Co3O4 silver-based composite material and preparation method and application thereof

Abstract

The invention relates to the technical field of energy conversion catalysis, in particular to a Co3O4 silver-based composite material and a preparation method and application thereof. According to the Co3O4 silver-based composite material, the components have strong interaction, the bifunctional electrocatalytic activity of ORR and OER is high, which is mainly attributed to the synergistic effect and strong interaction between fine Co3O4 nanocrystals and embedded Ag NPs, the surface area of the material is increased, and the oxygen vacancy concentration at an interface and the ratio of Co < 2 + > to Co < 3 + > are adjusted. The Co3O4 silver-based composite material disclosed by the invention has a smaller delta EOER-ORR potential difference and a smaller Todal slope, and excellent stability and methanol tolerance. The zinc air battery assembled by the Co3O4 silver-based composite material shows excellent charge and discharge performance, relatively high peak power density is realized, good stability is maintained in 100 charge and discharge cycles, and the voltage difference is only 0.84 V.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of energy conversion catalysis, in particular to a Co3O4 silver-based composite material and a preparation method and application thereof. BACKGROUND

[0002] Among high-efficiency electrochemical energy conversion and storage devices (EECSDs), rechargeable EECSDs represented by metal-air batteries and lithium-ion batteries have attracted extensive attention due to their low cost, high energy density, long cycle life, and fast charging and discharging capabilities. The performance of electrode materials is closely related to the performance of EECSDs. As a key component of EECSDs, the cathode material for oxygen reduction reaction (ORR) and the anode material for oxygen evolution reaction (OER) are usually limited by slow kinetics and high overpotential.

[0003] Currently, noble metal-based materials such as platinum carbon, RuO2 and IrO2 are still the most effective electrocatalysts for ORR or OER. However, due to limitations such as resource scarcity, limited activity and insufficient stability, platinum, iridium and ruthenium-based catalysts face major challenges in large-scale applications.

[0004] Among numerous materials, transition metal oxides (TMOs) have attracted extensive attention in the field of electrocatalysts due to their low cost, resource abundance, environmental friendliness and excellent catalytic performance. Among them, cobalt oxide (Co3O4) is considered to be a promising OER electrocatalyst, but its ORR catalytic activity and electrical conductivity are low. Co3O4 exhibits a spinel structure, in which Co 2+ and Co 3+ ions occupy tetrahedral (8a) and octahedral (16a) sites, respectively. In fact, Co3O4 realizes ORR reaction through mutual transformation of different valence cations. On the other hand, as an efficient ORR electrocatalyst, silver (Ag) itself has excellent electrical conductivity. However, the OER activity and stability of Ag are obviously limited, and Ag is easily oxidized to form Ag2O in the process of continuous oxygen evolution.

[0005] Researchers have successfully synthesized a bifunctional electrocatalyst with both ORR and OER activities by mechanically mixing Co3O4 nanoparticles with Ag nanoparticles (Ag NPs), exhibiting significantly superior performance compared to single components. However, the relatively weak contact between Co3O4 and Ag NPs leads to reduced conductivity and charge transfer in the bifunctional electrocatalyst; insufficient heterointerface between the Co3O4 nanoparticles and Ag NPs results in limited synergistic effects; and in long-term stability tests, this weak interaction easily induces local polarization, leading to nanoparticle aggregation and further impairing the catalytic performance of the bifunctional electrocatalyst. In summary, the inter-component interactions in this mixture are inherently limited: Co3O4 and Ag NPs are only in physical contact, lacking effective electronic synergistic effects, which hinders the effective regulation of the adsorption energy of intermediates. Summary of the Invention

[0006] In view of this, the present invention provides a Co3O4 silver-based composite material, its preparation method and application. The Co3O4 silver-based composite material provided by the present invention has strong interactions between components and high bifunctional electrocatalytic activity of ORR and OER.

[0007] The present invention provides a Co3O4 silver-based composite material, comprising Co3O4 nanocrystals and Ag NPs embedded in the Co3O4 nanocrystals.

[0008] Preferably, the mass ratio of Co3O4 nanocrystals to Ag NPs in the Co3O4 silver-based composite material is 1.8~2.2:3.

[0009] This invention also provides a method for preparing the Co3O4 silver-based composite material described above, comprising the following steps: (1) CoOOH and silver source were mixed and subjected to a solid-phase reaction to obtain the precursor; (2) The precursor is heat-treated to obtain the Co3O4 silver-based composite material.

[0010] Preferably, the molar ratio of cobalt in the CoOOH to silver in the silver source is 1:2.8~3.2.

[0011] Preferably, the solid-phase reaction is carried out at room temperature; the solid-phase reaction takes place for more than 300 minutes; and the solid-phase reaction is carried out under grinding conditions.

[0012] Preferably, the heat treatment temperature is 245~255 degrees Celsius, and the holding time is 170~190 minutes; the first heat treatment is carried out in a protective atmosphere.

[0013] Preferably, the preparation method of CoOOH includes the following steps: mixing Co(NO3)2 solution, ammonia water and hydrogen peroxide in a second mixture to carry out an oxidation reaction.

[0014] Preferably, the concentration of the Co(NO3)2 solution is 0.8~1.2M; the concentration of the ammonia solution is 1.4~1.8M; the volume ratio of the Co(NO3)2 solution to the ammonia solution is 0.9~1.1:1; the concentration of the hydrogen peroxide solution is 0.8~1.0M; and the molar ratio of Co(NO3)2 to hydrogen peroxide in the Co(NO3)2 solution is 4:4.8~5.2.

[0015] Preferably, the oxidation reaction is carried out at room temperature for more than 300 minutes.

[0016] The present invention also provides the application of the Co3O4 silver-based composite material described in the above scheme or the Co3O4 silver-based composite material obtained by the preparation method described in the above scheme in high-efficiency electrochemical energy conversion and storage devices.

[0017] This invention provides a Co3O4 silver-based composite material. The Co3O4 silver-based composite material provided by this invention exhibits strong interactions between its components and possesses bifunctional activity for both ORR and OER, with high bifunctional electrocatalytic activity for both ORR and OER. This excellent catalytic activity is mainly attributed to the synergistic effect and strong interaction between the fine Co3O4 nanocrystals and the embedded Ag NPs, which not only enhances the surface area of ​​the material but also modulates the oxygen vacancy concentration and Co at the interface. 2+ and Co 3+ The proportion. Specifically, the Co3O4 silver-based composite material provided by this invention has a smaller ΔE. OER-ORR The Co3O4 silver-based composite material provided by this invention achieves a significant ORR half-wave potential (0.75V) at 10... The lower coupling low OER potential (1.47V). The Co3O4 silver-based composite material provided by this invention exhibits near-ideal ORR selectivity, with an electron transfer number of 4.03, and achieves this through a small Tafel slope (33.4V). This demonstrates excellent OER kinetics. Furthermore, the zinc-air battery (ZAB) assembled using the Co3O4 silver-based composite material of this invention exhibits excellent charge-discharge performance, achieving a relatively high peak power density (124.32). It maintains good stability throughout 100 charge-discharge cycles, with a voltage difference of only 0.84V. This invention emphasizes the importance of the synergistic effect of multiple strategies in improving catalytic performance, providing valuable theoretical insights for enhancing catalytic performance.

[0018] This invention also provides a method for preparing the Co3O4 silver-based composite material described above. This invention employs a two-step method: first, Ag NPs are embedded into a CoOOH matrix to obtain a CoOOH-Ag NPs precursor via a solid-state reaction; then, the CoOOH-Ag NPs precursor is pyrolyzed to synthesize the Co3O4 silver-based composite material. In this composite material, the transition metal oxide Co3O4 and the embedded metal nanoparticles Ag NPs exhibit strong interactions. Compared to physical mixtures of Ag NPs, Co3O4, or Co3O4-Ag NPs, the Co3O4 silver-based composite material provided by this invention exhibits excellent bifunctional oxygen electrocatalytic activity, comparable to that of commercial catalysts (e.g., commercial platinum-carbon and RuO2 noble metal catalysts, which are composites of platinum-carbon and RuO2).

