A nickel sulfide / nickel oxide electrode, a preparation method and application thereof

Abstract

The application belongs to the technical field of nanocomposites, and particularly relates to a nickel sulfide / nickel oxide electrode and a preparation method and application thereof. The nickel sulfide / nickel oxide electrode comprises nickel sulfide, nickel oxide and a conductive current collector, the nickel sulfide and the nickel oxide are transversely and alternately arranged on the surface of the conductive current collector, or the nickel oxide is coated on the surface of the nickel sulfide to form a core-shell structure and is loaded on the surface of the conductive current collector. The nickel sulfide species grown or loaded on the conductive current collector is a substrate, and the nickel sulfide / nickel oxide electrode is prepared by an electrochemical controllable reconstruction method of substrate concentration modulation. Based on the effective balance of competitive adsorption among multiple substrates, the nickel sulfide / nickel oxide electrode can efficiently oxidize ethanol, glycerol, glucose, benzyl alcohol, furfuryl alcohol, 5-hydroxymethyl furfural and other small molecules of biomass-derived alcohols into high-value products, and realizes efficient value-added of biomass derivatives.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials technology, specifically relating to a nickel sulfide / nickel oxide electrode, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Since the Industrial Revolution, while the development and utilization of fossil fuels have significantly improved people's living standards, they have also caused serious energy crises and environmental pollution. Against this backdrop, the efficient development and utilization of renewable resources is regarded as an effective way to achieve green and sustainable development.

[0004] Biomass energy, as the fourth largest energy source after coal, oil, and natural gas, boasts advantages such as abundant reserves, renewability, and low pollution. The efficient development and utilization of biomass energy is a crucial pathway to achieving green, low-carbon, and sustainable development. For example, biomass such as cellulose, lignin, and chitin can be chemically processed to depolymerize into small-molecule alcohols, known as biomass-derived alcohols. These can be further catalytically oxidized into higher-value-added aldehydes and acids, thus realizing the value-added of biomass.

[0005] According to the inventors, the electrocatalytic oxidation of small-molecule biomass-derived alcohols, powered by renewable electricity, has become a research hotspot in recent years due to its high reaction efficiency and mild reaction conditions. Researchers have demonstrated that noble metal-based catalysts such as platinum, iridium, ruthenium, and gold can be used for the oxidation of small-molecule biomass-derived alcohols such as ethanol, glycerol, and 5-hydroxymethylfurfural. However, their activity and selectivity are generally low. Furthermore, limited reserves and high costs make it difficult for noble metal-based catalysts to meet the requirements of large-scale industrial production. Recently, non-noble metal transition metal-based catalysts such as nickel, iron, cobalt, and copper have been shown to have high catalytic activity and reaction selectivity for the electrooxidation of various small-molecule biomass-derived alcohols. For example, catalysts such as nickel oxide, nickel nitride, nickel phosphide, iron oxide, cobalt oxide, cobalt nitride, nano-copper, and copper hydroxide have shown good performance in the oxidation of small-molecule alcohols such as ethanol, ethylene glycol, glycerol, glucose, furfuryl alcohol, and 5-hydroxymethylfurfural. However, their activity, selectivity, and stability still fall short of industrial requirements. The reason for this is that the oxidation reaction of small molecules of alcohols derived from biomass requires both small alcohol molecules and hydroxide ions (OH-). - Both catalysts participate in the reaction, and their competitive adsorption on the electrode surface is a significant factor limiting performance improvement. Furthermore, uncontrollable reconfiguration of the catalyst during the reaction leads to poor operational stability.

[0006] Therefore, there is an urgent need to develop a non-precious metal-based catalyst with ultra-high activity, product selectivity and ultra-high operational stability for the electro-oxidation of small molecules of biomass-derived alcohols to meet the needs of practical production applications. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a nickel sulfide / nickel oxide electrode, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] In a first aspect, the present invention provides a nickel sulfide / nickel oxide electrode, comprising nickel sulfide, nickel oxide and a conductive current collector, wherein the nickel sulfide and the nickel oxide are arranged alternately in the transverse direction on the surface of the conductive current collector, or the nickel oxide is coated on the surface of the nickel sulfide to form a core-shell structure load on the surface of the conductive current collector.

[0010] Preferably, the nickel oxide includes one or more of nickel oxide, nickel hydroxide, nickel hydroxy oxide, defective nickel oxide, defective nickel hydroxide, and defective nickel hydroxy oxide.

