Methanol oxidation catalyst for regulating and controlling electronic structure and morphology of Cu (OH) 2 by electrochemically driving Co doping and preparation method of methanol oxidation catalyst

Abstract

The invention discloses a methanol oxidation catalyst for regulating and controlling the electronic structure and morphology of Cu (OH) 2 by electrochemically driving Co doping and a preparation method of the methanol oxidation catalyst, and relates to the technical field of electrocatalytic materials. The preparation method comprises the following steps: depositing CoCu alloy spherical particles on the surface of a substrate through electro-deposition in a deep eutectic solvent containing Co < 2 + > and Cu < 2 + >, and then converting the CoCu alloy spherical particles into a Co-Cu (OH) 2 nanorod array through in-situ electrochemical cyclic voltammetry activation in an alkaline solution through dissolution and recrystallization, namely the methanol oxidation catalyst. On the basis of an electrodeposition and in-situ electrochemical activation two-step method, the morphology (nanorod array), the phase structure (inhibiting generation of CuO) and the electronic structure (Co-to-Cu electron transfer) of Cu (OH) 2 are cooperatively regulated and controlled through Co doping, and the MOR activity and stability of Cu (OH) 2 are remarkably improved.

Description

An electrochemically driven Co-doped catalyst for controlling the electronic structure and morphology of Cu(OH)₂ and its preparation method Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to a methanol oxidation catalyst and its preparation method that uses electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)2. Background Technology

[0002] Direct methanol fuel cells (DMFCs) are considered ideal energy devices for portable electronic devices, electric vehicles, and other fields due to their advantages such as wide availability of fuel, high energy density, and environmental friendliness. Methanol oxidation (MOR) is the core anode reaction of DMFCs, but its kinetics are slow, requiring highly efficient catalysts to accelerate the reaction.

[0003] Existing MOR catalysts mainly rely on precious metals such as Pt, Pd, and Ru. Although they have high activity, they are expensive (Pt market price exceeds 200 yuan / g) and scarce in resources (abundance in the Earth's crust < 100%. The defects of DMFCs, such as susceptibility to poisoning by reaction intermediates (e.g., CO_ads), severely limit their large-scale application. Therefore, the development of non-precious metal catalysts with high crustal abundance (Cu crustal abundance of approximately 68 ppm) and low cost has become a research hotspot.

[0004] Cu-based catalysts (such as Cu, CuO, and Cu(OH)2) have attracted attention due to their certain catalytic activity for MOR, but pure Cu-based catalysts have inherent defects: low activity: the adsorption and desorption equilibrium of Cu for MOR intermediates is difficult to control, resulting in slow reaction kinetics; poor stability: under electrochemical conditions, they are prone to oxidation (generating inactive CuO), dissolution, or agglomeration; and difficulty in synergistic control of morphology and electronic structure: traditional preparation methods (such as high-temperature calcination and chemical precipitation) cannot simultaneously achieve the synergy of "high specific surface area morphology" and "optimized electronic structure", making it difficult to overcome the bottleneck of activity and stability.

[0005] In recent years, electrochemical activation technology has been used to in-situ control catalyst structure, generating defect-rich and highly active metastable phases (such as Cu(OH)₂) through dissolution and recrystallization. Simultaneously, lattice strain engineering, through doping-induced lattice distortion, modulates the d-band centers of Cu, optimizing intermediate adsorption energies. However, the synergistic mechanism between electrochemical activation and lattice strain engineering remains unclear in current research, making it difficult to achieve precise control over the morphology, phase structure, and electronic structure of Cu-based catalysts, resulting in their MOR performance still failing to meet practical requirements. Summary of the Invention

[0006] The purpose of this invention is to provide an electrochemically driven Co-doping catalyst for regulating the electronic structure and morphology of Cu(OH)2 and its preparation method, in order to solve the problems of high cost and poor activity and stability of existing methanol oxidation catalysts such as noble metal catalysts and Cu-based catalysts in the prior art.

[0007] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention: a method for preparing a methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)2, comprising the following steps: in Co-containing... 2+ and Cu 2+ CoCu alloy spherical particles are deposited on the substrate surface by electrodeposition in a deep eutectic solvent. Then, in an alkaline solution, the CoCu alloy spherical particles are dissolved and recrystallized into a Co-Cu(OH)2 nanorod array, which is the methanol oxidation catalyst.

[0008] This invention uses a deep eutectic solvent as the electrodeposition medium to prepare CoCu alloy spherical particle precursors, and then induces their dissolution and recrystallization through in-situ electrochemical activation to form Co-doped Cu(OH)₂ nanorod arrays. Based on the two-step method of "electrodeposition + in-situ electrochemical activation", the morphology (nanord array), phase structure (inhibition of CuO formation), and electronic structure (Co-to-Cu electron transfer) of Cu(OH)₂ are synergistically controlled by Co doping, significantly improving its MOR activity and stability. Specifically, Co is uniformly doped into the Cu(OH)₂ lattice or surface at a content of 4.5-5.1 wt.%, inducing lattice expansion, electronic state redistribution, and Cu-O coordination environment regulation, inhibiting CuO formation and promoting the stable existence of Cu(OH)₂.

[0009] Furthermore, the eutectic solvent is composed of ethylene glycol (EG) and choline chloride (ChCl) in a molar ratio of 1.5-2.5:1.

[0010] Furthermore, the substrate comprises nickel (Ni) foil, nickel wire, or nickel foam with a purity ≥99.99%.

