La and Ca double-doped Co3O4 electrocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a La and Ca double-doped Co3O4 electrocatalyst and a preparation method and application thereof, and relates to the technical field of electrolyzed water catalysts.The preparation method comprises the steps that a Pt coating titanium mesh (PTL) serves as a substrate and a working electrode, and a Co-LaCa film is deposited on the surface of the substrate and the working electrode by using a self-made target material through a magnetron sputtering method; and washing, drying and calcining the obtained PTL sheet to obtain the catalyst. According to the invention, Ca and La are doped on the surface of Co3O4 to construct a hydrophilic-hydrophobic coupling structure, so that the acidic OER stability is remarkably improved. Ca is introduced to generate high-activity unsaturated Co sites, so that activity and stability are balanced, interface water interaction is promoted, formation and conversion of reaction intermediates are accelerated, the water / catalyst interface microenvironment is optimized at the atomic level, and a new way is provided for improving catalytic stability.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis catalysts, and in particular to a La and Ca dual-doped Co3O4 electrocatalyst, a preparation method thereof, and applications thereof. Background Art

[0002] Proton exchange membrane water electrolysis (PEMWE) has become an important technology for future hydrogen production due to its efficient utilization of renewable energy. However, the strongly acidic and highly oxidizing environment makes OER catalysts heavily dependent on scarce and expensive iridium, limiting their large-scale application. Therefore, the development of highly active and stable non-precious metal catalysts is crucial for the commercialization of PEMWE. Spinel oxides (AB2O4) are highly promising OER catalysts due to their tunable electronic structure, excellent stability, and excellent ability to manipulate oxygen intermediates. Heteroatom doping can optimize the metal oxidation state distribution, modulate the B-site electronic structure, and introduce oxygen vacancies, thereby enhancing charge transport and improving catalytic activity. However, the precise and controllable synthesis of doped spinel oxides remains challenging. Conventional wet synthesis methods are prone to uneven distribution or agglomeration of the doping element, affecting catalytic stability. Furthermore, the manipulation of B-O bond strength significantly affects the adsorption capacity of oxygen intermediates. Therefore, exploring efficient and precise doping strategies is crucial to improving the OER activity and stability of spinel oxides, providing new directions for the application of non-precious metal catalysts in PEMWE. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a La and Ca dual-doped Co3O4 electrocatalyst and its preparation method and application.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] <First Aspect>

[0006] The present invention provides a La and Ca doped Co3O4 electrocatalyst, wherein La partially replaces Co in Co3O4. 3+ ions, Ca partially replaces Co in Co3O4 2+ ion.

[0007] As an embodiment, in the La and Ca dual-doped Co3O4 electrocatalyst, the mass ratio of Co, La and Ca is 100:(30-200):(5-200).

[0008] As an embodiment, in the La and Ca dual-doped Co3O4 electrocatalyst, the mass ratio of Co, La and Ca is 100:(35-40):(5-15).

[0009] In some embodiments, in the La and Ca dual-doped Co3O4 electrocatalyst, the mass ratio of Co, La and Ca is (51.34-52.51):(20.99-21.08):(4.01-4.25).

[0010] <Second Aspect>

[0011] The present invention provides a method for preparing a La and Ca doped Co3O4 electrocatalyst, comprising the following steps:

[0012] A Co-La-Ca composite target is used to deposit Co, La, and Ca elements on a substrate material by a magnetron sputtering method. The mass ratio of Co, La, and Ca in the composite target is 100:(30-200):(5-200), and the deposition thickness is 2.1-2.3 μm, thereby obtaining a substrate with La-Ca-Co deposited on the surface.

[0013] The substrate with La-Ca-Co deposited on the surface is calcined at 300-500° C. for 3-5 hours in an air atmosphere, and after cooling, the La and Ca dual-doped Co3O4 electrocatalyst is obtained on the surface of the substrate.

[0014] As an embodiment, the mass ratio of Co, La and Ca in the composite target is 100:(35-40):(5-15).

[0015] As an embodiment, the mass ratio of Co, La and Ca in the composite target is (51.34-52.51):(20.99-21.08):(4.01-4.25).

[0016] In some embodiments, the mass ratio of Co, La, and Ca in the composite target is 52.34:20.08:5.25.

