An electrocatalyst with improved catalytic performance by ohmic contact and application thereof

Abstract

This invention discloses an electrocatalyst with enhanced catalytic performance through an ohmic contact and its applications. A NiMo alloy is anchored on the surface of a semiconductor NiCuP microflower using electrodeposition. By precisely controlling the work function matching between NiMo and NiCuP, an ohmic contact heterointerface is successfully constructed. This effectively eliminates the Schottky barrier at the heterostructure interface and removes the energy barrier for interfacial charge transport, thereby significantly optimizing the intrinsic conductivity of the catalyst and accelerating the transfer of electrons from the catalyst interior to the surface active sites. Benefiting from this efficient interfacial electron transport channel, the catalyst exhibits significantly enhanced catalytic activity in the cathode hydrogen evolution reaction. In the anodic half-reaction, a more thermodynamically favorable FOR is used instead of OER, enabling energy-saving hydrogen production by coupling the cathode HER at a lower battery voltage. Simultaneously, at the anode, furfural, a biomass-derived platform molecule, is efficiently converted into high-value-added furoic acid.

Description

Technical Field

[0001] This invention belongs to the field of novel material preparation technology, specifically relating to an electrocatalyst whose catalytic performance is enhanced by ohmic contact and its application. Background Technology

[0002] Hydrogen energy, as an ideal energy carrier with high energy density and water as its combustion byproduct, is considered an important component of the future energy system. Exploring green and low-carbon hydrogen production pathways, particularly water electrolysis technology driven by renewable energy, has become a global research hotspot. However, traditional water electrolysis processes typically require high overpotentials, especially in the oxygen evolution reaction (OER) at the anode, leading to low energy efficiency and high costs. Utilizing the electrical energy generated during the anode reaction to drive other valuable chemical reactions, thereby improving overall energy utilization efficiency or altering the thermodynamic equilibrium of the reaction and lowering the formation energy barrier of the target product, is key to reducing the cost of industrial-scale water electrolysis for hydrogen production.

[0003] Biomass resources, as a renewable carbon resource, are crucial for achieving carbon neutrality through their high-value utilization. Furfural, an important biomass platform compound, contains a furan ring and an aldehyde group in its molecular structure, exhibiting high chemical activity. It can be converted into high-value-added chemicals through various reactions such as oxidation and hydrogenation. Among these, the electrochemical oxidation (FOR) reaction of furfural can achieve its directional functional group transformation at ambient temperature and pressure by adjusting the potential and selecting a suitable catalyst. However, FOR involves multiple electron and proton transfer steps and is easily interfered with by the oxidation-evolution reaction (OER) at high current densities, leading to a decrease in selectivity and Faraday efficiency. Therefore, developing and optimizing catalysts that preferentially perform FOR at high current densities is particularly necessary for large-scale furfural coupled with the hydrogen evolution reaction (HER) to achieve the closure of the carbon cycle.

[0004] To enhance catalytic activity, multi-metal components or heterojunctions can be introduced to optimize the electronic structure and modulate the adsorption behavior of key intermediates. Metal / semiconductor heterojunctions, in particular, can form unique electronic structures at the interface, significantly improving electron transfer rates and promoting the adsorption of FOR intermediates and OH*. However, an inherent energy barrier or potential barrier often exists between the metal and semiconductor, hindering electron or hole transport at the interface and generating significant charge transfer resistance, a key bottleneck limiting catalytic reaction rates. Depending on the work function matching between the metal and semiconductor, either a Schottky contact or an ohmic contact can form. In a Schottky contact, the interfacial space charge and Fermi level pinning effect impede electron transfer between the metal and semiconductor, forming a Schottky barrier. In an ohmic contact, the interfacial energy barrier caused by the traditional Schottky barrier is eliminated, allowing seamless electron transport between the metal and semiconductor, significantly reducing energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide an electrocatalyst with enhanced catalytic performance through ohmic contact and its application in order to reduce the energy barrier of water electrolysis reaction and increase the added value of the product.