[0019] This invention also provides the application of the Co3O4 silver-based composite material described in the above-described scheme or the Co3O4 silver-based composite material prepared by the above-described scheme in high-efficiency electrochemical energy conversion and storage devices. In the Co3O4 silver-based composite material provided by this invention, the Co3O4 nanoparticles and Ag NPs synergistically enhance catalytic performance, enabling it to serve as a bifunctional oxygen electrocatalyst for high-efficiency electrochemical energy conversion and storage devices, especially rechargeable EECSDs such as zinc-air batteries. It exhibits low cost and excellent stability. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This diagram shows the synthetic route of the Co3O4 silver-based composite material and the characterization diagrams of Co3O4, Co(OH)2, CoOOH, Ag NPs, and the Co3O4 silver-based composite material. Specifically, a is the synthetic route of the Co3O4 silver-based composite material; b is the XRD diffraction pattern of Co3O4, Co(OH)2, CoOOH, and the Co3O4 silver-based composite material; c is the XRD diffraction pattern of Ag NPs and the Co3O4 silver-based composite material; and d is a partial XRD image of c. Figure 2Images show electron microscopy (EM) images of Co3O4 and Co3O4-silver composite materials; where a is a scanning electron microscope (SEM) image of Co3O4; b is a scanning electron microscope (SEM) image of the Co3O4-silver composite material; c is a transmission electron microscope (TEM) image of Co3O4; d is a TEM image of the Co3O4-silver composite material; e is a high-resolution TEM image of Co3O4; f is a high-resolution TEM image of the Co3O4-silver composite material; g is a scanning TEM image of the Co3O4-silver composite material; h~j are elemental distribution maps of Co, O, and Ag in the Co3O4-silver composite material. Figure 3 The images show the spectra, N2 adsorption-desorption isotherms, pore size distributions, TGA and corresponding DTG curves of Co3O4, Ag NPs, and Co3O4 silver-based composites; where a is the high-resolution XPS spectrum of Co 2p for Co3O4 and Co3O4 silver-based composites; b is the high-resolution XPS spectrum of O 1s for Co3O4 and Co3O4 silver-based composites; c is the high-resolution XPS spectrum of Ag 3d for Ag NPs and Co3O4 silver-based composites; and d is the high-resolution XPS spectrum of Co 2p for Co3O4 and Co3O4 silver-based composites. 2+ and Co 3+ Proportion and O vac and O lat The scale is as follows: e represents the electron paramagnetic resonance (EPR) spectra of the Co3O4 silver-based composite material and the physical mixture of Co3O4 and Ag NPs; f represents the N2 adsorption-desorption isotherms of Co3O4, Ag NPs, and the Co3O4 silver-based composite material, with the inset showing the pore size distribution; g represents the Raman spectra of Co3O4 and the Co3O4 silver-based composite material; h represents the TGA curves of the Co3O4 and Co3O4 silver-based composite material measured under N2 flow; i represents the DTG curves corresponding to the TGA curves. Figure 4 The ORR catalytic performance characterization results are shown for Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs; where a represents the ORR catalytic performance of Co3O4 and Ag NPs in O2. 2- Saturated and N 2- In a saturated 0.1M KOH solution at 50 Cyclic voltammetry (CV) curves of Co3O4, Co3O4 silver-based composite, commercial platinum-carbon, and RuO2 noble metal catalysts were obtained by scanning rate measurement; b represents the cyclic voltammetry (CV) curves of Co3O4, Co3O4 silver-based composite, commercial platinum-carbon, and RuO2 noble metal catalysts at O2 scanning rate. 2-Linear sweep voltammetry (LSV) curves of Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs were measured at 1600 rpm in a saturated 0.1 M KOH solution; c represents the ORR onset potential (@-0.1) of the physical mixtures of Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs. ), half-wave potential and limiting current density; d is the Tafel slope of Co3O4, Ag NPs, Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalyst, and physical mixture of Co3O4 and Ag NPs; e is the Koutecky-Levich (KL) curve of Co3O4 silver-based composite in the potential range of 0.2~0.5V, and the inset in e shows the linear sweep voltammetry (LSV) curve of Co3O4 silver-based composite at speeds of 400~2025rpm; f is the electron transfer number of Co3O4, Ag NPs, Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalyst, and physical mixture of Co3O4 and Ag NPs; g is the coefficient of performance of Co3O4, Ag NPs, Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalyst, and physical mixture of Co3O4 and Ag NPs. Double-layer capacitance curves of NPs physical mixtures; h represents methanol permeation results of Co3O4 silver-based composite material, commercial platinum-carbon and RuO2 noble metal catalysts; i represents the current-time (it) galvanostatic response of Co3O4 silver-based composite material, commercial platinum-carbon and RuO2 noble metal catalysts. Figure 5 The ORR catalytic performance characterization results of Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, physical mixtures of Co3O4 and Ag NPs, and cobalt oxide-based catalysts are shown below. Specifically, a) is the linear sweep voltammetric curve of the OER for Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs; b) is the OER Tafel curve for Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs; c) is the OER Tafel curve for Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts at 10... The current galvanostatic potential curves at different current densities are shown in Figure d; d represents the current galvanostatic potential curves of the Co3O4 silver-based composite material at different current densities in a 1.0 M KOH electrolyte; e represents the potential difference (ΔE) of the Co3O4 silver-based composite material; f represents a comparison of the bifunctional activities of the Co3O4 silver-based composite material and representative cobalt oxide-based catalysts reported in recent years. Figure 6 The catalytic mechanism of Co3O4 silver-based composite materials in ORR and OER; Figure 7 The diagrams show the structure and characterization of a zinc-air battery. Specifically, a is a schematic diagram of a household zinc-air battery; b is a structural assembly diagram of a household zinc-air battery; c is the open-circuit potential; d shows the charge-discharge polarization and corresponding power density curves of a zinc-air battery assembled with a commercial platinum-carbon and RuO2 noble metal catalyst and Co3O4 silver-based composite material; e shows the discharge curves of a zinc-air battery assembled with Co3O4 silver-based composite material at different current densities; f is a demonstration of a zinc-air battery assembled with Co3O4 silver-based composite material, which can stably supply power (illustrated as a battery-powered digital watch); g is a demonstration of a zinc-air battery assembled with Co3O4 silver-based composite material, which can stably supply power (illustrated as an undriven fan); and h shows the charge-discharge performance of a zinc-air battery assembled with a commercial platinum-carbon and RuO2 noble metal catalyst and Co3O4 silver-based composite material. Figure 8 The images are the electronic image of Co3O4, its corresponding elemental distribution image, and its EDS energy spectrum; where a is the electronic image of Co3O4; b~d are the corresponding elemental distribution images of Co3O4; and e is the EDS energy spectrum of Co3O4. Figure 9 The images show the electron image, elemental distribution image, and EDS spectrum of the Co3O4 silver-based composite material; where a is the electron image of the Co3O4 silver-based composite material; b~e are the elemental distribution images of the Co3O4 silver-based composite material; and f is the EDS spectrum of the Co3O4 silver-based composite material. Figure 10 The particle size distribution diagrams are shown for Co3O4 nanoparticles and Ag nanoparticles; where a is the particle size distribution diagram for Co3O4 nanoparticles and b is the particle size distribution diagram for Ag nanoparticles. Figure 11 The images show transmission electron microscope (TEM) images of the Co3O4 silver-based composite material at different magnifications; where a is the TEM image at a 100 nm scale and b is the TEM image at a 50 nm scale. Figure 12The images show scanning transmission electron microscopy (STEM) images of Co3O4 silver-based composite materials and the corresponding elemental distribution maps of Co, O, and Ag; where a~d are STEM images and corresponding elemental distribution maps of Co, O, and Ag at a 100 nm scale; and e~h are STEM images and corresponding elemental distribution maps of Co, O, and Ag at a 250 nm scale. Figure 13 The LSV curves of a 20 wt% platinum-carbon catalyst measured in an oxygen-saturated 0.1 M KOH solution and the OER LSV curves of RuO2 recorded in a 1.0 M KOH solution are shown below. Specifically, a) is the LSV curve of the 20 wt% platinum-carbon catalyst measured in an oxygen-saturated 0.1 M KOH solution; b) is the OER LSV curve of RuO2 recorded in a 1.0 M KOH solution. Figure 14 The figures show the coulomb-voltammetry (KL) curves of Ag NPs, Co3O4, a physical mixture of Co3O4 and Ag NPs, and a physical mixture of platinum-carbon and RuO2 in the potential range of 0.2–0.5 V. The inset shows the linear sweep KL curves in the range of 400–2025 rpm. Among them, a is the KL curve of Ag NPs in the potential range of 0.2–0.5 V; b is the KL curve of Co3O4 in the potential range of 0.2–0.5 V; c is the KL curve of the physical mixture of Co3O4 and Ag NPs in the potential range of 0.2–0.5 V; and d is the KL curve of the physical mixture of platinum-carbon and RuO2 in the potential range of 0.2–0.5 V. Figure 15 Cyclic voltammetry curves of Ag NPs, Co3O4, a physical mixture of Co3O4 and Ag NPs, a physical mixture of platinum-carbon and RuO2, and a Co3O4 silver-based composite material are shown at different scan rates within a potential window of 1.05–1.15 V. Specifically, a represents the cyclic voltammetry curve of Ag NPs; b represents the cyclic voltammetry curve of Co3O4; c represents the cyclic voltammetry curve of the Co3O4 silver-based composite material; d represents the cyclic voltammetry curve of the physical mixture of Co3O4 and Ag NPs; and e represents the cyclic voltammetry curve of the physical mixture of platinum-carbon and RuO2. Figure 16 Nyquist plot of Co3O4 and Co3O4 silver-based composite material; Figure 17 To determine the J of the Ag NPs and Co3O4 silver-based composite material at a potential of 0.80V during the ORR process. k Curves and MA and SA values; where a is the J of the Ag NPs and Co3O4 silver-based composite material. k Curve; b represents the MA and SA values ​​of the Ag NPs and Co3O4 silver-based composite material; Figure 18 OER potential (E@10) of Ag NPs, Co3O4, physical mixtures of Co3O4 and Ag NPs, commercial platinum-carbon and RuO2 noble metal catalysts, and OER catalysts RuO2, Co3O4 silver-based composites. ) and current density (J@1.70V); Figure 19 The MA curves and SA curves of Ag NPs and Co3O4 silver-based composites, as well as a comparison of MA and SA values, are shown at a potential of 1.63V during the OER process. Specifically, a represents the MA curve of Ag NPs and Co3O4 silver-based composites; b represents the SA curve of Ag NPs and Co3O4 silver-based composites; and c represents a comparison of MA and SA values ​​of Ag NPs and Co3O4 silver-based composites. Figure 20 The ORR and OER bifunctional oxygen electrocatalytic activities of Co3O4 silver-based composite material in 0.1M KOH solution were evaluated. Detailed Implementation

[0022] The present invention provides a Co3O4 silver-based composite material, comprising Co3O4 nanocrystals and Ag NPs embedded in the Co3O4 nanocrystals.

[0023] In this invention, the mass ratio of the Co3O4 nanocrystals to Ag NPs is preferably 1.8~2.2:3, more preferably 2:3.

[0024] This invention also provides a method for preparing the Co3O4 silver-based composite material described above, comprising the following steps: (1) CoOOH and silver source were mixed and subjected to a solid-phase reaction to obtain the precursor; (2) The precursor is heat-treated to obtain the Co3O4 silver-based composite material.

[0025] This invention involves mixing CoOOH and a silver source (denoted as the first mixture) and subjecting them to a solid-phase reaction to obtain a precursor. In this invention, the CoOOH is preferably brown CoOOH; the CoOOH is preferably dried before use; and the target moisture content after drying is preferably no higher than 5.0%.

[0026] In this invention, the method for preparing CoOOH preferably includes the following steps: mixing Co(NO3)2 solution, ammonia water and hydrogen peroxide (denoted as the second mixture) to carry out an oxidation reaction.

[0027] In this invention, the solvent of the Co(NO3)2 solution is preferably water; the concentration of the Co(NO3)2 solution is preferably 0.8~1.2M, more preferably 1M; the concentration of the ammonia solution is preferably 1.4~1.8M, more preferably 1.6M; and the volume ratio of the Co(NO3)2 solution to the ammonia solution is preferably 0.9~1.1:1, more preferably 1:1.

[0028] In this invention, the concentration of hydrogen peroxide is preferably 0.8~1.0M; the molar ratio of Co(NO3)2 to hydrogen peroxide in the Co(NO3)2 solution is preferably 4:4.8~5.2, more preferably 4:5.

[0029] In this invention, the temperature of the second mixing is preferably room temperature (24-27 degrees Celsius); the method of the second mixing preferably includes the following steps: adding Co(NO3)2 solution to ammonia water and stirring to obtain a suspension of Co(OH)2 blue precipitate, and then adding hydrogen peroxide dropwise to the suspension of Co(OH)2 blue precipitate; the stirring time is preferably 30 minutes; the rate of dropwise addition is preferably 55-65 drops per minute.

[0030] In this invention, the oxidation reaction temperature is preferably room temperature (24-27 degrees Celsius), and the holding time is preferably 300 minutes or more, more preferably 300-350 minutes. Through this oxidation reaction, the blue precipitate gradually transforms into a brown CoOOH precipitate.

[0031] In this invention, the silver source is preferably a silver salt; the silver salt is preferably silver nitrate (AgNO3).

[0032] In this invention, the molar ratio of cobalt in CoOOH to silver in the silver source is preferably 1:2.8~3.2, more preferably 1:3.

[0033] In this invention, the first mixing is preferably carried out in an agate mortar.

[0034] In this invention, the temperature of the solid-phase reaction is preferably room temperature (24-27 degrees Celsius); the time of the solid-phase reaction is preferably 300 minutes or more, more preferably 300 minutes; the solid-phase reaction is preferably carried out under grinding conditions. This invention enables the raw materials to react fully through grinding, during which the raw materials are first liquefied and then solidified into powder.

[0035] In this invention, the solid-phase reaction preferably includes sequential washing and drying of the resulting product; the washing preferably includes sequential water washing and alcohol washing; the water used for water washing is preferably deionized water; the alcohol used for alcohol washing is preferably ethanol; the drying temperature is preferably 55-65 degrees Celsius, and the holding time is preferably 11-13 hours. Through the above treatment, this invention eliminates any residual free salt ions in the system.

[0036] After obtaining the precursor, the present invention subjectes the precursor to heat treatment (referred to as the first heat treatment) to obtain the Co3O4 silver-based composite material. In the present invention, the temperature of the first heat treatment is preferably 245~255 degrees Celsius, more preferably 250 degrees Celsius, and the holding time is preferably 170~190 minutes, more preferably 180 minutes; the first heat treatment is preferably carried out in a protective atmosphere; the protective atmosphere is preferably nitrogen.

[0037] In this invention, the process of first heat treatment preferably includes heating; the heating rate is preferably 5 degrees Celsius per minute.

[0038] The present invention also provides the application of the Co3O4 silver-based composite material described in the above scheme or the Co3O4 silver-based composite material obtained by the preparation method described in the above scheme in high-efficiency electrochemical energy conversion and storage devices.

[0039] The Co3O4 silver-based composite material provided by this invention has the synergistic effect of Co3O4 nanoparticles and Ag NPs to improve catalytic performance. It can be used as a bifunctional oxygen electrocatalyst for high-efficiency electrochemical energy conversion and storage devices, especially rechargeable EECSDs such as zinc-air batteries. It has low cost and excellent stability.

[0040] To further illustrate the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] In a specific embodiment of the present invention, cobalt nitrate hexahydrate was purchased from Maclean's; hydrogen peroxide, silver nitrate, ammonia solution, potassium hydroxide and zinc acetate were all purchased from China National Pharmaceutical Group Chemical Reagent Co., Ltd.; platinum carbon (20wt%), carbon black (XC-72R), RuO2 and nafiloyl (5wt%) were all purchased from Suzhou Sinopharm Technology Co., Ltd.

[0042] Example 1 This embodiment prepares a Co3O4 silver-based composite material, and the specific steps are as follows: At room temperature (25°C), 40 mL of Co(NO3)2 (1M) solution was slowly added to 40 mL of ammonia (1.6M) solution. After stirring continuously for 30 minutes, a suspension of blue Co(OH)2 precipitate gradually formed. Next, 56 mL of H2O2 (0.05 mol) solution was added dropwise to the above suspension. After 300 minutes of continuous reaction, the blue precipitate gradually turned into a brown CoOOH precipitate.