[0011] Preferably, the conductive current collector includes one or more of the following: nickel foam, iron foam, titanium foam, nickel sheet, iron sheet, titanium sheet, carbon paper, carbon cloth, glassy carbon, and conductive glass.

[0012] In a second aspect, the present invention provides a method for preparing a nickel sulfide / nickel oxide electrode as described in the first aspect, characterized by comprising the following steps:

[0013] Using a conductive current collector loaded with nickel sulfide as the working electrode, electrochemical oxidation is carried out in an electrolyte containing small molecules of biomass-derived alcohols to obtain the nickel sulfide / nickel oxide electrode.

[0014] The biomass-derived alcohol molecules include one or more of ethanol, glycerol, glucose, benzyl alcohol, furfuryl alcohol, and 5-hydroxymethylfurfural, and the concentration of the biomass-derived alcohol molecules is 0-50 mmol / L.

[0015] Preferably, the electrochemical oxidation system is a two-electrode system or a three-electrode system, and the electrochemical oxidation method includes one or more of continuous cyclic voltammetry, continuous linear voltammetry, constant potential electrolysis, or constant current electrolysis.

[0016] More preferably, in a two-electrode system, the applied potential for cyclic voltammetry or continuous linear voltammetry is 1.0-3.5V; or, in a three-electrode system, using a standard hydrogen electrode as a reference electrode, the applied potential for cyclic voltammetry or continuous linear voltammetry is 1.0-3.0V.

[0017] Preferably, the electrolyte is a neutral electrolyte or an alkaline electrolyte.

[0018] Preferably, the method for preparing the nickel sulfide-loaded conductive current collector includes one or more of the following methods:

[0019] (1) Place the conductive current collector loaded with nickel hydroxide or nickel oxide and sulfur powder in a tube furnace for calcination.

[0020] (2) The conductive current collector loaded with nickel hydroxide or nickel oxide is placed in an aqueous solution of thiourea to carry out a hydrothermal reaction.

[0021] (3) Nickel sulfide and carbon black are dissolved in a mixed solvent of isopropanol-water-Nafion to prepare a slurry. The slurry is sprayed onto a conductive current collector and dried.

[0022] More preferably, the method for preparing the conductive current collector loaded with nickel hydroxide or nickel oxide includes one or more of the following preparation methods:

[0023] (1) The conductive current collector is placed in an aqueous solution containing nickel salt and urea for hydrothermal reaction;

[0024] (2) Electrochemical oxidation is carried out in an electrolyte containing nickel salt by using a conductive current collector as the working electrode.

[0025] Thirdly, the present invention provides the application of the nickel sulfide / nickel oxide electrode as described in the first aspect in the electro-oxidation of biomass-derived alcohol small molecules, characterized in that the biomass-derived alcohol small molecules include one or more of ethanol, glycerol, glucose, benzyl alcohol, furfuryl alcohol, and 5-hydroxymethylfurfural.

[0026] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0027] The present invention provides a nickel sulfide / nickel oxide electrode that can be obtained by electrochemical oxidation of a precursor electrode loaded with sulfides. During the oxidation process, an electrolyte containing small molecules of biomass-derived alcohols is used to regulate the surface reconstruction process of the nickel sulfide / nickel oxide electrode, thereby regulating the catalytic activity of the nickel sulfide / nickel oxide electrode.

[0028] The present invention provides a nickel sulfide / nickel oxide electrode that is prepared by hydrothermal method, solvothermal method, solid phase method, electrodeposition method and electro-oxidation method, which has the characteristics of simple process, low equipment requirements and easy large-scale production.

[0029] Experiments have shown that the nickel sulfide / nickel oxide electrode provided by this invention can achieve higher activity, product selectivity, and stability in the electro-oxidation and value-added process of biomass-derived alcohols, and is expected to meet the needs of industrial production. This electrode can achieve product selectivity exceeding 98% for the oxidation of various biomass-derived alcohols, including ethanol, glycerol, glucose, furfuryl alcohol, benzyl alcohol, and 5-hydroxymethylfurfural, with a current density exceeding 300 mA cm⁻¹. -2 And it can maintain a high degree of stability during long-term operation. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 In Figure a, XRD pattern of the initial nickel sulfide electrode prepared in Example 1 is shown; in Figures b and c, scanning electron microscope images of the initial nickel sulfide electrode prepared in Example 1 are shown.

