Double-ligand nickel-based catalyst as well as preparation method and application thereof

Abstract

The invention relates to a double-ligand nickel-based catalyst as well as a preparation method and application thereof. The double-ligand nickel-based catalyst comprises a substrate and an active component loaded on the substrate, the active component comprises double ligands Ni (OH) xXy, x + y = 2, y is more than or equal to 0.1 and less than or equal to 1, and X comprises any one or a combination of at least two of S, Se or Te. The double-ligand Ni (OH) xXy (X = S, Se or Te) catalyst is constructed by partially replacing an OH ligand of nickel hydroxide in situ through a sulfur group element (S, Se or Te) ligand, the catalyst has two coordination environments of Ni-O and Ni-X (X = S, Se or Te) at the same time, synergistic catalysis can be carried out by utilizing double active sites, OER side reaction is inhibited, and selective efficient oxidation of HMF under high current density is realized.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic furfural oxidation technology, and more particularly to a dual-ligand nickel-based catalyst, its preparation method, and its uses. Background Technology

[0002] Large-scale hydrogen production technology is a key technology for achieving sustainable development of hydrogen energy. Among them, water electrolysis hydrogen production technology can produce "green" hydrogen without pollution using renewable electricity, making it an ideal hydrogen production method. However, due to the high potential of the oxygen evolution reaction (OER) at the anode, the overall energy consumption of water decomposition is increased, which greatly limits the practical application of water electrolysis hydrogen production.

[0003] Oxidation reactions of organic molecules are considered an ideal alternative to OER (Organic Emission Reactions), among which the electro-oxidation of 5-hydroxymethylfurfural (HMF) has attracted widespread attention due to its favorable thermodynamics and economic efficiency. Coupled with the hydrogen evolution reaction, it can reduce system energy consumption and produce the value-added chemical 2,5-furandicarboxylic acid (FDCA), thus achieving two benefits in one step.

[0004] Currently, existing design strategies for electrocatalysts suitable for the HMFOR reaction system mainly include element doping, alloying, defect engineering, and heterostructure construction. The catalysts involved are primarily non-noble metal catalysts (Ni, Co, Fe, Cu, etc.), which possess excellent catalytic activity and cost-effectiveness. Among them, nickel-based catalysts, with abundant 3d electrons and unique eg orbitals, can effectively enhance the covalent nature of metal-oxygen bonds and optimize the adsorption / desorption behavior of oxygen-containing intermediates, making them one of the most widely studied non-noble metal catalysts for HMFOR. However, current catalysts suitable for the electrocatalytic furfural oxidation reaction system still suffer from technical problems such as insufficient intrinsic selectivity and energy efficiency imbalance.

[0005] Specifically, existing non-precious metal catalysts face a critical technological bottleneck in achieving high potentials and industrial-grade current densities due to intense competition in the oxygen evolution reaction (OER). As the operating potential increases, the selective adsorption and regulation capabilities of the single active sites of traditional nickel-based catalysts for OH⁻ and HMF molecules become insufficient. This prevents the catalyst from maintaining preferential adsorption and activation of HMF molecules across a wide potential range, leading to runaway reaction pathways and a significant enhancement of OER side reactions. This not only results in the inefficient consumption of a large amount of electrical energy but also causes a sharp decline in the Faraday efficiency of the HMF oxidation reaction with increasing current density, ultimately causing a simultaneous decrease in both the target reaction activity and selectivity, severely hindering the industrialization of this technology.

[0006] The oxidation process of HMF on nickel-based catalysts involves two steps: electrochemical and non-electrochemical. First, Ni 2+ -OH is oxidized to Ni in the presence of OH⁻. 3+-O; then the HMF molecule spontaneously undergoes nucleophilic dehydrogenation, and H transfers to Ni. 3+ -O is reduced to Ni(OH)2, thus forming a reversible redox cycle. During this process, Ni... 2+ -OH and Ni containing electrophilic lattice oxygen 3+ -O are the active sites and key intermediates for the formation of HMFOR in nickel-based catalysts, respectively, thus promoting the formation of HMFOR in Ni-based catalysts. 2+ -OH is electro-oxidized to Ni 3+ The rate of -O can effectively improve the intrinsic activity of the catalyst. On the other hand, the rate of spontaneous nucleophilic dehydrogenation of HMF molecules determines the supply and transport of protons and electrons, and is also a key factor affecting the oxidation efficiency of furfural. Therefore, most current research focuses on optimizing Ni 2+ / Ni 3+ The reversibility of redox reactions and the hydrogen dissociation process of HMF molecules reduce the reaction initiation potential.