[0006] An electrocatalyst NiMo@NiCuP / NF with enhanced catalytic performance via an ohmic contact, comprising:

[0007] 1) Dissolve 0.30-0.32 M nickel chloride hexahydrate, 0.20-0.23 M trisodium citrate dihydrate and 0.02-0.08 M sodium molybdate dihydrate in 30 mL of deionized water and stir thoroughly until clear; adjust the pH to 9.5 with sodium carbonate solution, and use the resulting mixture as the electrolyte;

[0008] 2) Using NiCuP / NF as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, at 10-20 mA·cm -2 A constant current electrodeposition was performed at a current density for 300 s, and the resulting electrode was NiMo@NiCuP / NF.

[0009] The NiCuP / NF is prepared by the following method:

[0010] a. After cutting the nickel foam, it is ultrasonically cleaned in hydrochloric acid, acetone and ethanol in sequence, and then dried for later use;

[0011] b. Dissolve nickel source, copper source, urea and ammonium fluoride in deionized water, immerse the pretreated NF in the above solution, stir and transfer to a high-pressure reactor for hydrothermal reaction;

[0012] c. After the reaction system has cooled to room temperature, the resulting product is washed and dried to obtain the precursor;

[0013] d. The obtained precursor and phosphorus source were placed downstream and upstream of a tube furnace, respectively, and subjected to low-temperature phosphating treatment under an inert atmosphere to obtain NiCuP / NF;

[0014] In the electrolyte described in step 1), there are 0.32 M nickel chloride hexahydrate and 0.23 M trisodium citrate dihydrate;

[0015] The nickel source in step b is nickel nitrate hexahydrate with a concentration of 10 mM; the copper source is copper nitrate hexahydrate with a concentration of 20 mM; the hydrothermal reaction temperature is 150℃ and the reaction time is 12 h.

[0016] The phosphorus source in step d is disodium hydrogen phosphite, and the amount used is 0.2 g; the high-temperature phosphating treatment is carried out under a nitrogen atmosphere at 5°C·min. -1The temperature was increased to 300℃ at a heating rate and held for 2 hours.

[0017] The application of the electrocatalyst NiMo@NiCuP / NF, which enhances catalytic performance through ohmic contact, in the furfural electrochemical reforming-assisted hydrogen evolution reaction.

[0018] A two-electrode system for the electro-oxidation coupled hydrogen evolution reaction of furfural is provided, in which NiMo@NiCuP / NF is used as both the cathode and anode working electrodes to construct a two-electrode electrolytic cell. Hydrogen gas is generated at the cathode by the hydrogen evolution reaction, and furfural oxidation reaction is generated at the anode to produce furoic acid.

[0019] The anolyte of the electrolytic cell is an alkaline solution containing furfural, and the catholyte is an alkaline solution.

[0020] A membrane electrode device for the electro-oxidation coupled hydrogen evolution reaction of furfural is provided, wherein NiMo@NiCuP / NF is used as the cathode and anode respectively, and an anion exchange membrane is used to separate the cathode chamber and the anode chamber to construct a membrane electrode electrolysis device; the anode electrolyte is an alkaline solution containing furfural, and the cathode electrolyte is an alkaline solution.

[0021] The electrolyte circulation rate is 100-200 mL / min; the device achieves efficient hydrogen evolution at the cathode and highly selective conversion of furfural to furoic acid at the anode.

[0022] This invention provides an electrocatalyst with enhanced catalytic performance through an ohmic contact and its application. The invention anchors a NiMo alloy onto the surface of a semiconductor NiCuP microflower using electrodeposition. By precisely controlling the work function matching between NiMo and NiCuP, an ohmic contact heterojunction is successfully constructed. The formation of this ohmic contact effectively eliminates the Schottky barrier at the heterostructure interface, removing the energy barrier for interfacial charge transport, thereby significantly optimizing the intrinsic conductivity of the catalyst and accelerating the transfer of electrons from the catalyst interior to the surface active sites. Thanks to this efficient interfacial electron transport channel, the catalyst exhibits significantly enhanced catalytic activity in the cathodic hydrogen evolution reaction (HER). In a dual-electrode system for furfural electrooxidation coupled with HER, the thermodynamically more favorable furfural oxidation reaction (FOR) replaces the kinetically sluggish oxygen evolution reaction (OER) in the anodic half-reaction, achieving energy-efficient hydrogen production by coupling the cathodic HER at a lower battery voltage. Simultaneously, at the anode, the biomass-derived platform molecule furfural is efficiently converted into high-value-added furoic acid. This coupling strategy significantly reduces the input voltage requirement of the electrolyzer, enabling energy-saving hydrogen production and achieving high-value conversion of biomass resources at the anode. This invention provides a high-speed electron transport channel for FOR coupling HER by constructing an ohmic contact interface. This interface engineering strategy is a key structural basis for improving the overall activity, selectivity, and stability of the catalyst, providing an important new approach for designing next-generation high-performance multifunctional electrocatalysts to meet future energy and chemical industry needs. Attached Figure Description