[0043] Accurately weigh 0.05 mol of dry brown CoOOH and 0.15 mol of AgNO3, mix them to obtain a mixture, and then transfer the mixture to an agate mortar. The mixture is continuously ground at room temperature (25°C) for 300 minutes to carry out a solid-phase reaction. After the solid-phase reaction is complete, the product is washed with deionized water and ethanol, and then dried at 60°C for 12 hours. Subsequently, under a N2 atmosphere, the temperature is increased at a heating rate of 5°C per minute, and heat-treated at 250°C for 180 minutes to obtain the Co3O4 silver-based composite material.

[0044] Comparative Example 1 Preparation of Co3O4: First, at room temperature (25°C), 40 mL of Co(NO3)2 (1M) solution was slowly added to 40 mL of ammonia (1.6M) solution. After continuous stirring for 30 minutes, a suspension of blue Co(OH)2 precipitate gradually formed. Next, 56 mL of H2O2 (0.05 mol) solution was added dropwise to the suspension. After 300 minutes of continuous reaction, the blue precipitate gradually transformed into a brown CoOOH precipitate. The resulting brown precipitate was then filtered, washed with deionized water and ethanol, and dried at 60°C for 12 hours. Subsequently, under a N2 atmosphere, the temperature was increased at a rate of 5°C per minute, and heat-treated at 250°C for 180 minutes to obtain black Co3O4 powder.

[0045] Comparative Example 2 Preparation of Co(OH)2: The same preparation method as Comparative Example 1 was used to obtain a blue precipitate of Co(OH)2. Subsequent steps are omitted.

[0046] Comparative Example 3 Preparation of CoOOH: The same preparation method as Comparative Example 1 was used to obtain a brown precipitate of CoOOH, and subsequent steps were omitted.

[0047] Comparative Example 4 Preparation of AgCoO2: The same preparation method as in Example 1 was used, except that air was used instead of N2 atmosphere to obtain AgCoO2.

[0048] Comparative Example 5 Preparation of a physical mixture of Co3O4 and Ag NPs: Co3O4 prepared in Comparative Example 1 and commercially available Ag NPs were dispersed in deionized water at a mass ratio of 2:3. After repeated sonication and stirring, the mixture was filtered and washed with deionized water and ethanol. The mixture was then dried at 60 degrees Celsius for 12 hours to obtain a physical mixture of Co3O4 and Ag NPs.

[0049] Test Example 1 1) Material characterization: In this test case, the X-ray powder diffractometer (XRD) was a Bruker D8 Advance diffractometer from Germany, equipped with a CuKα radiation source, scanning 10–80 degrees in the 2θ range at a scan rate of 5 degrees per minute at 30 kV and 10 mA.

[0050] The scanning electron microscope (SEM) used is a Zeiss Gemini 360 microscope with an accelerating voltage of 3.0 kV.

[0051] The energy-dispersive X-ray spectroscopy (EDS) system coupled with SEM is UltimMax40.

[0052] The X-ray photoelectron spectroscopy (XPS) on the thermoelectric K-ALPHA spectrometer uses a monochromatic Al Kα X-ray source (1486.68 electron volts).

[0053] The X-ray source operates at an anode voltage of 12.0 kV and a filament current of 6.0 mA.

[0054] All tests were conducted in ultra-high vacuum (P < 10). -9 (The process is carried out under millibars).

[0055] The spectra were collected using an instrument with an analyzer work function of 4.2 electron volts.

[0056] High-resolution spectra were recorded with a pass energy of 50 electron volts and a step size of 0.05 electron volts.

[0057] The binding energy is calibrated by referencing the C 1s peak of the epiphytic carbon to 284.8 eV.

[0058] Transmission electron microscopy (TEM) was performed using a Hitachi F200, which operates at an accelerating voltage of 200 kV and a probe current of ~7.5 nanoamps. TEM sample preparation was as follows: the powder sample was ultrasonically dispersed in ethanol for 60 minutes, and then the resulting suspension was dropped onto a copper grid supported on an ultrathin carbon film and allowed to air dry.

[0059] The energy-dispersive X-ray spectroscopy (EDS) system coupled to the TEM is an Oxford X-MaxN 80T IE250, with an EDS spectral acquisition time range of 35–55 seconds.

[0060] The electron paramagnetic resonance (EPR) spectrometer used is a Bruker MS 5000.

[0061] N2 adsorption-desorption isotherm analysis was performed using a North Shore PS2-1588 analyzer at 77.3 Kelvin.

[0062] Before measurement, the sample was degassed under vacuum at 150 degrees Celsius for 300 minutes.

[0063] Specific surface area was calculated using the Brunal-Emmett-Taylor (BET) method within a relative pressure range of 0.04 to 0.32 (the ratio of P to P0).

[0064] The pore size distribution was derived using the Barrett-Joyner-Halenda (BJH) model based on the desorption branch of the isotherm.

[0065] Raman spectra were acquired using a HORIBA XploRA Nano spectrometer (Japan), with a 532 nm laser as the excitation source, and the measurement range was 100–1000 cm⁻¹. -1 Inside.

[0066] The thermal stability and composition of the catalyst use Swiss-made... Thermogravimetric analysis was used for evaluation.

[0067] The test was conducted in a pure N2 atmosphere at a flow rate of 50 ml per minute.

[0068] The samples were heated from 30 degrees Celsius to 1000 degrees Celsius at a constant heating rate of 10 degrees Celsius per minute.

[0069] The thermal behavior of the material was analyzed based on the recorded thermogravimetric (TG) and differential thermogravimetric (DTG) curves.

[0070] 2) Electrochemical measurements: Electrochemical measurements were performed on a CS300M workstation using a three-electrode system. The working electrode was a glassy carbon disk electrode, the counter electrode was a platinum mesh electrode, and the reference electrode was a mercury-mercury oxide electrode. The preparation steps of the working electrode are as follows: First, the working electrode surface was polished using alumina powder. Next, 2.5 mg of the sample and 2.5 mg of XC-72R were accurately weighed. They were uniformly dispersed in a mixed solution consisting of 150 μL of deionized water, 340 μL of ethanol, and 10 μL of narflon. The mixture was sonicated for 60 minutes to prepare a uniform ink. Subsequently, 10 μL of the ink was drop-coated onto the working electrode surface. After solvent evaporation and the formation of a uniform thin film, the preparation of the working electrode was complete. Finally, it was used to measure a diameter of 4 mm (~0.1256 cm). 2 A rotating disk electrode (RDE) is used. Thus, the total solid loading (50% active catalyst and 50% XC-72R carbon) is ~0.8. The active catalyst loading is ~0.4%. To ensure comparability of experiments, all electrodes used for electrochemical measurements were prepared using the same method, and their mass loading was strictly maintained at the same level.

[0071] In addition, ORR and OER were tested at room temperature using a CS 300M electrochemical workstation and a standard three-electrode system, i.e., using a platinum mesh as the counter electrode, and Hg... HgO (1.0 M KOH) was used as the reference electrode, and a glassy carbon electrode (rotating disk electrode (RDE)) was used as the working electrode. Unless otherwise specified, all ORR measurements were performed in an oxygen-filled 0.1 M KOH aqueous solution, and all OER measurements were performed in a 1.0 M KOH aqueous solution. The reference electrode was HgO (1.0 M KOH) relative to the reversible hydrogen electrode potential (HgO in alkaline solution). The following equation was used for calibration of the HgO electrode (the standard electrode potential is 0.098V): ; Throughout the testing process, high-purity oxygen was continuously introduced to ensure an adequate oxygen supply. Oxygen (O2) was introduced into the electrolyte for at least 30 minutes before each test. The electrocatalytic activity of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) was determined using a PINE rotating disk electrode (RDE) apparatus. Before testing, the glassy carbon electrode was polished to a mirror finish and thoroughly cleaned. Then, to remove surface impurities and activate the electrode, 30 cyclic voltammetry (CV) pre-scans were performed before testing. The CV curve was measured at a scan rate of 10. The linear sweep voltammetry (LSV) curve was measured at a scan rate of 1600 rpm and a rotation speed of 1600 rpm. For the oxygen reduction reaction (ORR), the onset potential (E) was... onset A current density of -0.1 mA / cm² is defined as a current density of -0.1 mA / cm². 2The potentials [1,2]. Impedance measurements were performed using a CHI 760E electrochemical workstation at a potential of 0.70 V (relative to RHE) in a frequency range of 100,000 Hz to 0.1 Hz. The double-layer capacitance (C0) was obtained by varying the scan rate within a non-Radial potential window (1.05–1.15 V (relative to RHE)). dl The ORR stability of the samples was obtained by constant current testing at 800 rpm and 0.6 V (relative to RHE) for 20,000 seconds in an oxygen-saturated 0.1 M KOH electrolyte. The OER stability test was performed using a chronopotentiometric method, with the potential range set between 1.4 and 2.5 V (relative to RHE) and the current density maintained at 10 mA / cm². 2 In the chronoamperometry test, 0.1M methanol was added to the electrolyte to test methanol tolerance.

[0072] The number of electrons transferred (n) in the redox reaction (OXR) at different electrode potentials was calculated using the Koutecký-Levich (KL) equation.

[0073] ; Where i is the measured current density, i K and i L These are the kinetic current density and the limiting current density, respectively, where n is the number of electrons transferred, and F is the Faraday constant. F =96485C / cm), k is the electron transfer rate constant, and C0 is the total concentration of O2 ( C 0 =1.2×10 -3 (mol / L), D0 is the diffusion coefficient of O2 (D0 = 1.9 × 10⁻⁶ mol / L). -5 In 0.1M KOH, v is the dynamic viscosity of the electrolyte (0.01 cm / s). 2 / s), where ω is the electrode rotation speed.

[0074] The methods for determining catalyst loading, mass activity (MA), and specific activity (SA) are as follows: The total catalyst loading on the glassy carbon electrode was maintained at 0.4 mg / cm³. 2 Given that the mass ratio of Co3O4 to Ag in the Co3O4 silver-based composite material is 2:3, the Ag loading is determined to be 0.24 mg / cm³. 2 .

[0075] C obtained by the cyclic voltammetry method within a non-Radaic potential window dl The value was used to estimate the electrochemically active surface area (ECSA). The formula for calculating ECSA is: ECSA = C dl / C s Among them, for the analysis related to ORR, the specific capacitance (C) will be used. s The value is taken as 0.035 mF / cm. 2 (representing a smooth Ag surface), and for the analysis related to OER, the specific capacitance is taken as 0.040 mF / cm. 2 (Represents oxide surface).

[0076] For the oxygen reduction reaction (ORR), the kinetic current density (J / L) was first derived from the measured current at 0.80 V relative to the RHE using the Koutecký-Levich equation. k ): J k =(J×J lim ) / (J lim –J). Then calculate the mass activity, MA. Ag,ORR =J k / 0.24mg / cm 2 By normalizing the kinetic current to the specific surface area (ECSA), the specific activity is obtained: SA ORR =J k / ECSA.

[0077] For the OER, since mass transport limitations are negligible, the total current density (J) was directly used for activity normalization at a potential of 1.63V. The mass activity of the OER was calculated as MA. Ag,OER =J / 0.24mg / cm 2 The specific activity of SA OER =J / ECSA.

[0078] 3) Zinc-air battery test: The zinc-air battery (ZAB) uses a 0.6 mm thick zinc plate as the anode and the Co3O4 silver-based composite material prepared in Example 1 as the cathode catalyst. The electrolyte consists of a mixture of 6.0 M KOH and 0.2 M ZnAc2. For the air cathode, the Co3O4 silver-based composite material (4 mg), XC-72R (1 mg), and 5 wt% Nafion solution (20 μL) were first uniformly dispersed in ethanol (480 μL) to form a homogeneous ink. The resulting ink was then drop-coated onto an electrode composite substrate (carbon paper, waterproof and breathable membrane, nickel foam), with a Co3O4 silver-based composite material loading of 3... The resulting electrode was then dried overnight at 60°C to ensure complete solvent evaporation and film stability. For comparison, the Co3O4 silver-based composite material was replaced with a commercial platinum-carbon and RuO2 noble metal catalyst to prepare a mixed air cathode composed of platinum-carbon and RuO2 (mass ratio 1:1). The electrochemical performance tests of ZABs in this invention were all performed using a CS 300M electrochemical workstation.