[0011] Furthermore, the Co 2+ The concentration of Cu in the deep eutectic solvent is 8-12 mM. 2+ The concentration in the deep eutectic solvent is 45-55 mM.

[0012] Optionally, the preparation steps of the deep eutectic solvent include: mixing ethylene glycol (EG) and choline chloride (ChCl) at a molar ratio of 1.5-2.5:1 and stirring at 343-363 K for 1.5-2.5 h to obtain the deep eutectic solvent (Ethaline, abbreviated as Eth).

[0013] This deep eutectic solvent has good electrical conductivity and solubility, and can stably dissolve Co. 2+ and Cu 2+ This provides a suitable environment for electrodeposition.

[0014] Furthermore, the molar ratio of ethylene glycol to choline chloride is 1.5-2.5:1, preferably 2:1. If the molar ratio of ethylene glycol to choline chloride is too high, the conductivity of the solvent will decrease; if it is too low, the viscosity of the solvent will increase, affecting ion migration.

[0015] Optionally, the Co-containing 2+ and Cu 2+ The preparation steps of the deep eutectic solvent include: adding CoCl2·6H2O and CuCl2 to the deep eutectic solvent, followed by ultrasonic treatment to obtain the Co-containing solvent. 2+ and Cu 2+ Deep eutectic solvent.

[0016] Furthermore, in the presence of Co 2+ and Cu 2+ The steps of electrodepositing CoCu alloy spherical particles on a substrate surface in a deep eutectic solvent include: using the substrate as the working electrode, a graphite plate as the counter electrode, and Ag / Ag + The electrode serves as a reference electrode and contains Co. 2+ and Cu 2+ A three-electrode system was constructed using a deep eutectic solvent as the electrolyte, and an electrode was subjected to a voltage of -0.7 to -0.9 V against Ag at a temperature of 333–373 K. + Electrodeposition is performed at the deposition potential until the deposition charge (i.e., charge density) reaches 1.5–2.5 C cm⁻¹. -2 A substrate with CoCu alloy spherical particles covering its surface (i.e., CoCu alloy spherical particle electrode) is obtained.

[0017] Preferably, the applied deposition potential is -0.8 V vs. Ag. + Deposited to a charge of 2 C cm -2 .

[0018] During electrodeposition, the potential is too high (above -0.7 V vs. Ag). + The deposition rate is slow, resulting in small alloy spherical particles. A potential that is too low (below -0.9 V vs. Ag) will also lead to slow deposition rates. + If the deposition is too rapid, the alloy spherical particles will agglomerate. The charge density is between 1.5 and 2.5 C cm⁻¹. -2 Adjustments within this range can ensure that the coverage of alloy spherical particles is 80-90% (avoiding insufficient coverage leading to insufficient active sites, or excessive coverage leading to interlayer agglomeration).

[0019] Furthermore, the average diameter of the CoCu alloy spherical particles is 700-900 nm.

[0020] Optionally, before electrodeposition, a pretreatment step of the substrate is also included, specifically: the substrate is ultrasonically cleaned in ethanol and 2 M HCl solution for 5-10 min in sequence (if the substrate is nickel foam, ultrasonic cleaning for 10 min is required to ensure the removal of impurities in the pores), rinsed with deionized water and dried at room temperature.

[0021] Optionally, after the electrodeposition is completed, the process further includes ultrasonic cleaning and drying steps.

[0022] Furthermore, the alkaline solution includes a potassium hydroxide solution or a sodium hydroxide solution.

[0023] Furthermore, the concentration of the alkaline solution is 0.01-10 M, preferably 0.8-1.2 M, and more preferably 1 M.

[0024] Further, the step of converting CoCu alloy spherical particles into Co-Cu(OH)₂ nanorod arrays through in-situ electrochemical cyclic voltammetry activation in alkaline solution via dissolution and recrystallization includes: constructing a three-electrode system using a substrate covered with CoCu alloy spherical particles as the working electrode, a Pt wire as the counter electrode, Ag / AgCl as the reference electrode, and an alkaline solution as the electrolyte; and operating at 40-60 mV s⁻¹ within a potential range of 0.1-1.35 V vs. RHE. -1 Cyclic voltammetry was performed at a scanning rate to obtain a substrate (i.e., a Co-Cu(OH)2 rod electrode) with a surface covered by a Co-Cu(OH)2 nanorod array.

[0025] Furthermore, the potential range is preferably 0.14-1.30 V vs. RHE, and the scan rate is preferably 50 mV s. -1 .

[0026] If the potential range is too narrow, the alloy spherical particles will not be completely converted; if it is too wide, Cu(OH)2 will be oxidized to CuO. If the scanning rate is too fast, the morphology will be uneven; if it is too slow, the time consumption will be too long.

[0027] Furthermore, the cyclic voltammetric scan is performed 55-65 times.

[0028] Optionally, the Ag / AgCl is Ag / AgCl (3 M KCl).

[0029] Optionally, the cyclic voltammetric scan is performed at 298-333 K.

[0030] Optionally, after the cyclic voltammetric scan is completed, the process further includes a cleaning and drying step.

[0031] The second technical solution of the present invention: a methanol oxidation catalyst prepared by the above-described electrochemically driven Co doping method for regulating the electronic structure and morphology of Cu(OH)2 (i.e., a substrate with a Co-Cu(OH)2 nanorod array on its surface).