[0023] Figure 1 Scanning electron microscope image of NiMo@NiCuP / NF prepared in this invention;

[0024] Figure 2 Transmission electron microscopy image of NiMo@NiCuP / NF prepared in this invention;

[0025] Figure 3 Polarization curves of the HER catalysts prepared in Examples 1, 2, and 3 of this invention;

[0026] Figure 4 Polarization curves of the FOR catalysts prepared in Examples 1, 2, and 3 of this invention;

[0027] Figure 5 A comparison diagram of FOR and OER in Embodiment 6 of the present invention. Detailed Implementation

[0028] Example 1: Preparation of NiCuP / NF substrate

[0029] (1) Cut 0.5 mm thick NF (nickel foam) into 1×2 cm size, ultrasonically clean it in 1 M HCl, acetone and ethanol for 15 min in sequence, and then dry it in a vacuum drying oven at 60℃ for 12 h for later use.

[0030] (2) Dissolve 10 mM nickel nitrate hexahydrate, 10 mM copper nitrate hexahydrate, 30 mM urea and 10 mM ammonium fluoride in 50 mL of deionized water, and immerse the pretreated NF in the above solution. After stirring for 30 min, transfer to a 50 mL polytetrafluoroethylene-lined high-pressure reactor and react at 150 °C for 12 h.

[0031] (3) After the system is cooled to room temperature, the product is washed three times with deionized water and ethanol, and then dried in a vacuum drying oven at 80°C for 10 h to obtain the precursor.

[0032] (4) Place the dried precursor in a corundum boat and put it into the downstream region of a tube furnace; weigh 0.5 g of sodium dihydrogen phosphite into the upstream region. Under a nitrogen atmosphere, heat at 5 °C·min -1 The sample was heated to 300 °C at a heating rate and held for 2 h. The resulting sample was labeled as NiCuP / NF. As a comparison, NiP3 / NF and Cu3P / NF were synthesized using only nickel nitrate hexahydrate or copper nitrate hexahydrate as precursors, respectively, following the same procedure.

[0033] Example 2 Preparation of NiMo@NiCuP / NF electrocatalyst

[0034] (1) Dissolve 0.32 M nickel chloride hexahydrate, 0.23 M trisodium citrate dihydrate and 0.06 M sodium molybdate dihydrate in 30 mL of deionized water and stir thoroughly until clear. Adjust the pH of the mixture to 9.5 with sodium carbonate solution to use as electrolyte.

[0035] (2) Using the NiCuP / NF prepared in Example 1 as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, at 20 mA·cm -2 A constant current electrodeposition was performed at a current density for 300 s, and the resulting electrode was denoted as NiMo@NiCuP / NF. (3) As a comparison, NiP3 / NF and Cu3P / NF prepared in Example 1 were electrodeposited under the same conditions and labeled as NiMo@NiP3 / NF and NiMo@Cu3P / NF, respectively; blank NF without NiCuP loading was electrodeposited under the same conditions and labeled as NiMo / NF.

[0036] Example 3 Preparation of NiMo@NiCuP / NF electrocatalysts with different NiMo deposition amounts

[0037] Following the preparation method of Example 2, the difference lies in adjusting the concentration of sodium molybdate dihydrate in the electrolyte to 0.02 M, 0.04 M, 0.06 M, and 0.08 M, respectively. These were electrodeposited on NiCuP / NF substrates under the same conditions and denoted as NiMo(0.02)@NiCuP / NF, NiMo(0.04)@NiCuP / NF, NiMo(0.06)@NiCuP / NF, and NiMo(0.08)@NiCuP / NF, respectively. Electrochemical performance testing showed that when the molybdenum source concentration was 0.06 M, the prepared NiMo(0.06)@NiCuP / NF exhibited the best HER and FOR performance, indicating that an appropriate amount of NiMo deposition helps to form the optimal ohmic contact interface.

