In-situ growth of Cu-Ni alloy nanowires and preparation method thereof

Abstract

The application discloses in-situ grown Cu-Ni alloy nanowires and a preparation method thereof. The preparation method of the Cu-Ni alloy nanowires comprises the following steps: S1, carbon paper is immersed into a mixed solution of CuSO4, NiCl2 and NiSO4 for electrodeposition to obtain a Cu-Ni film; S2, the Cu-Ni film is reacted under alkaline conditions to obtain Cu-Ni hydroxide nanowires; S3, the Cu-Ni hydroxide nanowires are annealed to obtain Cu-Ni oxide nanowires; and S4, the Cu-Ni oxide nanowires are electrochemically reduced to obtain in-situ grown Cu-Ni alloy nanowires. The method can in-situ grow Cu-Ni alloy nanowires on carbon paper as a gas diffusion electrode, can electrochemically reduce CO2 to prepare C2H4, the faradic efficiency (FE) of producing C2H4 reaches 46.98%, and the current density reaches 231.81 mA / cm 2 2, which is obviously higher than that of bare copper nanowires (Cu NWs, 25.33%). The Cu-Ni alloy nanowires are in-situ constructed on carbon paper, and exhibit excellent stability, and can run for more than 8 hours under a large current.

Description

Technical Field

[0001] This invention relates to an in-situ grown Cu-Ni alloy nanowire and its preparation method, belonging to the field of electrocatalysis technology. Background Technology

[0002] Converting CO2 into valuable industrial products via electrocatalytic processes is a crucial method for sustainable development. In particular, reducing carbon dioxide into fuels and industrial feedstocks not only alleviates energy problems but also closes the carbon cycle and provides a viable solution for carbon neutrality. Therefore, designing and manufacturing high-performance electrocatalysts for specific high-value-added products is essential. In recent years, researchers have made significant progress in developing electrocatalysts, ultimately achieving high conversion efficiencies for carbon monoxide (CO), formic acid (HCOOH), methane (CH4), and other C1 products. Nevertheless, converting CO2 into multi-carbon products (C2) such as ethylene (C2H4) and ethanol (C2H5OH) remains a formidable challenge. C2H4, renowned for its high energy density, holds a strategically important position among industrial gases as a key compound. Metal catalysts, including Au, Ag, Sn, Ni, and Pb, exhibit a tendency to generate C1 products. Uniquely, copper-based catalysts demonstrate the ability to convert CO2 to C2H4 via a CC-coupling process. However, the efficient conversion of C2H4 is hampered by the high kinetic barrier of the CC-coupling process on the Cu catalyst surface and the stable adsorption of key intermediates. Currently, numerous strategies, such as crystal surface manipulation, single-atom synthesis, and defect engineering, are employed to modulate the physical or chemical properties of catalysts to improve adsorption and desorption processes. Researchers have designed a series of Au-Cu and Ag-Cu alloy catalysts that enhance CC coupling through the CO spillover effect, thereby significantly improving the selectivity and efficiency of Cu metal in C2H4 production. Nevertheless, to reduce application costs, it is necessary to move away from dependence on precious metals. Researchers have advanced the development of Cu-Zn, Cu-Sn, and Cu-Pd alloys, but the catalytic results have not met expectations. This invention is therefore proposed. Summary of the Invention

[0003] The purpose of this invention is to provide an in-situ grown Cu-Ni alloy nanowire, in which the interaction between Cu and Ni atoms significantly improves the efficiency of C-C coupling and exhibits excellent C2H4 selectivity and stability.

[0004] This invention employs a non-precious metal synergistic method and constructs in-situ Cu-Ni alloy nanowire structures on a gas diffusion layer (GDL), which can electrochemically reduce CO2 to C2H4 and CO, exhibiting excellent selectivity and stability.

