phase structure X-ray diffraction was used to characterize the phases of HPLC-NiP in Example 1, LC-NiP in Comparative Example 1, and HPLC-NiO in Comparative Example 2. The test conditions were Cu kα (λ=1.5406 Å), scan range 5–90°, and scan rate 5° / min.

[0046] Characterization results as follows Figure 4 As shown: Characteristic diffraction peaks of the Ni2P phase were observed in both HPLC-NiP and LC-NiP samples, indicating that both can form the Ni2P active phase under phosphating conditions. However, the characteristic NiO peaks were retained in the HPLC-NiO sample, and no Ni2P characteristic peaks were observed, indicating that the nickel component in the sample exists in the form of nickel oxide without phosphating treatment.

[0047] Therefore, the phosphating step is a necessary step in forming the Ni2P active phase. The preparation process adopted in this invention can effectively realize the conversion from NiO precursor to Ni2P active phase, thereby obtaining the target nickel phosphide material.

[0048] II. Benzyl alcohol electro-oxidation test The HPLC-NiP from Example 1 was prepared into a catalyst ink and then loaded onto a conductive substrate to serve as the anode working electrode.

[0049] Specifically, 5 mg of HPLC-NiP was weighed and added to 500 μL of deionized water, 450 μL of isopropanol, and 50 μL of Nafion solution (5 wt%). The mixture was ultrasonically dispersed for 90 min to obtain a uniform catalyst ink. The catalyst ink was then drop-coated onto a surface with an area of ​​1 cm². 2 The carbon cloth / nickel foam / carbon paper allows for a catalyst loading of 1 mg / cm³. 2 The electrode was dried at 60 °C for 10 h to obtain the HPLC-NiP anode working electrode.

[0050] The LC-NiP anode working electrode of Comparative Example 1 was prepared using the same method.

[0051] In an electrolyte containing 1 M KOH and 0.1 M benzyl alcohol, a linear sweep voltammetry test was performed using the anolyte as the working electrode, Ag / AgCl as the reference electrode, and graphite as the counter electrode, at a scan rate of 5 mV / s. Further Tafel slope and electrochemical impedance spectroscopy tests were conducted, with the electrochemical impedance spectroscopy frequency range being 10 Hz. -2 ~10 5 Hz, with a disturbance voltage of 5mV.

[0052] The test results are as follows: HPLC-NiP at 10 mA·cm -2 and 200 mA·cm -2 The required potentials at the current densities were 1.355 V (vs. RHE) and 1.454 V (vs. RHE), respectively. Further testing showed that the Tafel slope of HPLC-NiP was 26.7 mV·dec. -1 The charge transfer resistance is 1.49 Ω.

[0053] Under the same conditions, the benzyl alcohol electro-oxidation performance test results of the LC-NiP described in Comparative Example 1 showed that it exhibited good performance at 10 mA·cm⁻¹. -2 The required potential is 1.385 V (vs. RHE), and its maximum potential is only 100 mA·cm. -2 The required potential is 1.82 V; its Tafel slope is 34.9 mV·dec. -1 The charge transfer resistance is 3.18 Ω.

[0054] The comparison shows that HPLC-NiP requires a lower potential at the same current density, and has a smaller Tafel slope and lower charge transfer resistance, indicating that HPLC-NiP has faster benzyl alcohol electro-oxidation reaction kinetics and better interfacial charge transfer capability.

[0055] The above results demonstrate that the HPLC-NiP from Example 1 exhibits excellent electrocatalytic activity in the benzyl alcohol electrooxidation reaction. Combined with the characterization results, this superior performance is closely related to its high specific surface area, large pore volume, more open and interconnected three-dimensional network structure, better dispersion of the active component, and the formation of the Ni2P active phase.