[0038] Example 4: Structural Characterization of NiMo@NiCuP / NF

[0039] The morphology and structure of the NiMo@NiCuP / NF prepared in Example 2 were characterized. Figure 1 The scanning electron microscope (SEM) image of NiMo@NiCuP / NF is shown. It can be seen that after electrodeposition, the NiMo alloy is uniformly anchored on the NiCuP micro-flower surface, maintaining the original three-dimensional open structure. This structure facilitates electrolyte penetration and rapid gas release. Figure 2 High-resolution transmission electron microscopy (TEM) images of NiMo@NiCuP / NF are shown. A tight heterojunction interface is clearly observed between NiCuP and NiMo, with continuous lattice fringes and no obvious lattice mismatch, confirming the successful formation of a high-quality ohmic contact interface. Energy dispersive spectroscopy (EDS) results show that Ni, Mo, Cu, and P elements are uniformly distributed at the heterojunction interface, further confirming the successful anchoring of the NiMo alloy on the NiCuP surface.

[0040] Example 5: HER performance testing of NiMo@NiCuP / NF

[0041] The NiMo@NiCuP / NF electrode prepared in Example 2 was used as the working electrode, the Hg / HgO electrode as the reference electrode, and the graphite rod as the counter electrode. Electrochemical performance was tested on a CHI 760E electrochemical workstation. The electrolyte was a 1.0 M KOH solution. HER performance was tested. Figure 3 The HER polarization curves of different catalysts in Example 2 are shown. NiMo@NiCuP / NF exhibits the best HER catalytic activity, requiring only 13 mV overpotential to reach 10 mA·cm⁻¹. -2The current density of the catalyst is significantly higher than that of NiMo@NiP3 / NF (78 mV), NiMo@Cu3P / NF (105 mV), NiMo / NF (156 mV), and commercial Pt / C catalyst (32 mV). This indicates that the ohmic contact interface constructed between NiMo and NiCuP greatly improves the conductivity and electron transport efficiency of the catalyst. Example 6: FOR performance testing of NiMo@NiCuP / NF

[0042] The NiMo@NiCuP / NF prepared in Example 2 was used as the working electrode, the Hg / HgO electrode as the reference electrode, and the graphite rod as the counter electrode. Electrochemical performance was tested on a CHI 760E electrochemical workstation. The electrolyte was a 1.0 M KOH + 0.1 M furfural solution. FOR performance was tested. Figure 4 The FOR polarization curves for different catalysts in Example 2 are shown. NiMo@NiCuP / NF exhibits the best FOR catalytic activity, requiring only a potential of 1.35 V (vs. RHE) to reach 10 mA·cm⁻¹. -2 The current density is superior to that of the control sample. This is attributed to the fast electron transport channel provided by the ohmic contact interface, which accelerates the oxidation kinetics of furfural molecules. Figure 5 The oxygen evolution reaction (OER) of NiMo@NiCuP / NF in 1.0 M KOH and the FOR polarization curves in 1.0 M KOH + 0.1 M furfural were compared. At a current density of 100 mA·cm⁻², the potential required for FOR is approximately 210 mV lower than that for OER, indicating that replacing the kinetically sluggish OER with the thermodynamically more favorable FOR can significantly reduce anode energy consumption and achieve energy-efficient hydrogen production. Example 7: Construction and Performance Testing of a Furfural Electrooxidation Coupled with Hydrogen Evolution Dual-Electrode System

[0043] The NiMo@NiCuP / NF prepared in Example 2 was used as both the cathode and anode. A two-electrode system was constructed using an H-type electrolytic cell. The cathode electrolyte was 1.0 M KOH, and the anode electrolyte was 1.0 M KOH + 0.1 M furfural. An anion exchange membrane separated the cathode chamber and the anode chamber.

[0044] Example 8: Construction and Performance Testing of Membrane Electrode Device

[0045] The NiMo@NiCuP / NF prepared in Example 2 was cut to a size of 1×1 cm and used as the working electrodes for the cathode and anode, respectively. An anion exchange membrane separated the anode and cathode of the membrane electrode assembly. The anolyte was 1.0 M KOH + 0.1 M furfural, and the catholyte was 1.0 M KOH. A peristaltic pump was used to transfer the electrolyte solution from the reaction tank to the membrane electrode assembly at a flow rate controlled at 150 mL / min, thus constructing a complete membrane electrode electrolysis device.