[0032] Furthermore, the Co content in the methanol oxidation catalyst is 4.5-5.1 wt.% (i.e., the Co content in the Co-Cu(OH)2 nanorod array is 4.5-5.1 wt.%).

[0033] Furthermore, the average diameter of the nanorods in the methanol oxidation catalyst is 180-220 nm, and the length is 1-2 μm.

[0034] Furthermore, in the methanol oxidation catalyst, Co is in the form of Co 2+ It exists in a form that partially replaces Cu in the Cu(OH)2 lattice. 2+ (ionic radius Co) 2+ 0.74Å, Cu 2+ (0.72 Å), inducing Cu(OH)2 lattice expansion.

[0035] To verify the key role of the deep eutectic solvent system and Co doping strategy in the catalyst construction process of this invention, different solvent systems and different doped metal types were introduced as comparative examples while keeping the metal salt precursor (Cu salt) and electrodeposition and electrochemical activation conditions consistent.

[0036] First, in the solvent comparison experiment, the eutectic solvent of Ethaline was replaced with an aqueous NaCl solution (keeping the Cl ion concentration consistent with that in the eutectic solvent of Ethaline). The results showed that the samples obtained under non-eutectic solvent conditions were difficult to form a uniform and controllable precursor structure. After electrochemical activation, the morphological dispersion and structural integrity of the catalyst were significantly reduced, and its methanol oxidation catalytic activity was significantly inferior to that of the samples prepared using the Ethaline system. This indicates that the eutectic solvent plays an irreplaceable role in stabilizing the distribution of metal ions, regulating deposition behavior, and inducing subsequent structural evolution.

[0037] Secondly, in the comparative experiment of doped metal types, under the same metal salt concentration conditions, transition metal salts such as Ni, Fe, and Mn were used to replace Co salt for doping. The results showed that, compared with other metal-doped samples, the Co-doped sample was more likely to form a well-structured and well-oriented Cu(OH)₂ nanoarray structure after electrochemical activation. Its methanol oxidation reactivity and stability showed significant advantages, indicating that Co species have a unique synergistic effect in regulating the lattice structure and electronic state of Cu(OH)₂.

[0038] The third technical solution of the present invention: the application of the above-mentioned methanol oxidation catalyst in the methanol oxidation reaction.

[0039] Further, the application steps include: constructing a three-electrode system using the methanol oxidation catalyst as the working electrode, a Pt wire as the counter electrode, Ag / AgCl as the reference electrode, and a mixed solution of 1 M NaOH and 0.5 M CH3OH as the electrolyte, and applying the electrolyte at 298 K with a potential range of 1.20-1.85 V vs. RHE at a constant voltage of 50 mV s. -1 A voltammetric scan was performed at the scan rate.

[0040] Furthermore, the methanol oxidation catalyst is used as an anode catalyst in a direct methanol fuel cell when applied in the methanol oxidation reaction.

[0041] This invention discloses the following technical advantages: It provides a method for preparing a methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂. Through a template-free two-step method (electrodeposition plus in-situ electrochemical activation), the synergistic optimization of catalyst morphology, phase, and electronic structure is achieved, resulting in a highly active and stable Co-Cu(OH)₂ rod-shaped composite catalyst. The preparation method of this invention has advantages such as being template-free, having mild reaction conditions, controllable process, low cost, no pollution, stable product quality, and ease of large-scale preparation.

[0042] The methanol oxidation catalyst of this invention exhibits a mass activity ≥165 mA cm⁻¹ in the methanol oxidation reaction. -2 (3.1 times that of pure Cu(OH)2), current density retention rate ≥91% after 100,000s chronocurrent test (attenuation only 8.7%), activity retention rate ≥42% after 1000 cyclic voltammetric scans, combining high activity and high stability, can be used as an anode catalyst for direct methanol fuel cells, significantly reducing costs and improving device performance. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 shows the morphology and microstructure characterization of the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst in Example 1. Among them, (a) is the SEM image of the CoCu alloy spherical particles, (b) is the SEM image of the Co-Cu(OH)2 nanorod array catalyst, (c) is the TEM image of the Co-Cu(OH)2 nanorod array catalyst, (d) is the HRTEM image of the Co-Cu(OH)2 nanorod array catalyst, (e) is the HAADF-STEM image of the Co-Cu(OH)2 nanorod array catalyst, (f) is the EDS surface distribution mapping diagram of the Co-Cu(OH)2 nanorod array catalyst, (g) is the EDS line scan energy spectrum of the Co-Cu(OH)2 nanorod array catalyst, and (h) is the EDS elemental quantitative analysis bar chart of the Co-Cu(OH)2 nanorod array catalyst.

[0045] Figure 2 shows the structure and electronic state characterization of the Co-Cu(OH)2 nanorod array catalyst in Example 1. Among them, (a) is the XRD pattern of the Co-Cu(OH)2 nanorod array catalyst, (b) is a partial magnified view of (a), (c) is the Raman diagram of the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst, (d) is the XPS diagram of the 2p orbital of Cu element in the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst, (e) is the XPS diagram of the 2p orbital of Co element in the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst, and (f) is the XPS diagram of the 1s orbital of O element in the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst.

[0046] Figure 3 shows the SEM comparison images of catalysts with different Co contents before and after electrochemical activation in Comparative Examples 1-4. In Comparative Examples 1, (a) and (e) are before and after activation, respectively; (b) and (f) are before and after activation, respectively; (c) and (g) are before and after activation, respectively; and (d) and (h) are before and after activation, respectively.