[0079] 4) Material characterization: Figure 1 The diagram shows the synthetic route of the Co3O4 silver-based composite material and the characterization diagrams of Co3O4, Co(OH)2, CoOOH, Ag NPs and the Co3O4 silver-based composite material. Among them, a is the synthetic route of the Co3O4 silver-based composite material, b is the XRD diffraction pattern of Co3O4, Co(OH)2, CoOOH and the Co3O4 silver-based composite material, c is the XRD diffraction pattern of Ag NPs and the Co3O4 silver-based composite material, and d is a partial XRD image of c.

[0080] The preparation process of Co3O4 silver-based composite material is as follows: Figure 1 As shown in a. This invention uses Co(NO3)2 and ammonia as starting materials to synthesize a blue suspension of Co(OH)2 via direct precipitation. Next, H2O2 is added dropwise to the suspension while continuously stirring. Co(OH)2 gradually oxidizes to form brown CoOOH. Then, AgNO3 is uniformly dispersed in the CoOOH powder, forming a precursor through a solid-state reaction. Finally, the prepared precursor is heat-treated under a N2 atmosphere, releasing water vapor and oxygen to obtain a Co3O4 silver-based composite material.

[0081] The crystal structure and phase composition of the materials prepared in Example 1 and Comparative Examples 1-3 were characterized by XRD, and the results are as follows: Figure 1 As shown in b. According to Figure 1As shown in b, the diffraction peaks of Co(OH)2 at 19.1°, 32.6°, 38.1°, and 51.6° correspond to the (001), (100), (101), and (102) crystal planes of JCPDS No. 30-0443, confirming that it is Co(OH)2. The diffraction peaks at 20.0°, 38.9°, and 65.1° can be attributed to the (003), (012), and (110) crystal planes of CoOOH, as shown in the card index of JCPDS No. 07-0169. The diffraction peaks at 37.1°, 59.1°, and 65.3° are attributed to the (311), (511), and (440) crystal planes of Co3O4, respectively. These results are in excellent agreement with the standard database (JCPDS No. 42-1467), confirming that Co3O4 has a spinel structure. For the Co3O4 silver-based composite material, the diffraction peaks at 31.4°, 36.9°, and 59.2° can be attributed to the (220), (311), and (511) characteristic crystal planes of Co3O4; meanwhile, the diffraction peaks observed at 38.3°, 44.4°, 64.6°, and 77.5° are consistent with the (111), (200), (220), and (311) characteristic crystal planes of Ag, respectively (JCPDS No. 04-0783). These results confirm the coexistence of Ag nanoparticles and Co3O4 nanoparticles in the Co3O4 silver-based composite material. XRD results confirm the successful synthesis of the Co3O4 silver-based composite material.

[0082] To further confirm the existence of the Co3O4 silver-based composite material, this test example compares the Co3O4 silver-based composite material with pure Ag nanoparticles and AgCoO2 prepared in Comparative Example 4. The results are as follows: Figure 1 As shown in c in the diagram. According to... Figure 1 As can be seen from c, the diffraction peaks of Ag nanoparticles at 38.2°, 44.4°, 64.5°, and 77.4° correspond to the (111), (200), (220), and (311) crystal planes of JCPDS No. 04-0783, respectively. The absence of impurity peaks confirms that the sample is pure Ag nanoparticles. The diffraction peaks at 29.4°, 37.5°, 41.7°, and 65.3° correspond to the (006), (012), (104), and (110) crystal planes of JCPDS No. 25-0761, respectively, confirming that the material is AgCoO2. This is because during heat treatment in an air atmosphere, the CoOOH-Ag NPs precursor is converted to AgCoO2. Among them, Ag is oxidized to Ag in the presence of O2 in the air. + This helps stabilize Co 3+ In CoOOH. Subsequently, Ag + With Co 3+The reaction forms layered AgCoO2, and the specific reaction process is shown in the following equation: .

[0083] When the CoOOH-Ag NPs precursor is heat-treated under a N2 atmosphere, a Co3O4 silver-based composite material is formed instead of AgCoO2. In this composite material, Ag is present in Ag... 0 Its valence state is chemically inert, therefore it does not participate in chemical reactions. CoOOH dehydrates and is reduced to form Co3O4 with a spinel structure (where Co... 2+ and Co 3+ (Coexistence). For Co 2+ The stable existence of [something] requires a continuously hypoxic environment. The specific reaction process is shown in the following equation: .

[0084] The Co3O4 silver-based composite material not only exhibits diffraction peaks of Ag, but also diffraction peaks attributed to Co3O4. For clearer observation, Figure 1 A magnified view of part c is presented in Figure 1 Two diffraction peaks were clearly identified at 31.4° and 36.9°, corresponding to the (220) and (311) crystal planes of Co3O4, respectively. No diffraction peaks corresponding to Co3O4 were detected in pure Ag nanoparticles. These results further confirm the successful synthesis of the Co3O4 silver-based composite material.

[0085] Figure 2 Images are electron micrographs of Co3O4 and Co3O4-silver composite materials; where a is a scanning electron microscope image of Co3O4, b is a scanning electron microscope image of Co3O4-silver composite material, c is a TEM image of Co3O4, d is a TEM image of Co3O4-silver composite material, e is a high-resolution transmission electron microscope image of Co3O4, f is a high-resolution transmission electron microscope image of Co3O4-silver composite material, g is a scanning transmission electron microscope image of Co3O4-silver composite material; h~j are elemental distribution maps of Co, O, and Ag in Co3O4-silver composite materials.

[0086] according to Figure 2 As can be seen from 'a', Co3O4 exhibits a rough and fragmented surface morphology, which is due to the aggregation of numerous nanocrystals. This structural transformation is attributed to the collapse of the original morphology of the CoOOH precursor during prolonged heat treatment. EDS results show that the atomic ratio of Co to O is ~3:4, consistent with theoretical expectations (e.g., Figure 8 (As shown).

[0087] according to Figure 2As can be seen from b, unlike pure Co3O4, the Co3O4 silver-based composite material not only exhibits an aggregated Co3O4 structure, but also reveals the presence of large-sized Ag nanoparticles. Figure 9 The SEM-EDS analysis of the Co3O4 silver-based composite material is shown. Figure 9 It can be seen that the elements exhibit a uniform distribution, with the mass ratio of Co3O4 to Ag being ~2:3.

[0088] according to Figure 2 c and Figure 10 As can be seen from Figure a, the results of transmission electron microscopy (TEM) further confirm that Co3O4 is composed of aggregated nanocrystal particles with an average diameter of ~4.63 nm.

[0089] according to Figure 2 d, Figure 10 b and Figure 11 As can be seen in the TEM image of the Co3O4 silver-based composite material, Ag exists in the form of nanoparticles with an average diameter of ~28.06 nm, and many Co3O4 nanocrystals are dispersed around the embedded Ag NPs. The surface Co3O4 nanocrystals help to increase the specific surface area of ​​Ag NPs, thereby enhancing the electrocatalytic activity.

[0090] Figure 2 China and Figure 2 The images shown in Figure 1 are high-resolution transmission electron microscopy (HRTEM) images of Co3O4 and Co3O4 silver-based composite materials. Figure 2 The middle e shows distinct lattice fringes with interplanar spacings of 0.23 nm and 0.28 nm, corresponding to the (222) and (220) crystal planes of Co3O4, respectively; Figure 2 Clear lattice fringes were observed in the sample, with interplanar spacings of 0.24 nm and 0.20 nm, corresponding to the (311) crystal plane of Co3O4 and the (200) crystal plane of Ag, respectively. These results are consistent with the XRD results, indicating that the Co3O4 silver-based composite material consists of two phases: Co3O4 and Ag.

[0091] according to Figure 2 g~j and Figure 12 The elemental distribution diagram shows that Co and O elements exhibit a relatively uniform distribution in the Co3O4 silver-based composite material, while Ag elements appear to be more concentrated. This observation further supports the conclusion that the Co3O4 silver-based composite material is composed of Ag nanoparticles embedded in the Co3O4 matrix.

[0092] Figure 3The images show the spectra, N2 adsorption-desorption isotherms, pore size distributions, TGA and corresponding DTG curves of Co3O4, Ag NPs, and Co3O4 silver-based composites. Specifically, a is the high-resolution XPS spectrum of Co 2p for Co3O4 and Co3O4 silver-based composites; b is the high-resolution XPS spectrum of O 1s for Co3O4 and Co3O4 silver-based composites; c is the high-resolution XPS spectrum of Ag 3d for Ag NPs and Co3O4 silver-based composites; and d is the high-resolution XPS spectrum of Co 2p for Co3O4 and Co3O4 silver-based composites. 2+ and Co 3+ Proportion and O vac and O lat The proportions are as follows: e represents the EPR spectrum of the Co3O4 silver-based composite material and the physical mixture of Co3O4 and Ag NPs; f represents the N2 adsorption-desorption isotherm of Co3O4, Ag NPs and Co3O4 silver-based composite material; the inset is a pore size distribution diagram; g represents the Raman spectrum of Co3O4 and Co3O4 silver-based composite material; h represents the TGA curve of Co3O4 and Co3O4 silver-based composite material measured under N2 flow; and i represents the DTG curve corresponding to the TGA curve.

[0093] Table 1. Surface fractions of Co and O elements obtained from XPS spectral analysis

[0094] The valence states of various elements on the surface of the Co3O4 silver-based composite material were analyzed by XPS spectroscopy, and the results are as follows: Figure 3 As shown in Figure a. According to... Figure 3 As can be seen from a, the high-resolution Co 2p spectra of Co3O4 and Co3O4 silver-based composite materials exhibit two spin orbital peaks, corresponding to... and Among them, those located near 780.2 eV The peak can be decomposed into two peaks, corresponding to Co at ~781.9 eV. 2+ and ~780.0 eV of Co 3+ Similarly, located near 795.5 eV The peak can be decomposed into two peaks, attributed to Co at ~797.2 eV. 2+ and ~795.2 eV of Co 3+ Furthermore, two weak satellite peaks were observed at binding energies of approximately 786.4 eV and 804.5 eV, indicating that Co... 2+ and Co 3+ Cations coexist on the surface of both Co3O4 and the Co3O4 silver-based composite material; furthermore, the Co3O4 silver-based composite material was also clearly observed to have... and The orbital peak shifted by 0.5 eV relative to pure Co3O4 towards a lower binding energy direction. This negative shift in binding energy indicates that the electronic structure of the material has been optimized, which is beneficial to the rate of interfacial catalytic reactions. This negative shift can be attributed to the electronic effect generated by the strong interaction at the interface between the Co3O4 nanocrystals and Ag NPs. This interaction leads to the transfer of electrons from Ag NPs to Co3O4 until a new equilibrium state is established. Due to electron loss, the oxidation state of Ag NPs increases, while the large amount of Co in Co3O4... 3+ It is reduced to Co through electronic gain. 2+ , Figure 3 The data in d and Table 1 confirm this observation; by comparing the areas under the corresponding fitted peaks, the Co content of different sample surfaces was determined. 2+ and Co 3+ Atomic ratio, the results show that the Co in the Co3O4 silver-based composite material 2+ and Co 3+ The proportion (1.12) was higher than that of pure Co3O4 (0.82), indicating that Co... 2+ The presence of species on the surface of Co3O4 silver-based composite materials is more abundant, providing direct evidence for interfacial electron transfer. The redistribution of electrons ultimately leads to the formation of regions with opposite charges on both sides, thereby enhancing interfacial electron conduction and improving catalytic activity. Furthermore, Co... 2+ The elevated Co content, considered a major active site for OER, was observed in Co3O4 silver-based composites. 2+ and Co 3+ The ratio can further enhance its catalytic performance.

