A cobalt-manganese-strontium ternary metal catalyst, a preparation method and application thereof

Abstract

The present application relates to the technical field of water electrolysis catalysis, and discloses a cobalt-manganese-strontium ternary metal catalyst and a preparation method and application thereof.The cobalt-manganese-strontium ternary metal catalyst material has a rough surface, exists in the form of holes, has three metal oxides MnO2, Co3O4 and SrO2 phases, and has an amorphous and crystalline coexisting structure and a phase interface composed of crystal faces and amorphous faces.The preparation method comprises the following steps: preparing a precursor solution by mixing a manganese source solution, a cobalt source solution and a strontium source material;dropping the precursor solution on a pretreated conductive substrate; and performing a heating reaction, so that the cobalt-manganese-strontium ternary metal catalyst is obtained after the reaction is completed and the temperature is cooled to room temperature.The cobalt-manganese-strontium ternary metal catalyst has excellent acid OER catalytic activity.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis catalysis technology, specifically to a cobalt-manganese-strontium ternary metal catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen production via water electrolysis involves two half-reactions: the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Theoretically, water electrolysis for hydrogen production requires only a thermodynamic potential of 1.23 V. The OER is an electrochemical reaction involving four electrons and four protons coupled together, requiring higher energy (i.e., a higher overpotential) to overcome the kinetic barrier than HER. Acidic OER reactions play a crucial role in water electrolysis in PEM (proton exchange membrane) electrolyzers. To date, numerous highly active and stable non-noble metal electrocatalysts have been developed to drive acidic HER, including transition metal sulfides, phosphides, nitrides, and metal nanoparticles encapsulated in carbon materials. Current research focuses on designing and developing OER electrocatalysts to enhance electrode kinetics and stability. Various acidic OER catalysts have been reported, such as transition metal oxides, sulfides, selenides, and layered materials. However, most electrocatalysts cannot withstand strong acid environments and high anodic potentials, and are easily oxidized and dissolved. Currently, RuO2 and IrO2 are recognized as the most advanced acidic OER electrocatalysts, but they are both scarce precious metal materials, making large-scale application unlikely. This greatly limits the practical application of PEM electrolyzers for water electrolysis.

[0003] To address this issue, one approach is to couple noble metal elements with transition metal (TM)-based oxides to generate compounds, such as IrW-W2B alloy catalysts, Ir-Mn oxides, and IrO. x Compounds such as SrIrO3 exhibit good OER performance and improved stability in acids. Another approach is to design and synthesize metal-free catalysts based on TM-based materials, which demonstrate excellent OER activity and stability in acidic media. However, they still lag behind current advanced noble metal-based catalysts and are susceptible to acid corrosion, so further performance improvements are crucial for their practical applications.

[0004] Among many TM-based oxides, manganese oxide (MnO) x MnO possesses diverse valence states and crystal structures, exhibiting excellent electrocatalytic performance in various electrochemical reactions. xAs an important member of the manganese family, MnO2 has the potential to replace noble metals as an acidic OER catalyst due to its relatively high catalytic activity and stability. Early experiments have shown that manganese oxides can act as highly efficient bifunctional electrocatalysts for ORR and OER under alkaline conditions. Currently, there are also a few reports on the use of manganese-based oxides for acidic oxygen evolution reactions, but most of the reported materials have limited catalytic activity at 10 mA cm⁻¹. -2 The overpotential at current density is typically greater than 500 mV, so the activity of manganese-based materials for acidic OER reactions needs further improvement. Synergistic engineering is an important strategy for enhancing the intrinsic activity of OER catalysts. Therefore, combining MnO2 with other non-noble metal-based oxides can suppress MnO2 decomposition and stabilize catalytic sites. This coupling strategy is an effective way to regulate the electronic structure of MnO2, optimizing the adsorption and desorption energies of intermediates during the OER reaction, thereby significantly enhancing the intrinsic catalytic activity of the material. Among many transition metals, cobalt oxides have been theoretically and experimentally proven to have high activity for OER. Theoretical calculations show that the catalytic activity of Co3O4 is comparable to RuO2. However, this catalyst is prone to corrosion during the OER process; therefore, the dissolution problem still needs to be considered when developing Co catalysts for acidic OER. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cobalt-manganese-strontium ternary metal catalyst, its preparation method and application, in order to overcome the shortcomings of the prior art. The cobalt-manganese-strontium ternary metal oxide catalyst provided by the present invention has excellent acidic OER catalytic activity.