[0032] Figure 2 The XRD pattern of the nickel sulfide / nickel oxide electrode prepared in Example 1 is shown.

[0033] Figure 3 Here is a scanning electron microscope image of the nickel sulfide / nickel oxide electrode prepared in Example 5;

[0034] Figure 4 In Figure a, XRD pattern of the initial nickel sulfide electrode prepared in Example 2 is shown; in Figures b and c, scanning electron microscope images of the initial nickel sulfide electrode prepared in Example 2 are shown.

[0035] Figure 5 Image a is the XRD pattern of nickel sulfide powder prepared in Example 3; images b and c are scanning electron microscope images of nickel sulfide powder prepared in Example 3.

[0036] Figure 6 Image a is the XRD pattern of nickel sulfide powder prepared in Example 4; images b and c are scanning electron microscope images of nickel sulfide powder prepared in Example 4.

[0037] Figure 7 The graphs show the activity and selectivity of the electro-oxidation of 5-hydroxymethylfurfural in Experiment Example 1. a is the linear voltammetric scan curve, b is the Tafel plot, c is the potential-dependent curve of the selectivity of the electro-oxidation reaction of 5-hydroxymethylfurfural, and d is the concentration change graph of substrate, intermediate and product during the oxidation of 5-hydroxymethylfurfural. In the graph, vs. RHE represents the relative standard hydrogen electrode.

[0038] Figure 8This is the time-dependent curve of current density and Faraday efficiency during the electro-oxidation of 5-hydroxymethylfurfural in Experiment Example 2, where vs. RHE represents the relative standard hydrogen electrode;

[0039] Figure 9 The graphs show the activity and selectivity of the electro-oxidation of 5-hydroxymethylfurfural in Experiment Example 3. a is the linear voltammetric scan curve, b is the comparison of current density at a potential of 1.5V vs. RHE, c is the potential-dependent curve of the selectivity of the electro-oxidation reaction of 5-hydroxymethylfurfural, and d is the graph showing the concentration changes of substrate, intermediate and product during the oxidation of 5-hydroxymethylfurfural. In the graph, vs. RHE represents the relative standard hydrogen electrode.

[0040] Figure 10 This is the linear voltammetric scan curve of furfural electro-oxidation in Experiment Example 4, where vs. RHE represents the relative standard hydrogen electrode. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0042] Example 1

[0043] Nickel sulfide is grown in situ on a nickel foam conductive substrate with a nickel-sulfur ratio (nickel:sulfur) of 2:3, forming the initial nickel sulfide electrode (denoted as pristine Ni3S2). Specifically:

[0044] (1) Pretreatment of conductive nickel foam substrate: Cut commercially available nickel foam with a thickness of 1mm into 2*4cm pieces. 2 The sample was subjected to ultrasonic treatment for 20 minutes in sequence with anhydrous ethanol, acetone, 0.1M hydrochloric acid aqueous solution, deionized water, and anhydrous ethanol, followed by vacuum drying at 80℃ for 6 hours.

[0045] (2) Preparation of nickel hydroxide / nickel foam precursor electrode grown on nickel foam conductive current collector: The nickel hydroxide / nickel foam precursor electrode was obtained by hydrothermal method. Specifically, 1.6 mmol Ni(NO3)2·6H2O (0.4653 g), 3.85 mmol NH4F (0.1425 g), and 8 mmol urea (0.4805 g) were dissolved in 40 mL of deionized water in a stainless steel autoclave with a 50 mL Teflon liner. A pretreated nickel foam conductive substrate was vertically immersed in the autoclave, and then the autoclave was sealed. The reaction was carried out at 120 °C for 8 h. After natural cooling, the product was thoroughly washed with deionized water and ethanol, and dried to obtain the nickel hydroxide / nickel foam precursor electrode.

[0046] (3) Preparation of Ni3S2 electrode grown on nickel foam conductive current collector: pristine Ni3S2 electrode was obtained by hydrothermal sulfidation of the obtained nickel hydroxide / nickel foam precursor electrode. Specifically: 0.6 g Na2S·9H2O was dissolved in 30 mL of deionized water in a stainless steel autoclave with a 30 mL Teflon liner. One piece of the obtained nickel hydroxide / nickel foam precursor electrode was vertically immersed into the autoclave, and then the autoclave was sealed and reacted at 160 °C for 6 h. After natural cooling, the product was thoroughly washed with deionized water and ethanol to obtain the product, and dried to obtain the pristine Ni3S2 electrode.

