Self-supporting multi-scale porous CoNiZn alloy catalyst for fully decomposing water to produce hydrogen and preparation method of self-supporting multi-scale porous CoNiZn alloy catalyst

Abstract

The invention relates to the technical field of catalysts, and discloses a self-supporting multi-scale porous CoNiZn alloy catalyst for producing hydrogen by fully decomposing water and a preparation method of the self-supporting multi-scale porous CoNiZn alloy catalyst. A multi-scale porous CoNiZn alloy is constructed in situ on the surface of a foam CoNi alloy through zinc electroplating, annealing and zinc corrosion; the foam CoNi alloy serves as a substrate carrier, and meanwhile a metal source is provided for in-situ construction of the multi-scale porous CoNiZn alloy. The multi-scale porous CoNiZn alloy can generate abundant high-activity sites, the seamless integrated combination between the substrate and the alloy layer and the three-dimensional continuous through multi-scale porous structure can provide high electrolytic water mass transfer efficiency, and meanwhile, the long-term catalytic stability and corrosion resistance of the catalyst in an alkaline solution can be remarkably improved. The catalyst shows excellent hydrogen evolution, oxygen evolution and all-water decomposition electrocatalytic activity and stability in an alkaline medium, and has the characteristics of economic preparation process, simplicity, convenience, high efficiency and suitability for large-scale preparation.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a self-supporting multi-scale porous CoNiZn alloy catalyst for hydrogen production through water splitting and its preparation method. Background Technology

