Metal supported electrocatalyst, preparation method thereof, electrocatalyst ink and electrode

Abstract

The invention provides a metal supported electrocatalyst, a preparation method thereof, electrocatalyst ink and an electrode. The preparation method comprises the following steps: preparing a three-dimensional network-shaped aerogel matrix; the three-dimensional network-shaped aerogel matrix is soaked in a metal salt solution for stirring adsorption, and a metal salt-loaded three-dimensional network-shaped aerogel matrix is obtained; and placing the three-dimensional network-shaped aerogel matrix loaded with the metal salt in inert gas for heat treatment to obtain the metal-loaded electrocatalyst. According to the technical scheme, the stability can be improved while agglomeration of the nano metal particles can be avoided, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of chemistry and chemical engineering, and in particular to a metal-supported electrocatalyst and a preparation method thereof, electrocatalyst ink and an electrode. Background Art

[0002] Electrocatalytic CO2 reduction reaction (CO2RR) technology demonstrates tremendous potential and research value in carbon resource recycling and the efficient conversion of renewable energy. By closely integrating fundamental research with practical applications, this technology is expected to provide strong scientific support for mitigating CO2 emissions and achieving sustainable development.

[0003] Current metal-supported electrocatalyst systems face numerous technical bottlenecks in CO₂RR. For one thing, metal nanoparticles tend to agglomerate on common support materials (such as graphene, nanosheets, and carbon nanotubes), reducing the number of active sites for the catalytic reaction and, in turn, lowering catalytic efficiency and stability. Furthermore, existing preparation processes are generally complex and rely on costly precursors or specialized processing methods, hindering their feasibility for large-scale application.

[0004] To this end, a technical solution is needed that can solve the problems of unstable structure, poor metal dispersion and insufficient catalytic performance of existing CO2RR electrocatalyst materials, avoid the agglomeration of nanometal particles, improve stability and reduce manufacturing costs. Summary of the Invention

[0005] The present application aims to provide a metal-loaded electrocatalyst and its preparation method, electrocatalyst ink and electrode, which can prevent the agglomeration of nano-metal particles while improving stability and reducing manufacturing costs.

[0006] According to another aspect of the present application, a method for preparing a metal-supported electrocatalyst is provided, the method comprising:

[0007] Preparation of a three-dimensional network aerogel matrix;

[0008] Immersing the three-dimensional network aerogel matrix in a metal salt solution and performing stirring adsorption to obtain a three-dimensional network aerogel matrix loaded with metal salt;

[0009] The three-dimensional network aerogel matrix loaded with metal salt is placed in an inert gas for heat treatment to obtain the metal-loaded electrocatalyst.

[0010] According to some embodiments, preparing the three-dimensional network aerogel matrix includes:

[0011] The bacterial cellulose hydrogel is subjected to multiple cycles of alkaline solution and deionized water to obtain a cellulose hydrogel;

[0012] immersing the cellulose hydrogel into a tertiary butanol-water mixed solution for solvent replacement;

[0013] drying and shaping the cellulose hydrogel to obtain the three-dimensional network aerogel matrix.

[0014] According to some embodiments, the volume ratio of the tertiary butanol to water in the tertiary butanol-water mixed solution is 3:2.

[0015] According to some embodiments, drying and shaping the cellulose hydrogel comprises:

[0016] Drying and shaping the cellulose hydrogel by freezing or supercritical carbon dioxide (CO2) drying.

[0017] According to some embodiments, the loading amount of the metal salt solution is not more than the upper limit of the bearing capacity of the aerogel matrix, so as to avoid the agglomeration of nanoscale metal particles and maintain the stability of the electrocatalyst structure.

[0018] According to some embodiments, the three-dimensional network aerogel matrix loaded with the metal salt is placed in an inert gas for heat treatment, which comprises:

[0019] The heat treatment temperature is 600-900°C, the inert gas is argon (Ar) and / or nitrogen (N2), and the constant temperature time is not less than 2 hours, so as to carbonize the three-dimensional network aerogel into a carbon fiber aerogel matrix.

[0020] According to an aspect of the present application, a metal-loaded electrocatalyst is provided, which comprises: a carbon fiber aerogel matrix and nanoscale metal particles,

[0021] The carbon fiber aerogel matrix is a three-dimensional network structure;

[0022] The nanoscale metal particles are uniformly loaded on the surface of the carbon fiber aerogel matrix.

[0023] According to some embodiments, the metal comprises one or more of bismuth (Bi), tin (Sn), copper (Cu), and palladium (Pd).

[0024] According to some embodiments, the three-dimensional network carbon fiber aerogel matrix has a pore size distribution of 2-50 nm, a specific surface area of greater than 600 m 2 / g, and the nanoscale metal particles have an average particle size of less than 50 nm and a specific surface area of 200-500 m 2 / g.

[0025] According to another aspect of the present application, an electrocatalyst ink is provided, comprising: a metal-loaded electrocatalyst as described in any of the above items, an isopropyl alcohol solution, and a perfluorosulfonic acid polymer (Nafion) solution, wherein the electrocatalyst ink is used to achieve efficient selective conversion of CO2 reduction products in an H-type electrolytic cell or a flow electrolytic cell.

[0026] According to another aspect of the present application, an electrode is provided, which is used in a flow electrolysis cell. The electrode comprises: the electrocatalyst ink as described above and a carbon paper electrode. The electrocatalyst ink is uniformly loaded on the carbon paper electrode to obtain the electrode.

[0027] According to the embodiments of the present application, the metal-supported electrocatalyst of the present invention adopts a carbon fiber aerogel matrix with a three-dimensional network structure. The carbon fiber has good electron transport properties, and the three-dimensional network structure provides more reaction contact sites for the catalytic reactants. It is suitable for high current density operating conditions such as H-type electrolytic cells and flow electrolytic cells, which is conducive to efficient electron transfer and rapid diffusion of reactants. The carbon fiber aerogel matrix structure is versatile and universal, and can be widely used for the uniform loading and immobilization of various metal electrocatalysts such as Bi, Sn, Cu, and Pd, expanding its application scenarios in electrocatalytic CO2 reduction and other catalytic reactions.