[0047] Figure 4 shows the CV curves of the catalysts prepared in Example 1 and Comparative Examples 1-4.

[0048] Figure 5 shows the influence and mechanism analysis of Co doping on the phase transformation behavior and electrochemical properties of Cu in this invention. Among them, (a) is a schematic diagram of the phase evolution of Cu after Co doping during electrochemical activation, (b) is the X-ray diffraction (XRD) pattern of the undoped sample (the product of Comparative Example 1) after electrochemical activation, (c) is the electron paramagnetic resonance (EPR) spectrum of the undoped sample (the product of Comparative Example 1) and the Co-Cu(OH)2 sample (the product of Example 1), and (d) is a comparison of the cyclic voltammetry (CV) of the Cu2+ conversion potential in the undoped sample (the product of Comparative Example 1) and the Co-Cu(OH)2 sample (the product of Example 1).

[0049] Figure 6 shows the MOR performance test results of the catalysts. (a) shows the CV curves of different catalysts, (b) shows the CV curves of the Co-Cu(OH)2 nanorod array catalyst after multiple cycles, (c) shows the CV curves of the CuO spherical particle catalyst after multiple cycles, and (d) shows the current changes of the Co-Cu(OH)2 nanorod array catalyst and the CuO spherical particle catalyst at a constant potential of 1.6 V vs. RHE for 100,000 s.

[0050] Figure 7 shows the SEM images and CV curves of the catalysts prepared in Comparative Examples 5-7, where (a), (c), and (e) are the SEM images of Comparative Examples 5, 6, and 7, respectively, and (b), (d), and (f) are the CV curves of Comparative Examples 5, 6, and 7, respectively.

[0051] Figure 8 shows the SEM image and CV curve of the catalyst prepared in Comparative Example 8, where (a) is the SEM image and (b) is the CV curve. Detailed Implementation

[0052] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0053] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0054] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0055] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0056] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0057] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0058] In the following embodiments, comparative examples and test examples of the present invention, if room temperature is involved, it specifically refers to 20-30 ℃.

[0059] All raw materials used in the following embodiments, comparative examples and test examples of this invention are commercially available products.

[0060] Example 1 A method for preparing a methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)2, the steps are as follows: (1) Preparation of deep eutectic solvent: Weigh EG (4.60 g, 0.074 mol) and ChCl (5.40 g, 0.037 mol), add them to a 50 mL three-necked flask, place it in an oil bath at 353 K, and stir magnetically (500 rpm) for 2 h. During this period, observe the state of the solution: initially it is a turbid liquid, gradually becomes transparent after 1 h, and forms a homogeneous, non-layered deep eutectic solvent (Ethaline) after 2 h. Cool to 25 ℃, seal and store for later use.

[0061] (2) Ni foil pretreatment: Take a 1 cm × 1 cm × 1 mm Ni foil (purity ≥ 99.99%), and clean it by ultrasonic cleaning in ethanol (50 mL) and 2 M HCl solution (50 mL) for 5 min (power 300 W) in sequence. Rinse it with deionized water 3 times (10 mL each time) and air dry at room temperature.

[0062] (3) Preparation of electrolyte: Add CoCl2·6H2O (0.059 g, 0.2 mmol) and CuCl2 (0.135 g, 1.0 mmol) to 20 mL of the eutectic solvent prepared in step (1), and sonicate (300 W) for 30 min to ensure complete dissolution, to obtain electrolyte containing 10 mM Co 2+ and 50 mM Cu 2+ A deep eutectic solvent is used as the electrolyte.

[0063] (4) Electrodeposition: Pretreated Ni foil (as working electrode), two parallel graphite plates (twice the area of ​​the working electrode, as counter electrodes), Ag / Ag + A three-electrode system was constructed by inserting an electrode (as a reference electrode) into the electrolyte prepared in step (3), and placed in a 353 K thermostatic bath. A CHI760 D electrochemical workstation was used with the "potential constant mode" set, and -0.8 V vs. Ag was applied. + Electrodeposition was performed at the deposition potential, and the current-time curve was recorded. When the deposition charge reached 2 C cm⁻¹, the deposition was carried out. -2 Stop stirring at the designated time (approximately 15 minutes), and maintain the electrolyte stirring rate at 200 rpm during the deposition process.

[0064] (5) Post-processing: Take out the Ni foil, first ultrasonically clean it in ethanol (300 W, 3 min) to remove residual electrolyte, then ultrasonically clean it in deionized water (300 W, 3 min), and finally vacuum dry it at room temperature (0.08 MPa, 25 ℃, 2 h) to obtain Ni foil with CoCu alloy spherical particles on the surface (i.e. CoCu alloy spherical particle electrode). SEM observation shows that the average diameter of the CoCu alloy spherical particles is 600 nm (SEM image is shown in Figure 1(a)), and the coverage of the CoCu alloy spherical particles is 90%.

[0065] (6) Electrochemical activation: The Ni foil (as working electrode), Pt wire (0.5 mm in diameter, as counter electrode), and Ag / AgCl (3 M KCl) (as reference electrode) prepared in step (5) with CoCu alloy spherical particles on the surface were inserted into 100 mL of 1 M NaOH solution (aqueous solution) to construct a three-electrode system. The system was placed in a 298 K constant temperature bath and a CHI760 D electrochemical workstation was used with the "cyclic voltammetry mode" set. The voltammetry was performed at 50 mV s in the potential range of 0.14-1.30 V vs. RHE. -1 Cyclic voltammetry (CV) was performed at a scan rate of 120 mA cm⁻¹, with 60 consecutive cycles. The oxidation peak current in the first cycle was 120 mA cm⁻¹. -2 The oxidation peak current in the 60th cycle was 118 mA cm⁻¹.-2 The difference is less than 2%, and the current response is stable.