[0006] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows:

[0007] This invention provides a cobalt-manganese-strontium ternary metal catalyst. The material has a rough surface with pores and contains three metal oxides: MnO2, Co3O4, and SrO2. It has a structure in which amorphous and crystalline phases coexist, and has a phase interface composed of crystalline and amorphous planes.

[0008] According to the above scheme, Sr is distributed both on the surface and inside the catalyst; XRD diffraction characterization shows that there are characteristic diffraction peaks of SrO2, indicating that SrO2 oxide has good crystallinity.

[0009] According to the above scheme, the atomic ratio of Mn to Co in the above cobalt-manganese-strontium ternary metal catalyst is 3:1-5:1.

[0010] According to the above scheme, the atomic ratio of Co to Sr on the sample surface is 1:0.008-0.167.

[0011] A method for preparing a cobalt-manganese-strontium ternary metal catalyst involves preparing a precursor solution by mixing a manganese source, a cobalt source solution, and a strontium source substance; dropping the precursor solution onto a pretreated conductive substrate and heating it to react; and cooling the mixture to room temperature after the reaction is complete to obtain the cobalt-manganese-strontium ternary metal catalyst.

[0012] According to the above scheme, the conductive substrate is a carbon cloth substrate. The pretreatment of the carbon cloth substrate is as follows: the carbon cloth is cut, then soaked in concentrated nitric acid, and then ultrasonically cleaned with deionized water and anhydrous ethanol to obtain the pretreated carbon cloth substrate.

[0013] In the above scheme, the cobalt-strontium molar ratio in step (2) is 6:1-120:1, preferably 12-100:1, and more preferably 20-100:1.

[0014] In the above scheme, the manganese-cobalt molar ratio in step (2) is 3:1-5:1.

[0015] According to the above scheme, the manganese source material is manganese nitrate, the cobalt source material is cobalt nitrate, and the strontium source material is strontium chloride.

[0016] In the above scheme, the precursor droplets are heated on a heating plate on a pretreated carbon cloth substrate.

[0017] In the above scheme, the heating reaction in step (2) is carried out at a temperature of 150-400℃ for 2-12 hours.

[0018] The above-mentioned cobalt-manganese-strontium ternary metal catalysts are used in acidic OER catalysis.

[0019] The applicant's research found that introducing Sr into MnCo metal oxides roughens the catalyst surface and creates pores, which facilitates the full immersion of electrolyte during the reaction and increases the electrochemically active surface area. Simultaneously, the introduction of Sr can induce electron transfer, increasing the content of high-valence Co. The high-valence transition metal active sites will promote OER performance. Furthermore, the introduction of Sr can inhibit Co dissolution to some extent, thereby improving catalyst stability. On the other hand, the introduction of Sr can promote the increase of surface Co-OH groups, thus accelerating OER kinetics and exhibiting excellent OER catalytic activity.

[0020] Compared with existing technologies, the beneficial effects of this invention are:

[0021] The cobalt-manganese-strontium ternary metal catalyst provided by this invention has excellent acidic OER catalytic activity.

[0022] This invention provides a method for preparing a cobalt-manganese-strontium ternary metal catalyst. This method prepares a MnCoSr ternary metal catalyst by changing the ratio of Mn, Co, and Sr in the precursor solution using a one-step heating method. By changing the ratio of Mn, Co, and Sr in the precursor solution, MnCoSr ternary metal oxides with different Sr contents can be obtained. This method is convenient, simple, and controllable, and the prepared catalyst has excellent acidic OER catalytic activity. Attached Figure Description

[0023] Figure 1 Scanning electron microscope (SEM) images of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of the present invention and the MnCo oxide sample MCO2 prepared in Comparative Example 1, and the elemental distribution map of the MnCoSr trimetallic oxide.

[0024] Figure 2 Transmission electron microscope (TEM) image (ac) and EDX elemental mapping image (d) of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of the present invention.