[0028] According to some embodiments, the preparation of the metal-supported electrocatalyst described in the present invention uses bacterial cellulose, which is a readily available raw material, as a precursor to the carbon fiber aerogel. The preparation process is simple, avoids complex chemical treatments or high-cost raw materials, and has good process scalability and practical application potential.

[0029] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments.

[0031] Figure 1 A schematic diagram of a method for preparing the metal-supported electrocatalyst according to an exemplary embodiment.

[0032] Figure 2 A graph showing comparative experimental test results of the metal-supported electrocatalyst according to an example embodiment and a metal-supported electrocatalyst based on conventional graphite powder.

[0033] Figure 3 A graph showing comparative experimental test results for verifying the effect of carbonization temperature on the catalytic performance of Bi-loaded carbon fiber aerogel according to example embodiments.

[0034] Figure 4 Scanning electron microscope (SEM) images of carbon fiber aerogel according to example embodiments.

[0035] Figure 5 Characterization images of 0.01-Bi electrocatalyst according to example embodiment 2, (a) is SEM image, (b)-(c) are energy dispersive spectroscopy (EDS) element mapping.

[0036] Figure 6 Characterization images of 0.02-Bi electrocatalyst according to example embodiment 2, (a) is SEM image, (b)-(c) are energy dispersive spectroscopy (EDS) element mapping.

[0037] Figure 7 Characterization images of 0.03-Bi electrocatalyst according to example embodiment 2, (a) is SEM image, (b)-(c) are energy dispersive spectroscopy (EDS) element mapping.

[0038] Figure 8 Characterization images of 0.04-Bi electrocatalyst according to example embodiment 2, (a) is SEM image, (b)-(c) are energy dispersive spectroscopy (EDS) element mapping.

[0039] Figure 9 X-ray diffraction (XRD) patterns of electrocatalysts with different Bi loadings (0.01, 0.02, 0.03, 0.04) according to example embodiment 2.

[0040] Figure 10 SEM images of Sn metal electrocatalyst loaded on carbon fiber aerogel according to example.

[0041] Figure 11 SEM images of Cu metal electrocatalyst loaded on carbon fiber aerogel according to example.

[0042] Figure 12 Product Faradaic efficiency comparison of different Bi loading electrocatalysts within the measured potential range (-0.8~ -1.2V vs. RHE) according to example (wherein (a) is 0.01-Bi, (b) is 0.02-Bi, (c) is 0.03-Bi, (d) is 0.04-Bi).

[0043] Figure 13 Stability test results of 0.02-Bi electrocatalyst according to example embodiment 4, under -1.0V vs. RHE constant potential condition for 72 hours continuous running.

[0044] Figure 14 Structure schematic diagram of flow electrolytic cell used according to example embodiment 5.

[0045] Figure 15Results of Faradaic efficiency tests of the product of 0.02-Bi electrocatalyst in a flow electrolysis cell according to Example 5.

[0046] Figure 16 According to the example embodiment, the product Faraday efficiency test results of the same type of carbon fiber aerogel loaded with three metals Sn, Cu and Pd (the metal loading amount is 0.02M) in the flow electrolysis cell. DETAILED DESCRIPTION

[0047] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art. Like reference numerals in the drawings represent like or similar parts, and thus repetitive description thereof will be omitted.

[0048] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner.In the following description, many specific details are provided so as to provide a full understanding of the embodiments of the present application. However, it will be appreciated by those skilled in the art that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps etc. can be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0049] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically separate entities. That is, these functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0050] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, while others may be combined or partially combined. Therefore, the actual execution order may vary depending on the actual situation.

[0051] It should be understood that although the terms first, second, third, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Thus, the first component discussed below could be referred to as the second component without departing from the teachings of the present invention. As used herein, the term "and / or" includes any one and all combinations of one or more of the associated listed items.

[0052] The user information (including but not limited to user equipment information, user personal information, etc.) and data (including but not limited to data for analysis, stored data, displayed data, etc.) involved in the present application are all information and data authorized by the user or authorized by all parties, and the collection, use and processing of related data need to comply with relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation portal for user to choose authorization or refusal.

[0053] Those skilled in the art can understand that the drawings are only schematic diagrams of example embodiments, and the modules or flows in the drawings are not necessarily necessary for implementing the present application, and therefore cannot be used to limit the protection scope of the present application.

[0054] Electrocatalytic CO2 reduction reaction (CO2RR) technology shows great potential and research value in carbon resource recycling and efficient conversion of renewable energy. Through the close combination of basic research and practical application, this technology is expected to provide strong scientific support for alleviating CO2 emissions and achieving sustainable development.

[0055] Current metal-supported electrocatalyst systems still face many technical bottlenecks in electrocatalytic CO2 reduction (CO2RR). On the one hand, metal nanoparticles are prone to agglomeration on common support materials such as graphene, nanosheets, carbon nanotubes, etc., resulting in a decrease in active sites for catalytic reaction, and thus reducing catalytic efficiency and stability; on the other hand, the existing preparation process is generally complex, relying on high-cost precursors or special processing methods, which restricts the feasibility of large-scale application. Therefore, it is urgent to develop a new type of carbon-based aerogel-supported metal electrocatalyst system with stable structure, uniform loading dispersion, excellent catalytic performance and simple preparation process, to further promote the application of CO2 reduction technology, and also to popularize it to other catalytic application fields.

[0056] Compared with most of the current carriers used in applications, aerogel materials have ultra-high porosity, low density and high specific surface area due to their three-dimensional porous nanometer network structure, which helps to achieve efficient transport of reactants and charge transfer while inhibiting metal nanoparticle agglomeration and Ostwald ripening to some extent, prolonging the catalytic life. In particular, carbon fiber aerogel (CFA), its three-dimensional network structure can size limit metal nanoparticles, improve active site distribution and utilization.