[0066] (7) Post-processing: The activated electrode was removed, rinsed three times with deionized water, and air-dried at room temperature to obtain a Ni foil (i.e., Co-Cu(OH)2 rod-shaped electrode) with a black Co-Cu(OH)2 nanorod array catalyst on its surface. This is the methanol oxidation catalyst for electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)2. SEM and TEM observations showed that the Co-Cu(OH)2 nanorod array catalyst covered on the Ni surface was highly ordered and distributed in an array. The average diameter of the nanorods was 200 nm and the length was 1-2 μm (SEM image is shown in Figure 1(b), and TEM image is shown in Figure 1(c)). ICP-MS test showed that the Co content was 4.8 wt.%.

[0067] In addition, the high-resolution transmission electron microscope (HRTEM) image of the Co-Cu(OH)2 nanorod array catalyst prepared on the Ni foil surface in this embodiment is shown in Figure 1(d). It can be seen that the diameter of a single nanorod is about 200 nm and the length is about 1-2 μm. Its crystal mainly exposes the (131) and (041) crystal planes of Cu(OH)2, corresponding to interplanar spacings of about 0.208 nm and 0.238 nm, respectively, indicating that the formed nanorods have good crystallinity and clear crystal plane orientation. The high-angle annular dark field (HAADF-STEM) image of the Co-Cu(OH)2 nanorod array catalyst in scanning transmission electron microscope (STEM) mode is shown in Figure 1(e). It can be seen that the Cu(OH)2 nanorod framework structure is clear and the brightness contrast is uniform, indicating that the Co species are embedded or loaded on the surface of Cu(OH)2 nanorods in a highly dispersed form, achieving uniform doping under low content conditions. The energy dispersive X-ray spectroscopy (EDS) surface distribution mapping of the Co-Cu(OH)2 nanorod array catalyst is shown in Figure 1(d). Figure 1(f) shows the EDS line scan spectrum, Figure 1(g) shows the EDS elemental quantitative analysis (atomic percentage) bar chart, and Figure 1(h) shows the EDS elemental quantitative analysis (atomic percentage) bar chart. From (f) to (h), it can be seen that Cu, Co and O elements are uniformly distributed throughout the nanorod structure, and no obvious element enrichment or phase separation phenomenon was observed. The Co doping content is about 4.8 wt.%, indicating that Co is stably introduced into the Cu(OH)2 structure in a low-doping and uniformly distributed manner.

[0068] In addition, the structural and electronic state characterization diagrams of the Co-Cu(OH)2 nanorod array catalyst prepared on the Ni foil surface in this embodiment are shown in Figure 2. (a) is the X-ray diffraction (XRD) pattern of the Co-Cu(OH)2 nanorod array catalyst; (b) is a magnified view of (a); (c) is the Raman spectrum of the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst; (d) is the X-ray photoelectron spectroscopy (XPS) pattern of the 2p orbital of Cu in the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst; (e) is the XPS pattern of the 2p orbital of Co in the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst; and (f) is the XPS pattern of the 1s orbital of O in the CoCu alloy spherical particles and the Co-Cu(OH)2 nanorod array catalyst. The XRD test results show that the Co-Cu(OH)2 nanorod array catalyst forms a stable Cu(OH)2 crystalline phase. Compared to standard Cu(OH)₂, its diffraction peaks show a significant low-angle shift, indicating that the introduction of Co can induce lattice expansion and lattice strain in Cu(OH)₂. Combined with the difference in ionic radii, it can be determined that Co species partially enter the Cu(OH)₂ lattice through substitution doping, rather than simple physical adsorption, thus achieving stable control over the Cu(OH)₂ crystal structure. Raman spectroscopy results show that the sample exhibits typical Cu-OH structural characteristics after electrochemical activation, and the relevant vibrational peaks show an overall shift compared to standard Cu(OH)₂, indicating that Co doping can effectively regulate the Cu-OH coordination environment and enhance local structural stability, structurally confirming that Co has been successfully introduced into the Cu(OH)₂ lattice system. XPS results further show that after electrochemical activation, Cu in the catalyst mainly exists as Cu 2+ It exists in form, and Co eventually stabilizes into Co. 2+ The state indicates that Co can co-evolve with Cu species during electrochemical processes and stably exist on the surface or near-lattice region of Cu(OH)2, indicating the presence of Co. 2+ →Cu 2+ Electron transfer, i.e., Co in the catalyst as Co 2+ It exists in a form that partially replaces Cu in the Cu(OH)2 lattice. 2+ (ionic radius Co) 2+ 0.74Å, Cu 2+Co doping (0.72 Å) induces lattice expansion in Cu(OH)₂, generating lattice stress and enhancing the catalytic activity of active sites. These results collectively demonstrate that Co doping in this embodiment enables synergistic regulation of the Cu(OH)₂ lattice structure, local coordination environment, and electronic states, providing a reliable structural and electronic basis for the catalyst described in this invention to achieve stable structure and excellent catalytic performance under alkaline conditions.