[0095] like Figure 3 As shown in b, the high-resolution O 1s spectrum can be decomposed into three different peaks, corresponding to lattice oxygen (O) and lattice oxygen (O). lat ), oxygen vacancy (O vac ) and surface-adsorbed oxygen-containing species (O sur The values ​​are located at 530.2 eV, 531.6 eV, and 532.7 eV, respectively; according to the principle of electroneutrality, the Co in the sample... 2+ The increased content means that more oxygen vacancies are needed to maintain charge balance. Therefore, it can be inferred that the Co3O4 silver-based composite material has a richer abundance of oxygen vacancies than Co3O4. Figure 3 The data in d and Table 1 confirm this observation; the O of the sample vac and O lat The proportion is determined through further analysis. Figure 3 The peak area shown in b is used to derive the following results: O in the Co3O4 silver-based composite material. vac and O latThe ratio is 1.27, which is significantly higher than that of Co3O4 (0.71). This indicates that the heterostructure of the Co3O4 silver-based composite material can further activate lattice oxygen, thereby generating more surface oxygen vacancies. It is generally believed that oxygen vacancies can not only regulate the electronic structure of the material surface, thereby improving its adsorption capacity for various oxygen-containing intermediates, but also enhance the electrical conductivity of metal oxides and create additional active sites in ORR and OER processes, thereby promoting oxygen activation. Therefore, the increase of oxygen vacancies is beneficial to improving the bifunctional oxygen electrocatalytic performance of the Co3O4 silver-based composite material. In addition, it can be clearly observed that compared with pure Co3O4, the O 1s peak of the Co3O4 silver-based composite material shifts towards a lower binding energy direction. This phenomenon can be attributed to the regulatory effect of oxygen vacancies on the electron density and chemical potential of surface oxygen species in the following process: AgNPs, as electron donors, transfer valence electrons to Co3O4 nanocrystals; that is, the increase in the concentration of positively charged oxygen vacancies can also attract electrons, thereby enhancing the electron cloud density of adjacent lattice oxygen, ultimately leading to the negative shift of the O 1s peak.

[0096] Figure 3 Figure 'c' shows the XPS high-resolution spectrum of Ag in the Co3O4 silver-based composite material. Two distinct characteristic peaks were observed at approximately 368.2 eV and 374.2 eV, corresponding to... and The orbitals; furthermore, they can be deconvolved into four peaks, among which the dominant peaks at approximately 781.4 eV and 780.0 eV can be attributed to Ag. 0 The species, and the shoulder peaks at approximately 796.4 eV and 795.0 eV indicate Ag + This is consistent with the XRD results, further confirming that silver ions were effectively reduced to metallic silver during the solid-state reaction; Ag + The presence of this material may be due to the strong interaction between the Co3O4 nanocrystals and the Ag NPs support; furthermore, compared with the bare Ag NPs sample, the Co3O4 silver-based composite material exhibits [significantly different properties]. and The shift of the peak towards higher binding energies further confirms the electronic effect between Co3O4 and Ag NPs, resulting from the strong interaction between these two components. Due to the difference in work function and electron affinity between Co3O4 and Ag, directional electron transfer occurs from Ag NPs to Co3O4, providing strong evidence for a robust interfacial contact between the Co3O4 nanocrystals and the Ag NPs support. In fact, the directional electron transfer specifically alters the electronic structure of the Ag NPs surface, enhancing the intrinsic activity of the active sites and thus optimizing the performance of the adsorption reaction intermediates. This modification increases the sensitivity of Ag NPs to the reaction and promotes the generation of more reactive oxygen species.

[0097] For oxygen vacancies (O vac The density of ) was further quantified in this invention using electron paramagnetic resonance (EPR) analysis, and the results are as follows: Figure 3 As shown in e, the Co3O4 silver-based composite exhibits a more pronounced EPR signal than the physical mixture of Co3O4 and Ag NPs, which can be attributed to the Zeeman effect caused by unpaired single electrons trapped at surface oxygen vacancies; the above EPR results indicate that the oxygen vacancy concentration of the Co3O4 silver-based composite is relatively high, which is consistent with the XPS results.

[0098] The N2 adsorption-desorption isotherms and pore size distribution curves of the above samples were measured, and the results are as follows: Figure 3 As shown in f in the figure. According to Figure 3 As can be seen from f, the Co3O4 silver-based composite material exhibits a type IV isotherm and a significant type H3 hysteresis loop in the relatively high-pressure region, indicating the presence of a mesoporous structure; according to Figure 3 As shown in the inset of Figure f, the Co3O4 silver-based composite material exhibits a clear peak in pore size distribution within the range of 2–50 nm; according to the BJH method, the average pore size of the Co3O4 silver-based composite material is calculated to be 10.51 nm; furthermore, the specific surface areas of AgNPs, the Co3O4 silver-based composite material, and the physical mixture of Co3O4 and AgNPs, calculated by the BET method, are 1.24 47.62 and 45.53 Among them, the Co3O4 silver-based composite material exhibits the highest specific surface area. This open porous structure not only exposes more catalytic active sites, but also promotes efficient mass transfer and diffusion.

[0099] To further investigate the interfacial interaction between Co3O4 and Ag NPs, Raman scattering spectroscopy was used for analysis, and the results are as follows: Figure 3 As shown in g. According to Figure 3Five distinct Raman characteristic peaks can be observed in g, located at 177 cm⁻¹. -1 461cm -1 501cm -1 598cm -1 and 665cm -1 , respectively corresponding to the F of spinel Co3O4 2g 1 E g F 2g 2 F 2g 3 and A g 1 Phonon mode; where, located at 177cm -1 and 665cm -1 The peaks are attributed to Co, respectively. 2+ -O 2- and Co 3+ -O 2- Raman vibrations of the bond; notably, compared with Co3O4, the Raman peak of the Co3O4 silver-based composite material shows a significant blue shift, which can be attributed to the electron transfer of Ag NPs to Co3O4, which increases the local electron density and thus increases the lattice vibration frequency of the Co-O bond; this result is consistent with the XPS results and further confirms the significant electronic coupling effect at the interface of the Co3O4 silver-based composite material.

[0100] To test the thermal stability of Co3O4 silver-based composites and the interactions between their components, thermogravimetric analysis (TGA) was performed on Co3O4 and Co3O4 silver-based composites. The results are as follows: Figure 3 As shown by h in the diagram. According to... Figure 3As can be seen from the h values, both samples exhibit slight mass loss below 550°C, attributed to the desorption of physically adsorbed water and surface hydroxyl groups. This phenomenon is related to the material's inherently large specific surface area and its abundant surface unsaturated bonds and oxygen vacancies. For the pure Co3O4 sample, a significant mass loss step (5.95 wt%) was observed in the temperature range of 780–890°C, corresponding to its unique decomposition into CoO. Furthermore, in the high-temperature region, the actual mass loss of Co3O4 was adjusted, resulting in a loss of 6.28%, which is consistent with... The result is consistent with the theoretical value (6.65%) of spinel Co3O4 decomposition, further confirming the successful synthesis of the Co3O4 sample. In the Co3O4 silver-based composite, the mass loss associated with this decomposition step is reduced to 2.51 wt%. Based on the theoretical mass loss from the decomposition of pure Co3O4, the calculated mass fraction of Co3O4 in the Co3O4 silver-based composite is approximately 42.2 wt%, indicating an Ag content of approximately 57.8 wt%, consistent with EDS results. Notably, the kinetic behavior of the Co3O4 silver-based composite has changed significantly, such as... Figure 4 As shown in Figure i, the differential thermogravimetric analysis (DTG) peak temperature of pure Co3O4 decomposition is located at 871 degrees Celsius, while in the Co3O4 silver-based composite material, this peak shifts forward to 854 degrees Celsius. The decrease in decomposition temperature indicates that lattice oxygen is more easily released in the Co3O4 silver-based composite material, which can be attributed to the strong electronic interactions at the interface of the Co3O4 silver-based composite material, consistent with the XPS analysis results. The effective electron transfer from Ag NPs to Co3O4 weakens the Co-O bond, thereby reducing the activation energy of Co3O4 decomposition. These quantitative compositional data and the observed changes in thermal stability demonstrate that the present invention successfully constructs a Co3O4 silver-based composite material with strong electronic interactions.

[0101] Figure 4 The ORR catalytic performance characterization results are shown for Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs; where a represents the ORR catalytic performance of Co3O4 and Ag NPs in O2. 2- Saturated and N 2- In a saturated 0.1M KOH solution at 50 Cyclic voltammetry (CV) curves of Co3O4, Co3O4 silver-based composite, commercial platinum-carbon, and RuO2 noble metal catalysts were obtained by scanning rate measurement; b represents the cyclic voltammetry (CV) curves of Co3O4, Co3O4 silver-based composite, commercial platinum-carbon, and RuO2 noble metal catalysts at O2 scanning rate. 2-Linear sweep voltammetry (LSV) curves of Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs were measured at 1600 rpm in a saturated 0.1 M KOH solution; c represents the ORR onset potential (@-0.1) of the physical mixtures of Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs. ), half-wave potential and limiting current density; d is the Tafel slope of Co3O4, Ag NPs, Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalyst, and physical mixture of Co3O4 and Ag NPs; e is the Koutecky-Levich (KL) curve of Co3O4 silver-based composite in the potential range of 0.2~0.5V, and the inset in e shows the LSV curve of Co3O4 silver-based composite at speeds of 400~2025rpm; f is the electron transfer number of Co3O4, Ag NPs, Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalyst, and physical mixture of Co3O4 and Ag NPs; g is the coefficient of mass transfer of Co3O4, Ag NPs, Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalyst, and physical mixture of Co3O4 and Ag NPs. Double-layer capacitance curves of the NPs physical mixture; h represents the methanol permeation results of the Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalysts; i represents the current-time (it) galvanostatic response of the Co3O4 silver-based composite, commercial platinum-carbon and RuO2 noble metal catalysts.

[0102] The electrocatalytic performance of the oxygen reduction reaction of the above samples was systematically evaluated using rotating disk electrode (RDE) technology in a 0.1M KOH electrolyte, which was saturated with O2 and N2, respectively.

[0103] Table 2. Catalytic performance of samples in 0.1M KOH at 1600 rpm and ORR.

[0104] Cyclic voltammetry curves for Co3O4, Co3O4-silver composite materials, commercial platinum-carbon, and RuO2 noble metal catalysts are shown below. Figure 4 As shown in a, according to Figure 4As can be seen from 'a', no significant redox peaks were observed in any sample in the N2-saturated KOH electrolyte, while the redox peaks were obvious in the O2-saturated electrolyte: the Co3O4 silver-based composite material showed a significant reduction peak at 0.72 V, which was closer to the reduction peak of the commercial platinum-carbon (0.85 V) catalyst, while the reduction peak of Co3O4 (0.65 V) was lower, indicating that the Co3O4 silver-based composite material improved the catalytic activity.