Claims

1. An electrocatalyst NiMo@NiCuP / NF whose catalytic performance is enhanced by an ohmic contact, comprising: 1) Dissolve 0.30-0.32 M nickel chloride hexahydrate, 0.20-0.23 M trisodium citrate dihydrate and 0.02-0.08 M sodium molybdate dihydrate in 30 mL of deionized water and stir thoroughly until clear; adjust the pH to 9.5 with sodium carbonate solution, and use the resulting mixture as the electrolyte; 2) Using NiCuP / NF as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, at 10-20 mA·cm -2 A constant current electrodeposition was performed at a current density for 300 s, and the resulting electrode was NiMo@NiCuP / NF. The NiCuP / NF is prepared by the following method: a. After cutting the nickel foam, it is ultrasonically cleaned in hydrochloric acid, acetone and ethanol in sequence, and then dried for later use; b. Dissolve nickel source, copper source, urea and ammonium fluoride in deionized water, immerse the pretreated NF in the above solution, stir and transfer to a high-pressure reactor for hydrothermal reaction; c. After the reaction system has cooled to room temperature, the resulting product is washed and dried to obtain the precursor; d. The obtained precursor and phosphorus source were placed downstream and upstream of a tube furnace, respectively, and subjected to low-temperature phosphating treatment under an inert atmosphere to obtain NiCuP / NF.

2. The NiMo@NiCuP / NF electrocatalyst with enhanced catalytic performance via ohmic contact according to claim 1, characterized in that, In the electrolyte described in step 1), there is 0.06 M sodium molybdate dihydrate.

3. The NiMo@NiCuP / NF electrocatalyst with enhanced catalytic performance via ohmic contact according to claim 2, characterized in that, In the electrolyte described in step 1), there are 0.32 M nickel chloride hexahydrate and 0.23 M trisodium citrate dihydrate.

4. An electrocatalyst NiMo@NiCuP / NF with enhanced catalytic performance via an ohmic contact according to claim 1, 2, or 3, characterized in that, The nickel source in step b is nickel nitrate hexahydrate with a concentration of 10 mM; the copper source is copper nitrate hexahydrate with a concentration of 20 mM; the hydrothermal reaction temperature is 150℃ and the reaction time is 12 h.

5. The NiMo@NiCuP / NF electrocatalyst with enhanced catalytic performance via ohmic contact according to claim 4, characterized in that, The phosphorus source in step d is disodium hydrogen phosphite, and the amount used is 0.2 g; the high-temperature phosphating treatment is carried out under a nitrogen atmosphere at 5°C·min. -1 The temperature was increased to 300℃ at a heating rate and held for 2 hours.

6. The application of the NiMo@NiCuP / NF electrocatalyst with enhanced catalytic performance through ohmic contact as described in claim 1 in the assisted hydrogen evolution reaction of furfural electrochemical reforming.

7. A two-electrode system for the electro-oxidation coupled hydrogen evolution reaction of furfural, characterized in that, Using the NiMo@NiCuP / NF described in claim 1 as both the cathode and anode working electrodes, a two-electrode electrolytic cell is constructed. Hydrogen gas is generated at the cathode through a hydrogen evolution reaction, while furfural oxidation occurs at the anode to generate furoic acid.

8. The two-electrode system for furfural electrooxidation coupled with hydrogen evolution reaction according to claim 7, characterized in that, The anolyte of the electrolytic cell is an alkaline solution containing furfural, and the catholyte is an alkaline solution.

9. A membrane electrode device for the electro-oxidation coupling of furfural to hydrogen evolution reaction, characterized in that, Using the NiMo@NiCuP / NF described in claim 1 as the cathode and anode respectively, and separating the cathode chamber and anode chamber with an anion exchange membrane, a membrane electrode electrolysis device is constructed; the anode electrolyte is an alkaline solution containing furfural, and the cathode electrolyte is an alkaline solution.

10. A membrane electrode device for furfural electrooxidation coupled to hydrogen evolution reaction according to claim 9, characterized in that, The electrolyte circulation rate is 100-200 mL / min; the device achieves efficient hydrogen evolution at the cathode and highly selective conversion of furfural to furoic acid at the anode.

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