[0069] Comparative Example 1 is the same as Example 1, except that the addition of CoCl2·6H2O is omitted in step (3), so that the electrolyte does not contain Co. 2+ In this comparative example, step (5) yields a Ni foil with Cu spherical particles covering its surface, while step (7) yields a Ni foil with CuO covering its surface, meaning the Co content is 0 wt.%.

[0070] Comparative Example 2 is the same as Example 1, except that the amount of CoCl2·6H2O added in step (3) is changed, so that the Co content is increased. 2+ and Cu 2+ Co in the deep eutectic solvent, i.e., the electrolyte 2+ The concentration was 5 mM. In this comparative example, the final Ni foil surface-coated with the Co-Cu(OH)₂ catalyst had a Co content of 2.0 wt.% in the Co-Cu(OH)₂.

[0071] Comparative Example 3 is the same as Example 1, except that the amount of CoCl2·6H2O added in step (3) is changed, so that the Co content is increased. 2+ and Cu 2+ Co in the deep eutectic solvent, i.e., the electrolyte 2+ The concentration was 15 mM. In this comparative example, the final Ni foil surface-coated with the Co-Cu(OH)2 catalyst had a Co content of 12.7 wt.% in the Co-Cu(OH)2.

[0072] Comparative Example 4 is the same as Example 1, except that the amount of CoCl2·6H2O added in step (3) is changed, so that the Co content is increased. 2+ and Cu 2+ Co in the deep eutectic solvent, i.e., the electrolyte 2+ The concentration was 20 mM. In this comparative example, the final Ni foil surface-coated with the Co-Cu(OH)₂ catalyst had a Co content of 15.2 wt.% in the Co-Cu(OH)₂.

[0073] Comparison of morphology and MOR performance of catalysts with different Co contents in Test Example 1 (1) Morphology comparison Figure 3 shows the SEM comparison of catalysts with different Co contents before and after electrochemical activation in Comparative Examples 1-4. Among them, (a) and (e) are before and after activation of Comparative Example 1, respectively; (b) and (f) are before and after activation of Comparative Example 2, respectively; (c) and (g) are before and after activation of Comparative Example 3, respectively; and (d) and (h) are before and after activation of Comparative Example 4, respectively. It can be seen that Comparative Example 1 (Co content of 0 wt.%) still has spherical particles (diameter of about 800 nm) after activation; Comparative Example 2 (Co content of 2.0 wt.%) has irregular nanosheets on the surface after activation; Comparative Example 3 (Co content of 12.7 wt.%) has agglomerated nanosheets on the surface after activation; and Comparative Example 4 (Co content of 15.2 wt.%) has severely agglomerated nanosheet clusters on the surface after activation.

[0074] (2) MOR Performance Comparison: The MOR performance of the catalysts prepared in Example 1 and Comparative Examples 1-4 was tested. Specifically, a three-electrode system was constructed by inserting a Ni foil (as working electrode), a Pt wire (0.5 mm in diameter, as counter electrode), and Ag / AgCl (3 M KCl) (as reference electrode) with catalyst-coated surface prepared in each example or comparative example into a 100 mL mixed solution of 1 M NaOH + 0.5 M CH3OH (solvent is water). The system was placed in a 298 K constant temperature bath and tested using a CHI760 D electrochemical workstation at a potential range of 1.20-1.85 V vs. RHE at a constant voltage of 50 mV s. -1 The scan rate was used to scan, the CV curve was recorded, and the MOR peak current was read.

[0075] The test results (CV curves) are shown in Figure 4. In this figure, 10 mM Co + 50 mM Cu represents Example 1, 50 mM Cu represents Comparative Example 1, 5 mM Co + 50 mM Cu represents Comparative Example 2, 15 mM Co + 50 mM Cu represents Comparative Example 3, and 20 mM Co + 50 mM Cu represents Comparative Example 4. It can be seen that the MOR peak current of Example 1 is 165.5 mA cm⁻¹. -2 The peak current of MOR in Comparative Example 1 was 78.3 mA cm⁻¹. -2 The peak current of MOR in Comparative Example 2 was 110.2 mA cm⁻¹. -2 The peak current of MOR in Comparative Example 3 was 130.8 mA cm⁻¹. -2 The peak current of MOR in Comparative Example 4 was 95.6 mA cm⁻¹. -2 .

[0076] The morphology comparison and MOR performance comparison results show that rationally controlling the ratio of Co salt to Cu salt can effectively regulate the composition and structure of the catalyst, thereby achieving a significant improvement in catalytic performance.

[0077] (3) Effects and Mechanism Analysis of Co Doping on Phase Transformation Behavior and Electrochemical Properties of Cu As shown in Figure 5, (a) is a schematic diagram of the phase evolution of Cu after Co doping during electrochemical activation; (b) is the X-ray diffraction (XRD) pattern of the undoped sample (product of Comparative Example 1) after electrochemical activation; (c) is the electron paramagnetic resonance (EPR) spectrum of the undoped sample (product of Comparative Example 1) and the Co-Cu(OH)2 sample (product of Example 1); and (d) is the Cu content in the undoped sample (product of Comparative Example 1) and the Co-Cu(OH)2 sample (product of Example 1). 2+ Comparison of cyclic voltammetry (CV) of conversion potential.