[0002] The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are two half-reactions in the process of hydrogen production through water electrolysis. HER is a two-electron transfer process with rapid reaction kinetics; while OER is a four-proton / electron coupling reaction process with slow kinetics and a high overpotential. Currently, the widely used HER electrodes in alkaline electrolyzers are Raney nickel hydrogen production electrodes and pure nickel mesh oxygen evolution electrodes. These single nickel catalysts have limited intrinsic catalytic activity and large overpotentials, resulting in low energy conversion efficiency and high hydrogen production costs. Commercial Raney nickel has an interconnected three-dimensional framework and macroporous channels, providing efficient electron and ion transport, ensuring sufficient contact and smooth transport between active sites and the electrolyte. Moreover, the three-dimensional bulk framework can delay the corrosion and dissolution of the catalyst in alkaline solutions at high potentials. Given the practical application of alkaline water electrolysis for hydrogen production, developing high-performance bifunctional whole-electrolysis water electrocatalysts with structures similar to commercial Raney nickel can avoid additional preparation processes and reduce production costs. Effective strategies for improving electrode performance mainly involve enhancing catalytic activity and stability through the design of alloy composition and microstructure. Cobalt metal possesses an ideal electron density balance, enabling it to attract and release protons during hydrogen production. Furthermore, cobalt exhibits excellent high-temperature resistance and mechanical properties. Combining cobalt with nickel can improve the overall corrosion resistance and mechanical properties of the alloy. Adding a third metal element to a binary alloy can improve the activity of the catalytic sites, further enhancing the alloy's water electrolysis activity and corrosion resistance. Zinc metal, with its d10 electronic structure, can effectively regulate the electronic structure of nickel, reducing the adsorption free energy of reaction intermediates and lowering the reaction overpotential. In summary, this invention provides a self-supporting multi-scale porous CoNiZn alloy catalyst for hydrogen production through water splitting and its preparation method. The catalyst exhibits excellent hydrogen evolution, oxygen evolution, and total water splitting performance in alkaline media. It combines a simple and efficient preparation technique with low cost, effectively improving hydrogen production efficiency and promoting the large-scale application of hydrogen energy. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a self-supporting multi-scale porous CoNiZn alloy catalyst for hydrogen production through water splitting and its preparation method. The method utilizes amorphous foam CoNi alloy as a support, taking Ni and Co as metal sources. A ternary zinc-based alloy precursor is formed by electrodepositing zinc and then alloying its surface with zinc through heat treatment. Selective etching of a portion of the zinc yields an in-situ constructed multi-scale porous CoNiZn alloy on the substrate surface. The construction of micron-sized macropores and nanopores increases the catalyst's active surface area, enhances corrosion resistance, reduces the overpotential for water splitting, and improves catalytic stability. This method allows for the simultaneous, simple, and efficient construction of multi-scale porous alloy structures, exhibiting high hydrogen evolution, oxygen evolution, and electrocatalytic water splitting performance in alkaline media, as well as excellent catalytic stability. The solution of the present invention is: A self-supporting, multi-scale porous CoNiZn alloy catalyst for total water splitting and hydrogen production, which, in a 1.0 mol / L KOH solution at 500 mA / cm², exhibits high efficiency. 2 The hydrogen evolution overpotential at the current density is ≤229mV, and the oxygen evolution overpotential is ≤403mV; the catalyst, as a bifunctional electrode, generates 100mA / cm² under a 1.85V cell voltage-driven full water splitting. 2 The hydrogen production current has a residual current density of ≥87.7% after 300 hours of continuous output; The structure of the self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst is a multi-scale porous CoNiZn alloy layer in situ loaded on the surface of an amorphous foam CoNi alloy support. The foamed CoNi alloy carrier has a primary macroporous structure with a pore size of 100–300 μm. The CoNiZn alloy layer has secondary and tertiary pores, wherein the secondary pore diameter is 50-500 nm and the tertiary pore diameter is 3-20 nm; As a preferred technical solution, the atomic content of Ni in the foamed CoNi alloy carrier is 0-20%, and the atomic content of Co is 80-100%. As a preferred technical solution, the self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst has an amorphous CoNi substrate and a surface CoNiZn alloy with a β-Co1Zn1 intermetallic compound crystalline phase structure. The surface layer contains 25-40% Ni, 40-60% Co, and 15-30% Zn atoms. As a preferred technical solution, the self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst exhibits a low hydrogen evolution overpotential in alkaline media, responding to 500 and 1000 mA / cm² in 1.0 mol / L KOH solution. 2The required current densities are only 229 and 302 mV, respectively, and the response is 100 mA / cm at an overpotential of 176 mV. 2 The hydrogen evolution current has a residual current density of ≥94.9% after 500 hours of continuous output; As a preferred technical solution, the self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst exhibits a low oxygen evolution overpotential in alkaline media, responding to 500 and 1000 mA / cm² in 1.0 mol / L KOH solution. 2 The current densities required are only 403mV and 461mV overpotentials, respectively, and the response is 100mA / cm at an overpotential of 399mV. 2 The oxygen evolution current has a residual current density of ≥94.9% after 300 hours of continuous output; As a preferred technical solution, a self-supporting multi-scale porous CoNiZn alloy is used as a bifunctional electrode for water electrolysis, generating 100 mA / cm² under a 1.85V cell voltage-driven full water splitting. 2 The hydrogen production current has a residual current density of ≥87.7% after 300 hours of continuous output; This invention also discloses a method for preparing a self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst, comprising the following steps: S1. Pickling, ultrasonic cleaning and drying of foamed CoNi alloy; S2. Using the treated foamed CoNi alloy as the working electrode, zinc electrodeposition is performed in an electroplating solution composed of ZnSO4, Na2SO4, and H3BO3, with a platinum sheet as the counter electrode and a saturated calomel electrode as the reference electrode, at a constant potential of -1.7V for 1 hour; the concentration of ZnSO4 in the electroplating solution is 0.10–0.20 mol / L, and the pH value is 2.0–3.0. S3. After electrodeposition, the sample is placed in an inert gas atmosphere at 4-6℃ for min. -1 The heating rate was adjusted, and the temperature was held at 450℃ for 5 hours to obtain a ternary zinc-based alloy precursor. S4. The ternary zinc-based alloy precursor was immersed in a 0.5–2.0 mol / L NaOH solution at 23–30 °C, followed by washing and drying to obtain a self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst. As a preferred technical solution, in step S2, the concentration of ZnSO4 in the electroplating solution is adjusted to control the atomic content of zinc in the ternary zinc-based alloy precursor to be 60-80%. As a preferred technical solution, the soaking time in NaOH solution in step S4 is adjusted to 48 hours. The scientific basis for preparing a self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst using foamed CoNi alloy as a carrier via electroplating zinc-heat treatment alloying-selective zinc corrosion technique is as follows: 1) Using foamed CoNi alloy as a carrier and metal source, zinc has a low melting point and a very good catalytic effect on nickel electrolysis. It can control the annealing temperature to diffuse zinc to the surface of the foamed CoNi alloy carrier. 2) Metals cannot have completely identical electrochemical behaviors. By selecting a suitable corrosion environment, the relatively active zinc component can be selectively corroded and dissolved. For example, by controlling the zinc content in the zinc-based alloy precursor sample, it can be placed in NaOH solution at room temperature to selectively dissolve some zinc and form porous structures of different sizes on the surface, thereby obtaining a self-supporting multi-scale porous CoNiZn alloy whole water splitting hydrogen production catalyst. Compared with the prior art, the advantages of the present invention are: (1) This invention directly utilizes commercial CoNi foam alloy as a carrier and metal source. Through the process of electroplating zinc-heat treatment alloying-selective corrosion of some zinc, by controlling the content of electrodeposited zinc and the corrosion time of the ternary alloy precursor, the loading of surface CoNiZn alloy catalyst and the content of Zn can be adjusted, thereby optimizing the hydrogen production performance of water electrolysis. (2) The electronic interactions between various metal elements in the prepared CoNiZn alloy material can generate more highly active sites, which is beneficial to promoting mass transfer and accelerating reaction kinetics, and effectively improving the intrinsic activity of the catalyst; (3) Compared with materials of other morphologies, the material prepared by this method has a three-dimensional dual-continuous multi-scale porous self-supporting structure, which can avoid the shedding of active substances and the use of polymer binders, thereby improving the catalytic efficiency of the material. (4) The in-situ constructed integrated bulk structure can provide smooth electron and ion conduction, which is beneficial to obtaining high conductivity and catalytic stability. At the same time, the constructed multi-scale porous structure has higher structural stability than the nanostructure and can also increase the active surface area of ​​the catalyst. In addition, the preparation of self-supporting multi-scale porous CoNiZn alloy bifunctional catalyst by this method has the advantages of good reproducibility, high yield, and no loss of target material during the preparation process; In summary, the preparation of the self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst in the technical solution of this invention has the advantages of being simple, green, reproducible, and suitable for large-scale production. Attached Figure Description