[0007] However, to achieve industrial-grade high current density, these two points alone are insufficient; it is also necessary to address the critical issue of OER competitive adsorption under conditions involving OH⁻. Currently, there is a lack of precise site regulation strategies to fundamentally resolve OER competitive adsorption, and no similar ligand regulation strategy can achieve controllable adjustment of the selective adsorption process of OH⁻ and HMF at active sites.

[0008] Therefore, developing a novel nickel-based electrocatalyst that can precisely control the reaction pathway and maintain high activity and selectivity under high current density has become a core issue in promoting the industrial application of HMFOR technology. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a dual-ligand nickel-based catalyst, its preparation method, and its applications. The dual-ligand nickel-based catalyst of the present invention has two coordination environments: Ni-O and Ni-X (X=S, Se, Te). It can utilize the dual active sites for synergistic catalysis, suppress OER side reactions, and achieve selective and efficient oxidation of HMF at high current densities.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a dual-ligand nickel-based catalyst, the dual-ligand nickel-based catalyst comprising a substrate and an active component supported on the substrate; the active component comprising a dual-ligand Ni(OH). x X y Where x+y=2, 0.1≤y≤1, X includes any one or at least two of S, Se or Te, and typical but non-restrictive combinations include combinations of S and Se, combinations of Se and Te, combinations of S and Te, and combinations of S, Se and Te.

[0012] This invention constructs a dual-ligand Ni(OH) by in-situ partial substitution of the OH ligand of nickel hydroxide by a sulfur group element (S, Se, or Te) ligand. x X y This catalyst (X = S, Se, Te) possesses both Ni-O and Ni-X (X = S, Se, Te) coordination environments, exhibiting both strongly electrophilic Ni-S and weakly electrophilic Ni-O adsorption sites at the oxidation potential. According to the "hard acid-soft base" theory, the hard base OH⁻ tends to adsorb onto the strongly electrophilic Ni-S site, while HMF molecules adsorb onto the Ni-O site. This avoids the occupation of the Ni-O active site by OH⁻, suppressing OER side reactions and achieving spatial separation and synergistic activation of competing reactive species and the target substrate. Thus, the selective and efficient oxidation of HMF at high current densities can be achieved through synergistic catalysis using dual active sites.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0014] Preferably, the substrate comprises any one or a combination of at least two of nickel foam, carbon paper, or carbon cloth.

[0015] Preferably, X is S.

[0016] In a second aspect, the present invention provides a method for preparing a dual-ligand nickel-based catalyst as described in the first aspect, the method comprising the following steps:

[0017] (1) Mix nickel salt, slow-release precipitant, substrate etchant and solvent to obtain precursor solution, immerse substrate in precursor solution and obtain catalyst precursor through hydrothermal reaction;

[0018] (2) The mixed catalyst precursor and X source solution are subjected to a solvothermal ion exchange reaction to obtain the dual-ligand nickel-based catalyst.

[0019] This invention employs a simple hydrothermal reaction. First, a catalyst precursor with controllable morphology and structure, namely a nickel hydroxide precursor catalyst with a single ligand structure, is specifically synthesized on a substrate. Then, it is placed in an aqueous solution containing an X source for a second hydrothermal treatment. Through a mild ion exchange reaction at the solid-liquid interface, the X ions partially exchange with hydroxide ions, thereby converting the single ligand catalyst into a dual ligand catalyst.

[0020] If the X source solution is directly added to the precursor solution in step (1), the controllable introduction of X ions cannot be achieved, leading to uncontrollable side reactions and phase separation. For example, when Ni 2+Simultaneously reacting with OH⁻ and S in a high-temperature hydrothermal environment 2- When they meet, Ni is affected by the competing precipitation reaction. 2+ Will prioritize with S 2- This process combines to form thermodynamically more stable nickel sulfide. However, this process is rapid and lacks the conditions for controlled ion exchange. The two-step hydrothermal method used in this invention employs a precise "post-modification" strategy, performing a secondary hydrothermal reaction on the already formed solid Ni(OH)₂. In this case, the reaction occurs at the solid-liquid interface, and the reaction rate increases from S0... 2- The diffusion and exchange kinetics into the solid are controlled, the reaction is slow and controllable, and the degree of X incorporation can be precisely adjusted by regulating the reaction parameters.

[0021] Preferably, the nickel salt comprises any one or a combination of at least two of nickel nitrate, nickel chloride, or nickel sulfate.

[0022] Preferably, the slow-release precipitant comprises urea and / or ammonium carbonate, and the substrate etchant comprises ammonium fluoride and / or sodium fluoride.

[0023] Preferably, the slow-release precipitant is urea, and the substrate corrosive agent is ammonium fluoride.

[0024] Preferably, the solvent includes water.