[0078] As can be seen from the XRD pattern, under strongly alkaline conditions (1 M NaOH solution), undoped Cu spherical particles mainly form CuO after electrochemical activation, and the corresponding diffraction peaks are consistent with those of standard CuO (JCPDS no. 48-1548) (Figure 5(b)). In contrast, no obvious CuO characteristic diffraction peaks were observed in the Co-doped sample, and it tended to form the Cu(OH)2 phase (Figure 2(a)-(b)), indicating that Co doping significantly changed the phase transformation pathway of Cu species. As can be seen from the EPR spectrum (Figure 5(c)), the Co-Cu(OH)2 sample showed an obvious paramagnetic resonance signal at g=2.003, while this signal was significantly weakened or absent in the undoped CuO sample, indicating that paramagnetic centers related to oxygen vacancies were introduced in the Co-doped sample. As can be seen from the CV comparison, after Co doping, Cu... 2+ The relevant redox peaks show a significant cathode-direction shift compared to the undoped sample (Figure 5(d)), indicating that Co doping regulates the transformation potential of Cu species, thereby altering their electrochemical phase stability. In other words, the introduction of Co effectively changes the surface redox microenvironment of Cu species, thus preferentially promoting the formation of Cu(OH)2 both thermodynamically and kinetically.

[0079] In summary, moderate Co doping significantly alters the phase transformation pathway of Cu and the stability of the final product through the synergistic effect of electronic structure regulation and electrochemical potential modulation, suppressing CuO formation while promoting the preferential growth of Cu(OH)2. This coupling effect at the structural and electronic levels ultimately translates into highly efficient catalytic performance for methanol oxidation (Figure 5(a)).

[0080] Test Example 2 Comparison of MOR performance of different catalysts and stability test of Co-Cu(OH)2 (1) MOR performance of different catalysts Ni foil with black Co-Cu(OH)2 nanorod array catalyst on the surface prepared in Example 1, Ni foil with pure CuO catalyst on the surface prepared in Comparative Example 1, Ni foil with Co catalyst on the surface or Ni foil with Cu(OH)2 on the surface (as working electrode) and Pt wire (0.5 mm in diameter, as counter electrode) and Ag / AgCl (3 M KCl) (as reference electrode) were inserted into 100 mL of 1 M NaOH + 0.5 M CH3OH mixed solution to construct a three-electrode system. The system was placed in a constant temperature bath at 298 K and electrochemical workstation was used. The system was tested at 50 mV s in the potential range of 1.20-1.85 V vs. RHE. -1 The scan rate was used to scan and record the CV curves and read the MOR peak current. The CV curve results are shown in Figure 6(a). It can be seen that the MOR peak potential of the Co-Cu(OH)2 nanorod array catalyst is 1.45 V vs. RHE, and the peak current is 165.5 mAcm. -2 It is the best among all catalysts.

[0081] The preparation steps for the Ni foil with Co catalyst coating and the Ni foil with Cu(OH)₂ coating are as follows: 10 mg of commercially available Co or Cu(OH)₂ catalyst powder is mixed with 4 mL of ethylene glycol (as a dispersant), and 500 μL of Nafion solution is added as a binder to prepare a uniform catalyst ink. The obtained catalyst ink is uniformly drop-coated onto the surface of the pretreated Ni foil (pretreatment method is the same as in Example 1) to achieve a catalyst loading of 10 mg·cm⁻¹. -2 After drying, a catalyst support layer is formed, resulting in a Ni foil with a Co catalyst on its surface and a Ni foil with a Cu(OH)2 on its surface.

[0082] (2) Stability Test: Using either the Ni foil with a black Co-Cu(OH)₂ nanorod array catalyst surface prepared in Example 1 or the Ni foil with a CuO spherical particle catalyst surface prepared in Comparative Example 1 as the working electrode, 1000 consecutive scans were performed under the above test conditions. The CV curve for each cycle was recorded, and the MOR peak current was read. The results are shown in Figures 6(b) and (c), where (b) is the CV curve of the Co-Cu(OH)₂ nanorod array catalyst after multiple cycles, and (c) is the CV curve of the CuO spherical particle catalyst after multiple cycles. It can be seen that the first oxidation peak current of the Co-Cu(OH)₂ nanorod array catalyst is 165.5 mAcm⁻¹. -2The oxidation peak current for the 1000th time was 100.9 mA cm⁻¹. -2 The retention rate was 61.0%. The first oxidation peak current of the CuO spherical particle catalyst was 78.3 mA cm⁻¹. -2 The oxidation peak current for the 1000th time was 22.7 mA cm⁻¹. -2 The retention rate was only 28.9%.

[0083] In addition, at a constant potential of 1.6 V vs. RHE (other test conditions are the same as above), the current changes of the Co-Cu(OH)2 nanorod array catalyst (Example 1) and the CuO spherical particle catalyst (Comparative Example 1) were recorded for 100,000 s. The results are shown in Figure 6(d). It can be seen that the initial current of the Co-Cu(OH)2 nanorod array catalyst is 141 mA cm⁻¹. -2 The current at 100,000 s is 127 mA cm⁻¹ -2 The decay rate was 8.7%. The initial current of the CuO spherical particle catalyst was 81 mA cm⁻¹. -2 The current at 100,000 s is 35 mA cm. -2 The attenuation rate was 56.7%.

[0084] Comparative Example 5 is the same as Example 1, except that in step (3), CoCl2·6H2O is replaced with NiCl2·6H2O in equimolar form.