[0004] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. Figure 1 The structural characterization of the foamed CoNi alloy in Example 1 of the present invention is as follows: where a is a scanning electron microscope image (SEM), b is an X-ray powder diffraction pattern (XRD), and c is an X-ray energy dispersive spectroscopy composition analysis (EDS). Figure 2 The following are SEM images and EDS composition analyses of alloy precursors with different zinc contents obtained from electroplating solutions with different ZnSO4 concentrations in Example 1 of this invention: where a represents the alloy precursor Zn 0.1 / CoNi, b is the alloy precursor Zn 0.2 / CoNi; Figure 3 The following are SEM images and EDS analyses of the self-supporting multi-scale porous CoNiZn alloy obtained in Example 1 of this invention: where a is CoNiZn 0.1 Alloy, b is CoNiZn 0.2 alloy; Figure 4 The self-supporting multi-scale porous CoNiZn in Embodiment 1 of the present invention 0.2 Structural analysis of the alloy: where a is a transmission electron microscope (TEM) image, b is pore size distribution, and c is XRD; Figure 5 The electrolytic water electrolysis performance of the self-supporting multi-scale porous CoNiZn alloy and the comparative sample in 1.0 mol / L KOH solution is shown in the electrocatalytic test of this invention: where a is the polarization curve of the hydrogen evolution reaction, b is the stability of the hydrogen evolution reaction, c is the polarization curve of the oxygen evolution reaction, and d is the stability of the oxygen evolution reaction. Figure 6 This is a property analysis diagram of foamed CoNi and self-supporting multi-scale porous CoNiZn alloy electrodes used in the electrocatalytic testing of this invention: where a is the double-layer capacitance C. dl Curve b is the Nyquist (EIS) plot of the hydrogen evolution reaction, and curve c is the EIS plot of the oxygen evolution reaction. Figure 7 Self-supporting multi-scale porous CoNiZn for electrocatalytic testing in this invention 0.2 Comparison of the total water decomposition performance of the alloys: where a is the total water decomposition polarization curve and b is the total water decomposition stability. Detailed Implementation