[0005] The method for preparing Cu-Ni alloy nanowires provided by this invention includes the following steps:

[0006] S1. Electrodeposition is performed by immersing carbon paper in a mixed solution of CuSO4, NiCl2, and NiSO4 to obtain a Cu-Ni thin film;

[0007] S2. The Cu-Ni thin film is reacted under alkaline conditions to obtain Cu-Ni hydroxide nanowires;

[0008] S3. The Cu-Ni hydroxide nanowires are annealed to obtain Cu-Ni oxide nanowires.

[0009] S4. The Cu-Ni oxide nanowires are electrochemically reduced to obtain in-situ grown Cu-Ni alloy nanowires.

[0010] In the preparation method of the present invention, in step S1, the mixed solution is prepared with 0.1 M citrate buffer.

[0011] In the preparation method of the present invention, in step S1, the concentration of CuSO4 in the mixed solution is 0.05M-0.15M, the concentration of NiCl2 is 0.03M-0.08M, and the concentration of NiSO4 is 0.03M-0.08M.

[0012] In the preparation method of the present invention, in step S1, the electrodeposition time is 1500-2000s, and the obtained film is thoroughly dried under a nitrogen atmosphere.

[0013] In the preparation method of the present invention, in step S2, the alkaline condition is an aqueous solution of NaOH and (NH4)2S2O8, wherein the concentration of NaOH is 45-50 g / L and the concentration of (NH4)2S2O8 is 20-25 g / L.

[0014] In the preparation method of the present invention, in step S2, the reaction temperature is 2-8℃ and the time is 0.3-0.6h.

[0015] In the preparation method of the present invention, in step S3, the annealing temperature is 150-200℃ and the time is 0.5-2h, and the annealing is carried out in a muffle furnace.

[0016] In the preparation method of the present invention, in step S4, the electrochemical reduction is carried out in a flowing electrolytic cell using 0.50 M sodium sulfate solution as electrolyte, and a potential of -1.0 V (vs Ag / AgCl sat. KCl) can be applied for electrochemical reduction.

[0017] The in-situ grown Cu-Ni alloy nanowires prepared by the method of this invention can be used as gas diffusion electrodes, capable of electrochemically reducing C2H4 and CO. The Faraday efficiency (FE) for C2H4 production reaches 46.98%, and the current density reaches 231.81 mA / cm². 2 The stability of the Cu-Ni alloy nanowires significantly exceeds that of bare copper nanowires (Cu NWs, 25.33%). The Cu-Ni alloy nanowires of this invention, constructed in situ on a gas diffusion electrode, exhibit excellent stability, operating at high currents for over 8 hours. Attached Figure Description

[0018] Figure 1 This is an electron microscope image of the Cu-Ni thin film prepared in Example 1 of the present invention.

[0019] Figure 2 This is an electron microscope image of the cross-sectional thickness of the Cu-Ni thin film prepared in Example 1 of this invention.

[0020] Figure 3 This is a magnified cross-sectional view of the Cu-Ni thin film prepared in Example 1 of the present invention.

[0021] Figure 4 The Cu prepared in Example 1 of this invention x Ni y Electron micrograph of (OH)2 nanowires.

[0022] Figure 5 The Cu prepared in Example 1 of this invention x Ni y Magnified image of (OH)2 nanowires.

[0023] Figure 6 The Cu prepared in Example 1 of this invention x Ni y Electron micrograph of O nanowires.

[0024] Figure 7 This is an electron microscope image of the Cu-Ni nanowires prepared in Example 1 of this invention.

[0025] Figure 8 This is a TEM image of the Cu-Ni nanowires prepared in Example 1 of this invention.

[0026] Figure 9 This is an HR-TEM image of the Cu-Ni nanowires prepared in Example 1 of this invention.

[0027] Figure 10 The cross-sectional scanning electron microscope and EDS of Cu-Ni nanowires prepared in Example 1 of this invention are shown.

[0028] Figure 11This is the XRD pattern of Cu-Ni NWs prepared in Example 1 of this invention.