[0017] In some embodiments, the calcination parameters are 350-500° C. and 4 hours of heating.

[0018] As an embodiment, the heating rate of the calcination is 2-5°C / min.

[0019] In some embodiments, the heating rate of the calcination is 2.5-5° C. / min.

[0020] As an embodiment, the preparation method of the Co-La-Ca composite target material is: cold-pressing uniformly mixed Co, La and Ca powders into a mold, then heat-treating the mixture under a protective atmosphere, and obtaining the composite target material after cooling.

[0021] As an embodiment, the cold pressing is performed at a pressure of 400 to 600 MPa and for 10 to 30 minutes.

[0022] In some embodiments, the cold pressing is performed at a pressure of 500 MPa and for 20 minutes.

[0023] As an embodiment, the heat treatment is performed at a heating rate of 2 to 5°C / min and a temperature of 900 to 1200°C for 3 to 5 hours.

[0024] In some embodiments, the heat treatment is heating to 1200° C. and keeping the temperature for 4 hours.

[0025] In some embodiments, the heating rate of the heat treatment is 5° C. / min.

[0026] As an embodiment, the Co, La and Ca powders are mixed by ball milling.

[0027] As an embodiment, the ball milling parameters are: ball-to-material ratio 5:1-15:1, rotation speed 150-300 rpm, and time 120-240 min.

[0028] In some embodiments, the ball milling parameters are as follows: the ball milling medium is cemented carbide balls, the ball-to-material ratio is 10:1, the rotation speed is 200 rpm, and the time is 15 min.

[0029] As an embodiment, during the magnetron sputtering, the reaction chamber is first evacuated to a vacuum of 1×10 -6 Torr or less, and then introduce sputtering gas.

[0030] As an implementation plan, the magnetron sputtering parameters are: argon flow rate 20~50sccm, background vacuum ≤1×10-6Torr, chamber working pressure 1×10-3~5×10-3Torr, sputtering power using DC sputtering 80~120W, substrate temperature 15~25℃, target temperature 25~150℃, target-substrate distance 6~8cm, substrate rotation speed 10~20rpm, and sputtering time 20~30min.

[0031] In some embodiments, the magnetron sputtering parameters are: argon flow rate 20 sccm, chamber working pressure 0.5 Pa, sputtering power 100 W, substrate temperature 25°C, target temperature 50°C, target-substrate distance 7 cm, substrate rotation speed 15 rpm, and sputtering time 30 min.

[0032] In some embodiments, the La—Ca—Co deposition thickness is 2.2 μm.

[0033] As an embodiment, the purity of the Co, La and Ca powders is not less than 99.9%, D50 The particle sizes are 1-10 μm, 5-20 μm and 10-30 μm respectively.

[0034] In some embodiments, the D of the Co, La and Ca powders 50 The particle sizes are 8 μm, 10 μm and 20 μm respectively.

[0035] As an embodiment, the base material is platinum-coated titanium felt.

[0036] As an embodiment, the thickness of the base material is 100-400 μm.

[0037] In some embodiments, the base material has a thickness of 200 μm.

[0038] As an embodiment, the substrate material is first subjected to surface polishing and cleaning treatments before deposition.

[0039] As an embodiment, the base material is cleaned with pure water and anhydrous ethanol in sequence.

[0040] As an embodiment, after the magnetron sputtering is completed, the deposited sample is washed and vacuum-dried to obtain the substrate with La—Ca—Co deposited on the surface.

[0041] In some embodiments, after the magnetron sputtering is completed, the deposited sample is washed with deionized water.

[0042] As an embodiment, the vacuum degree of the vacuum drying is 1-10 Pa and the temperature is 50-70°C.

[0043] In some embodiments, the vacuum degree of the vacuum drying is 5 Pa and the temperature is 60°C.