[0005] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific embodiments. Example 1: A self-supporting multi-scale porous CoNiZn alloy catalyst for hydrogen production through water splitting and its preparation method. (1) The foamed CoNi alloy was immersed in 1 mol / L hydrochloric acid and ultrasonically treated for 10 min, then washed with anhydrous ethanol and deionized water respectively, and then dried. The surface structure, phase structure and composition analysis are as follows. Figure 1 As shown, the hole size is 100–300 µm, and the hole wall size is 50–80 µm; (2) Two electroplating solutions with different concentrations were prepared, with Na2SO4 concentration of 0.2 mol / L, H3BO3 concentration of 0.2 mol / L, and ZnSO4 concentration of 0.10 and 0.20 mol / L, respectively. The pH of the electroplating solution was adjusted to 2.50 ± 0.01 using 10% H2SO4 solution. CoNi foam alloy was used as the working electrode, Pt sheet as the counter electrode, and saturated calomel electrode as the reference electrode. Electrodeposition was performed at -1.7V for 1 h. The resulting samples were then subjected to argon or nitrogen atmosphere protection at 5℃ for 1 min. -1 By adjusting the heating rate and holding at 450℃ for 5 hours, two alloy precursors with different zinc contents were obtained, labeled as Zn. 0.1 / CoNi、Zn 0.2 / CoNi, then washed with deionized water and anhydrous ethanol and dried, its surface structure and composition are as follows Figure 2 As shown; (3) The sample obtained in step (2) above was etched in 1.0 mol / L NaOH solution at room temperature for 48 h, washed with ultrapure water 3 to 5 times, and dried normally (drying conditions were 60℃ vacuum drying oven for 6 hours) to obtain two self-supporting multi-scale porous CoNiZn alloys constructed in situ on the surface of foam CoNi alloy, which were labeled as CoNiZn. 0.1 and CoNiZn 0.2 Surface structure and alloy composition, such as Figure 3 As shown, the alloy surface obtained when the ZnSO4 concentration in the electroplating solution is 0.20 mol / L has a more uniform porous structure with pore sizes ranging from 50 to 500 nm, indicating that the porous structure can be optimized by controlling the zinc content in the alloy precursor. CoNiZn 0.1 The atomic percentage of metallic Ni is 35.5%, that of Co is 43.6%, and that of Zn is 20.9%. CoNiZn 0.2The atomic percentage of metallic Ni is 27.3%, Co is 44.6%, and Zn is 28.1%. (4) such as Figure 4 As shown, take the surface layer CoNiZn 0.2 High-resolution transmission electron microscopy (HRTEM) images and pore size distribution analysis of the alloy further revealed that the tertiary pore size in the surface alloy ranges from 3 to 20 nm. X-ray powder diffraction analysis showed that the surface CoNiZn alloy possesses a β-Co1Zn1 intermetallic compound crystalline phase structure. The electrocatalytic testing scheme of this invention is as follows: Self-supporting multi-scale porous CoNiZn prepared in the examples 0.2 The alloy was used as the working electrode, the carbon rod as the counter electrode, and the Hg / HgO electrode as the reference electrode. A 1.0 mol / L KOH solution was used as the electrolyte solution. The hydrogen evolution reaction (HER) / oxygen evolution reaction (OER) test temperature was 25±2℃; the total water splitting test temperature was 25±2℃; the stirring speed was 500 rpm; and the effective area of ​​the working electrode was 0.25 cm². 2 KOH solution purity: analytical grade (AR grade); electrochemical test results Figure 5 a shows the hydrogen evolution polarization curves of two alloy catalysts with foamed CoNi and Pt / C@CoNi. It is clear that the CoNiZn prepared by optimizing the parameters... 0.2 CoNiZn exhibits higher hydrogen evolution activity. 0.2 The electrode responds to 500 mA / cm 2 and 1000mA / cm 2 It requires only 229 mV and 302 mV overpotentials at current densities, exhibiting superior kinetic characteristics and catalytic activity far exceeding that of CoNiZn. 0.1 (η) 500 =270mV, η 1000 =333mV). For example... Figure 5 As shown in b, a 100mA / cm drive is applied at an overpotential of 176mV. 2 The hydrogen evolution current is continuously output. The residual current density was 94.9% after 500 hours. Figure 5 c shows the oxygen evolution polarization curves of two alloys with foamed CoNi and RuO2@CoNi. It is clear that the CoNiZn prepared by optimizing the parameters... 0.2 CoNiZn exhibits higher oxygen evolution activity. 0.2 The electrode responds to 500 mA / cm 2 and 1000mA / cm 2At current densities requiring only 403 mV and 461 mV overpotentials, it exhibits superior kinetic characteristics, and its catalytic activity is far superior to CoNiZn. 0.1 (η) 500 =416mV, η 1000 =470mV). For example... Figure 5 As shown in d, a 100mA / cm drive is applied at an overpotential of 399mV. 2 The oxygen evolution current, after continuous output for 300 hours, has a residual current density of 94.9%; CoNiZn 0.2 The catalyst was prepared in three parallel trials and electrochemically tested. The results showed: 500 mA / cm². 2 The overpotential deviations for hydrogen evolution and oxygen evolution are ±4mV. After a 500-hour hydrogen evolution stability test at an overpotential of 176mV, the residual current deviation is ±1.3%. After a 300-hour oxygen evolution stability test at an overpotential of 399mV, the residual current deviation is ±1.3%, demonstrating that the technical solution has good repeatability. CoNiZn 0.2 C dl The value is as high as 203 mF / cm 2 It is significantly higher than CoNiZn 0.1 (184 mF / cm) 2 The results showed that optimizing the porous structure and composition could significantly increase the number of catalytic active sites, such as... Figure 6 As shown in figure a. The Nyquist plot is fitted using the Randles equivalent circuit and is shown below. Figure 6 b and Figure 6 c), CoNiZn 0.2 Charge transfer resistance (R) to HER ct The Ω is only 2.82Ω, significantly lower than that of CoNiZn. 0.1 (5.26Ω), CoNiZn in the OER reaction 0.2 R at the catalyst-electrolyte interface of the electrode ct The smallest value is 8.21 Ω, significantly lower than CoNiZn. 0.1 (14.01Ω) indicates that optimizing the alloy composition and structure through preparation conditions can increase the active sites of the catalyst, improve the conductivity during water electrolysis, accelerate the interfacial electron transfer kinetics, and thus improve the performance of water electrolysis. CoNiZn 0.2 Smaller R ct This indicates that its more uniform porous structure and suitable composition resulted in faster electrocatalytic reaction kinetics; Self-supporting multi-scale porous CoNiZn 0.2 Alloys as bifunctional total water splitting catalysts, such as Figure 7As shown in Figure a, it exhibits superior water splitting activity compared to electrolyzers composed of commercial catalysts, producing 100 mA / cm² under a cell voltage of 1.85 V for total water splitting. 2 The hydrogen production current, after continuous output for 300 hours, has a residual current density of 87.7%, such as... Figure 7 As shown in b; The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A self-supporting multi-scale porous CoNiZn alloy catalyst for hydrogen production through water splitting, characterized in that: In a 1.0 mol / L KOH solution, at 500 mA / cm 2 The hydrogen evolution overpotential at the current density is ≤229mV, and the oxygen evolution overpotential is ≤403mV; the catalyst, as a bifunctional electrode, generates 100mA / cm² under a 1.85V cell voltage-driven full water splitting. 2 The hydrogen production current has a residual current density of ≥87.7% after 300 hours of continuous output; The structure of the self-supporting multi-scale porous CoNiZn alloy total water splitting hydrogen production catalyst is a multi-scale porous CoNiZn alloy layer constructed in situ on the surface of a foamed CoNi alloy substrate. The foamed CoNi alloy carrier has a primary macroporous structure with a pore size of 100–300 μm. The CoNiZn alloy layer has secondary and tertiary pores, wherein the secondary pore diameter is 50-500 nm and the tertiary pore diameter is 3-20 nm.