[0047] The obtained pristine Ni3S2 electrode was characterized in terms of phase and morphology. Figure 1 The XRD pattern shown in 'a' indicates that the surface of the pristine Ni3S2 electrode is composed of a well-crystallized Heazlewoodite phase Ni3S2; Figure 1 As can be seen from b and c, the pristine Ni3S2 electrode has a nanosheet array morphology.

[0048] A nickel sulfide / nickel oxide electrode, denoted as Ni3S2 / NiO, was prepared using a pristine Ni3S2 electrode via a substrate concentration-modulated electrochemically controllable surface reconstruction method. x -n, the specific preparation method is as follows:

[0049] In a three-electrode system, using a pristine Ni3S2 electrode as the working electrode, an Hg / HgO electrode as the reference electrode, and a graphite rod as the counter electrode, five consecutive linear voltammetric (LSV) scans were performed in a 1M KOH electrolyte containing different concentrations of 5-hydroxymethylfurfural (HMF) to achieve electrochemically controllable surface reconstruction. The potential range of the LSV scans was 1.2–1.8 V vs. RHE, and the scan rate was 5 mV / s. After rinsing the electrodes with deionized water following the five LSV scans and drying, Ni3S2 / NiO was obtained. x -n electrode, where n is the concentration of HMF in the electrolyte during LSV scanning. Representatively, HMF concentrations of 0, 5, 15, and 30 mmol / L were used, and the resulting electrodes were denoted as Ni3S2 / NiO. x -0,5,15,30.

[0050] The obtained electrodes were characterized in terms of phase and morphology. Figure 2 The XRD patterns shown indicate that after electrochemically controllable surface reconstruction, Ni3S2 / NiO x The phases at -0, 5, 15, and 30°C all remained as the well-crystallized Heazlewoodite phase Ni3S2; Figure 3The scanning electron microscope images shown indicate that as the concentration of HMF in the electrolyte increases during the electrochemically controlled surface reconstruction process, the morphology of the electrode decreases compared to the pristine Ni3S2 electrode, suggesting that the electrochemically controlled surface reconstruction process can be modulated by the concentration of the substrate HMF.

[0051] Example 2

[0052] A nickel sulfide initial electrode (denoted as Initial Ni3S2(on CC)) is formed by in-situ growth on a carbon cloth (CC) conductive substrate with a nickel-sulfur ratio (nickel:sulfur) of 2:3. Specifically:

[0053] (1) Pretreatment of carbon cloth conductive substrate: Cut commercially available carbon cloth into 2*4cm pieces. 2 The sample was placed in a round-bottom flask containing 50 mL of concentrated nitric acid and heated under reflux at 100 °C for 2 hours. After natural cooling, it was rinsed with deionized water until neutral, then rinsed with anhydrous ethanol and dried under vacuum at 80 °C for 6 hours.

[0054] (2) Preparation of nickel hydroxide / carbon cloth precursor electrode grown on carbon cloth conductive current collector: The nickel hydroxide / carbon cloth precursor electrode was obtained by hydrothermal method. Specifically, 1.6 mmol Ni(NO3)2·6H2O (0.4653 g) and 8 mmol urea (0.4805 g) were dissolved in 40 mL deionized water in a stainless steel autoclave with a 50 mL Teflon liner. A pretreated foamed nickel conductive substrate was vertically immersed into the autoclave, and then the autoclave was sealed. The reaction was carried out at 180 °C for 12 h. After natural cooling, the product was thoroughly washed with deionized water and ethanol, and dried to obtain the nickel hydroxide / carbon cloth precursor electrode.

[0055] (3) Preparation of Initial Ni3S2(on CC) electrode grown on carbon cloth conductive current collector: The Initial Ni3S2(on CC) electrode was obtained by hydrothermal sulfidation of the obtained nickel hydroxide / carbon cloth precursor electrode. Specifically, 0.1 g of thiourea was dissolved in 30 mL of deionized water in a stainless steel autoclave with a 30 mL Teflon liner. One piece of the obtained nickel hydroxide / carbon cloth precursor electrode was vertically immersed in the autoclave, and then the autoclave was sealed and reacted at 160 °C for 10 h. After natural cooling, the product was thoroughly washed with deionized water and ethanol to obtain the product. After drying, the Initial Ni3S2(on CC) electrode was obtained.