[0085] In this comparative example, after electrochemical activation and post-treatment, a nanostructure mainly composed of Ni-doped Cu(OH)₂ was formed on the surface of the Ni foil. However, its morphology distribution was uneven, with localized nanosheet stacking, making it difficult to form a highly ordered nanorod array structure (SEM image shown in Figure 7(a)). MOR performance testing (using the same method as in Test Example 1, and the obtained CV curve shown in Figure 7(b)) showed that the MOR peak current of the catalyst prepared in this comparative example was 71.6 mA cm⁻¹. -2 .

[0086] Comparative Example 6 is the same as Example 1, except that in step (3), CoCl2·6H2O is replaced with FeCl3·6H2O in equimolar form.

[0087] In this comparative example, the Cu(OH)₂ structure in the sample obtained after electrochemical activation and post-treatment was less intact, with obvious structural collapse and discontinuous growth in local areas (SEM image shown in Figure 7(c)). According to the MOR performance test (test method same as in Test Example 1, CV curve obtained is shown in Figure 7(d)), the MOR peak current of the catalyst prepared in this comparative example was 89.8 mA cm⁻¹. -2 .

[0088] Comparative Example 7 is the same as Example 1, except that in step (3), CoCl2·6H2O is replaced with MnCl2·4H2O in equimolar form.

[0089] In this comparative example, after electrochemical activation and post-treatment, short-sized, non-oriented Mn-doped Cu(OH)₂ nanostructures were formed on the Ni foil surface, and no regular array characteristics were observed (SEM image shown in Figure 7(e)). MOR performance testing (using the same method as in Example 1, the obtained CV curve is shown in Figure 7(f)) showed that the MOR peak current of the catalyst prepared in this comparative example was 127.9 mA cm⁻¹. -2 .

[0090] Comparative Example 8 is the same as Example 1, except that the preparation step of the eutectic solvent is omitted and the 20 mL eutectic solvent in step (3) is replaced with 20 mL NaCl aqueous solution (concentration of 3.3 M).

[0091] In this comparative example, after electrochemical activation and post-treatment, a porous, rough layer structure composed of irregularly packed nanoparticles was formed on the Ni foil surface. The overall structure exhibited a continuous distribution but with significant local agglomeration, forming a three-dimensional porous morphology (SEM image shown in Figure 8(a)). MOR performance testing (using the same method as in Example 1, the obtained CV curve is shown in Figure 8(b)) showed that the MOR peak current of the catalyst prepared in this comparative example was 101.6 mA cm⁻¹. -2 .

[0092] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂, characterized in that, Includes the following steps: In Co 2+ and Cu 2+ CoCu alloy spherical particles are deposited on the substrate surface by electrodeposition in a deep eutectic solvent. Then, in an alkaline solution, the CoCu alloy spherical particles are dissolved and recrystallized into a Co-Cu(OH)2 nanorod array, which is the methanol oxidation catalyst.

2. The preparation method of the methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂ as described in claim 1, characterized in that, The eutectic solvent is a mixture of ethylene glycol and choline chloride in a molar ratio of 1.5-2.5:1; and / or the substrate comprises nickel foil, nickel wire, or nickel foam.

3. The method for preparing the methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂ as described in claim 1, characterized in that, The Co 2+ The concentration of Cu in the deep eutectic solvent is 8-12 mM. 2+ The concentration in the deep eutectic solvent is 45-55 mM.

4. The preparation method of the methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂ as described in claim 1, characterized in that, In Co 2+ and Cu 2+ The steps of electrodepositing CoCu alloy spherical particles on a substrate surface in a deep eutectic solvent include: using the substrate as the working electrode, a graphite plate as the counter electrode, and Ag / Ag + The electrode serves as a reference electrode and contains Co. 2+ and Cu 2+ A three-electrode system was constructed using a deep eutectic solvent as the electrolyte, and an electrode was subjected to a voltage of -0.7 to -0.9 V against Ag at a temperature of 333–373 K. + Electrodeposition was performed at the deposition potential until the deposition charge was 1.5-2.5 C cm⁻¹. -2 A substrate with CoCu alloy spherical particles covering its surface was obtained.

5. The method for preparing the methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂ as described in claim 1, characterized in that, The alkaline solution includes a potassium hydroxide solution or a sodium hydroxide solution; and / or, the concentration of the alkaline solution is 0.01-10 M.

6. The method for preparing the methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂ as described in claim 1, characterized in that, The steps for converting CoCu alloy spherical particles into Co-Cu(OH)₂ nanorod arrays through in-situ electrochemical cyclic voltammetry activation in alkaline solution include: constructing a three-electrode system using a substrate coated with CoCu alloy spherical particles as the working electrode, a Pt wire as the counter electrode, Ag / AgCl as the reference electrode, and an alkaline solution as the electrolyte; and activating the array at 40-60 mV s⁻¹ within a potential range of 0.1-1.35 V vs. RHE. -1 Cyclic voltammetry was performed at a scanning rate to obtain a substrate with a surface covered by a Co-Cu(OH)2 nanorod array.

7. The method for preparing the methanol oxidation catalyst with electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)₂ as described in claim 6, characterized in that, The cyclic voltammetric scan is performed 55-65 times.

8. A methanol oxidation catalyst prepared by the method described in any one of claims 1-7, which uses electrochemically driven Co doping to regulate the electronic structure and morphology of Cu(OH)2.

9. A methanol oxidation catalyst as described in claim 8, characterized in that, The Co content in the methanol oxidation catalyst is 4.5-5.1 wt.%.

10. The use of a methanol oxidation catalyst as described in any one of claims 8-9 in a methanol oxidation reaction.

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