[0044] <Third Aspect>

[0045] The present invention provides an application of a La and Ca dual-doped Co3O4 electrocatalyst in electrocatalytic hydrogen evolution.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1) Target preparation and precise element control

[0048] The present invention ensures uniform dispersion of Co, La, and Ca by first fully grinding them. A composite target material is obtained through cold pressing and heat treatment, and the preparation method is simple and convenient. Furthermore, the ratio of Co, La, and Ca can be precisely controlled by combining magnetron sputtering technology. By simply changing the target material composition, thin films with different formulation ratios can be prepared on a substrate material. Further calcination treatment is performed to prepare a LaCa-Co3O4 electrocatalyst having a hexagonal porous stacked nanosheet structure. Because the ratio of elements such as La and Ca is precisely controlled through the self-made target material, the catalyst has excellent repeatability and stability. The electrocatalyst has a high specific surface area, uniform doping, and excellent catalytic performance. At the same time, its hydrophilicity is significantly improved, which can promote the rapid diffusion and accumulation of reactants and effectively increase the catalytic rate.

[0049] 2) Preparation of high-purity electrocatalyst films by magnetron sputtering

[0050] Using magnetron sputtering technology, a uniform La-Ca-Co thin film is deposited on the PTL surface. This technology is performed in a vacuum environment, avoiding impurity contamination and enabling the production of high-purity thin films. It is particularly suitable for the preparation of materials such as electrocatalysts, which require extremely high purity. Furthermore, magnetron sputtering introduces a magnetic field, which improves sputtering efficiency, making the process more stable and efficient than conventional sputtering. By precisely controlling sputtering parameters such as power, time, and gas flow, the film thickness and performance can be precisely controlled, achieving uniform deposition over a large area and ensuring consistent film thickness and composition distribution. Furthermore, magnetron sputtering can be performed at low temperatures (e.g., room temperature), making it suitable for heat-sensitive substrates (such as PTL), avoiding damage to the substrate caused by high temperatures and reducing energy consumption. During sputtering, high-energy particles bombard the PTL substrate, enhancing the adhesion between the La and Ca particles and the Co3O4 film and PTL substrate, significantly improving the stability and durability of the catalyst. Furthermore, magnetron sputtering enables uniform deposition of materials on complex-shaped substrates (such as porous PTL meshes), greatly expanding its application range.

[0051] 3) Advantages of base materials

[0052] Platinized titanium felt (PTL) was selected as the substrate, fully utilizing the titanium mesh's high mechanical strength, good conductivity, and corrosion resistance. The Pt coating ensures the substrate's catalytic activity and chemical stability, providing stable support and excellent electron transport pathways for the electrocatalyst. The prepared LaCa-Co3O4 hexagonal nanosheets are evenly distributed on the surface of the Pt-coated Ti mesh, densely stacked to form a uniform coating. High-magnification SEM images show that the nanosheet surface is rich in microporous structures, increasing the specific surface area, providing favorable channels for electrolyte diffusion, and promoting sufficient contact between the electrolyte and the catalyst.

[0053] 4) Excellent electrocatalyst performance

[0054] Co3O4 serves as a hydrophilic surface for acidic OER, and lanthanide elements (La) are introduced as hydrophobic sites due to their unique relative hydrophobicity to regulate the interfacial water environment, disrupt the ordered interfacial water hydrogen bond network, stabilize the skeleton oxygen atoms, and inhibit lattice oxygen dissolution. At the same time, the introduction of leachable Ca elements successfully produces highly active unsaturated Co sites. The hydrophilicity of Ca effectively promotes interaction with interfacial water and accelerates the formation and conversion of reaction intermediates. This atomic-level hydrophilic (Co) hydrophobic (La) coupling motif (LaCa-Co3O4) significantly improves the stability of acidic OER compared to traditional OER materials, achieves a balance between activity and stability, improves the water / catalyst interface microenvironmental effect at the atomic level, and opens up a new path to improve catalytic stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0056] Figure 1 1 is a comparative XRD graph of the electrocatalysts prepared in Example 1 of the present invention and Comparative Example 3;

[0057] Figure 2 1 is a comparative XRD graph of the electrocatalysts prepared in Example 1 and Comparative Examples 1 and 2 of the present invention;

[0058] Figure 3 is a SEM image of the electrocatalyst prepared in Example 1 of the present invention;

[0059] Figure 4 This is a SEM image of the electrocatalyst prepared in Comparative Example 1 of the present invention;

[0060] Figure 5 This is a SEM image of the electrocatalyst prepared in Comparative Example 2 of the present invention;

[0061] Figure 6 TEM image of the LaCa-Co3O4 catalyst prepared in Example 1 of the present invention;