[0025] Preferably, the molar ratio of the nickel salt, the slow-release precipitant, and the substrate etchant is 1:4-6:4-6, for example, it can be 1:4:4, 1:5:4, 1:6:4, 1:4:5, 1:5:5, 1:6:5, 1:4:6, 1:5:6, or 1:6:6, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the concentration of nickel ions in the precursor solution is 30 mmol / L-50 mmol / L, for example, it can be 30 mmol / L, 35 mmol / L, 40 mmol / L, 45 mmol / L or 50 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the temperature of the hydrothermal reaction is 120℃-180℃, for example, it can be 120℃, 130℃, 140℃, 150℃, 160℃, 170℃ or 180℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0028] Preferably, the hydrothermal reaction time is 4h-8h, for example, it can be 4h, 5h, 6h, 7h or 8h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the X source solution comprises an X source and a solvent.

[0030] Preferably, the molar concentration of the X source solution is 2 mmol / L-20 mmol / L, for example, it can be 2 mmol / L, 3 mmol / L, 5 mmol / L, 8 mmol / L, 10 mmol / L, 12 mmol / L, 15 mmol / L, 18 mmol / L or 20 mmol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] This invention further controls the molar concentration of the X source solution to 2 mmol / L-20 mmol / L. The molar concentration of the X source solution affects the crystal structure, chemical composition, and catalytic performance of the final catalyst. If the molar concentration of the X source solution is too high, the reaction becomes rapid, the Ni(OH)2 structure is destroyed, and the mild ion exchange reaction is transformed into a dissolution-reprecipitation reaction, resulting in the formation of thermodynamically more stable independent NiX phases, such as NiS and NiSe2. If the molar concentration of the X source solution is too low, the exchange will be insufficient, and X ions will only attach in the form of physical adsorption or weak surface bonding, failing to successfully incorporate into the Ni(OH)2 lattice to form stable Ni-X bonds. These weakly bonded surface species will rapidly dissolve or detach in subsequent electrocatalytic reactions, ultimately causing the catalyst to revert to ordinary nickel hydroxide instead of forming a true dual-ligand catalyst.

[0032] Preferably, the X source includes any one or a combination of at least two of the following: sulfur source, selenium source, or tellurium source. Typical but non-limiting combinations include combinations of sulfur source and selenium source, combinations of selenium source and tellurium source, combinations of sulfur source and tellurium source, and combinations of sulfur source, selenium source, and tellurium source.

[0033] Preferably, the sulfur source includes any one or a combination of at least two of sodium sulfide, thiourea, thioacetamide, or sodium thiosulfate. Typical but non-limiting combinations include combinations of sodium sulfide and thiourea, combinations of thiourea and thioacetamide, combinations of thioacetamide and sodium thiosulfate, combinations of sodium sulfide, thioacetamide, and sodium thiosulfate, combinations of thiourea, thioacetamide, and sodium thiosulfate, and combinations of sodium sulfide, thiourea, thioacetamide, and sodium thiosulfate.

[0034] Preferably, the selenium source includes sodium selenite and / or selenium tetrachloride.

[0035] Preferably, the tellurium source includes sodium tellurate and / or tellurium tetrachloride.

[0036] Preferably, the temperature of the solvothermal ion exchange reaction is 100℃-140℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃ or 140℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] This invention further controls the temperature of the solvothermal ion exchange reaction to 100℃-140℃. The temperature of the solvothermal ion exchange reaction affects the dominant reaction pathway and the structure and performance of the final catalyst. Too low a temperature leads to insufficient reaction kinetics, making it difficult for chalcogen ions to overcome the diffusion barrier and enter the nickel hydroxide lattice. Only limited and uneven surface adhesion can be achieved, or even ineffective ion exchange may occur, resulting in the final product retaining almost all the properties of the original nickel hydroxide with minimal modification. Too high a temperature causes the reaction to shift from a mild and controllable ion exchange to a violent dissolution-reprecipitation process. This not only completely destroys the fine nanostructure constructed in the first step but also promotes the formation of thermodynamically more stable independent nickel sulfide or nickel selenide impurities, thus losing the intended dual-site synergistic structure. For chemically more reactive selenium and tellurium sources, excessively high temperatures can also exacerbate the side reaction of water oxidation, causing ineffective loss of raw materials and surface contamination.

[0038] Preferably, the time for the solvothermal ion exchange reaction is 4h-8h, for example, it can be 4h, 5h, 6h, 7h or 8h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the process further includes washing and drying after the solvothermal ion exchange reaction and before obtaining the dual-ligand nickel-based catalyst.