[0029] Figure 12 This is the XRD pattern of the Cu(111) peak.

[0030] Figure 13 This is the LSV diagram of Cu-Ni NWs prepared in Example 1 of this invention.

[0031] Figure 14 It is the Faraday efficiency of Cu-Ni NWs.

[0032] Figure 15 It is the Faraday efficiency of Cu NWs.

[0033] Figure 16 The current density of Cu-Ni NWs and Cu NWs prepared in Example 1 of this invention is shown. Detailed Implementation

[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0035] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0036] In the following examples, all reagents were used immediately upon receipt without further purification. Copper sulfate (CuSO4, 99.99%), nickel sulfate (NiSO4, 99.99%), nickel chloride (NiCl2, 99.99%), potassium bicarbonate (KHCO3, 99.7%), and boric acid (H3BO3, 99.8%) were all provided by Sinopharm Chemical Reagent Co., Ltd. Sodium sulfate (Na₂SO₄, 99%), sodium hydroxide (NaOH, 99%), citric acid (C₆H₈O₇), ammonium persulfate (NH₄)₂S₂O₈, 98%), hydrochloric acid (HCl, AR), and anhydrous ethanol (C₂H₅OH) were prepared using Aladdin reagents. Carbon dioxide (CO₂, 99.999%), nitrogen (N₂, 99.999%), and argon (Ar, 99.999%) were used according to the receiving volume. The gas diffusion layer (GDL, hydrophobic carbon paper, Sigrette 22 BB) and anion exchange membrane (3PK-130) were purchased from Gauss Associates. Ultrapure water with a resistivity of 18.45 MΩ cm was prepared in the laboratory.

[0037] In the following examples, the electrochemical testing method is as follows:

[0038] Electrochemical tests were conducted in a flow electrolyzer at ambient temperature. The flow electrolyzer was a three-electrode cell with three compartments. A 3PK-130 anion exchange membrane was used as the separator between the anode and cathode, an Ag / AgCl electrode (KCl saturated, salt bridge) was used as the reference electrode, 1 M KOH was used as the electrolyte, an iridium oxide mesh (3 × 1 cm) was used as the counter electrode, and the working electrode was fixed to a size of 2 × 0.5 cm with a gasket. CO2 flowed into the gas compartment at a rate of 30 sccm and diffused through the gas diffusion layer into the cathode, where electroreduction occurred at the gas-liquid-solid three-phase interface. The outflowing gaseous products were sampled at fixed intervals (15 min) and quantitatively analyzed using GC. A peristaltic pump was used to assist in the circulation of the catholyte (10 mL / min) and anolyte (40 mL / min). Electrochemical reaction data were collected using a CHI760E electrochemical workstation, and the Faraday efficiency of the liquid and gaseous products was calculated based on the collected charge information. All electrochemical tests were performed using solution resistance to compensate for the IR voltage drop, and all potentials were converted to RHE values. Linear scan voltammetry was used at a scan rate of 20 mV / s.

[0039] Example 1: Preparation of Cu-Ni NWs

[0040] A hydrophobic carbon paper (1×3 cm) was cleaned with anhydrous ethanol and 0.5 M HCl aqueous solution, respectively. The carbon paper was rinsed with ultrapure water, and the support layer was protected with a covering tape. Then, the carbon paper was immersed in a mixed solution of 0.1 M CuSO4, 0.07 M NiCl2, and 0.03 M NiSO4 (with 0.1 M citrate buffer) and electrodeposited for 1500 s. The resulting carbon paper coated with a Cu-Ni film was thoroughly dried under a nitrogen atmosphere.

[0041] Carbon paper coated with a Cu-Ni thin film was placed in 100 mL of an aqueous solution containing 4.8 g NaOH and 2.282 g (NH4)2S2O8. The mixture was then allowed to react at 5 °C for 30 minutes. After thorough washing and drying, a blue hydroxide was obtained. Subsequently, the sample was annealed in a muffle furnace at 200 °C for 2 h to form a black oxide. Electrochemical reduction was performed in a flowing electrolytic cell using 0.50 M sodium sulfate solution as the electrolyte and a potential of -1.0 V (vs Ag / AgCl sat.KCl) to obtain an in-situ grown Cu-Ni alloy nanowire gas diffusion electrode.