[0057] To this end, the present application proposes a metal-supported electrocatalyst and preparation method, electrocatalyst ink and electrode, which can solve the problems of unstable structure, poor metal dispersibility and insufficient catalytic performance of existing CO2RR electrocatalyst materials, avoid the agglomeration of nano-metal particles, improve stability and reduce manufacturing costs. According to an embodiment, the metal-supported electrocatalyst of the present invention adopts a carbon fiber aerogel matrix with a three-dimensional network structure. The carbon fiber has good electron transport properties. The three-dimensional network structure provides more reaction contact sites for the catalytic reactants, is suitable for high current density operating conditions such as H-type electrolytic cells and flow electrolytic cells, and is conducive to efficient electron transfer and rapid diffusion of reactants. The carbon fiber aerogel matrix structure is versatile and universal, and can be widely used for the uniform loading and immobilization of various metal electrocatalysts such as Bi, Sn, Cu, Pd, etc., to expand its application scenarios in electrocatalytic CO2 reduction and other catalytic reactions.

[0058] According to some embodiments, the preparation of the metal-supported electrocatalyst described in the present invention uses bacterial cellulose, which is a readily available raw material, as a precursor of the carbon fiber aerogel. The preparation process is simple, avoids complex chemical treatment or high-cost raw materials, and has good process scalability and practical application potential.

[0059] The exemplary embodiments of the present application are described below with reference to the accompanying drawings.

[0060] Figure 1 A schematic diagram of a method for preparing the metal-supported electrocatalyst according to an exemplary embodiment.

[0061] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a method for preparing a metal-supported electrocatalyst. Figure 1 , the preparation method comprises:

[0062] In S101 , a three-dimensional network aerogel matrix is ​​prepared.

[0063] According to some embodiments, a sol-gel method combined with freeze drying or supercritical drying technology is first used to prepare an aerogel matrix with a three-dimensional network structure. The matrix has a uniformly distributed nanopore structure with a pore size range of 2 to 50 nm and a specific surface area greater than 600 m 2 / g, and possesses excellent porosity and conductivity, making it suitable as a high-performance carrier for electrocatalysts. The present invention utilizes a three-dimensional aerogel as a carrier to spatially confine metal nanoparticles, improving their dispersion and size uniformity, effectively inhibiting their aggregation, and thereby enhancing the stability of the catalytic reaction.

[0064] In S103 , the three-dimensional network aerogel matrix is ​​immersed in a metal salt solution for stirring and adsorption to obtain a three-dimensional network aerogel matrix loaded with metal salt.

[0065] According to some embodiments, the three-dimensional network aerogel matrix prepared above is immersed in a salt solution containing one or more metal ions such as Bi, Sn, Cu, Pd, etc., and is fully adsorbed under stirring conditions so that the metal ions are uniformly attached to the surface of the aerogel to form a precursor material loaded with metal salts, that is, a three-dimensional network aerogel matrix loaded with metal salts.

[0066] According to some embodiments, during the preparation process, metal salt precursors (such as Bi(NO3)3, SnCl2, Cu(NO3)2, etc.) are mainly loaded on the three-dimensional carbon fiber aerogel skeleton through physical adsorption. Since the aerogel matrix has a highly porous structure and a large specific surface area, there are abundant pores and surface defect sites on its surface, which can provide a good carrier for the adsorption of metal salts. During the subsequent reduction or heat treatment process, the metal salt is reduced to metal nanoparticles and anchored in situ on the aerogel skeleton, thereby forming a metal-supported electrocatalyst with a stable structure and uniform dispersion.

[0067] In S105 , the three-dimensional network aerogel matrix loaded with metal salt is placed in an inert gas for heat treatment to obtain the metal-loaded electrocatalyst.

[0068] According to some embodiments, the aerogel matrix loaded with metal salts is then placed in an inert gas (such as nitrogen or argon) protective atmosphere for high-temperature heat treatment. Under the action of pyrolysis, the metal salt is reduced to nano-scale metal particles, which are evenly distributed on the surface of the aerogel, and finally a metal-loaded electrocatalyst is obtained. At this time, the cellulose undergoes a pyrolysis and carbonization reaction, mainly undergoing steps such as dehydration and dehydroxylation to form a stable carbon fiber skeleton with low graphitization. At the same time, the metal precursor decomposes and reduces to form uniformly dispersed metal nanoparticles. In this process, on the one hand, the three-dimensional porous structure of the aerogel is retained, and on the other hand, it is given good electrical conductivity and catalytic activity. Subsequently, it is naturally cooled to room temperature to obtain a carbon fiber aerogel-loaded metal electrocatalyst. The average particle size of the obtained metal particles is less than 50nm, and the specific surface area is 200~500m 2 / g, with good dispersibility and catalytic activity. The prepared carbon fiber aerogel has high porosity and large specific surface area, which is conducive to exposing more catalytic active sites, thereby improving the reaction rate and selectivity of the reduction reaction.

[0069] According to some embodiments, the pore size distribution (2-50 nm) and specific surface area (>600 m 2 / g) determines its ability to transport gaseous reactants (such as CO2), which is conducive to the formation of highly dispersed active sites and the improvement of reaction rate. In addition, the particle size of metal nanoparticles in metal-supported electrocatalysts is less than 50nm and the specific surface area is 200-500m 2 / g can provide sufficient exposure of active sites to ensure the selectivity and catalytic efficiency of the reaction.

[0070] To verify the importance of the above parameters, we compared the test of the Bi metal loaded electrocatalyst system (Bi@C) with the conventional graphite powder (specific surface area of about 10 m 2 / g) as the matrix. Under the same preparation and test conditions, its faradic efficiency was significantly lower than that of the sample using carbon fiber aerogel matrix, and the test results are shown in Figure 2 , wherein the loading amount of Bi is 0.02M.