[0105] To further verify this observation, at a scan rate of 10 Under these conditions, linear sweep voltammetry (LSV) curves were measured for Co3O4, Ag NPs, Co3O4-silver composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs. The results are as follows: Figure 4 As shown in b. According to Figure 4 As can be seen from b, the Co3O4 silver-based composite material exhibits superior ORR performance compared to physical mixtures of Ag NPs, Co3O4, and Co3O4 and Ag NPs, with correspondingly lower onset potentials (E). onset ), half-wave potential ( ) and limiting current density (J Lim Value summary in Figure 4 In Tables c and 2; under oxygen saturation conditions, the J values ​​of Ag NPs, Co3O4, Co3O4 silver-based composites, physical mixtures of Co3O4 and Ag NPs, commercial platinum-carbon and RuO2 noble metal catalysts were compared. Lim The values ​​were measured as -3.1. -3.9 -4.6 -4.4 and -5.4 J of Co3O4 silver-based composite materials Lim The high J value can be attributed to its large BET specific surface area, which not only reduces mass transfer resistance but also promotes rapid transport of reactants and enhances oxygen diffusion; in practical applications, it maintains a high J value during continuous high-power output operation. Lim This helps maintain efficient response and mitigate performance degradation due to mass transfer limitations, a factor crucial for improving the dynamic response and stability of the equipment. (Corrected E) onset This typically indicates that the catalyst possesses higher intrinsic activity and a more favorable thermodynamic driving force, which is one of the key indicators for evaluating ORR catalyst performance. For example... Figure 13 c and Figure 4 As shown in a, compared with Ag NPs (0.86V), Co3O4 (0.82V), and a physical mixture of Co3O4 and Ag NPs (0.90V), the E of the Co3O4 silver-based composite material is...onset The positive E value (0.93V) is closer to that of commercial platinum-carbon and RuO2 noble metal catalysts (0.96V) and 20wt% platinum-carbon catalysts (1.01V), and the positive E value of the Co3O4 silver-based composite material is also closer. onset The high value is mainly attributed to the high concentration of oxygen vacancies on its surface (which promotes O2 adsorption), reduced charge transfer resistance (intercalated Ag NPs provide an efficient and stable electron transfer pathway for the reaction), and robust TMO support interactions (which promote intermediates such as -OOH, -O, and -OH). However, E onset This only represents the characteristics of the initial stage of the reaction. To more accurately assess the overall catalytic activity of the material, further... The analysis clearly shows that the half-wave potential (0.75 V) of the Co3O4 silver-based composite is closer to that of commercial platinum-carbon and RuO2 noble metal catalysts (0.81 V) and state-of-the-art 20 wt% platinum-carbon catalysts (0.86 V) than that of Ag NPs (0.70 V), Co3O4 (0.65 V), and physical mixtures of Co3O4 and Ag NPs (0.68 V). This indicates that the Co3O4 silver-based composite exhibits excellent electrocatalytic activity in oxygen reduction, which is mainly attributed to the robust interaction between Ag NPs and Co3O4, where Ag NPs act as conductive channels in the composite, providing Co 2+ and Co 3+ The redox pair improved the overall ORR activity.

[0106] The excellent ORR electrocatalytic activity of the Co3O4 silver-based composite material was further confirmed by Tafel curve analysis, as shown in the results. Figure 4 The values ​​of d and Table 3 are shown in the table.

[0107] Table 3. Catalytic activity of Co3O4 silver-based composite materials

[0108] according to Figure 4 As can be seen from d in Table 3, the Co3O4 silver-based composite material (132.2) The Tafel slope of is less than that of Ag NPs (148.7). ), Co3O4 (737.4) A physical mixture of Co3O4 and Ag NPs (140.1) It is closer to commercial platinum-carbon and RuO2 precious metal catalysts (89.9%). This indicates that the Co3O4 silver-based composite material exhibits excellent kinetic properties as an electrocatalyst and effectively enhances the oxygen reduction reaction. This is likely due to the introduction of Co3O4, which increases the oxygen adsorption affinity on the Ag NP surface, lowers the activation energy for O2 adsorption and OO bond breaking, and significantly reduces the energy barrier for rate-determining steps (e.g., the formation or dissociation of -OOH). It is worth noting that commercial platinum-carbon and RuO2 noble metal catalysts are widely used benchmark systems for evaluating the performance of bifunctional oxygen electrocatalysis. However, since RuO2 exhibits negligible activity for the oxygen reduction reaction, its introduction inevitably increases the Tafel slope; the measured Tafel slope for commercial platinum-carbon and RuO2 noble metal catalysts is 89.9%. .

[0109] Low Tafel slopes are typically associated with efficient four-electron reaction pathways. To further elucidate the ORR kinetics of different samples, the linear sweep voltammetry (LSV) curves of the aforementioned samples were measured at various rotational speeds, and the results are as follows: Figure 10 e and Figure 4 As shown. According to Figure 10 e and Figure 4 It can be seen that J Lim The ORR increases with increasing rotational speed, a trend that can be attributed to accelerated mass transfer processes and reduced oxygen diffusion distance. Furthermore, the Koutecky-Levich curves at different potentials show a nearly parallel linear relationship, indicating that the ORR of all samples follows first-order reaction kinetics.

[0110] Based on the KL curve, the number of electrons transferred (n) in the sample with a potential range of 0.2~0.5V was further determined, and the results are as follows: Figure 14 f and Figure 15 As shown, the n-value of the Co3O4 silver-based composite (4.03) is almost the same as that of the commercial platinum-carbon and RuO2 noble metal catalyst (4.04), indicating that in the oxygen reduction reaction, the Co3O4 silver-based composite, like the commercial platinum-carbon and RuO2 noble metal catalyst, mainly follows a four-electron reaction pathway, which is beneficial for achieving high energy conversion efficiency. For comparison, the n-values ​​of Ag NPs, Co3O4, and the physical mixture of Co3O4 and Ag NPs are 2.66, 3.19, and 3.47, respectively. Notably, some two-electron reactions occur, resulting in lower selectivity for these materials compared to the Co3O4 silver-based composite. This suggests that the synergistic effect between Ag and Co3O4 can promote the decomposition of O2 into OH- while mitigating the accumulation of H2O2. Furthermore, Table 4 systematically compares the kinetic performance of the Co3O4 silver-based composite with recently reported bifunctional electrocatalysts in ORR, covering E onset , Jlim Key parameters include Tafel slope and n.

[0111] Table 4. Comparison of ORR kinetic parameters of Co3O4 silver-based composite material with those of reported bifunctional electrocatalysts

[0112] The sources of the reported materials are as follows (Tables 4-6): [1] Material reported from Zhang Z, Xing Z, Luo X, Cheng C, Liu X. Denselypopulated macrocyclic dicobalt sites in ladder polymers for low-overpotentialoxygen reduction catalysis. Nature Communications. 2025;16:921; [2] The material is reported from Retuerto M, Calle-Vallejo F, Pascual L, Lumbeeck G, Fernandez-Diaz MT, Croft M, et al. La 1.5 Sr 0.5 NiMn 0.5 Ru 0.5 O6 Double Perovskite with Enhanced ORR / OER Bifunctional Catalytic Activity. ACS Applied Materials& Interfaces. 2019;11:21454–64; [3] Material reported from Li T, Wang Z, Wang L, Wang M, Liu YQ. Nd and Ni Co-doped spinel Co3O4 nanosheet as an effective electrocatalyst for oxygenevolution reaction. Applied Catalysis B: Environment and Energy. 2024;352:123990; [4] Materials reported in Fu L, Yao Y, Ma J, Zhang Z, Wang G, Wei W. Nanoflower-like NiCo2O4 Composite Graphene Oxide as a Bifunctional Catalyst for Zinc-AirBattery Cathode. Langmuir. 2024;40:6990–7000; [5] Materials reported in Behera A, Seth D, Agarwal M, Haider MA, BhattacharyyaAJ. Exploring Cu-Doped Co3O4 Bifunctional Oxygen Electrocatalysts for AqueousZn-Air Batteries. ACS Applied Materials & Interfaces. 2024;16:17574–86; [6] Materials reported in Yuan B, Zou J, Jian J, Wang J, Xu H, Zhang X, et al.Promoting the bifunctional oxygen catalytic activity of the perovskite andCo3O4 heterostructure by introducing oxygen vacancies. International Journalof Hydrogen Energy. 2024;80:801–9; [7] Materials reported in Chutia B, Patowary S, Misra A, Rao KN, Bharali P.Morphology Effect of Co3O4 Nanooctahedron in Boosting Oxygen Reduction andOxygen Evolution Reactions. Energy & Fuels. 2022;36:13863–72; [8] The material is reported from Xiao M, Sun H, Zhu F, Meng Y. Regulation of Co3O4 morphology via ionic liquid for efficient bifunctional electrocatalysts. Journal of Alloys and Compounds. 2024;970:172718; [9] The material is reported from Wang W, Chen J-Q, Tao Y-R, Zhu S-N, Zhang Y-X, Wu X-C. Flowerlike Ag-Supported Ce-Doped Mn3O4 Nanosheet Heterostructure for a Highly Efficient Oxygen Reduction Reaction: Roles of Metal Oxides in Ag Surface States. ACS Catalysis. 2019;9:3498–510;

[10] The material is reported from Retuerto M, Calle-Vallejo F, Pascual L, Lumbeeck G, Fernandez-Diaz MT, Croft M, et al. La 1.5 Sr 0.5 NiMn 0.5 Ru 0.5 O6 Double Perovskite with Enhanced ORR / OER Bifunctional Catalytic Activity. ACS Applied Materials & Interfaces. 2019;11:21454–64;

[11] The material is reported from Qin Q, Jang H, Wang Y, Zhang L, Li Z, Kim MG, et al. Gettering La Effect from La3IrO7 as a Highly Efficient Electrocatalyst for Oxygen Evolution Reaction in Acid Media. Advanced Energy Materials. 2020;11:2003561;

[12] The material is reported from Zheng X, Qin M, Ma S, Chen Y, Ning H, Yang R, et al. Strong Oxide-Support Interaction over IrO2 / V2O5 for Efficient pH-Universal Water Splitting. Advanced Science. 2022;9:e2104636;

[13] The material is reported from Zhang K, Liang X, Wang Y, Zou Y, Zhao X, Chen H, et al. Support-tuned iridium reconstruction with crystalline phase dominating acidic oxygen evolution. Nature Communications. 2025;16:8164;

[14] The material is reported from Cao X, Qin H, Zhang J, Chen X, Jiao L. Regulation of Oxide Pathway Mechanism for Sustainable Acidic Water Oxidation. Journal of the American Chemical Society. 2024;146:32049;

[15] The material is reported from Wei L, Wang J, Zhao Z, Yang X, Jiao S, Cao F, et al. Co / Co3O4 nanoparticles embedded into thin O-doped graphitic layer as bifunctional oxygen electrocatalysts for Zn-air batteries. Chemical Engineering Journal. 2022;427:130931;

[16] Material reported from Lu Q, Guo Y, Mao P, Liao K, Zou X, Dai J, et al. Richatomic interfaces between sub-1 nm RuOx clusters and porous Co3O4 nanosheets boost oxygen electrocatalysis bifunctionality for advanced Zn-air batteries. Energy Storage Materials. 2020;32:20-29.

[0113] Table 4 shows that the Co3O4 silver-based composite material exhibits excellent ORR performance and promotes a highly efficient four-electron transfer pathway. This enhanced catalytic activity is mainly attributed to the unique interfacial structure between Co3O4 and Ag nanoparticles, which induces strong electronic interactions and effectively modulates the concentration of oxygen vacancies and Co. 2+ and Co 3+ The ratio is adjusted to optimize the adsorption and desorption behavior of oxygen intermediates.

[0114] Electrochemical active surface area (ECSA) can be measured by electrochemical double-layer capacitance (C). dl Quantitative evaluation was performed, therefore, the present invention conducted cyclic voltammetry (e.g., in the non-Radida region) in the non-Radida region. Figure 4 (As shown) to test the system, and then C was calculated. dl It showed a linear correlation with ECSA, as shown in the results. Figure 4 As shown in g and Table 3. Figure 16 As can be seen from g in Table 3, the Co3O4 silver-based composite material (2.34 g / g) C dl The value is higher than Ag NPs (1.03). ), Co3O4 (1.19) A physical mixture of Co3O4 and Ag NPs (0.95) This indicates that the Co3O4 silver-based composite has a large ECSA, and that AgNPs and Co3O4 activate additional active sites at the interface, thereby enhancing the reaction kinetics. Figure 4 The Nyquist plot obtained from electrochemical impedance spectroscopy (EIS) is shown. The EIS curves were analyzed by fitting the equivalent circuit shown in the figure, where R... s W, R ctQ and Q represent the solution resistance between the electrolyte and the electrode, the Warburg impedance related to the diffusion process, the charge transfer resistance, and the phase-constant element, respectively. In the high-frequency region, the semi-circular diameter of the Co3O4 silver-based composite material is smaller than that of Co3O4, indicating that the charge transfer resistance (Rct) of the Co3O4 silver-based composite material is lower than that of Co3O4. This is one of the key factors that makes the Co3O4 silver-based composite material exhibit excellent electrocatalytic activity.

[0115] Figure 4 The value of 'h' in the figure represents the methanol tolerance test results obtained by the chronoamperometry (it) method, based on... Figure 4 As can be seen from h, at the instant of injection of 1.0M methanol, the commercial platinum-carbon and RuO2 noble metal catalyst electrodes exhibit significant current loss. In contrast, the response current of the Co3O4 silver-based composite electrode remains stable with negligible changes, indicating that the Co3O4 silver-based composite has excellent resistance to methanol permeation.