[0025] Figure 3 The XRD patterns of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of this invention and the MnCo oxide sample MCO2 prepared in Comparative Example 1 are shown.

[0026] Figure 4 The high-resolution XPS spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of this invention and the MnCo oxide sample MCO2 prepared in Comparative Example 1 are shown.

[0027] Figure 5 The MnCoSr trimetallic oxide samples prepared in Examples 1-4 of this invention and the oxide samples MCO2, MnO2, Co3O4, and MnSrO prepared in Comparative Example 1 are examples of the oxide samples prepared in Examples 1-4 of this invention. x and CoSrO x The OER performance test chart.

[0028] Figure 6 The image shows the Faraday efficiency (FE) of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of this invention.

[0029] Figure 7 The MnCoSr trimetallic oxide sample, MCSO2 oxide sample, MCO2, MnO2, Co3O4, and MnSrO prepared in Example 2 of this invention x CoSrO x In the OER performance test, the sweep rates were 20, 40, 60, 80, 100, and 120 mV s. -1 The CV curve at that time.

[0030] Figure 8 The MnCoSr trimetallic oxide sample, MCSO2 oxide sample, MCO2, MnO2, Co3O4, and MnSrO prepared in Example 2 of this invention x CoSrO x Fitting curves of capacitance current and scan rate in OER performance testing (a) and LSV curves normalized by electrochemical active surface area (b).

[0031] Figure 9 The SEM (ac) and EDS (d) spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of the present invention and the MnCo oxide sample MCO2 prepared in Comparative Example 1 after OER performance stability testing are shown.

[0032] Figure 10 The XRD patterns and Raman spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of this invention and the MnCo oxide sample MCO2 prepared in Comparative Example 1 after OER performance stability testing are shown.

[0033] Figure 11 XPS spectrum of MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 of this invention after OER performance stability test. Detailed Implementation

[0034] The technical solution of the present invention will be described in detail below with reference to specific embodiments. However, the described embodiments are only some embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] In the specific implementation, the carbon cloth Cyber ​​electrochemical material WOS1011; 50% manganese nitrate solution (Mn(NO3)2), cobalt nitrate (Co(NO3)2·6H2O), strontium chloride (SrCl2·6H2O), and anhydrous ethanol were all analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd.; concentrated nitric acid (HNO3) was of superior grade and purchased from Sinopharm Chemical Reagent Co., Ltd.

[0036] Example 1

[0037] A method for preparing a cobalt-manganese-strontium ternary metal catalyst includes the following steps:

[0038] (1) Pretreatment of carbon cloth substrate

[0039] Cut out carbon cloth with a size of 2cm×2cm, soak it in a beaker containing 100mL of concentrated nitric acid for 48h, and then sonicate it with deionized water and anhydrous ethanol for 30min respectively to remove the surface oxides, and obtain the pretreated carbon cloth substrate.

[0040] (2) Preparation of MnCoSr oxide

[0041] First, dissolve 9.3 mL of 50% manganese nitrate solution, 0.01 mol Co(NO3)2·6H2O, and 0.1 mmol SrCl2·6H2O in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 h. After the reaction was completed and cooled to room temperature, MnCoSr oxide was obtained and named MCSO1, which was used as a cobalt-manganese-strontium ternary metal catalyst.

[0042] Example 2

[0043] A method for preparing a cobalt-manganese-strontium ternary metal catalyst includes the following steps:

[0044] (1) Pretreatment of carbon cloth substrate

[0045] Cut out carbon cloth with a size of 2cm×2cm, soak it in a beaker containing 100mL of concentrated nitric acid for 48h, and then sonicate it with deionized water and anhydrous ethanol for 30min respectively to remove the surface oxides, and obtain the pretreated carbon cloth substrate.

[0046] (2) Preparation of MnCoSr oxide

[0047] First, dissolve 9.3 mL of 50% manganese nitrate solution, 0.01 mol Co(NO3)2·6H2O, and 0.4 mmol SrCl2·6H2O in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 h. After the reaction was completed and cooled to room temperature, MnCoSr oxide was obtained and named MCSO2, which was used as a cobalt-manganese-strontium ternary metal catalyst.