[0040] Preferably, the drying temperature is 50℃-70℃, for example, it can be 50℃, 55℃, 60℃, 65℃ or 70℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the drying time is 2h-8h, for example, it can be 2h, 3h, 4h, 5h, 6h, 7h or 8h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0043] (1) The substrate was ultrasonically cleaned for 10 min-30 min in sequence with 1 mol / L-3 mol / L hydrochloric acid, deionized water and ethanol to obtain the pretreated substrate; nickel salt, urea and ammonium fluoride were dissolved in deionized water in a molar ratio of 1:4-6:4-6 to obtain a precursor solution with a nickel ion concentration of 30 mmol / L-50 mmol / L; the pretreated substrate was immersed in the precursor solution and hydrothermally reacted at 120℃-180℃ for 4 h-8 h; the substrate was washed with deionized water and dried to obtain the catalyst precursor.

[0044] (2) The mixed catalyst precursor and the X source solution with a molar concentration of 2 mmol / L-20 mmol / L were subjected to a solvothermal ion exchange reaction at 100℃-140℃ for 4h-8h. The product was washed with deionized water and dried at 50℃-70℃ for 2h-8h to obtain the dual-ligand nickel-based catalyst.

[0045] Thirdly, the present invention provides the use of the dual-ligand nickel-based catalyst as described in the first aspect, wherein the dual-ligand nickel-based catalyst is used in the field of electrocatalytic furfural oxidation.

[0046] The present invention provides a dual-ligand nickel-based catalyst that enhances the selectivity of nickel-based catalysts for electrocatalytic furfural oxidation using a dual-ligand strategy. On one hand, it constructs dual-ligand active centers with differentiated adsorption functions: by precisely controlling the coordination environment of the nickel-based catalyst, a dual-ligand structure containing two active sites is constructed, achieving spatial separation and synergistic activation of competing reactive species (OH⁻) and the target substrate (HMF), thus mechanistically solving the problem of insufficient selectivity in traditional catalyst reaction pathways. On the other hand, it achieves simultaneous improvement in target reaction selectivity and activity: under conditions significantly lower than the oxygen evolution reaction potential, it achieves an industrial-grade current density (≥500 mA / cm²). 2 The efficient electro-oxidation of HMF under these conditions broadens the dominant potential reaction window and suppresses OER side reactions, thereby comprehensively improving the current density, Faraday efficiency, and energy economy in the electrocatalytic conversion of furfural.

[0047] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects:

[0049] (1) This invention introduces sulfur group element ligands into nickel hydroxide to construct a “Ni-X / Ni-O” dual-site structure, so that the catalyst has two adsorption sites, strong electrophilic Ni-S and weak electrophilic Ni-O, under oxidation potential. According to the “soft and hard acid-base” theory, hard base OH⁻ tends to adsorb on the strong electrophilic Ni-S site, while HMF molecules will adsorb on the Ni-O site, thereby avoiding the occupation of Ni-O active site by OH⁻, inhibiting OER side reaction, and realizing the spatial separation and synergistic activation of competing reactive species and target substrate.

[0050] (2) This invention precisely separates the two key steps of precursor construction and ion exchange modification. First, under mild conditions, a nickel hydroxide monoligand catalyst substrate is specifically and controllably grown to provide a structurally stable template for subsequent reactions. Then, in the second step of solvothermal ion exchange, the concentration of chalcogen source and the reaction temperature are independently controlled to achieve controllable gradient doping of chalcogen elements. This avoids the phase separation problem caused by the competitive precipitation of different anions in the traditional one-step method, ensuring that the target chalcogen elements precisely replace part of the hydroxyl groups in the crystal lattice through chemical bonding, rather than simply attaching or forming independent impurity phases. Its core innovation lies in the successful preparation of a dual-ligand catalyst with both stable nickel-oxygen active sites and modified nickel-chalcogen active sites through stepwise control.

[0051] (3) The dual-ligand nickel-based catalyst provided by this invention can broaden the advantageous reaction window to achieve efficient and selective oxidation of HMF, and can drive 500 mA·cm at low potential (below 1.5V (vs. RHE)). -2 The industrial-grade current density far surpasses that of most reported HMFOR electrocatalysts. Simultaneously, its high intrinsic adsorption selectivity for HMF molecules effectively suppresses OER side reactions over a wide potential window, widening the activity gap between HMFOR and OER, thus achieving a balance between high Faradaic efficiency and high energy conversion efficiency. Attached Figure Description

[0052] Figure 1 This is a transmission electron microscope image of the dual-ligand nickel-based catalyst prepared in Example 1 of this invention;

[0053] Figure 2 This is the Raman spectrum of the dual-ligand nickel-based catalyst prepared in Example 1 of this invention;

[0054] Figure 3 The linear sweep voltammetry (LSV) curves of the dual-ligand nickel-based catalyst prepared in Example 1 of this invention and the single-ligand nickel-based catalyst prepared in Comparative Example 1 are shown.