2. The self-supporting multi-scale porous CoNiZn alloy total water splitting hydrogen production catalyst as described in claim 1, characterized in that: The foamed CoNi substrate has an amorphous structure, with Ni atomic content of 0-20% and Co atomic content of 80-100%.

3. The self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst as described in claim 1, characterized in that: The CoNiZn alloy layer has a β-Co1Zn1 intermetallic compound crystal phase structure, with an atomic content of 25-40% for Ni, 40-60% for Co, and 15-30% for Zn.

4. The self-supporting multi-scale porous CoNiZn alloy total water splitting hydrogen production catalyst as described in claim 1, characterized in that: Response of 100 mA / cm at an overpotential of 176 mV. 2 The hydrogen evolution current has a residual current density ≥94.9% after 500 hours of continuous output; the response is 100 mA / cm² at an overpotential of 399 mV. 2 The oxygen evolution current has a residual current density of ≥94.9% after continuous output for 300 hours.

5. A method for preparing a self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst as described in any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Pickling, ultrasonic cleaning and drying of foamed CoNi alloy; S2. Using the treated foamed CoNi alloy as the working electrode, zinc electrodeposition is performed in an electroplating solution composed of ZnSO4, Na2SO4, and H3BO3, with platinum as the counter electrode and a saturated calomel electrode as the reference electrode, at a constant potential of -1.7V for 0.5-2 hours; the concentration of ZnSO4 in the electroplating solution is 0.10-0.20 mol / L, and the pH value is 2.0-3.

0. S3. After electrodeposition, the sample is placed in an inert gas atmosphere at 4-6℃ for min. -1 The heating rate was adjusted, and the temperature was held at 450℃ for 5 hours to obtain a ternary zinc-based alloy precursor. S4. The ternary zinc-based alloy precursor was immersed in a 0.5–2.0 mol / L NaOH solution at 23–30 °C, followed by washing and drying to obtain a self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst.

6. The preparation method of the self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst as described in claim 5, characterized in that: In step S2, the concentration of ZnSO4 in the electroplating solution is adjusted to control the atomic content of zinc in the ternary zinc-based alloy precursor to be between 60% and 90%.

7. The preparation method of a self-supporting multi-scale porous CoNiZn alloy water-splitting hydrogen production catalyst as described in claim 5, characterized in that: The soaking time in NaOH solution in S4 is adjusted to 24–72 hours.

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