[0056] The obtained Initial Ni3S2 (on CC) electrode was characterized in terms of phase and morphology. Figure 4 The XRD pattern shown in 'a' indicates that the surface of the Initial Ni3S2 (on CC) electrode is composed of a well-crystallized Heazlewoodite phase Ni3S2; Figure 4 As can be seen from b and c, the Initial Ni3S2 (on CC) electrode has a spherical nanoparticle morphology.

[0057] The initial Ni3S2(on CC) electrode was prepared by an electrochemically controlled surface reconstruction method based on substrate concentration modulation, resulting in a nickel sulfide / nickel oxide electrode, denoted as Ni3S2 / NiO. x -n (on CC), specifically:

[0058] In a three-electrode system, an Initial Ni3S2 (on CC) electrode was used as the working electrode, an Hg / HgO electrode as the reference electrode, and a graphite rod as the counter electrode. Five consecutive linear voltammetric (LSV) scans were performed in a 1M KOH electrolyte containing different concentrations of 5-hydroxymethylfurfural (HMF) to achieve electrochemically controllable surface reconstruction. The potential range of the LSV scans was 1.2–1.8 V vs. RHE, and the scan rate was 5 mV / s. After rinsing the electrodes with deionized water following the five LSV scans and drying, Ni3S2 / NiO was obtained. x -n electrode, where n is the concentration of HMF in the electrolyte during LSV scanning. Representatively, HMF concentrations of 0, 5, 15, and 30 mmol / L were used, and the resulting electrodes were denoted as Ni3S2 / NiO. x -0,5,15,30(on CC).

[0059] Example 3

[0060] First, nickel sulfide powder (denoted as NiS) with a sulfur-to-nickel ratio (nickel:sulfur) of 1:1 was obtained. Then, the obtained NiS was drop-coated onto a nickel foam conductive current collector to form the initial nickel sulfide electrode (denoted as pristine NiS / Ni Foam). Specifically:

[0061] (1) Preparation of NiS powder: NiS powder was obtained by a one-step hydrothermal method. Specifically, 1 mmol L-cysteine ​​and 1 mmol Ni(CH3COO)2·4H2O were dissolved in a water-isopropanol mixed solvent (containing 15 mL deionized water and 5 mL isopropanol) in a stainless steel autoclave with a 30 mL Teflon liner. The autoclave was then sealed and reacted at 160 °C for 10 h. After natural cooling, the precipitate was separated by centrifugation and washed three times each with deionized water and anhydrous ethanol. The precipitate was then vacuum dried at 80 °C for 6 h to obtain NiS powder. The phase and morphology of the obtained NiS powder were characterized by... Figure 5 The XRD pattern shown in 'a' indicates that the NiS powder is a well-crystallized NiS containing two phases, corresponding to JCPDS:12-0041 and JCPDS:02-1081 standard cards, respectively; Figure 5As can be seen from b and c, NiS powder has a spherical morphology formed by the self-assembly of ultrathin nanosheets.

[0062] (2) Preparation of NiS catalyst slurry: 20 mg of prepared NiS powder and 5 mg of carbon black were ultrasonically dispersed in a mixed solvent of isopropanol-water-Nafion (containing 1 mL isopropanol, 0.5 mL deionized water and 0.2 mL Nafion solution) for 1 hour to obtain a black NiS catalyst slurry.

[0063] (3) Preparation of pristine NiS / Ni Foam electrode loaded on nickel foam conductive current collector: The initial NiS electrode was obtained by drop coating the NiS catalyst slurry obtained in step (2) of this embodiment onto the pretreated nickel foam conductive substrate. Specifically, 0.5 mL of NiS catalyst slurry was evenly drop coated in 5 portions onto the nickel foam conductive current collector obtained in step (1) of Example 1 of this invention, and vacuum dried at 80°C for 2 hours to obtain the pristine NiS / Ni Foam electrode.