[0055] Figure 4These are potentiostatic oxidation performance graphs of the dual-ligand nickel-based catalyst prepared in Example 1 of this invention and the single-ligand nickel-based catalyst prepared in Comparative Example 1.

[0056] Figure 5 This is a graph showing the potentiostatic oxidation performance of the dual-ligand nickel-based catalyst prepared in Example 1 of this invention during 6 cycles. Detailed Implementation

[0057] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0058] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0059] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0060] Example 1

[0061] This embodiment provides a dual-ligand nickel-based catalyst, which includes a nickel foam substrate and Ni(OH) supported on the nickel foam substrate. 1.2 S 0.8 Dual ligands;

[0062] The preparation method of the dual-ligand nickel-based catalyst provided in this embodiment includes the following steps:

[0063] (1) The foamed nickel substrate was ultrasonically cleaned for 15 min in sequence with 3 mol / L hydrochloric acid, deionized water and anhydrous ethanol to obtain the pretreated substrate; nickel nitrate, urea and ammonium fluoride were dissolved in deionized water in a molar ratio of 1:4.5:4.5 to obtain a precursor solution with a nickel ion concentration of 30 mmol / L. The pretreated substrate was immersed in the precursor solution and hydrothermally reacted at 160℃ for 4 h. After washing the substrate with deionized water and drying it, the catalyst precursor was obtained.

[0064] (2) The mixed catalyst precursor and a sodium sulfide nonahydrate solution with a molar concentration of 10 mmol / L were subjected to a solvothermal ion exchange reaction at 130 °C for 8 h. The product was washed with deionized water and dried at 60 °C for 6 h to obtain Ni(OH). 1.2 S 0.8 Biligand nickel-based catalyst.

[0065] Transmission electron microscopy image of the prepared dual-ligand nickel-based catalyst is shown below. Figure 1 As shown, from Figure 1 As can be seen from this, the prepared Ni(OH) 1.2 S 0.8 The dual-ligand catalyst has a nanosheet structure.

[0066] The Raman spectrum of the prepared biligand nickel-based catalyst is shown in the figure. Figure 2 As shown, from Figure 2 As can be seen from this, the prepared Ni(OH) 1.2 S 0.8 The dual-ligand catalyst possesses both Ni-O and Ni-S structures.

[0067] Example 2

[0068] This embodiment provides a dual-ligand nickel-based catalyst, which includes a nickel foam substrate and Ni(OH) supported on the nickel foam substrate. 1.3 Se 0.7 Dual ligands;

[0069] The preparation method of the dual-ligand nickel-based catalyst provided in this embodiment includes the following steps:

[0070] (1) The foamed nickel substrate was ultrasonically cleaned for 20 min in sequence with 2 mol / L hydrochloric acid, deionized water and anhydrous ethanol to obtain the pretreated substrate; nickel chloride, urea and ammonium fluoride were dissolved in deionized water in a molar ratio of 1:4:4 to obtain a precursor solution with a nickel ion concentration of 40 mmol / L. The pretreated substrate was immersed in the precursor solution and hydrothermally reacted at 140℃ for 6 h. After washing the substrate with deionized water and drying it, the catalyst precursor was obtained.

[0071] (2) The mixed catalyst precursor and a selenium tetrachloride solution with a molar concentration of 5 mmol / L were subjected to a solvothermal ion exchange reaction at 120 °C for 6 h. The product was washed with deionized water and dried at 50 °C for 8 h to obtain Ni(OH). 1.3 Se 0.7 Biligand nickel-based catalyst.

[0072] Example 3

[0073] This embodiment provides a dual-ligand nickel-based catalyst, which includes a nickel foam substrate and Ni(OH) supported on the nickel foam substrate. 1.5 Te 0.5 Dual ligands;

[0074] The preparation method of the dual-ligand nickel-based catalyst provided in this embodiment includes the following steps:

[0075] (1) The foamed nickel substrate was ultrasonically cleaned for 30 min in sequence with 1 mol / L hydrochloric acid, deionized water and anhydrous ethanol to obtain the pretreated substrate; nickel sulfate, urea and ammonium fluoride were dissolved in deionized water in a molar ratio of 1:6:6 to obtain a precursor solution with a nickel ion concentration of 50 mmol / L. The pretreated substrate was immersed in the precursor solution and hydrothermally reacted at 130℃ for 8 h. After washing the substrate with deionized water and drying it, the catalyst precursor was obtained.

[0076] (2) The mixed catalyst precursor and a 3 mmol / L tellurium tetrachloride solution were subjected to a solvothermal ion exchange reaction at 100 °C for 4 h. The product was washed with deionized water and dried at 70 °C for 2 h to obtain Ni(OH). 1.5 Te 0.5 Biligand nickel-based catalyst.