[0071] The three-dimensional network aerogel matrix is prepared by sequentially treating bacterial cellulose hydrogel with alkaline solution and deionized water multiple times to obtain cellulose hydrogel; the cellulose hydrogel is immersed in a tert-butyl alcohol-water mixed solution for solvent replacement; and the cellulose hydrogel is dried to form the three-dimensional network aerogel matrix. Specifically, the bacterial cellulose hydrogel with a size of about 1x1x1 cm 3 is sequentially treated with alkaline solution (for example, a NaOH solution with a mass fraction of 4-10 wt.%) and deionized water multiple times to remove sugar and impurities, and obtain pure cellulose hydrogel. For example, the alkaline solution treatment time is 4-6 hours, the deionized water treatment time is 4-6 hours, and the repeated treatment is 3-5 times until pH=7.

[0072] The solvent replacement is then performed with a tert-butyl alcohol / water mixed solution, preferably, the volume ratio of tert-butyl alcohol to water is 2:3. The prepared aerogel has high porosity and large specific surface area, which is beneficial to expose more catalytically active sites, thereby improving the reaction rate and selectivity of the reduction reaction. Moreover, by using readily available bacterial cellulose as the precursor of the aerogel, the preparation process is simple, avoids complex chemical treatment or high-cost raw materials, and has good process scalability and practical application potential.

[0073] Then, the obtained cellulose aerogel is slowly immersed in a metal salt solution (such as Bi(NO3)3, concentration ≤0.05M) for 4-6 hours to allow the metal precursor to be fully loaded. The loading amount of the metal salt solution is not more than the upper limit of the carrying capacity of the aerogel matrix, so as to avoid the aggregation of metal nanoparticles and maintain the stability of the electrocatalyst structure. The cellulose hydrogel is then dried by freeze drying or supercritical CO2 drying. For example: CO2 supercritical drying is performed at a temperature of 35-45℃ and a pressure of 8-12MPa, vacuum freeze drying is performed for 4-6 hours; or under the conditions of a temperature of -50 to -80℃ and a vacuum degree of <5Pa, the continuous drying is performed for 24 hours. Preferably, vacuum freeze drying is performed.

[0074] Finally, the three-dimensional network aerogel matrix loaded with metal salt is placed in an inert gas for heat treatment, the heat treatment temperature is 600-900°C, the inert gas is argon (Ar) and / or nitrogen (N2), and the constant temperature time is not less than 2 hours (low temperature, easy carbonization is insufficient; and high temperature is easy to damage the structure), so that the three-dimensional network aerogel is carbonized into a carbon fiber aerogel matrix. Specifically, the cellulose aerogel loaded with metal precursor prepared above is placed in a tube furnace, heated to 600-900°C under an inert atmosphere (such as N2or Ar, preferably Ar gas), and held for 2 hours, and then naturally cooled to room temperature. The three-dimensional network aerogel is carbonized into a carbon fiber aerogel matrix, and the metal supported electrocatalyst is obtained.

[0075] To verify the effect of carbonization temperature on the electrocatalytic performance of Bi-loaded carbon fiber aerogel, we selected three typical temperature points of 600°C, 750°C and 900°C for comparison experiments. Under the same constant temperature time (2 hours) and consistent atmosphere (argon), the Bi-loaded carbon fiber aerogel electrocatalyst (Bi loading is 0.02M) was prepared, and its CO2RR catalytic performance at -1.0V vs. RHE potential is shown in Figure 3

[0076] As can be seen from Figure 3 , the Faraday efficiency of the HCOOH product of the catalyst is more than 90% at a temperature of 600-900°C, therefore, 600-900°C is selected as a reasonable range of carbonization temperature. Carbonization is insufficient at a temperature lower than this range, and the structure is obviously damaged at a temperature higher than this range, which is not conducive to improving the performance of the material.

[0077] According to some embodiments, the metal supported electrocatalyst of the present application is suitable for an electrocatalytic CO2 reduction catalytic reaction system, and can be used for electrocatalytic reduction of CO2 to carbon monoxide (CO), formic acid (HCOOH), methanol (CH3OH), ethylene (C2H4), ethanol (C2H5OH) and other high value-added chemicals in KHCO3, KOH electrolyte. It can also be used for photocatalytic CO2 conversion, methanol reforming, volatile organic compound (VOC) degradation, electrocatalytic N2 reduction and other catalytic reactions. The metal supported electrocatalyst of the present application plays a key role in improving the current density, product selectivity and electrocatalyst stability of electrocatalytic CO2 reduction, especially under the condition of uniform dispersion of metal loading (such as Bi, Sn, Cu, etc.) and uniform grain size, which has high Faraday efficiency for target products.

[0078] ​The object of the present invention is to provide a metal-supported electrocatalyst, which comprises: a carbon fiber aerogel matrix and nano-scale metal particles, wherein the carbon fiber aerogel matrix is ​​a three-dimensional network structure; the nano-scale metal particles are uniformly supported on the surface of the carbon fiber aerogel matrix.

[0079] Figure 4 Scanning electron microscope (SEM) image of a carbon fiber aerogel according to example embodiments.

[0080] According to some embodiments, see Figure 4 , the carbon fiber aerogel matrix has a three-dimensional network-like porous structure, which is composed of mutually cross-linked carbon fibers to form a three-dimensional skeleton, and a large number of pores with nanometer sizes are distributed therein. This three-dimensional network structure not only gives the material excellent mechanical strength and stability, but also enables it to have an extremely high specific surface area and good pore connectivity, which is conducive to the rapid transmission of reactants and products. The three-dimensional network structure provides abundant surface sites and anchoring points for the uniform loading of nanoscale metal particles, so that the metal particles can be stably distributed on the surface of the carbon fiber aerogel and are not prone to agglomeration or falling off. This structural design significantly improves the overall performance of the electrocatalyst, including catalytic activity, selectivity and cycle life, and is suitable for a variety of catalytic reaction systems, such as oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), CO2 conversion, and degradation of environmental pollutants.