[0048] Example 3

[0049] A method for preparing a cobalt-manganese-strontium ternary metal catalyst includes the following steps:

[0050] (1) Pretreatment of carbon cloth substrate

[0051] Cut out carbon cloth with a size of 2cm×2cm, soak it in a beaker containing 100mL of concentrated nitric acid for 48h, and then sonicate it with deionized water and anhydrous ethanol for 30min respectively to remove the surface oxides, and obtain the pretreated carbon cloth substrate.

[0052] (2) Preparation of MnCoSr oxide

[0053] First, dissolve 9.3 mL of 50% manganese nitrate solution, 0.01 mol Co(NO3)2·6H2O, and 0.8 mmol SrCl2·6H2O in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 h. After the reaction was completed and cooled to room temperature, MnCoSr oxide was obtained and named MCSO3, which was used as a cobalt-manganese-strontium ternary metal catalyst.

[0054] Example 4

[0055] A method for preparing a cobalt-manganese-strontium ternary metal catalyst includes the following steps:

[0056] (1) Pretreatment of carbon cloth substrate

[0057] Cut out carbon cloth with a size of 2cm×2cm, soak it in a beaker containing 100mL of concentrated nitric acid for 48h, and then sonicate it with deionized water and anhydrous ethanol for 30min respectively to remove the surface oxides, and obtain the pretreated carbon cloth substrate.

[0058] (2) Preparation of MnCoSr oxide

[0059] First, dissolve 9.3 mL of 50% manganese nitrate solution, 0.01 mol Co(NO3)2·6H2O, and 1.5 mmol SrCl2·6H2O in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 h. After the reaction was completed and cooled to room temperature, MnCoSr oxide was obtained and named MCSO4, which was used as a cobalt-manganese-strontium ternary metal catalyst.

[0060] Comparative Example

[0061] (1) Pretreatment of carbon cloth substrate

[0062] Cut out carbon cloth with a size of 2cm×2cm, soak it in a beaker containing 100mL of concentrated nitric acid for 48h, and then sonicate it with deionized water and anhydrous ethanol for 30min respectively to remove the surface oxides, and obtain the pretreated carbon cloth substrate.

[0063] (2) Preparation of MnCo oxide

[0064] First, dissolve 9.3 mL of 50% manganese nitrate solution and 0.01 mol of Co(NO3)2·6H2O in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 hours. After the reaction was completed and cooled to room temperature, MnCo oxide was obtained and named MCO2.

[0065] (3) Preparation of Mn oxides

[0066] First, dissolve 9.3 mL of 50% manganese nitrate solution in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, use a pipette to transfer the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 hours. After the reaction was completed and cooled to room temperature, Mn oxide was obtained and named MnO2.

[0067] (4) Preparation of Co oxide

[0068] First, dissolve 0.01 mol of Co(NO3)2·6H2O in 20 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, use a pipette to transfer the precursor solution at a rate of 150 μL·cm⁻¹. -2 A certain amount of the solution was dropped onto the pretreated carbon cloth substrate and reacted at 250°C on a heating plate for 5.5 hours. After the reaction was completed and cooled to room temperature, Co oxide was obtained and named Co3O4.

[0069] (5) Preparation of MnSr oxide

[0070] First, dissolve 9.3 mL of 50% manganese nitrate solution and 0.4 mmol of SrCl₂·6H₂O in 10.7 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A small amount of the solution was dropped onto a pretreated carbon cloth substrate, and the reaction was carried out at 250°C on a heating plate for 5.5 h. After the reaction was completed and cooled to room temperature, MnSr oxide was obtained and named MnSrO. x .

[0071] (6) Preparation of CoSr oxide

[0072] First, dissolve 0.01 mol Co(NO3)2·6H2O and 0.4 mmol SrCl2·6H2O in 20 mL of deionized water and stir for 30 min to form a homogeneous solution as the precursor solution. Then, pipette the precursor solution at a rate of 150 μL·cm⁻¹. -2 A small amount of the solution was dropped onto a pretreated carbon cloth substrate, and the reaction was carried out at 250°C on a heating plate for 5.5 h. After the reaction was completed and cooled to room temperature, CoSr oxide was obtained and named CoSrO. x .

[0073] Test Example 1

[0074] This test is used to illustrate the microstructure of the cobalt-manganese-strontium ternary metal catalyst material of the present invention.