[0056] III. Electrolytic Hydrogen Production Experiment To evaluate the performance of the HPLC-NiP prepared in Example 1 in the electro-oxidation coupled hydrogen production of benzyl alcohol, tests were conducted using both a two-electrode electrolysis system and a flow electrolysis cell system. The two-electrode electrolysis system was used to investigate the effect of benzyl alcohol as the anodic oxidation substrate on the overall cell voltage; the flow electrolysis cell system was used to investigate the hydrogen production energy consumption performance of the system of this invention compared to the landmark water electrolysis oxygen evolution system.

[0057] (1) Cell voltage test of dual-electrode electrolysis system A two-electrode electrolysis system was constructed using HPLC-NiP from Example 1 as the anode catalyst and Pt / C as the cathode catalyst. Cell voltage changes were tested in alkaline electrolytes containing and without benzyl alcohol. Test conditions: Cathode area 1 cm². 2 Anode area 1 cm 2 The test method used was the linear sweep voltammetry.

[0058] The test results are as follows: In a 1 M KOH + 0.1 M benzyl alcohol electrolyte, 10 mA·cm⁻¹ was achieved. -2 and 200 mA·cm -2 The required cell voltages at the current densities are 1.345 V and 1.557 V, respectively; while in 1 M KOH electrolyte without benzyl alcohol, the required cell voltages at the same current densities are 1.568 V and 1.944 V, respectively.

[0059] The results above show that, at the same current density, introducing benzyl alcohol as the anodic oxidation substrate significantly reduces the required cell voltage for the two-electrode system. Specifically, at 10 mA·cm⁻¹... -2 The voltage drop at the bottom of the tank is 0.223 V, at 200 mA·cm. -2 The cell voltage decreased by 0.387 V. This result indicates that replacing the traditional oxygen evolution reaction with the benzyl alcohol electro-oxidation reaction as the anode reaction can effectively reduce the overall electrolysis voltage and energy consumption. It also shows that the HPLC-NiP of Example 1 is suitable for constructing an organic small molecule oxidation coupled hydrogen production system, especially at higher current densities, it can still maintain a low cell voltage, showing good application potential and energy-saving advantages.

[0060] (2) Energy consumption test of hydrogen production in a flow electrolyzer The continuous hydrogen production energy consumption of the system of this invention was evaluated using a flow electrolyzer. The system using Pt / C as the cathode, HPLC-NiP as the anode, and 1 M KOH + 0.1 M benzyl alcohol as the electrolyte was designated as the system of this invention; the system using Pt / C as the cathode, RuO2 as the anode, and 1 M KOH as the electrolyte was designated as the conventional alkaline water electrolysis hydrogen production control system. Test conditions: both the cathode area and anode area were 4 cm². 2 The current density is 50 mA·cm. -2 .

[0061] The test results are as follows: The system of this invention can achieve stable hydrogen production, with a unit hydrogen production energy consumption of 3.71 kWh·Nm³. -3 The energy consumption per unit hydrogen production in the conventional alkaline water electrolysis hydrogen production control system is 4.07 kWh·Nm³. -3 The former reduces hydrogen production by approximately 8.85% compared to the latter. Furthermore, under the same current density and after 30 min of reaction, both the system of this invention and the conventional alkaline water electrolysis hydrogen production control system produced 41 mL of hydrogen, indicating that the system of this invention can effectively reduce the energy consumption per unit of hydrogen production while maintaining stable hydrogen production output. These results demonstrate that the hierarchical porous carbon-supported nickel phosphide catalyst provided by this invention can replace the traditional anolytical oxygen evolution reaction through the anolytical benzyl alcohol oxidation reaction, thereby reducing the overall energy consumption for electrolytic hydrogen production.

[0062] IV. Stability Evaluation Using the HPLC-NiP catalyst from Example 1 as the anode catalyst, constant current continuous electrolysis tests were conducted in an electrolyte containing 1 M KOH and 0.1 M benzyl alcohol. The test conditions were: constant current density 10 mA·cm⁻¹. -2 Continuous operation time is 60 hours.