[0116] Stability is a key indicator for evaluating the application potential of catalysts. This invention evaluated the ORR durability of the samples using the chronoamperometry (it) method, and the results are as follows: Figure 4 As shown in i and Table 3. Figure 17 As shown in Figure 1 and Table 3, after a stability test of 20,000 seconds, the Co3O4 silver-based composite material retained 90.7% of its initial current density, exceeding the 87.2% retention rate of commercial platinum-carbon and RuO2 noble metal catalysts. The superior stability of the Co3O4 silver-based composite material can be attributed to its unique structural features. The spinel structure (AB2O4) of the Co3O4 supported on the surface itself possesses excellent mechanical strength, resisting structural collapse during the ORR process. In alkaline media, a stable CoOOH protective layer can rapidly form on the Co3O4 surface, effectively inhibiting Co... 3+ The dissolution trend is relatively small; generally, Co3O4 forms a stable protective shell around the Ag support, effectively preventing its aggregation or Ostwald maturation during long-term stability testing, which could otherwise occur due to the high surface energy of the nanoparticles; the four-electron transfer pathway in the Co3O4 silver-based composite material significantly reduces the generation of H2O2, mitigating the loss of active sites caused by H2O2 corrosion of the electrode during long-term durability testing, thereby improving the electrode's lifespan; compared with Ag NPs, the Co3O4 silver-based composite material has a larger specific surface area, which helps to improve mass transfer and diffusion efficiency, thereby mitigating local overpotentials caused by mass transfer limitations, and thus reducing structural stress.

[0117] To quantitatively assess the intrinsic activity of the catalyst and the utilization rate of silver, this invention further calculates the mass activity (MA). @Ag ) and specific activity (SAECSA ), the result is as follows Figure 17 As shown in a. According to Figure 17 As can be seen from 'a' in the figure, the kinetic current density (J) of the Co3O4 silver-based composite material is... k The higher J values ​​compared to Ag NPs indicate faster ORR kinetics; at 0.80 V vs. RHE, the J values ​​of the Co3O4 silver-based composite material are higher. k The value reached -1.55 , is Ag NPs (-0.42) The MA of the Co3O4 silver-based composite material is 3.7 times that of the silver-based composite material after normalization by the mass of silver. @Ag Up to 6.38 , approximately Ag NPs (1.05) 6 times (e.g.) Figure 5 (As shown in b), SA of Co3O4 silver-based composite material ECSA Value (0.023) It is also 1.6 times that of the latter (0.014). ), MA @Ag and SA ECSA The enhancement indicates that the strong interfacial interaction between Co3O4 and Ag NPs not only improves the catalytic efficiency per unit mass of silver (MA) @Ag Furthermore, it enhances the intrinsic catalytic activity of the active sites (SA). ECSA Furthermore, the Co3O4 silver-based composite material exhibits comparable mass activity and specific activity (as shown in Table 5) compared to other recently reported advanced silver-based and non-precious metal catalysts. This synergistic effect is the key reason for the excellent ORR performance of the Co3O4 silver-based composite material.

[0118] Figure 5 The ORR catalytic performance characterization results of Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, physical mixtures of Co3O4 and Ag NPs, and cobalt oxide-based catalysts are shown below. Specifically, a) is the linear sweep voltammetric curve of the OER for Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs; b) is the OER Tafel curve for Co3O4, Ag NPs, Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts, and physical mixtures of Co3O4 and Ag NPs; c) is the OER Tafel curve for Co3O4 silver-based composites, commercial platinum-carbon and RuO2 noble metal catalysts at 10... The galvanostatic potential curves at different current densities are shown in Figure d. d represents the galvanostatic potential curves of the Co3O4 silver-based composite material in a 1.0 M KOH electrolyte at different current densities. e represents the potential difference (ΔE) of the Co3O4 silver-based composite material. f represents a comparison of the bifunctional activities of the Co3O4 silver-based composite material with those of representative cobalt oxide-based catalysts reported in recent years.

[0119] In addition to its excellent ORR activity, Co3O4 silver-based composites also exhibit significant OER activity. Figure 13 a and Figure 13 Figure b shows the linear sweep voltammetric curves of the OER data obtained from the samples. The results indicate that the Co3O4 silver-based composite material exhibits the most outstanding OER electrocatalytic activity; furthermore, according to Figure 18 b in Figure 5 As shown in Table 2, at a current density of 10 At this time, the potential of the Co3O4 silver-based composite material (1.47V) was significantly lower than that of Ag NPs (1.71V), Co3O4 (1.55V), a physical mixture of Co3O4 and Ag NPs (1.49V), a commercial platinum-carbon and RuO2 noble metal catalyst (1.51V), and the OER catalyst RuO2 (1.49V). This indicates that the combination of Ag NPs and Co3O4 in this invention significantly improves the catalytic activity, and a lower overpotential is required to achieve the same current density. When the potential is set at 1.70V, the Co3O4 silver-based composite material (170.09V) exhibits significantly lower potential. The current density of is significantly higher than that of Ag NPs (8.94). ), Co3O4 (91.25) A physical mixture of Co3O4 and Ag NPs (118.51) ) and commercial platinum-carbon and RuO2 precious metal catalysts (105.63) This means that, at the same current density, the Co3O4 silver-based composite material requires a lower overpotential to drive the reaction, indicating that the combination of Ag and Co3O4 in this invention not only improves the electrocatalytic activity of OER but also improves energy utilization efficiency.

[0120] The OER kinetics of the sample were analyzed using Tafel curves, and the results are as follows: Figure 5 As shown in section b and Table 3. According to... Figure 19 As can be seen from Table b and Table 3, the Co3O4 silver-based composite material (33.4) ) and Ag NPs (185.2 ), Co3O4 (86.7) A physical mixture of Co3O4 and Ag NPs (42.6) ), commercial platinum-carbon and RuO2 precious metal catalysts (67.1) Compared to the Co3O4 silver-based composite, it exhibits the smallest Tafel slope; the above results indicate that the reaction kinetics of pure Ag are slower than those of Co3O4 silver-based composites, which can be mainly attributed to the relatively high energy barrier for OO bond formation in Ag and the lack of effective OO bond formation sites on its surface; compared to Co3O4 silver-based composites, the reaction kinetics of pure Co3O4 are relatively slower, mainly due to the inherently high charge transfer resistance and slow electron transfer rate of Co3O4; the synergistic combination of Ag and Co3O4 in this invention effectively overcomes the kinetic limitations of single-component catalysts; the Co3O4 silver-based composite exhibits excellent OER kinetic performance and achieves a significantly faster reaction rate.

[0121] To further reveal the nature of the catalyst, this invention calculates the mass activity (MA) based on Ag loading. @Ag ) and specific activity (SA ECSA ), the result is as follows Figure 19 a and Figure 19 As shown in b in the figure.

[0122] Table 5. Mass activity (MA) of Co3O4 silver-based composite material and reported catalysts Ag ) and specific activity (SA ECSA )

[0123] according to Figure 19 a and Figure 19 As can be seen from b in the figure, the MA of the Co3O4 silver-based composite material is... @Ag and SA ECSA The curve was significantly higher than that of Ag NPs throughout the entire test potential range; specifically, at a potential of 1.63V vs. RHE, the MA of the Co3O4 silver-based composite material was significantly higher. @Ag Reached 368.9 This is approximately Ag NPs (11.7). 32 times (e.g.) Figure 5 (as shown in c); This indicates that the combination of Co3O4 and Ag NPs in this invention significantly improves the utilization rate of noble metals; at the same time, the SA of the Co3O4 silver-based composite material... ECSA (1.51) It is also much higher than Ag NPs (0.18). This confirms that Ag itself has very low OER catalytic activity in the Co3O4 silver-based composite material, indicating that Ag is not an active site for OER. The superior OER performance of the Co3O4 silver-based composite material can be attributed to the strong interactions at their interface, which increases the oxygen vacancy concentration on the Co3O4 surface and optimizes the OER of Co. 2+ and Co 3+ The ratio of these components increases the intrinsic activity of the Co3O4 active sites. Notably, compared to many advanced catalysts already reported, the Co3O4 silver-based composite catalyst also exhibits good mass activity and specific activity (as shown in Table 5), which is attributed to the unique interfacial interactions of the Co3O4 silver-based composite.

[0124] Long-term stability is crucial for the practical application of catalysts. At 10 Electrochemical impedance spectroscopy was performed on electrodes prepared from Co3O4 silver-based composite materials and commercial platinum-carbon and RuO2 noble metal catalysts at a current density of [value missing]. The results are as follows: Figure 5 As shown in c in the figure and in Table 3. Figure 5 As can be seen from c in Table 3, the commercial platinum-carbon and RuO2 noble metal catalysts reached a cutoff voltage of 2.5V after 25,840 seconds of operation, thus almost completely losing their catalytic activity; in contrast, the Co3O4 silver-based composite material showed a potential decrease of only 0.01V after 40,000 seconds of continuous operation.

[0125] The OER performance of the Co3O4 silver-based composite material was further compared with that of several reported high-performance electrocatalysts, as shown in Table 6.

[0126] Table 6. OER parameters of Co3O4 silver-based composite material and reported catalysts under 1.0 M KOH conditions.

[0127] As shown in Table 6, compared with recently reported high-performance electrocatalysts, the Co3O4 silver-based composite material exhibits superior performance at 10... The resulting structure exhibits a lower potential, a smaller Tafel slope, and superior stability. This enhanced kinetic behavior and excellent stability can be attributed to the strong interfacial interaction between Co3O4 and Ag NPs. This interaction effectively modulates the concentration of oxygen vacancies and optimizes the Co content. 2+ and Co 3+ The proportion, thereby promoting the rate-determining step in the OER pathway.

[0128] Furthermore, the OER stability of the Co3O4 silver-based composite electrode was evaluated over a 7-hour period at different current densities, and the results are as follows: Figure 5 As shown by d in the diagram. According to... Figure 5As can be seen from d, the voltage of the Co3O4 silver-based composite electrode increases with increasing current density (10). 20 40 and 80 The voltage increases (1.51V, 1.62V, 1.71V, and 1.81V) as the current density decreases (80V). 40 20 and 10 The voltage decreased (1.81V, 1.72V, 1.64V and 1.59V), ultimately decreasing by 0.08V relative to the initial potential.

[0129] All the above results demonstrate that the Co3O4 silver-based composite exhibits superior OER stability compared to commercial noble metal catalysts. This can be attributed to the synergistic effect between Co3O4 and Ag. In this invention, Ag NPs are embedded in Co3O4 nanocrystals, effectively suppressing the migration, aggregation, and oxidation of Ag at high potentials, thereby maintaining the stability of the active interface. At the same time, the high conductivity of Ag NPs alleviates local polarization, thus preventing material corrosion caused by non-uniform charge density. The high specific surface area of ​​the Co3O4 silver-based composite also promotes effective mass transfer and diffusion, thereby reducing the decrease in electrode stability caused by concentration polarization.

[0130] To further evaluate and compare the bifunctional oxygen electrocatalytic activity of different samples, the OER (E0) was calculated. j =10 ) and ORR ( The potential difference (ΔE) between them OER-ORR ), ΔE OER-ORR The lower the value, the more favorable the sample's bifunctional catalytic performance for both ORR and OER, as shown in the results. Figure 5 As shown in e and Table 2. According to Figure 5 As can be seen from e in Table 2, the ΔE of the Co3O4 silver-based composite material (0.72V) OER-ORR The values ​​are comparable to those of commercial platinum-carbon and RuO2 noble metal catalysts (0.70 V), and significantly lower than those of AgNPs (1.01 V), Co3O4 (0.90 V), and physical mixtures of Co3O4 and AgNPs (0.81 V). Furthermore, a comparative analysis was conducted on the differences in ORR and OER bifunctional activities between the Co3O4 silver-based composite and recently reported catalysts, with results as follows: Figure 20As shown in f in the figure. The results show that the catalytic performance of the Co3O4 silver-based composite material is significantly better than that of most cobalt oxide-based catalysts, including NdNi-Co3O4-2, Co3O4@NiMoO4-L, and MnCo-450. Based on the above results, the Co3O4 silver-based composite material can be regarded as a bifunctional electrocatalyst that exhibits excellent ORR and OER activities simultaneously. In addition, this invention also evaluated the Co3O4 silver-based composite material in 0.1M KOH electrolyte (e.g., Figure 6 The OER performance shown in the figure achieves 10. The potential required for the current density was 1.55 V, slightly higher than the 1.47 V obtained in 1.0 M KOH; this difference can be attributed to the pH-dependent kinetics of the OER; ΔE calculated in 0.1 M KOH... OER-ORR With a voltage of only 0.80V, its excellent bifunctional electrocatalytic activity is further verified.