[0081] According to some embodiments, the pore size distribution of the three-dimensional network carbon fiber aerogel matrix is ​​2 to 50 nm, and the specific surface area is greater than 600 m 2 / g; the average particle size of the metal nanoparticles is less than 50nm, and the specific surface area is 200 to 500m 2 / g. The metal-supported electrocatalyst of the present invention is composed of a carbon fiber aerogel matrix and nano-scale metal particles supported on its surface. The carbon fiber aerogel matrix has a three-dimensional network structure with a pore size distribution of 2 to 50 nm, which has higher surface energy and catalytic activity; the specific surface area is greater than 600 m 2 / g, showing excellent porosity and high specific surface area characteristics, which is beneficial to the mass transfer process of reactants and products and provides sufficient surface space for the loading of metal particles.

[0082] According to some embodiments, the surface of the carbon fiber aerogel matrix is ​​uniformly loaded with nano-scale metal particles with an average particle size of less than 50 nm, and the specific surface area ranges from 200 to 500 m 2 / g. The metal includes one or more of bismuth (Bi), tin (Sn), copper (Cu), and palladium (Pd). Due to the small size and large specific surface area of the metal particles, the electrocatalyst exposes more active sites, thereby significantly improving its catalytic performance. Moreover, the uniform distribution of the metal particles on the surface of the carbon fiber aerogel helps to prevent particle agglomeration, improve catalytic efficiency and stability, and improve the stability and recycling performance of the electrocatalyst. The metal-loaded electrocatalyst described in the present application adopts the composite structure as described above, and is particularly suitable for various catalytic reaction systems, such as oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), CO2 conversion, environmental pollutant degradation, and electrocatalytic reaction, and has a wide application prospect.

[0083] According to some embodiments, the metal-loaded electrocatalyst described in the present application enhances the electron transport performance in the catalytic reaction process by adopting a three-dimensional carbon fiber aerogel structure with a high specific surface area, while improving the catalytic reaction active sites, slowing down the metal nanoparticle agglomeration and deactivation phenomenon, and can be stably operated in a continuous electrocatalytic reaction system for more than 72 hours.

[0084] In order to more clearly understand the technical concept, implementation path and beneficial effects of the present application, the present application will be further described in detail below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the technical solutions of the present application, and are not limited to the present application. Any equivalent modifications and substitutions made without departing from the spirit of the present application shall be included in the protection scope of the present application.

[0085] In the following examples, the raw materials used are all commercially available products that can be directly purchased. For example: bacterial cellulose hydrogel, bismuth nitrate (Bi(NO3)3, 99.9%), sodium hydroxide (NaOH, AR), potassium bicarbonate (KHCO3, AR), potassium hydroxide (KOH, AR), dimethyl sulfoxide (DMSO, 99.8%), and tert-butyl alcohol (C4H 10 O, AR), Nafion (5wt.%). D2O, 99.9% ethanol (C2H5OH, AR). 18.2MΩcm ultrapure water is taken from the Rephile water supply system. All reagents are used directly without further purification. (In the following examples, the normal temperature mentioned is 25±5℃.)

[0086] Example 1: Preparation of three-dimensional network carbon fiber aerogel matrix

[0087] 1. The bacterial cellulose hydrogel with a size of about 1×1×1cm 3 was immersed in a 6wt.% NaOH alkaline solution for 4 hours, during which the bacterial cellulose hydrogel changed from white to reddish brown.

[0088] 2. Wash the bacterial cellulose hydrogel with excess deionized water for ≥3 times, each time for 4 hours, until the bacterial cellulose hydrogel turns white again and the pH is 7, so as to remove sugars and impurities and obtain pure fiber aerogel.

[0089] 3. Solvent replacement was performed with a mixed solution of tert-butanol / water (volume ratio of 2:3), followed by vacuum freeze drying (conditions of -50 to -80 ° C, vacuum degree of 0.1 mbar), and a three-dimensional network aerogel matrix was obtained after continuous drying for 24 hours.

[0090] Example 2: Preparation of Bi metal electrocatalyst supported on carbon fiber aerogel

[0091] 1. The cellulose aerogel prepared in Example 1 was immersed in Bi(NO3)3 salt solutions of different concentrations (0.01, 0.02, 0.03, and 0.04 M) and magnetically stirred at 100 rpm for 2 hours to ensure complete immersion.

[0092] 2. Cellulose aerogels loaded with metal precursors of different concentrations were obtained by vacuum freeze drying (conditions of -50 to -80°C and vacuum degree of <5 Pa) after continuous drying for 24 hours.

[0093] 3. Heat treatment was performed in a tube furnace at 700°C in an Ar atmosphere at a heating rate of 5°C / min for 2 hours, followed by natural cooling to room temperature to obtain carbon fiber aerogel-supported Bi metal electrocatalysts with different loadings. These were labeled as 0.01-Bi, 0.02-Bi, 0.03-Bi, and 0.04-Bi, respectively.

[0094] 4. The microstructure of the prepared electrocatalyst was characterized by scanning electron microscopy (SEM).

[0095] See also Figure 5 、 6 , 7, it can be seen that in 0.01-Bi, 0.02-Bi, and 0.03-Bi samples, Bi nanoparticles are evenly distributed on the surface of the carbon fiber skeleton, and no obvious agglomeration phenomenon is observed, indicating that the metal particles can be well anchored to the aerogel substrate under low concentration loading conditions. Figure 8 Due to the high precursor concentration in the 0.04-Bi sample, Bi nanoparticles exhibited significant agglomeration, locally disrupting the carbon fiber aerogel structure and reducing overall stability. This allows the optimal Bi metal salt loading concentration range to be determined, ensuring the morphological uniformity and structural integrity of the electrocatalyst. The crystal form of the prepared electrocatalyst was characterized using X-ray diffractometer (XRD).