[0042] Example 2: Characterization of Cu-Ni NWs

[0043] GDEs prepared by catalyst ink coatings struggle to utilize their inherent advantages, suffering from problems such as hindered CO2 mass transfer, slow electron transport, and insufficient exposure of catalytic active sites, resulting in suboptimal CO2RR results. In contrast, nanoarray electrodes constructed in situ on GDLs can promote rapid CO2 and charge transport, thereby significantly enhancing reaction kinetics.

[0044] In Example 1 of this invention, a Cu-Ni alloy film was constructed on GDL by electrodeposition as a precursor for nanowire structures. Figure 1 The cross-sectional image shows that the deposited alloy film is distributed on the outer surface of the GDL, with a thickness of approximately 6.95 μm. Figure 2 and Figure 3 The continuous and uniform thin films ensure their electrical connection with the carbon paper substrate. Under alkaline conditions, the Cu-Ni alloy thin film transforms into Cu. x Ni y (OH)₂ nanowires ( Figure 4 and Figure 5 ). By annealing Cu in a muffle furnace x Ni y (OH)2 yields Cu x Ni y O nanowires ( Figure 6 Subsequently, CuO was electrochemically reduced in situ to Cu-Ni alloy nanowires (Cu-Ni NWs) in a flowing electrochemical cell. Figure 7 ).

[0045] The one-dimensional linear structure of Cu-Ni NW was confirmed by transmission electron microscopy, and its width was approximately 65 nm. Figure 8 Furthermore, HR-TEM revealed that Cu NW consists of nanocrystals exhibiting different crystal orientations, with abundant grain boundaries indicating a surface full of defects, and the rich microporous structure promoting CO2 mass transfer. Figure 9 Cross-sectional SEM image ( Figure 10 The results show that after nanoscale processing, Cu-Ni NWs are uniformly distributed on the GDL surface without obvious gaps or cracks, exhibiting good adhesion to the GDL substrate. EDS images also support this result. Compared with nanowire / GDL electrodes prepared by catalyst ink coating, the abundant open spaces between nanowires constructed in situ on GDL promote the diffusion and adsorption of reactants to the catalyst surface and facilitate rapid charge transfer, significantly enhancing the CO2RR reaction kinetics.

[0046] The crystal composition of the Cu-Ni NWs sample was determined by X-ray diffraction (XRD) patterns. Figure 11The results were confirmed. Cu-Ni NWs exhibited diffraction peaks similar to those of standard copper (ICDD No. 98-000-0172), corresponding to the (111), (200), and (220) planes of copper. Compared to the original Cu NW, the peaks corresponding to air-oxidized CuO and Cu2O in the Cu NW disappeared due to Ni doping. The more chemically active nickel prevented the oxidation of Cu NW, a phenomenon consistent with the behavior observed in Cu-Ni corrosion-resistant alloys.

[0047] Furthermore, due to the low Ni loading and relatively weak crystallinity, no diffraction data for the nickel phase were observed. Figure 12 In the study, the Cu(111) peak of the Ni-Cu NW was observed to shift slightly to a higher diffraction angle, located between the Cu(111) and Ni(111) standard peaks. This is attributed to the incorporation of Ni atoms into the Cu crystal phase, resulting in lattice strain, which confirms the formation of the alloy.

[0048] Example 3: Electrocatalytic CO2 performance of Cu-Ni NWs

[0049] Ni-Cu NW was loaded onto a flow cell, and 1 M KOH was used as the electrolyte to rigorously evaluate the electroreduction activity of CO2.