[0077] Example 4

[0078] This embodiment provides a dual-ligand nickel-based catalyst. The only difference from Example 1 is that, when preparing the dual-ligand nickel-based catalyst, the molar concentration of the sodium sulfide nonahydrate solution in step (2) is 1 mmol / L, while the other preparation steps remain unchanged, and the chemical formula of the resulting product is adapted to the change.

[0079] Example 5

[0080] This embodiment provides a dual-ligand nickel-based catalyst. The only difference from Example 1 is that, when preparing the dual-ligand nickel-based catalyst, the molar concentration of the sodium sulfide nonahydrate solution in step (2) is 40 mmol / L, while the other preparation steps remain unchanged, and the chemical formula of the resulting product is adapted to the change.

[0081] Example 6

[0082] This embodiment provides a dual-ligand nickel-based catalyst. The only difference from Example 1 is that the temperature of the solvothermal ion exchange reaction in step (2) is 80°C when preparing the dual-ligand nickel-based catalyst. The other preparation steps remain unchanged, and the chemical formula of the resulting product changes accordingly.

[0083] Example 7

[0084] This embodiment provides a dual-ligand nickel-based catalyst. The only difference from Example 1 is that the temperature of the solvothermal ion exchange reaction in step (2) is 160°C when preparing the dual-ligand nickel-based catalyst. The other preparation steps remain unchanged, and the chemical formula of the resulting product changes accordingly.

[0085] Comparative Example 1

[0086] This comparative example provides a nickel-based catalyst, which differs from Example 1 only in that sodium sulfide nonahydrate solution was not added in step (2) when preparing the nickel-based catalyst, while the other preparation steps remain unchanged.

[0087] Comparative Example 2

[0088] This comparative example provides a nickel-based catalyst, which differs from Example 1 only in that, when preparing the nickel-based catalyst, the sodium sulfide nonahydrate solution in step (2) is added to the precursor solution, thereby omitting step (2) and obtaining a nickel-based catalyst prepared by a one-step hydrothermal method.

[0089] Comparative Example 3

[0090] This comparative example provides a nickel-based catalyst, which differs from Example 1 only in that step (2) is replaced by calcination at 500°C for 3 hours in an NH3 atmosphere, while the other preparation steps remain unchanged.

[0091] test:

[0092] 1. Structural characterization: For the comparative examples and embodiments prepared, the materials were characterized and analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HADDF-STEM), elemental mapping (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy.

[0093] 2. Performance Testing: The electrochemical performance of the catalyst was tested using a three-electrode system. All tests were conducted in an H-type electrolytic cell. The catalyst was fixed with a platinum sheet electrode clamp as the working electrode, and an Hg / HgO electrode and a platinum wire electrode were used as the reference and counter electrodes, respectively. A DuPont proton exchange membrane (Nafion 117) was used to separate the anode and cathode chambers. The electrolyte in both the cathode and anode chambers was a 1M KOH solution. During the test, 100 mmol / L HMF was added to the anode chamber. The cyclic voltammetry curve scan range was 0~1.2V (vs. Hg / HgO), and the scan rate was 5mV / s.

[0094] 3. Quantitative Analysis: Potentiostatic electrolysis was performed at a potential of 1.5V (vs. RHE). After electrolysis, 5μL of electrolyte was extracted, diluted to 1mL with ultrapure water, and analyzed by Agilent 1260Ⅱ high-performance liquid chromatography. A Shimadzu C18 column (4.6×150mm, 5μm) was used for separation, and the products were monitored at 265nm with a UV detector. Mobile phase A was 5% ammonium formate aqueous solution, and mobile phase B was methanol, with a ratio of A to B of 7:3. The flow rate was 0.5mL·min. -1 .

[0095] The dual-ligand catalysts and nickel-based catalysts prepared in the examples and comparative examples were cut to appropriate sizes to serve as working electrodes, constructing a three-electrode system. HMFOR and OER electrochemical tests were performed at corresponding concentrations of different types of electrolytes. The test results are shown in Table 1 below. Figure 3 As shown.

[0096] The dual-ligand catalysts and nickel-based catalysts prepared in the examples and comparative examples were cut to appropriate sizes to serve as working electrodes. H-type electrolyzers were constructed, and constant-potential oxidation tests were performed at different furfural concentrations. Product quantification analysis was conducted, and the test results are as follows. Figure 4 and Figure 5 As shown.