[0062] Figure 7 Graph showing the OER performance of the electrocatalysts in Example 1 and Comparative Examples 1 to 4 of the present invention in a 0.5 mol / L H2SO4 solution;

[0063] Figure 8 Graph showing the OER performance of the electrocatalysts prepared in Examples 1, 4, and 5 of the present invention in a 0.5 mol / L H2SO4 solution;

[0064] Figure 9 The electrocatalysts prepared in Example 1 and Comparative Example 3 of the present invention were -2The stability comparison chart below;

[0065] Figure 10 Polarization curves of the electrocatalysts prepared in Example 1 and Comparative Example 3 of the present invention in the PEMWE system;

[0066] Figure 11 The LaCa-Co3O4 catalyst prepared in Example 1 of the present invention was heated in the PEMWE system at 1 A·cm -2 stability under . DETAILED DESCRIPTION

[0067] The present invention will be described in detail below with reference to the examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that those skilled in the art may make several adjustments and improvements without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0068] For ease of understanding, the spinel structure of Co3O4 mentioned below is first explained:

[0069] The general formula of spinel structure is AB2O4, where A is a divalent cation and B is a trivalent cation. 2- The ions are densely packed in cubic form to form a structural framework, with A occupying the tetrahedral gaps and B occupying the octahedral gaps;

[0070] For spinel structured Co3O4, the A position is composed of Co 2+ Occupied, position B is occupied by Co 3+ occupy.

[0071] Example 1

[0072] This embodiment provides a method for preparing LaCa-Co3O4 material, comprising the following steps:

[0073] S1. Cut a 200 μm thick platinum-coated titanium felt (PTL) into a size of 2.5 cm × 1 cm, and polish it with 500-mesh, 600-mesh, 800-mesh, and 1000-mesh silicon carbide (SiC) water-abrasive sandpaper to obtain a PTL sheet with a surface roughness Ra of 0.8 to 1.2 μm. Then, ultrasonically treat the PTL sheet in pure water for 3 minutes to remove surface impurities, rinse it with anhydrous ethanol five times, and dry it at room temperature to use as the substrate material.

[0074] S2, Co, La and Ca powder with purity ≥99.9%, D 50The particle sizes were 8 μm, 10 μm, and 20 μm, respectively. Powders were weighed according to the mass ratio of Co:La:Ca = 52.34:20.08:5.25 and placed in a ball mill. The ball milling medium was a cemented carbide ball with a diameter of 0.5 cm. The ball-to-material ratio was 10:1. The ball milling was carried out at a speed of 200 rpm for 15 min to ensure uniform mixing.

[0075] S3, the uniformly mixed powder is placed into a mold and cold pressed into a target material on a hydraulic press at a pressure of 500 MPa for 20 minutes;

[0076] S4. Place the cold-pressed target in a high-temperature sintering furnace, heat it to 1200°C at a heating rate of 5°C / min in an argon atmosphere (flow rate of 20 sscm), keep it at that temperature for 4 hours, and then cool it naturally to room temperature to obtain a dense Co-La-Ca composite target;

[0077] S5. Fix the PTL sheet in the magnetron sputtering equipment and install the Co-La-Ca composite target on the target holder. Set the sputtering parameters: first evacuate the reaction chamber to 1×10 -6 Torr or less, to minimize the interference of impurity gases; then, Ar was used as the sputtering gas, with a flow rate of 20 sccm, a chamber operating pressure of 0.5 Pa, a power supply mode of DC, a sputtering power of 100 W, a substrate temperature of 25°C, a target temperature of 50°C, a target-substrate distance of 7 cm, a substrate rotation speed of 15 rpm, and a sputtering time of 30 min. A LaCa-Co material with a deposition thickness of 2.18 μm was obtained on the surface of the PTL sheet, which is represented as a PTL-LaCa-Co substrate;

[0078] S6. Rinse the surface of the PTL-LaCa-Co substrate obtained in step S5 three times with deionized water to remove loose sediments, and then place the PTL-LaCa-Co substrate in a vacuum drying oven and dry it at 60° C. for 12 h;

[0079] S7. The dried PTL-LaCa-Co substrate was transferred to an alumina crucible, placed in a muffle furnace, and heated to 350°C at 5°C / min in an air atmosphere. After keeping the temperature for 4 hours, the substrate was naturally cooled to room temperature to obtain a LaCa-Co3O4 catalyst on the surface of the PTL.