[0075] Figure 1 Scanning electron microscope (SEM) images (ad) of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 and the MnCo oxide sample MCO2 prepared in the comparative example, and elemental distribution map (e) of the MnCoSr trimetallic oxide are shown, where (a) and (b) are SEM images of MCO2, and (c) and (d) are SEM images of MCSO2. Figure 1 It can be seen that the MnCo bimetallic oxide material exhibits a smooth bulk structure; after introducing Sr metal to obtain the MnCoSr trimetallic oxide, the surface of the material becomes rough and larger pores appear. The appearance of pores also facilitates the full penetration of electrolyte during the reaction, increasing the electrochemically active surface area. EDS scanning tests were performed on the micro-area surface of the MnCoSr trimetallic oxide sample to obtain EDS-mapping elemental mapping maps. Figure 1 (e) shows that the Mn, Co, Sr and O elements are evenly distributed on the surface of MCSO2. The atomic percentages of Mn and Co are close to 4:1, indicating that the introduction of Sr does not affect the formation of Mn and Co oxides. However, the Sr content is relatively low, which may be because most of the Sr oxides are deposited inside the sample, while the Sr content on the surface is relatively low. The atomic percentages of the elements on the sample surfaces of MCO2 and MCSO2 are shown in Table 1.

[0076] Table 1

[0077]

[0078] Test Example 2

[0079] This test is used to illustrate the microstructure of the cobalt-manganese-strontium ternary metal catalyst material of the present invention.

[0080] Figure 2 Transmission electron microscopy (TEM) image (ac) and EDX elemental mapping image (d) of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2. Figure 2 The HRTEM images (a), (b), and (c) show that there are lattice stripes with lattice spacings of 0.45 nm and 0.29 nm, corresponding to the (004) and (211) crystal planes of MnO2; lattice stripes with a lattice spacing of 0.24 nm, corresponding to the (400) crystal plane of Co3O4; and lattice stripes with lattice spacings of 0.26 nm and 0.25 nm, corresponding to the (202) and (113) crystal planes of SrO2. Figure 2 The distinct layered structure in (b) indicates that the bulk structure of MCSO2 is formed by the layer-by-layer stacking of three mixed metal oxides. In summary, MCSO2 is composed of three metal oxides: MnO2, Co3O4, and SrO2. Furthermore, MCSO2 exhibits a structure where amorphous and crystalline phases coexist, possessing a phase interface composed of crystalline and amorphous planes. The presence of this interface is beneficial for optimizing the adsorption of intermediates and electron transfer during the OER process, thereby improving the intrinsic activity of the material. Additionally, the presence of the amorphous phase has a positive effect on improving the stability of the reaction system.

[0081] Test Example 3

[0082] This test is used to illustrate the phase and crystal structure of the cobalt-manganese-strontium ternary metal catalyst material of the present invention.

[0083] Figure 3 The XRD patterns of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 and the MnCo oxide sample MCO2 prepared in the comparative example are shown. Figure 3 It can be seen that the diffraction peaks at 27.5°, 35.7°, and 59.6° belong to SrO2 (PDF#3-872). Compared with the diffraction peaks of MnO2 and Co3O4, the peaks of SrO2 are sharper and have higher intensity, indicating that strontium oxide has better crystallinity among trimetallic oxides.