[0096] like Figure 9As shown, the peak positions at 2-theta = 22.39°, 27.24°, 37.95°, 39.62°, and 48.71° correspond to the (003), (012), (104), (110), and (202) crystal planes of Bi, respectively (according to standard JCPDS#85-1329). The diffraction intensity of a single crystal plane of Bi crystal in the electrocatalyst increases with the increase of Bi content. The specific surface area and pore size distribution parameters of the electrocatalyst in Example 2 were analyzed using a specific surface area test instrument and the Barrett-Joyner-Halenda (BJH) method. The carbon fiber aerogel-supported Bi metal electrocatalyst in Example 2 maintained a high specific surface area of ​​more than 500 m 2 / g, with a pore size distribution of 20-50nm, showing the typical characteristics of a mesoporous structure. These structural features enable the synergistic integration of carbon fiber aerogel and Bi metal within the electrocatalyst framework to effectively increase the electrochemically active surface area and optimize the charge transfer pathway, thereby improving the overall catalytic performance of CO2RR.

[0097] According to some embodiments, the same method as in Example 2 above can be used to replace the Bi(NO3)3 salt solution with a metal salt solution such as PdCl2, SnCl2, or Cu(NO3)3. The same treatment method can be used to obtain carbon fiber aerogel-supported Pd metal electrocatalyst, carbon fiber aerogel-supported Sn metal electrocatalyst, and carbon fiber aerogel-supported Cu metal electrocatalyst. Figure 10 、 11 Example in .

[0098] The present invention also provides an electrocatalyst ink, which includes: a metal-loaded electrocatalyst as described in any of the above items, an isopropanol solution, and a Nafion solution, and the electrocatalyst ink is used to achieve efficient selective conversion of CO2 reduction products in an H-type electrolytic cell or a flow electrolytic cell. Among them, carbon fiber has good electron transport properties, and the three-dimensional network structure provides more reaction contact sites for the catalytic reactants. It is suitable for high current density operating conditions such as H-type electrolytic cells and flow electrolytic cells, which is conducive to efficient electron transfer and rapid diffusion of reactants. The present invention improves the reaction efficiency by optimizing the electrocatalyst structure and ink formula. In the scheme of the present invention, the prepared metal-loaded electrocatalyst is used as the active material of the working electrode, and its unique three-dimensional porous network structure can achieve high current density (>100mA cm -2 ) Rapid capture and efficient reduction of CO2 molecules.

[0099] The application also provides an electrode for use in a flow electrolysis cell, the electrode comprising: an electrocatalyst ink as described above and a carbon paper electrode, the electrocatalyst ink being uniformly loaded on the carbon paper electrode to obtain the electrode. The application can regulate target products by adjusting the metal species, carrier structure and ink composition. The electrocatalyst in the form of ink is convenient to coat on the carbon paper electrode or other electrode substrate, is suitable for various electrochemical systems, is compatible with H-type electrolysis cells and flow electrolysis cells, and has good expansibility. Preferably, the working electrode area of the flow electrolysis cell can be 1 cm 2 , and is suitable for acidic, neutral and alkaline electrolyte systems.

[0100] Example 3: Preparation of the carbon fiber aerogel loaded Bi metal electrocatalyst ink and electrode

[0101] 1. 5 mg of electrocatalyst and 20 μL of Nafion were mixed with 980 μL of CH3OH solution, and then ultrasonic treatment was performed for 2 hours to form a uniform electrocatalyst ink.

[0102] 2. 10 μL of the electrocatalyst ink was sprayed on a 1 cm x 1 cm carbon paper, which was vacuum dried for 2 hours and used as a working electrode.

[0103] Example 4: Use of the electrode prepared in Example 3 for electrocatalytic CO2 reduction performance test

[0104] 1. The working electrodes of 0.01-Bi, 0.02-Bi, 0.03-Bi and 0.04-Bi electrocatalysts were prepared in the above manner.

[0105] 2. Electrochemical test (all the electrochemical tests were performed on a CHI-760E electrochemical workstation.)

[0106] An H-type electrolysis cell was used, and Nafion 117 film was used to separate the cathode and anode chambers. The working electrode and a reference electrode (Ag / AgCl) were placed in the cathode chamber, and a counter electrode (Pd sheet: 1 cm x 1 cm) was placed in the anode chamber. The electrolyte was a 0.5 mol L -1 KHCO3 solution.

[0107] Before the electrochemical test, high-purity N2 (99.999%) was introduced into the cathode and anode chambers for more than 30 minutes to remove air in the electrolyte and electrolysis cell. Subsequently, high-purity CO2 (99.999%) was injected for more than 30 minutes to ensure that the electrolyte was completely saturated with CO2, at which time the pH value of the KHCO3 solution was 7.2.

[0108] 2.1. Electrochemical test

[0109] The present example includes the following electrochemical tests: linear sweep curves (LSV) were performed between 0 V and -1.8 V vs. RHE at a scan rate of 50 mV / s. Electrochemical impedance spectroscopy (EIS) tests were performed at -0.5 V vs. RHE with a frequency range of 400 kHz to 0.1 Hz and an amplitude of 5 mV. Constant potential (i-t) tests were performed at different potentials, and stability tests were performed at a constant potential of -1.0 V vs. RHE for 72 hours.

[0110] The products of the present example were determined by gas chromatography and nuclear magnetic resonance (NMR), respectively. The gaseous products included CO and H2, and the liquid product was HCOOH. The electrodes prepared using the 0.01-Bi, 0.02-Bi, 0.03-Bi, and 0.04-Bi electrocatalysts were determined, respectively, and the results are shown in Tables 1-4, respectively. Figure 12

[0111] From Table 1, it can be seen that the electrode prepared using the 0.01-Bi electrocatalyst had the highest Faraday efficiency for HCOOH (formic acid) at all test potentials, approaching or reaching 100%. The Faraday efficiencies for CO (carbon monoxide) and H2 (hydrogen) were relatively low and did not change much at different potentials. Figure 12 From Table 2, it can be seen that the electrode prepared using the 0.02-Bi electrocatalyst also had a relatively high Faraday efficiency for HCOOH at all test potentials, approaching 100% at most potentials, but decreasing slightly at -0.8 V. The Faraday efficiencies for CO and H2 were still relatively low and did not change much over the entire potential range.