[0064] A pristine NiS / Ni Foam electrode, denoted as NiS / Ni(OH)2-n, was fabricated using a substrate concentration-modulated electrochemically controllable surface reconstruction method. Specifically:

[0065] In a three-electrode system, a pristine NiS / Ni Foam electrode was used as the working electrode, an Hg / HgO electrode as the reference electrode, and a graphite rod as the counter electrode. Five consecutive linear voltammetric (LSV) scans were performed in a 1M KOH electrolyte containing different concentrations of furfuryl alcohol to achieve electrochemically controllable surface reconstruction. The potential range of the LSV scans was 1.2–1.8 V vs. RHE, and the scan rate was 5 mV / s. After rinsing the electrodes with deionized water for the five LSV scans and drying them, NiS / Ni(OH)2-n electrodes were obtained, where n is the concentration of furfuryl alcohol in the electrolyte during the LSV scans. Representatively, electrodes with furfuryl alcohol concentrations of 0, 25, and 50 mmol / L were designated as NiS / Ni(OH)2-0, 25, and 50, respectively.

[0066] Example 4

[0067] In this embodiment, nickel sulfide powder (denoted as NiS2) with a sulfur-to-nickel ratio (nickel:sulfur) of 1:2 was first obtained. Then, the obtained NiS2 was sprayed onto a titanium foam conductive current collector to form a nickel sulfide initial electrode (denoted as pristine NiS2 / TiFoam). Specifically:

[0068] (1) Preparation of NiS2 powder: NiS2 powder was obtained by a one-step solvothermal method. Specifically, 1.25 g of Na2S2O3 and 1.6 mmol of Ni(NO3)2·6H2O were dissolved in 16 mL of anhydrous ethanol in a stainless steel autoclave with a 30 mL Teflon liner. The autoclave was then sealed and reacted at 160 °C for 16 h. After natural cooling, the precipitate was separated by centrifugation and washed three times each with deionized water and anhydrous ethanol. The precipitate was then vacuum dried at 80 °C for 6 h to obtain NiS2 powder. The phase and morphology of the obtained NiS2 powder were characterized by... Figure 6 The XRD pattern shown in 'a' indicates that the NiS2 powder has good crystallinity; Figure 6 As can be seen from b and c, NiS2 powder has a nanoparticle morphology with a well-defined crystal plane structure.

[0069] (2) Preparation of NiS2 catalyst slurry: 20 mg of prepared NiS powder and 5 mg of carbon black were ultrasonically dispersed in isopropanol-water-Nafion mixed solvent (containing 1 mL isopropanol, 0.5 mL deionized water and 0.2 mL Nafion solution) for 1 hour to obtain black NiS2 catalyst slurry.

[0070] (3) Preparation of NiS2 initial electrode loaded on titanium foam conductive current collector: The NiS2 initial electrode is obtained by spraying the NiS2 catalyst slurry obtained in step (2) of this embodiment onto the titanium foam conductive substrate. Specifically, 0.5 mL of NiS2 catalyst slurry is uniformly sprayed onto the titanium foam conductive current collector in 5 portions and vacuum dried at 80°C for 2 hours to obtain pristine NiS2 / Ti Foam.

[0071] A pristine NiS2 / Ti Foam electrode, denoted as NiS2 / Ni(OH)2-n, was fabricated using a substrate concentration-modulated electrochemically controllable surface reconstruction method. Specifically:

[0072] In a three-electrode system, a pristine NiS2 / Ti Foam electrode was used as the working electrode, an Hg / HgO electrode as the reference electrode, and a graphite rod as the counter electrode. Five consecutive linear voltammetric (LSV) scans were performed in a 1M KOH electrolyte containing different concentrations of furfuryl alcohol to achieve electrochemically controllable surface reconstruction. The potential range of the LSV scans was 1.2–1.8 V vs. RHE, and the scan rate was 5 mV / s. After rinsing the electrodes with deionized water for the five LSV scans and drying them, NiS2 / Ni(OH)2-n electrodes were obtained, where n is the concentration of furfuryl alcohol in the electrolyte during the LSV scans. Representatively, electrodes with furfuryl alcohol concentrations of 0, 25, and 50 mmol / L were designated as NiS2 / Ni(OH)2-0, 25, and 50, respectively.