[0084] Figure 4 The high-resolution XPS spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 and the MnCo oxide sample MCO2 prepared in Comparative Example 1 are shown. Figure 4 (a) is the high-resolution XPS spectrum of Mn 2p, where the two peaks at 642.40 eV and 654.10 eV correspond to Mn 2p, respectively. 3 / 2 and Mn 2p 1 / 2 Deconvolution on the two tracks can be fitted to Mn. 4+ (644.35eV, 654.64eV) and Mn3+ (642.36eV, 653.65eV). The spin-orbit splitting energy difference of Mn 2p is 11.7eV, which is consistent with the MnO2 reported in some literature. Figure 4 (b) is the high-resolution XPS spectrum of Co 2p. The two peaks at 780.62 eV and 795.63 eV in the MCSO2 sample correspond to Co 2p and 795.63 eV, respectively. 3+ Co 2p 3 / 2 and Co 2p 1 / 2 The spin orbitals, with two peaks at 782.42 eV and 797.23 eV, correspond to Co, respectively. 2+ Co 2p 3 / 2 and Co 2p 1 / 2 Spin orbitals. Compared to the MCO2 sample, the MCSO2 sample belongs to the Co group. 2+ The peak shifted by approximately +0.48 eV, demonstrating the regulatory effect of Sr introduction on its electronic coordination environment. 3+ / Co 2+ The atomic ratio can be obtained by calculating the relative area of ​​the fitted curve. Co in the MCSO2 sample 3+ With Co 2+ The peak area ratio was 1.45:1, while the Co content in the MCO2 sample was... 3+ With Co 2+ The peak area ratio of 1.01:1 further illustrates that the introduction of Sr can induce electron transfer, thereby increasing the content of high-valence Co, and the high-valence transition metal active sites will promote OER performance. Figure 4 (c) is the high-resolution XPS spectrum of Sr 3d, which can be fitted as two doublets. The doublet with lower binding energy (133.62 eV, 135.44 eV) corresponds to Sr in the SrO2 lattice, while the doublet with higher binding energy (134.60 eV, 136.75 eV) may originate from some Sr on the surface, such as Sr(OH)2 or Sr(NO3)2. Figure 4 (d) is the high-resolution XPS spectrum of O1s, which can be divided into three peaks through fitting. The peak at 530.08 eV corresponds to the lattice oxygen in the three oxides, the peak at 531.41 eV corresponds to the hydroxyl group in the water molecules adsorbed on the surface, and the peak at 532.92 eV corresponds to the water adsorbed on the sample surface. In summary, the above analysis shows that the introduction of Sr can effectively regulate the electronic structure of the material, thereby promoting electron transfer in the OER process and effectively improving the electrocatalytic activity of the sample.

[0085] Test Example 4

[0086] This test is used to illustrate the OER performance of the cobalt-manganese-strontium ternary metal catalyst material of the present invention.

[0087] In 0.5 mol / L H₂SO₄, using a three-electrode system on a CHI660E workstation, the MnCoSr trimetallic oxide samples prepared in Examples 1-4 and the oxide samples MCO₂, MnO₂, Co₃O₄, and MnSrO₂ prepared in comparative examples were compared. x and CoSrO x OER performance evaluation was conducted. Among other things... Figure 5 (a) Linear sweep voltammetry (LSV) of MnCoSr trimetallic oxides prepared with different proportions of Sr in the precursor solution; Figure 5 (b) consists of MCO2, MnO2, Co3O4, and MnSrO. x CoSrO x Linear sweep voltammogram (LSV) of MCSO2; Figure 5 (c) consists of MCO2, MnO2, Co3O4, and MnSrO x CoSrO x Tafel curves of MCSO2; Figure 5 (d) consists of MCO2, MnO2, Co3O4, and MnSrO. x CoSrO x Electrochemical impedance spectroscopy (EIS) of MCSO2; Figure 5 (e) consists of MCO2, MnO2, Co3O4, and MnSrO. x CoSrO x OER stability test curves of MCSO2 at constant current density. Figure 5 As shown in (a), the MCSO2 sample exhibits the highest OER catalytic performance at 10 mA cm⁻¹. -2 At the given current density, its overpotential is 332 mV, which is superior to MCO2 (393 mV). Figure 5 As shown in (b), with the bimetallic oxide MnSrO x CoSrO x Compared to MCO2, MCSO2 exhibits the best OER performance and is also significantly superior to single-metal oxides, indicating that the synergistic effect among the three-metal mixed oxides enables the material to exhibit excellent performance. Figure 5 (c) Tafel slope of MCOS2 (58.9mV dec) -1 The concentration was significantly lower than that of other comparative samples, indicating that it has faster reaction kinetics. Figure 5 As shown in (d), MCSO2 has the smallest R ct This indicates that the charge transfer rate is the fastest during the reaction, which is beneficial to enhancing the activity of OER. Figure 5 (e) provides the results for different samples at 10 mA cm⁻¹. -2The vt change curve under current density. As can be seen, MCSO2 maintained good performance during the 100-hour stability test, proving its good stability in acidic OER and demonstrating its application prospects and value in the electrolysis of acidic water for oxygen evolution reaction.