[0112] Figure 12 From Table 3, it can be seen that the electrode prepared using the 0.03-Bi electrocatalyst had a Faraday efficiency for HCOOH approaching 100% at all test potentials, indicating good selectivity. The Faraday efficiencies for CO and H2 were still relatively low and did not change much.

[0113] From Table 4, it can be seen that the electrode prepared using the 0.04-Bi electrocatalyst had a Faraday efficiency for HCOOH approaching 100% at -1.0 V and -0.9 V, but decreased at other potentials. The Faraday efficiencies for CO and H2 were relatively low at all potentials and did not change much. Figure 12 From Table 4, it can be seen that the electrode prepared using the 0.04-Bi electrocatalyst had a Faraday efficiency for HCOOH approaching 100% at -1.0 V and -0.9 V, but decreased at other potentials. The Faraday efficiencies for CO and H2 were relatively low at all potentials and did not change much.

[0114] Figure 12 From Table 4, it can be seen that the electrode prepared using the 0.04-Bi electrocatalyst had a Faraday efficiency for HCOOH approaching 100% at -1.0 V and -0.9 V, but decreased at other potentials. The Faraday efficiencies for CO and H2 were relatively low at all potentials and did not change much.

[0115] ​​​As Bi concentration increases (from 0.01M to 0.04M), the selectivity for HCOOH decreases slightly at certain potentials, particularly at 0.04M Bi. The selectivity for CO and H2 is low in all cases, indicating that the electrocatalyst primarily promotes the formation of HCOOH. At more negative potentials (such as -1.2V and -1.1V), the selectivity for HCOOH is generally high. At more positive potentials (such as -0.8V), the selectivity for HCOOH decreases under certain conditions.

[0116] In summary, it can be seen that the electrodes with different Bi concentrations at different potentials mainly promote the generation of HCOOH, while having low selectivity for CO and H2. As the Bi concentration increases, the selectivity for HCOOH decreases slightly at certain potentials, but generally maintains a high selectivity.

[0117] 2.2 Stability Test

[0118] The stability test of 0.02-Bi electrocatalyst was carried out under a constant potential of -1.0V vs. RHE for 72 hours, and the test data were as follows: Figure 13 As shown in . Among them, the 0.02-Bi electrocatalyst has the highest Faraday efficiency of HCOOH product at -1.0V vs.RHE, which is 96.73±1.45%, showing extremely high product selectivity. Moreover, in the stability test, its stability reached 72 hours. During the entire test process, the Faraday efficiency of HCOOH product of the electrocatalyst remained above 90% during the stability operation process, and the Faraday efficiency remained at 90.63% at the end of the operation, indicating that the electrocatalyst still has excellent electrochemical stability and structural durability during the long-term reaction process. Compared with traditional carbon nanotubes, graphene and other carrier-loaded electrocatalysts that are prone to metal agglomeration and poor stability, the three-dimensional carbon fiber aerogel framework constructed by the present invention can effectively anchor Bi nanoparticles, prevent their migration and agglomeration, and promote reactant diffusion and charge transfer, thereby achieving high activity, high selectivity and long-term stability. It provides a new catalytic material system with practical application potential for the electrocatalytic CO2 reduction reaction.

[0119] Example 5: Carbon fiber aerogel loaded with Bi metal electrocatalyst

[0120] The flow electrolysis cell is composed of a gas diffusion electrode (GDE, 2 × 3 cm 2 ) flow cell reactor. Pd sheet was used as the counter electrode and saturated Ag / AgCl electrode was used as the reference electrode. Figure 14 The electrolyte used was 1 M KOH solution. During the measurement, high-purity CO2 (99.999%) gas was directly introduced into the working electrode at a flow rate of 20 sccm.

[0121] Electrocatalytic CO2 reduction performance test in a flow electrolytic cell: The Faradaic efficiency of each product (including H2, CO, HCOOH) in the current density test range of -50 to -250 mA using 0.02-Bi electrocatalyst in a flow electrolytic cell is shown in Figure 2. Figure 15 .

[0122] In addition to the above examples, we also conducted comparative tests on the electrocatalytic performance of the same type of carbon fiber aerogels loaded with three metals, Sn, Cu and Pd. The metal loading of the electrocatalysts CFAs, Sn@CFAs, Cu@CFAs and Pd@CFAs was 0.02M. At a potential of -1.0V vs. RHE, the catalytic efficiency of each product was as follows: Figure 15 shown.

[0123] Depend on Figure 16 The test results show that the main product of the carbon fiber aerogel-loaded Sn metal electrocatalyst (Sn@CFAs) is formic acid (HCOOH), and the Faraday efficiency is significantly improved compared to the unloaded metal aerogel. The main products of the carbon fiber aerogel-loaded Cu metal electrocatalyst (Cu@CFAs) are formic acid and a small amount of ethylene (C2H4) products, and under the same reaction conditions, it also shows better electrocatalytic activity than the unloaded metal carbon fiber aerogel. The main product of the carbon fiber aerogel-loaded Pd metal electrocatalyst (Pd@CFAs) is CO, which also shows that the Faraday efficiency of the CO product after Pd loading is better than that of the unloaded metal carbon fiber aerogel.

[0124] Comparative Example 1: Using Carbon Fiber Aerogel (CFAs) Electrocatalyst

[0125] The difference from the preparation method in Example 2 is that the metal salt solution impregnation step is not performed in Comparative Example 1. Instead, the cellulose aerogel prepared in Example 1 is directly placed in a tubular furnace and heat-treated directly in the tubular furnace at 700°C in an Ar gas atmosphere with a heating rate of 5°C / min. The temperature is maintained constant for 2 hours, and then naturally cooled to room temperature to obtain a carbon fiber aerogel (CFAs) electrocatalyst.

[0126] CO2 electroreduction performance test: The gas phase products include CO and H2, which are measured by gas chromatography and nuclear magnetic resonance (NMR).