[0050] Prior to testing, all samples underwent an activation process involving 20 cyclic voltammetry (CV) cycles from 0 to -1 V (relative to RHE). Cu NWs in situ loaded onto GDL under identical conditions served as a control group for consistent experimental evaluation. Initially, each catalyst was subjected to linear sweep voltammetry in Ar and CO2 atmospheres to ensure comprehensive analysis.

[0051] like Figure 13 As shown, the reaction initiation time of Cu-Ni NWs is earlier than that of Cu NWs, and the current density is significantly greater than that of Cu NWs. This indicates that the Cu-Ni NWs of the present invention adsorb CO2 more quickly and react electrochemically, and promotes the accelerated kinetics of CC coupling.

[0052] The efficacy of CO2RR was assessed by applying electrode potentials ranging from -0.7 V to 1.2 V (relative to RHE). Gas phase products were analyzed using online gas chromatography (GC). The distribution of the main product FE for different catalysts is shown below. Figure 14 and Figure 15 As shown, the Cu-Ni NW achieved the highest C2H4 selectivity (46.98%) at -1 V, with a current density of 231.81 mA / cm². 2 ( Figure 16Cu NWs achieved a carbon product Faradaic efficiency of 56.11% at an applied potential of -1.0 V. However, Cu NWs exhibited poor selectivity, with a relatively uniform distribution of CO (25.62%), CH4 (14.88%), and C2H4 (16.99%), and no obvious dominant product, indicating poor selectivity.

[0053] Compared with bare Cu NW, Cu-Ni NW exhibits significantly enhanced C2H4 selectivity, demonstrating the catalytic advantages of alloy nanowires.

[0054] In contrast, Cu-Ni interface materials in thin film form produce only ~18% formate products.

[0055] The three-dimensional nanoarray structure of this invention provides abundant active sites, greatly enhancing the mass transfer process and promoting C-C coupling dynamics. This is also attributed to the synergistic interaction between Cu and Ni atoms, creating a favorable environment for accelerating chemical transformation.

Claims

1. A method for preparing Cu-Ni alloy nanowires, comprising the following steps: S1, immersing carbon paper into a mixed solution of CuSO4, NiCl2 and NiSO4 for electrodeposition to obtain a Cu-Ni film; S2, reacting the Cu-Ni film under alkaline conditions to obtain Cu-Ni hydroxide nanowires; In step S2, the alkaline conditions are an aqueous solution of NaOH and (NH4)2S2O8, the concentration of NaOH is 45-50 g / L, and the concentration of (NH4)2S2O8 is 20-25 g / L; S3, annealing the Cu-Ni hydroxide nanowires to obtain Cu-Ni oxide nanowires; In step S3, the annealing temperature is 150-200℃; S4, electrochemically reducing the Cu-Ni oxide nanowires to obtain in-situ grown Cu-Ni alloy nanowires.

2. The method of claim 1, wherein: In step S1, the mixed solution is prepared from citric acid buffer.

3. The production method according to claim 1 or 2, characterized by: In step S1, in the mixed solution, the concentration of CuSO4 is 0.05M-0.15M, the concentration of NiCl2 is 0.03M-0.08M, and the concentration of NiSO4 is 0.03M-0.08M.

4. The production method according to claim 1 or 2, characterized by: In step S1, the electrodeposition time is 1500-2000s.

5. The production method according to claim 1 or 2, characterized by: In step S2, the reaction temperature is 2-8℃, and the reaction time is 0.3-0.6h.

6. The production method according to claim 1 or 2, characterized by: In step S3, the annealing time is 0.5-2h.

7. The production method according to claim 1 or 2, characterized by: In step S4, the electrochemical reduction is carried out in a flowing electrolytic cell with sodium sulfate solution as electrolyte.

8. Cu-Ni alloy nanowires prepared by the method of any one of claims 1-7.

9. Use of the Cu-Ni alloy nanowires of claim 8 as a gas diffusion electrode for electrochemical reduction of CO2 to produce ethylene.

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