[0088] To test the selectivity of MCSO2 for O2 in acidic electrolytes, it was subjected to water electrolysis OER reaction in an H-type electrolytic cell. The products at the working electrode were collected for gas chromatography detection, and the obtained Faraday efficiency (FE) results are as follows: Figure 6 As shown in the figure. Oxygen in the product was detected by GC, and the average FE value of O2 was 95.3%, which proves that the MCSO2 sample has excellent OER selectivity during the reaction.

[0089] Figure 7 (af) are MnO2, Co3O4, and MnSrO in sequence. x CoSrO x The voltammetric cycle curves of MCO2 and MCSO2 were obtained, and the double-layer capacitance (Cdl) of each sample could be calculated from them. Figure 8 The fitted plot of capacitance current and scan rate (a) and the LSV curve normalized to electrochemical active surface area (ECSA) are shown. Figure 8 As shown in (a), compared with other samples, the MCOS2 sample has the highest Cdl value of 343.5 μF·cm⁻¹. -2 This indicates that the introduction of Sr can effectively increase the electrochemical active surface area (ECSA) of the material, providing more reactive sites for the OER reaction. The normalized LSV obtained after normalization shows that MCSO2, in addition to having an increased number of active sites, also possesses the highest intrinsic activity. Furthermore, the normalized LSVs of MnO2 and Co3O4 are not significantly different from those of MnSrOx and CoSrOx, suggesting that Sr does not act as a reactive site but mainly plays a role in regulating the material structure.

[0090] Test Example 5

[0091] This test is used to illustrate the morphology and structure of the cobalt-manganese-strontium ternary metal catalyst material of the present invention after OER performance stability testing.

[0092] Figure 9 The SEM (ac) and EDS (d) spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 and the MnCo oxide sample MCO2 prepared in Comparative Example 1 after OER performance stability testing are shown. Figure 9(ac) It can be seen that large cracks appeared on the surface of MnCo bimetallic oxide (MCO2) after the stability test, indicating that its bulk structure was corroded by sulfuric acid during the reaction. In contrast, the bulk structure of MnCoSr trimetallic oxide (MCOS2) was more intact, proving that the sample had good stability. Many large pores and white particle precipitates appeared on the sample surface, which may be because the SrO2 deposited inside the sample precipitated in the form of strontium salt (SrSO4). Table 2 shows the surface element atomic percentages of the samples before and after the test. It can be seen that after the stability test of MCO2, the Mn:Co ratio changed from 4.02:1 to 9.95:1, indicating that the performance degradation was due to the dissolution of Co during the reaction. After the stability test of MCSO2, the Mn:Co:Sr ratio changed from 4.14:1:0.048 to 6:1:0.22, indicating that the introduction of Sr can inhibit the dissolution of Co to a certain extent, thereby improving the stability of the material. The increase in Sr content may be due to the precipitation of Sr inside the sample.

[0093] Table 2

[0094]

[0095] Figure 10 The XRD patterns and Raman spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 and the MnCo oxide sample MCO2 prepared in the comparative example after OER performance stability testing are shown. Figure 10 As can be seen from the XRD comparison in (a), the XRD peaks did not change significantly before and after the performance test, which proves that the sample structure was relatively stable during the reaction process. Figure 10 (b) Raman comparison shows that after the MCSO2 reaction, the temperature at 456 cm⁻¹ -1 The presence of a peak indicates that a phase transition occurred on the Co3O4 surface during the reaction, resulting in the formation of Co-OH groups. This provides more active sites for the OER reaction, promoting O2 release. In contrast, MCO2 did not undergo a phase transition during the reaction, suggesting that the introduction of Sr promotes the increase of surface Co-OH groups, thereby accelerating OER kinetics.