[0063] Test results are as follows Figure 5 As shown: After 60 hours of continuous operation, the working potential of HPLC-NiP increased by less than 25 mV, indicating that the material has good electrochemical stability under the conditions of benzyl alcohol electro-oxidation reaction.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A hierarchical porous carbon-supported nickel phosphide catalyst, characterized in that, It is prepared by the following method: (1) Preparation of lignin-derived hierarchical porous carbon support, Lignin was mixed with pore-forming auxiliary components, calcined, and then the calcined product was acid-washed and dried to obtain lignin-derived hierarchical porous carbon support. (2) Preparation of composite materials loaded with nickel precursors, A lignin-derived hierarchical porous carbon support was mixed with a nickel source, placed in an organic solvent, impregnated, dried, and calcined to obtain a composite material loaded with a nickel precursor. (3) Preparation of hierarchical porous carbon-supported nickel phosphide catalyst, The composite material with nickel precursor and phosphorus-containing reagent were placed in a reactor and subjected to gas-phase phosphating treatment to obtain a hierarchical porous carbon-supported nickel phosphide catalyst.

2. The hierarchical porous carbon-supported nickel phosphide catalyst according to claim 1, characterized in that, In step (1), the lignin is at least one of alkali-degraded lignin, alkali lignin, enzymatically hydrolyzed lignin, and organic solvent lignin; the pore-forming auxiliary component is at least one of basic zinc carbonate and basic calcium carbonate.

3. The hierarchical porous carbon-supported nickel phosphide catalyst according to claim 1, characterized in that, In step (1), the mass ratio of lignin to pore-forming auxiliary components is 1:(0.5-2); the calcination conditions are: calcination at 850-1000℃ for 1-4 hours under an inert gas atmosphere; the acid washing conditions are: acid washing in acid solution at a solid-liquid mass ratio of 1:(20-40) for 6-24 hours.

4. The hierarchical porous carbon-supported nickel phosphide catalyst according to claim 1, characterized in that, In step (2), the nickel source is at least one of nickel nitrate, nickel chloride, nickel sulfate, nickel acetate or their hydrates; and the organic solvent is at least one of ethanol, methanol or isopropanol.

5. The hierarchical porous carbon-supported nickel phosphide catalyst according to claim 1, characterized in that, In step (2), the mass ratio of the lignin-derived hierarchical porous carbon support to the nickel source is (0.3~0.5):1; the impregnation conditions are: impregnation in an organic solvent for 1~4 hours; the calcination conditions are: calcination at 350~450℃ for 1~4 hours under an inert gas atmosphere.

6. The hierarchical porous carbon-supported nickel phosphide catalyst according to claim 1, characterized in that, In step (3), the phosphorus-containing reagent is at least one of sodium hypophosphite monohydrate, sodium hypophosphite, and ammonium hypophosphite.

7. The hierarchical porous carbon-supported nickel phosphide catalyst according to claim 1, characterized in that, In step (3), the mass ratio of the composite material loaded with nickel precursor to the phosphorus-containing reagent is 1:(20~60); the conditions for the gas phase phosphating treatment are: calcination at 250~350℃ for 0.5~3h under an inert gas atmosphere.

8. The application of the hierarchical porous carbon-supported nickel phosphide catalyst according to any one of claims 1 to 7 in the electro-oxidation coupled hydrogen production of benzyl alcohol.

9. A method for producing hydrogen from benzyl alcohol via electro-oxidation coupling, characterized in that, The steps are as follows: Using the hierarchical porous carbon-supported nickel phosphide catalyst described in claim 1 as the anode catalyst and Pt / C as the cathode catalyst, the anode and cathode are loaded onto a conductive substrate to form a dual-electrode electrolysis system. Electrolysis is carried out in a system containing an alkaline electrolyte and a benzyl alcohol substrate, thereby realizing cathode hydrogen production.

10. The method for producing hydrogen from benzyl alcohol via electro-oxidation coupling according to claim 9, characterized in that, The conductive substrate is at least one of nickel foam, carbon paper, carbon cloth, and titanium mesh; the electrolyte is an aqueous KOH solution with a concentration of 0.5~2 mol / L; and the benzyl alcohol has a concentration of 0.05~0.5 mol / L.

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