[0097] like Figure 3 As shown, the Ni(OH) prepared in Example 1 was subjected to treatment in the corresponding electrolyte. x S y The LSV (Laser Vapor Spectrometry) tests were performed on the Ni(OH)₂ / NF dual-ligand catalyst and the Ni(OH)₂ / NF single-ligand catalyst prepared in Comparative Example 1. x S y The HMFOR current density of the / NF dual-ligand catalyst increases sharply with increasing potential, reaching 500 mA / cm² at 1.47 V (vs. RHE). 2 The current density was compared with that of the OER catalyst. Within the corresponding potential range, the current density of HMFOR was significantly higher than that of OER. Furthermore, the difference in HMFOR and OER activity between the two-ligand catalyst was much greater than that between the Ni(OH)2 / NF single-ligand catalyst (Table 1).

[0098] like Figure 4 As shown, a constant potential oxidation test was performed within a given potential window, and the Ni(OH) prepared in Example 1 was obtained. x S yThe / NF dual-ligand catalyst achieved an FDCA yield of up to 97% and a selectivity of up to 98%. In contrast, the Ni(OH)2 / NF single-ligand catalyst prepared in Comparative Example 1 only achieved an FDCA yield of 69%. This comparison strongly demonstrates the crucial role of the dual active centers in achieving efficient and selective electro-oxidation of HMF in dual-ligand catalysts.

[0099] After six cycles of testing, the HMF conversion, FDCA yield, and Faraday efficiency of the dual-ligand catalyst prepared in Example 1 were as follows: Figure 5 As shown, this demonstrates its good stability.

[0100] Table 1

[0101]

[0102] The test results show that:

[0103] (1) As can be seen from Examples 1-3, the present invention constructs a dual-ligand Ni(OH) by in-situ partial substitution of the OH ligand of nickel hydroxide by sulfur group element (S, Se or Te) ligand. x X y The catalyst (X=S, Se, Te) possesses both Ni-O and Ni-X (X=S, Se, Te) coordination environments, enabling synergistic catalysis using dual active sites, suppressing OER side reactions, and achieving selective and efficient oxidation of HMF at high current densities.

[0104] (2) As can be seen from the comparison between Example 1 and Examples 4-5, the present invention precisely controls the molar concentration of the X source solution within the critical range of 2-20 mmol / L. Too high a concentration will trigger a violent dissolution-reprecipitation reaction, destroy the precursor structure and generate NiX impurity phase; too low a concentration will not be able to drive an effective ion exchange reaction, forming unstable surface deposits. Neither of these can obtain a target dual-ligand catalyst with stable Ni-X bonds, resulting in unsatisfactory catalytic effect.

[0105] (3) A comparison of Example 1 with Examples 6-7 shows that the present invention precisely controls the temperature of the second-step solvothermal ion exchange reaction within the critical range of 100-140℃. Too low a temperature results in insufficient reaction kinetics, preventing effective ion exchange and causing modification failure; too high a temperature causes the reaction path to destructive dissolution-reprecipitation, generating impurities. Only within a suitable temperature window can controllable ion exchange be achieved, synthesizing a target dual-ligand catalyst with good catalytic performance.

[0106] (4) As can be seen from Example 1 and Comparative Example 1, the present invention can significantly optimize the electronic structure of the catalyst and obtain highly efficient bifunctional active sites by precisely introducing some chalcogenide ions (S, Se, Te) as second ligands into the nickel hydroxide lattice, thereby achieving excellent electrocatalytic furfural oxidation activity and selectivity. However, when no X source (S, Se or Te) is introduced, it is impossible to regulate the adsorption energy of the reactants and construct a stable synergistic catalytic interface through bifunctional active sites, thus failing to achieve the technical effect of improving the conversion efficiency and selectivity of the target organic molecules.

[0107] (5) As can be seen from Example 1 and Comparative Example 2, the present invention, by performing the precursor growth and ion exchange processes in steps and precisely controlling the reaction parameters of the secondary hydrothermal process, can obtain a catalyst with uniform doping, intact morphology and structure, and stable Ni-O and Ni-S dual active sites, thereby achieving highly selective HMF electrocatalytic oxidation performance. However, when the X source is introduced in a one-step method through blending, it is impossible to achieve controllable solid-liquid interface ion exchange. Instead, it will generate impurity phases due to competitive precipitation reactions, thus failing to obtain the preset synergistic catalytic effect.

[0108] (6) As can be seen from Example 1 and Comparative Example 3, the present invention can achieve strong regulation of the electronic structure of Ni by introducing chalcogen elements (S, Se, Te) with significant electronegativity differences from O as second ligands onto nickel hydroxide, thereby optimizing the electronic state and achieving excellent HMF electrocatalytic oxidation performance. However, when the X source (S, Se or Te) is replaced with other elements, it is impossible to achieve sufficient electronic feedback and significant electronegativity difference provided by chalcogen elements, making it difficult to effectively reshape the electronic structure and adsorption performance of the catalyst, resulting in limited catalyst modification effect.