[0127] Test results: No liquid HCOOH product was detected, indicating that the activity of the comparative electrocatalyst for the reduction of CO2 to HCOOH was extremely low. The relevant data are detailed in Table 1.

[0128] Comparative Example 2: Using Bi2O3 catalyst

[0129] CO2 electro-reduction performance test: the CO2 electro-reduction performance test of Comparative Example 2 is consistent with the test method of Example 2. The difference is that the catalytic product of Comparative Example 2 is determined by gas chromatograph and nuclear magnetic resonance (NMR), and the determination of gaseous products includes CO and H2, and no liquid phase HCOOH product is detected, indicating that the activity of the catalyst of this comparative example for the reduction of CO to HCOOH is very low. The HCOOH faradic efficiency is significantly lower than that of Example 2, and the specific value is shown in Table 1.

[0130] Table 1: Test results of faradic efficiency of HCOOH product generated in the electrocatalytic CO2 reduction reaction

[0131]

[0132] The above comparative experiment shows that the lack of metal loading (Comparative Example 1) or the lack of three-dimensional aerogel carrier (Comparative Example 2) significantly reduces the faradic efficiency of the electrocatalyst for the HCOOH product, thereby verifying the effectiveness of the three-dimensional aerogel carrier and the metal loading synergistic structure design used in the present application.

[0133] According to some embodiments, the metal-loaded electrocatalyst of the present application uses a three-dimensional network structure of carbon fiber aerogel matrix, and the carbon fiber has good electronic transmission performance. The three-dimensional network structure provides more reaction contact sites for the catalytic reactants, is suitable for high current density operating conditions such as H-type electrolytic cell and flow electrolytic cell, and is conducive to efficient electron transfer and rapid diffusion of reactants. The carbon fiber aerogel matrix structure has universality and generality, and can be widely used for uniform loading and immobilization of Bi, Sn, Cu, Pd and other metal electrocatalysts, thereby expanding its application scenarios in electrocatalytic CO2 reduction and other catalytic reactions.

[0134] According to some embodiments, the preparation of the metal-loaded electrocatalyst of the present application uses bacterial cellulose as the precursor of the carbon fiber aerogel, which is easy to obtain, and the preparation process is simple, avoiding complex chemical treatment or high-cost raw materials, and has good process amplification and practical application potential.

[0135] Through the above detailed description of the examples and comparative examples, those skilled in the art can clearly understand the concept and technical solutions of the present application, and can realize or apply the present application accordingly.

[0136] It should be understood that, for those skilled in the art, various forms of improvement, replacement or equivalent deformation of these embodiments can be made without departing from the core idea of the present application. The technical principles and features disclosed herein can also be applied to other types of embodiments, therefore, the protection scope of the present application should not be limited to the specific embodiments listed in the specification, but should cover all solutions meeting the technical principles and innovative spirit of the present application.

[0137] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a metal-supported electrocatalyst, characterized in that: The preparation method comprises: Preparation of a three-dimensional network aerogel matrix; Immersing the three-dimensional network aerogel matrix in a metal salt solution and performing stirring adsorption to obtain a three-dimensional network aerogel matrix loaded with metal salt; The three-dimensional network aerogel matrix loaded with metal salt is placed in an inert gas for heat treatment to obtain the metal-loaded electrocatalyst.

2. The preparation method according to claim 1, characterized in that The preparation of the three-dimensional network aerogel matrix comprises: The bacterial cellulose hydrogel is subjected to multiple cycles of alkaline solution and deionized water to obtain a cellulose hydrogel; immersing the cellulose hydrogel in a tert-butyl alcohol-water mixed solution for solvent replacement; The cellulose hydrogel is dried and formed to obtain the three-dimensional network aerogel matrix.

3. The preparation method according to claim 2, characterized in that In the tert-butanol-water mixed solution, the volume ratio of the tert-butanol to water is 3:

2.

4. The preparation method according to claim 2, characterized in that The cellulose hydrogel is dried and formed, comprising: The cellulose hydrogel is dried and formed by freezing or supercritical carbon dioxide drying.

5. The preparation method according to claim 1, characterized in that The loading amount of the metal salt solution is not greater than the upper loading limit of the aerogel matrix.

6. The preparation method according to claim 1, characterized in that The three-dimensional network aerogel matrix loaded with metal salt is placed in an inert gas for heat treatment, comprising: The heat treatment temperature is 600-900° C., the inert gas is argon and / or nitrogen, and the constant temperature time is not less than 2 hours, so that the three-dimensional network aerogel is carbonized into a carbon fiber aerogel matrix.

7. A metal-supported electrocatalyst, characterized in that The metal-supported electrocatalyst comprises: a carbon fiber aerogel matrix and nano-scale metal particles, wherein: The carbon fiber aerogel matrix is ​​a three-dimensional network structure; The nano-scale metal particles are uniformly loaded on the surface of the carbon fiber aerogel matrix.

8. The metal-supported electrocatalyst according to claim 7, characterized in that The metal includes one or more of bismuth, tin, copper, and palladium.

9. The metal-supported electrocatalyst according to claim 7, characterized in that The pore size distribution of the three-dimensional network carbon fiber aerogel matrix is ​​2 to 50 nm, and the specific surface area is greater than 600 m 2 / g; the average particle size of the metal nanoparticles is less than 50nm, and the specific surface area is 200 to 500m 2 / g.

10. An electrocatalyst ink, characterized in that: The electrocatalyst ink comprises: a metal-supported electrocatalyst as described in any one of claims 7 to 9, an isopropyl alcohol solution, and a perfluorosulfonic acid polymer solution. The electrocatalyst ink is used in an H-type electrolytic cell or a flow electrolytic cell to achieve selective conversion of carbon dioxide reduction products.

11. An electrode, characterized in that: The electrode is used in a flow electrolysis cell, and comprises: the electrocatalyst ink as claimed in claim 10 and a carbon paper electrode, wherein the electrocatalyst ink is uniformly loaded on the carbon paper electrode.

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