[0131] Figure 6 The catalytic mechanism of Co3O4 silver-based composite materials in ORR and OER.

[0132] The excellent bifunctional catalytic activity of the Co3O4 silver-based composite material in this invention can be well explained based on the structure-activity relationship for ORR and OER, such as... Figure 7 As shown: Co located at octahedral and tetrahedral coordination sites 2+ and Co 3+ Redox pairs, along with surface oxygen vacancies, provide abundant active sites, which are conducive to the reaction of O2 and OH. - Adsorption and activation of Co; 2+ Ions and Co 3+ Ion coexistence, Co 2+ Ions exhibit higher activity for ORR, Co 3+ The ions exhibit higher activity towards OER, contributing to the enhanced bifunctional electrocatalytic performance of the material; Ag NPs modulate the electronic structure of Co3O4, enhancing the intrinsic activity of the active sites through strong TMO-supported interactions; electron transfer from Ag NPs to Co3O4 can effectively modulate the Co... 2+ and Co 3+The ratio and oxygen vacancy concentration enhance catalytic activity, and this electron transfer is crucial for both OER and ORR. For OER, it effectively modulates the adsorption free energy of oxidized intermediates (-O, -OOH) at Co sites, thereby reducing the reaction overpotential. For ORR, the presence of AgNPs is equally crucial, as Ag itself is a highly efficient ORR catalyst. Furthermore, Ag NPs at the interface activate adsorbed O2 molecules, promoting the crucial OO bond breaking, while the oxygen-vacancy-rich Co3O4 surface provides abundant sites for subsequent protonation steps. This synergistic effect significantly accelerates the overall ORR kinetics. Ag NPs, as a highly conductive pathway, promote rapid electron transfer, thereby minimizing polarization losses caused by charge accumulation. The electronic synergistic effect between Ag NPs and Co3O4 effectively optimizes the adsorption free energy of reaction intermediates, thus promoting efficient OO bond breaking and rapid proton migration. At the Ag NPs-Co3O4 interface, Ag NPs primarily promote O2 adsorption and provide electrons for ORR, while electronically regulated Co3O4 effectively mediates the intrinsic multi-step proton-coupled electron transfer process of ORR and OER. Optimized Co... 2+ and Co 3+ To ensure that neither reaction is affected by the rate-limiting step, the Co3O4 shell effectively protects the embedded Ag NPs core under the harsh conditions of OER, thereby maintaining the high conductivity characteristics of the metallic state. This synergistic effect effectively prevents the Co active sites from being over-oxidized into inert Co due to charge localization. 4+ The high BET specific surface area and ECSA of the Co3O4 silver-based composite material enhance the operational stability of the catalyst in the OER process. This provides a rich solid-liquid-gas three-phase interface for the reaction, reducing mass transfer resistance and promoting the exchange of oxygen and protons (OH-). - The high efficiency of oxygen transport and prevention of performance degradation caused by mass transfer limitations are achieved. Ag NPs, acting as a stable support for Co3O4 nanocrystals, promote the uniform dispersion of Co3O4 nanocrystals through strong interfacial interactions, effectively preventing their aggregation and thus enhancing the stability of the catalytic reaction. Simultaneously, the Co3O4 nanocrystals form a stable protective layer around the embedded Ag NPs, effectively preventing the oxidation of Ag NPs during long-term oxygen evolution. These factors collectively contribute to the superior bifunctional catalytic performance of the Co3O4 silver-based composite material in ORR and OER.

[0133] Figure 7The diagrams show the structure and characterization of a zinc-air battery. Specifically, a is a schematic diagram of a household zinc-air battery; b is a structural assembly diagram of a household zinc-air battery; c is the open-circuit potential; d shows the charge-discharge polarization and corresponding power density curves of a zinc-air battery assembled with a commercial platinum-carbon and RuO2 noble metal catalyst and Co3O4 silver-based composite material; e shows the discharge curves of a zinc-air battery assembled with Co3O4 silver-based composite material at different current densities; f is a demonstration of a zinc-air battery assembled with Co3O4 silver-based composite material, which can stably supply power (illustrated as a battery-powered digital watch); g is a demonstration of a zinc-air battery assembled with Co3O4 silver-based composite material, which can stably supply power (illustrated as an undriven fan); and h shows the charge-discharge performance of a zinc-air battery assembled with a commercial platinum-carbon and RuO2 noble metal catalyst and Co3O4 silver-based composite material.

[0134] Given the excellent ORR and OER bifunctional electrocatalytic activity exhibited by Co3O4 silver-based composite materials, they show great promise as air cathode materials in metal-air batteries, such as... Figure 7 As shown in Figure a, this invention uses a Co3O4 silver-based composite material as the air cathode catalyst, a mixed solution of 0.2M ZnAc2 and 6.0M KOH as the electrolyte, and a zinc plate as the anode to prepare a zinc-air battery (ZAB). For comparison, ZABs were assembled using commercial platinum-carbon and RuO2 noble metal catalysts as cathode materials. Figure 7 Figure b shows the structural assembly diagram of the prepared ZAB. Figure 7 As shown in c, the open-circuit voltage of ZAB based on Co3O4 silver-based composite material is 1.52V (the inset shows a photograph of the self-assembled Co3O4 silver-based composite ZAB and the measured open-circuit voltage value), which is close to the theoretical value of 1.65V and significantly higher than that of ZAB based on commercial platinum-carbon and RuO2 noble metal catalysts (1.40V).

[0135] Figure 7 Figure d shows the charge / discharge polarization curves and corresponding power density curves. It can be seen that the discharge curve of the zinc-air battery based on the Co3O4 silver-based composite material is only slightly lower than that of the zinc-air battery based on commercial platinum-carbon and RuO2 noble metal catalysts. Furthermore, compared with noble metal catalysts, the Co3O4 silver-based composite material exhibits superior charging performance. These results can be attributed to the excellent bifunctional oxygen electrocatalytic performance of the Co3O4 silver-based composite material. Meanwhile, the Co3O4 silver-based composite zinc-air battery (124.32...) It exhibits peak power density comparable to commercial platinum-carbon and RuO2 noble metal catalysts (139.12). The results above indicate that the Co3O4 silver-based composite zinc-air battery exhibits excellent charge-discharge performance.

[0136] Discharge curves at various current densities, such as Figure 7 As shown in 'e', ​​each discharge plateau lasts for 10 minutes. According to... Figure 7 As can be seen from 'e', ​​when the current density increases from 5... Increase to 40 Then it dropped to 5 At that time, the discharge plateau was effectively recovered, and only a small voltage drop was observed; this behavior indicates that the Co3O4 silver-based composite zinc-air battery has good reversibility. Figure 7 f and Figure 7 The image in section g demonstrates a practical application of a Co3O4 silver-based composite zinc-air battery, which can stably power light-emitting diode (LED) lights, electronic watches, and small electric fans. Figure 7 The image shows a zinc-air battery based on commercial platinum-carbon and RuO2 precious metal catalysts and a zinc-air battery based on Co3O4 silver-based composite material in 4... Charge-discharge cycle performance at current density, each cycle consisting of a 10-minute charge period and a 10-minute discharge period. According to... ​ As can be seen from the data, although the discharge voltage of the zinc-air battery based on commercial platinum-carbon and RuO2 noble metal catalysts is relatively stable, its charging voltage exhibits significant fluctuations. After 100 test cycles, the charge-discharge voltage difference increases to 0.98V, which is higher than the 0.84V observed in the Co3O4 silver-based composite zinc-air battery. This indicates that the ZAB assembled from the Co3O4 silver-based composite exhibits excellent charge-discharge cycle stability, and these results are consistent with the patterns observed in catalytic stability tests conducted in ORR and OER. Compared with commercial platinum-carbon and RuO2 noble metal catalysts, the Co3O4 silver-based composite exhibits superior overall stability, which further supports the practical potential of the Co3O4 silver-based composite as a bifunctional electrocatalyst.

[0137] The Co3O4 silver-based composite material of this invention exhibits the most outstanding bifunctional electrocatalytic activity of ORR and OER, with an OER potential of 1.47V (@10). The potential of ORR is 0.75V (@ Furthermore, compared to commercial platinum-carbon and RuO2 noble metal catalysts, the Co3O4 silver-based composite exhibits superior methanol tolerance and long-term stability; the ZAB assembled using the Co3O4 silver-based composite as the air cathode maintains good stability even after 100 charge-discharge cycles; the charge-discharge voltage difference of this battery is only 0.84V, lower than the 0.98V observed in ZAB based on commercial platinum-carbon and RuO2 noble metal catalysts. The superior catalytic activity and stability can be attributed to the strong interaction between Ag NPs and the Co3O4 component; the directional transfer of electrons modulates the oxygen vacancy concentration and Co at the interface. 2+ With Co 3+ The ratio was adjusted to improve the overall bifunctional catalytic activity of the Co3O4 silver-based composite material; during the oxygen reduction and oxygen evolution reactions, the Co3O4 silver-based composite material exhibited a ΔE of 0.72V. OER-ORR The value is significantly lower than that of the physical mixture of Co3O4 and Ag NPs (0.81V). This invention not only demonstrates a class of electrode materials with significant practical application potential that could drive the large-scale commercialization of electrochemical energy storage systems (EECS), but also thoroughly investigates the synergistic catalytic mechanism between variable-valence transition metal oxides and metal particles in the field of electrocatalysis.

[0138] The embodiments of the present invention have been described above; however, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A C03O4 silver-based composite material, characterized in that, The Co3O4 silver-based composite material comprises Co3O4 nanocrystals and Ag NPs embedded in the Co3O4 nanocrystals.

2. The Co304 silver-based composite material according to claim 1, characterized in that, The mass ratio of the Co3O4 nanocrystals to the Ag NPs in the Co3O4 silver-based composite material is 1.8-2.2:

3.

3. The method for preparing the Co304 silver-based composite material according to any one of claims 1-2, characterized in that, The method comprises the following steps: (1) mixing CoOOH and a silver source to perform a solid-phase reaction to obtain a precursor; (2) performing heat treatment on the precursor to obtain the Co3O4 silver-based composite material.

4. The production method according to claim 3, characterized by, The molar ratio of cobalt in the CoOOH to silver in the silver source is 1:2.8-3.

2.

5. The preparation method according to claim 3, characterized in that, The temperature of the solid-phase reaction is room temperature, and the time of the solid-phase reaction is more than 300 minutes. The solid-phase reaction is performed under grinding conditions.

6. The preparation method according to claim 3, characterized in that, The temperature of the heat treatment is 245-255 degrees Celsius, and the holding time is 170-190 minutes. The first heat treatment is performed in a protective atmosphere.

7. The preparation method according to claim 3, characterized in that, The method for preparing the CoOOH comprises the following steps: mixing a Co(NO3)2 solution, ammonia water and hydrogen peroxide solution to perform an oxidation reaction.

8. The preparation method according to claim 7, characterized in that, The concentration of the Co(NO3)2 solution is 0.8-1.2 M. The concentration of the ammonia water is 1.4-1.8 M. The volume ratio of the Co(NO3)2 solution to the ammonia water is 0.9-1.1:

1. The concentration of the hydrogen peroxide solution is 0.8-1.0 M. The molar ratio of Co(NO3)2 in the Co(NO3)2 solution to hydrogen peroxide in the hydrogen peroxide solution is 4:4.8-5.

2.

9. The preparation method according to claim 7, characterized in that, The temperature of the oxidation reaction is room temperature, and the holding time is more than 300 minutes.

10. The Co3O4 silver-based composite material of any one of claims 1-2 or the Co3O4 silver-based composite material obtained by the method of any one of claims 3-9 is applied to high-efficiency electrochemical energy conversion and storage devices.

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