[0096] Figure 11 XPS spectra of the MnCoSr trimetallic oxide sample MCSO2 prepared in Example 2 after OER performance stability testing. Figure 11 As shown in (a) and (b), the characteristic peak values ​​of the Mn 2p and Co 2p high-resolution XPS spectra did not change significantly after the performance test, indicating that the MnO2 and Co3O4 structures inside the MCSO2 sample were stable during the reaction process. Figure 11(c) is the high-resolution XPS spectrum of Sr 3d. The Sr content in the lattice and the surface Sr content can be compared by calculating the relative area of ​​the fitted curve. As shown in the figure, the surface Sr content increases after the performance test, which further proves that SrO2 will gradually precipitate during the reaction, which is consistent with the previous analysis. The precipitation of SrO2 inside the sample will lead to some larger pores on the material surface, which is beneficial to increasing the electrochemical active surface area of ​​the material, thereby improving the sample activity. On the other hand, the alkaline earth metal Sr leached in the reaction can form a loose structure, which will then collapse into an amorphous structure, which is also beneficial to improving the OER activity and stability in acidic media.

[0097] In summary, the cobalt-manganese-strontium ternary metal catalyst provided by this invention exhibits excellent acidic OER catalytic activity at 10 mA·cm⁻¹. -2 At a current density of 332mV, it exhibits excellent performance and can operate continuously for 100 hours. CV and EIS tests show that the cobalt-manganese-strontium ternary metal catalyst sample has a large electrochemical active surface area, a small electrochemical impedance, and a high intrinsic activity, which is more conducive to the OER reaction. This work provides a new solution for developing efficient and stable acidic OER catalysts.

[0098] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and its improved concept, should be covered within the scope of protection of the present invention.

Claims

1. A cobalt-manganese-strontium ternary metal catalyst, characterized in that: The cobalt-manganese-strontium ternary metal catalyst material has a rough surface with pores and contains three metal oxides: MnO2, Co3O4, and SrO2. It exhibits a structure where amorphous and crystalline phases coexist, with a phase interface composed of crystalline and amorphous planes. The preparation method of the cobalt-manganese-strontium ternary metal catalyst is as follows: a precursor solution is prepared by mixing a manganese source solution with a cobalt source and a strontium source. The molar ratio of cobalt to strontium in the precursor solution is 6:1-120:1, and the molar ratio of manganese to cobalt is 3:1-5:

1. The precursor solution is dropped onto a pretreated conductive substrate and subjected to a heating reaction at a temperature of 150-400℃ for 2-12 hours. After the reaction is completed and cooled to room temperature, the cobalt-manganese-strontium ternary metal catalyst is obtained.

2. The cobalt-manganese-strontium ternary metal catalyst according to claim 1, characterized in that: Sr is distributed both on the surface and inside the catalyst, and the strontium oxide SrO2 has good crystallinity.

3. The cobalt-manganese-strontium ternary metal catalyst according to claim 1, characterized in that: The atomic ratio of Mn to Co in the cobalt-manganese-strontium ternary metal catalyst is 3:1-5:

1.

4. The cobalt-manganese-strontium ternary metal catalyst according to claim 1, characterized in that: The atomic ratio of Co to Sr on the surface of the cobalt-manganese-strontium ternary metal catalyst material is 1:0.008-0.

167.

5. The method for preparing the cobalt-manganese-strontium ternary metal catalyst according to claim 1, characterized in that: A precursor solution was prepared by mixing a manganese source solution with a cobalt source and a strontium source. The molar ratio of cobalt to strontium in the precursor solution was 6:1-120:1, and the molar ratio of manganese to cobalt was 3:1-5:

1. The precursor solution was dropped onto a pretreated conductive substrate and heated to react at a temperature of 150-400°C for 2-12 hours. After the reaction was completed and cooled to room temperature, the cobalt-manganese-strontium ternary metal catalyst was obtained.

6. The preparation method according to claim 5, characterized in that: The cobalt-strontium molar ratio is 12-100:

1.

7. The preparation method according to claim 5, characterized in that: The manganese source is manganese nitrate, the cobalt source is cobalt nitrate, and the strontium source is strontium chloride; the conductive substrate is a carbon cloth substrate, and the carbon cloth substrate is pretreated by cutting the carbon cloth, immersing it in concentrated nitric acid, and then ultrasonically cleaning it with deionized water and anhydrous ethanol to obtain the pretreated carbon cloth substrate.

8. The application of the cobalt-manganese-strontium ternary metal catalyst according to any one of claims 1-4 in acidic OER catalysis.

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