[0073] Experimental Example 1

[0074] This test case tested the Ni3S2 / NiO described in Example 1. x The activity and selectivity of the -n electrode and the pristine Ni3S2 electrode in the electrooxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid were studied. Specifically:

[0075] In the three-electrode system, using the Ni3S2 / NiO described in Example 1... x Using the -n electrode and the pristine Ni3S2 electrode as the working electrode, the Hg / HgO electrode as the reference electrode, and the graphite electrode as the counter electrode, linear voltammetry (LSV) scanning was performed in a 1M KOH electrolyte containing 20 mmol / L HMF. Figure 7 As shown in a, Ni3S2 / NiO x The -15 electrode achieved a current density of 366 mA / cm² at a potential of 1.5 V vs. RHE. 2 This performance surpasses that of most publicly available and reported performance. The Tafel curves of the above electrodes were tested using a steady-state method, as shown in the figure. Figure 7 As shown in b, Ni3S2 / NiO x The -15 electrode exhibited the lowest Tafel slope at 58 mV / dec, indicating the fastest reaction kinetics. Furthermore, the selectivity of the electrode for HMF electro-oxidation and the competitive oxygen evolution reaction was monitored by gas chromatography and liquid chromatography. Figure 7 As shown in c, at a potential below 1.6V vs. RHE, Ni3S2 / NiO x The -15 electrode almost quantitatively induces the HMF oxidation reaction, effectively suppressing the competitive oxygen evolution side reaction. Since the HMF electro-oxidation process involves multiple intermediates, such as 2,5-furandicarboxylic acid (DFF), 5-hydroxymethyl-2-furanic acid (HMFCA), and 5-formyl-2-furanic acid (FFCA), the selectivity of the electrode for the final product 2,5-furandicarboxylic acid (FDCA) is also an important factor to be investigated. Figure 7 As shown in d, Ni3S2 / NiO x The -15 electrode exhibits extremely high selectivity for FDCA, with a Faraday efficiency of 98%. All the above tests demonstrate that the Ni3S2 / NiO electrode obtained through electrochemically controllable surface reconstruction modulated by substrate concentration is effective. x The -15 electrode can efficiently catalyze the electro-oxidation of HMF.

[0076] Experimental Example 2

[0077] This experimental example examined the Ni3S2 / NiO described in Example 1. xThe operational stability of the -n electrode for HMF electro-oxidation. Specifically:

[0078] The Ni3S2 / NiO described in Example 5 was evaluated in a device where the anolyte was expanded to 2 liters. x The operational stability of the -n electrode for HMF electro-oxidation was assessed using a 1M KOH aqueous solution containing 20 mmol / L HMF. Stability testing was conducted via potentiostatic electrolysis at 1.5 V vs. RHE, with HMF replenished every 4 hours and the electrolyte replaced every 24 hours. Figure 8 As shown, Ni3S2 / NiO x The -n electrode exhibits excellent HMF electro-oxidation stability, with both activity and selectivity remaining highly stable over more than 100 hours of operation.

[0079] Experimental Example 3

[0080] This experimental example examined the Ni3S2 / NiO described in Example 2. x The activity and selectivity of the -n(on CC) electrode in the electrooxidation of 2,5-furandicarboxylic acid using HMF. Specifically:

[0081] In the three-electrode system, using the Ni3S2 / NiO described in Example 2... x Using the -n(on CC) electrode and the InitialNi3S2(on CC) electrode as the working electrodes, the Hg / HgO electrode as the reference electrode, and the graphite electrode as the counter electrode, linear voltammetry (LSV) scanning was performed in a 1M KOH electrolyte containing 20 mmol / L HMF. Figure 9 As shown in a and b, Ni3S2 / NiO x The -15 (on CC) electrode achieves a current density of 204 mA / cm² at a potential of 1.5 V vs. RHE. 2 This performance surpasses most publicly available and reported results. Furthermore, the selectivity of the electrode for HMF electro-oxidation and the competitive oxygen evolution reaction was monitored by gas chromatography and liquid chromatography. Figure 9 As shown in c, at potentials below 1.6V vs. RHE, Ni3S2 / NiO x The HMF oxidation reaction occurred almost quantitatively at the -15 (onCC) electrode, effectively suppressing the competitive oxygen evolution side reaction. Furthermore, the Ni3S2 / NiO ratio was investigated by liquid chromatography. x The selectivity of the -15 (on CC) electrode for FDCA products. For example... Figure 9 As shown in d, Ni3S2 / NiO xThe -15 (on CC) electrode exhibits extremely high selectivity for FDCA, achieving a Faraday efficiency of 98%. All the above tests demonstrate that the Ni3S2 / NiO electrode obtained through electrochemically controllable surface reconstruction modulated by substrate concentration is effective. x The -15 (on CC) electrode can efficiently catalyze the electro-oxidation of HMF.