[0109] In summary, this invention constructs a dual-ligand Ni(OH) by in-situ partial substitution of the OH ligand of nickel hydroxide by a sulfur group element (S, Se, or Te) ligand. x X y The catalyst (X=S, Se, Te) possesses both Ni-O and Ni-X (X=S, Se, Te) coordination environments, enabling synergistic catalysis using dual active sites, suppressing OER side reactions, and achieving selective and efficient oxidation of HMF at high current densities.

[0110] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A dual-ligand nickel-based catalyst characterized in that, The double-ligand nickel-based catalyst comprises a substrate and an active component loaded on the substrate; The active component includes a bi-ligand Ni(OH) x X y wherein x + y = 2, 0.1 < y < 1, and X includes any one or a combination of at least two of S, Se, or Te.

2. The dual-ligand nickel-based catalyst of claim 1, wherein, The substrate comprises any one or a combination of at least two of foamed nickel, carbon paper or carbon cloth; Preferably, X is S.

3. A process for the preparation of the dual-ligand nickel-based catalyst according to claim 1 or 2, characterized in that, The preparation method comprises the following steps: (1) mixing a nickel salt, a slow-release precipitant, a substrate corrosion agent and a solvent to obtain a precursor solution, immersing the substrate in the precursor solution, and obtaining a catalyst precursor through a hydrothermal reaction; (2) mixing the catalyst precursor and an X source solution to obtain the double-ligand nickel-based catalyst through a solvothermal ion exchange reaction.

4. The production method according to claim 3, characterized by, The nickel salt comprises any one or a combination of at least two of nickel nitrate, nickel chloride or nickel sulfate; Preferably, the slow-release precipitant comprises urea and / or ammonium carbonate, and the substrate corrosion agent comprises ammonium fluoride and / or sodium fluoride; Preferably, the slow-release precipitant is urea, and the substrate corrosion agent is ammonium fluoride; Preferably, the solvent comprises water; Preferably, the molar ratio of the nickel salt, the slow-release precipitant and the substrate corrosion agent is 1:4-6:4-6; Preferably, the concentration of nickel ions in the precursor solution is 30 mmol / L-50 mmol / L.

5. The production method according to claim 3 or 4, characterized by, The temperature of the hydrothermal reaction is 120°C-180°C; Preferably, the time of the hydrothermal reaction is 4h-8h.

6. The method of any one of claims 3-5, wherein, The X source solution comprises an X source and a solvent; Preferably, the molar concentration of the X source solution is 2 mmol / L-20 mmol / L; Preferably, the X source comprises any one or a combination of at least two of a sulfur source, a selenium source or a tellurium source; Preferably, the sulfur source comprises any one or a combination of at least two of sodium sulfide, thiourea, thioacetamide or sodium thiosulfate; Preferably, the selenium source comprises sodium selenite and / or selenium tetrachloride; Preferably, the tellurium source comprises sodium tellurate and / or tellurium tetrachloride.

7. The method of any one of claims 3-6, wherein, The temperature of the solvothermal ion exchange reaction is 100°C-140°C; Preferably, the time of the solvothermal ion exchange reaction is 4h-8h.

8. The method of any one of claims 3-7, wherein, After the solvothermal ion exchange reaction, the preparation method further comprises washing and drying before obtaining the double-ligand nickel-based catalyst; Preferably, the temperature of the drying is 50°C-70°C; Preferably, the time of the drying is 2h-8h.

9. The method of any one of claims 3-8, wherein, The preparation method comprises the following steps: (1) sequentially using 1mol / L-3mol / L hydrochloric acid, deionized water and ethanol to ultrasonically clean the substrate for 10min-30min to obtain a pretreated substrate; dissolving a nickel salt, urea and ammonium fluoride in deionized water according to a molar ratio of 1:4-6:4-6 to obtain a precursor solution with a nickel ion concentration of 30 mmol / L-50 mmol / L, immersing the pretreated substrate in the precursor solution, and hydrothermally reacting at 120°C-180°C for 4h-8h to obtain a catalyst precursor; (2) mixing the catalyst precursor with a X source solution with a molar concentration of 2 mmol / L-20 mmol / L, and carrying out a solvothermal ion exchange reaction at 100 ℃-140 ℃ for 4 h-8 h, and then washing the product with deionized water and drying at 50 ℃-70 ℃ for 2 h-8 h to obtain the double-ligand nickel-based catalyst.

10. Use of the dual-ligand nickel-based catalyst according to claim 1 or 2, characterized in that, The double-ligand nickel-based catalyst is used in the field of electrocatalytic oxidation of furfural.

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