[0082] Test Example 4

[0083] This experimental example tested the activity of the NiS / Ni(OH)2-n electrode described in Example 3 for the electrooxidation of furfuryl alcohol to furoic acid. Specifically:

[0084] In the three-electrode system, the NiS / Ni(OH)2-n electrode described in Example 3 was used as the working electrode, the Hg / HgO electrode as the reference electrode, and the graphite electrode as the counter electrode. Linear voltammetry (LSV) scanning was performed in a 1M KOH electrolyte containing 50 mmol / L furfuryl alcohol. Figure 10 As shown, the NiS / Ni(OH)2-25 electrode achieves a current density of 332 mA / cm² at a potential of 1.5 V vs. RHE. 2 This performance surpasses most publicly available and reported performance.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nickel sulfide / nickel oxide electrode, characterized in that, The electrode comprises nickel sulfide, nickel oxide, and a conductive current collector. The nickel sulfide and nickel oxide are arranged alternately in the transverse direction on the surface of the conductive current collector, or the nickel oxide coats the surface of the nickel sulfide to form a core-shell structure that loads the conductive current collector. The nickel sulfide / nickel oxide electrode is prepared by electrochemical oxidation in an electrolyte containing biomass-derived alcohol molecules, using the conductive current collector loaded with nickel sulfide as the working electrode. The biomass-derived alcohol molecules include one or more of furfuryl alcohol and 5-hydroxymethylfurfural.

2. The nickel sulfide / nickel oxide electrode according to claim 1, characterized in that, The nickel oxide includes one or more of nickel oxide, nickel hydroxide, nickel hydroxy oxide, defective nickel oxide, defective nickel hydroxide, and defective nickel hydroxy oxide.

3. The nickel sulfide / nickel oxide electrode according to claim 1, characterized in that, The conductive current collector includes one or more of the following: nickel foam, iron foam, titanium foam, nickel sheet, iron sheet, titanium sheet, carbon paper, carbon cloth, glassy carbon, and conductive glass.

4. A method for preparing a nickel sulfide / nickel oxide electrode as described in any one of claims 1-3, characterized in that, Includes the following steps: Using a conductive current collector loaded with nickel sulfide as the working electrode, electrochemical oxidation is carried out in an electrolyte containing small molecules of biomass-derived alcohols to obtain the nickel sulfide / nickel oxide electrode. The biomass-derived alcohol molecules include one or more of furfuryl alcohol and 5-hydroxymethylfurfural, and the concentration of the biomass-derived alcohol molecules is 0-50 mmol / L.

5. The preparation method according to claim 4, characterized in that, The electrochemical oxidation system is a two-electrode system or a three-electrode system, and the electrochemical oxidation method includes one or more of continuous cyclic voltammetry, continuous linear voltammetry, constant potential electrolysis, or constant current electrolysis.

6. The preparation method according to claim 5, characterized in that, In a two-electrode system, the applied potential for cyclic voltammetry or continuous linear voltammetry is 1.0–3.5 V; or, in a three-electrode system, using a standard hydrogen electrode as a reference electrode, the applied potential for cyclic voltammetry or continuous linear voltammetry is 1.0–3.0 V.

7. The preparation method according to claim 4, characterized in that, The electrolyte is a neutral electrolyte or an alkaline electrolyte.

8. The preparation method according to claim 4, characterized in that, The method for preparing the nickel sulfide-loaded conductive current collector includes one or more of the following methods: (1) Place the conductive current collector loaded with nickel hydroxide or nickel oxide and sulfur powder in a tube furnace for calcination; (2) The conductive current collector loaded with nickel hydroxide or nickel oxide is placed in an aqueous solution of thiourea to carry out a hydrothermal reaction; (3) Nickel sulfide and carbon black are dissolved in a mixed solvent of isopropanol-water-Nafion to prepare a slurry. The slurry is sprayed onto a conductive current collector and dried.

9. The preparation method according to claim 8, characterized in that, The method for preparing the conductive current collector loaded with nickel hydroxide or nickel oxide includes one or more of the following methods: (1) The conductive current collector is placed in an aqueous solution containing nickel salt and urea for a hydrothermal reaction; (2) Electrochemical oxidation is carried out in an electrolyte containing nickel salt by using a conductive current collector as the working electrode.

10. The application of the nickel sulfide / nickel oxide electrode as described in any one of claims 1-3 in the electro-oxidation of small molecules of biomass-derived alcohols, characterized in that, The biomass-derived alcohol molecules include one or more of furfuryl alcohol and 5-hydroxymethylfurfural.

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