[0080] Example 2

[0081] This embodiment provides a method for preparing LaCa-Co3O4 material, comprising the following steps:

[0082] S1. Cut a 200 μm thick platinum-coated titanium felt (PTL) into a size of 2.5 cm × 1 cm, and polish it with 500-mesh, 600-mesh, 800-mesh, and 1000-mesh silicon carbide (SiC) water-abrasive sandpaper to obtain a PTL sheet with a surface roughness Ra of 0.8 to 1.2 μm. Then, ultrasonically treat the PTL sheet in pure water for 3 minutes to remove surface impurities, rinse it with anhydrous ethanol five times, and dry it at room temperature to use as the substrate material.

[0083] S2, Co, La and Ca powder with purity ≥99.9%, D 50 The particle sizes were 8 μm, 10 μm, and 20 μm, respectively. Powders were weighed according to the mass ratio of Co:La:Ca = 52.34:20.08:5.25 and placed in a ball mill with carbide balls as the ball-to-material ratio of 10:1. The milling was carried out at a speed of 200 rpm for 15 min to ensure uniform mixing.

[0084] S3, the uniformly mixed powder is placed into a mold and cold pressed into a target material on a hydraulic press at a pressure of 500 MPa for 20 minutes;

[0085] S4. Place the cold-pressed target in a high-temperature sintering furnace, heat it to 1200°C at a heating rate of 5°C / min in an argon atmosphere (flow rate of 20 sscm), keep it at that temperature for 4 hours, and then cool it naturally to room temperature to obtain a dense Co-La-Ca composite target;

[0086] S5. Fix the PTL sheet in the magnetron sputtering equipment and install the Co-La-Ca composite target on the target holder. Set the sputtering parameters: first evacuate the reaction chamber to 1×10 -6 Torr or less, minimize the interference of impurity gases; then use Ar as sputtering gas, flow rate 20sccm, power mode: DC, sputtering power 100W, substrate temperature 25℃, target temperature 50℃, target-substrate distance 7cm, substrate rotation speed 15rpm, sputtering time 30min, and obtain a LaCa-Co material with a deposition thickness of 2.22μm on the surface of the PTL sheet, namely the PTL-LaCa-Co substrate;

[0087] S6. Rinse the surface of the PTL-LaCa-Co substrate obtained in step S5 three times with deionized water to remove loose sediments, and then place the PTL-LaCa-Co substrate in a vacuum drying oven and dry it at 60°C for 12 hours.

[0088] S7. The dried PTL-LaCa-Co substrate was transferred to an alumina crucible, placed in a muffle furnace, and heated to 400°C at a rate of 2.5°C / min in an air atmosphere. After keeping the temperature for 4 hours, the substrate was naturally cooled to room temperature to obtain a LaCa-Co3O4 catalyst on the surface of the PTL.

[0089] Example 3

[0090] This embodiment provides a method for preparing LaCa-Co3O4 material, comprising the following steps:

[0091] S1. Cut a 200 μm thick platinum-coated titanium felt (PTL) into a size of 2.5 cm × 1 cm, and polish it with 500-mesh, 600-mesh, 800-mesh, and 1000-mesh silicon carbide (SiC) water-abrasive sandpaper to obtain a PTL sheet with a surface roughness Ra of 0.8 to 1.2 μm. Then, ultrasonically treat the PTL sheet in pure water for 3 minutes to remove surface impurities, rinse it with anhydrous ethanol five times, and dry it at room temperature to use as the substrate material.

[0092] S2, Co, La and Ca powder with purity ≥99.9%, D 50 The particle sizes were 8 μm, 10 μm, and 20 μm, respectively. Powders were weighed according to the mass ratio of Co:La:Ca = 52.34:20.08:5.25 and placed in a ball mill. The ball milling medium was cemented carbide balls with a ball-to-material ratio of 10:1. The milling was carried out at a speed of 200 rpm for 15 min to ensure uniform mixing.

[0093] S3, the uniformly mixed powder is placed into a mold and cold pressed into a target material on a hydraulic press at a pressure of 500 MPa for 20 minutes;

[0094] S4. Place the cold-pressed target in a high-temperature sintering furnace, heat it to 1200°C at a heating rate of 5°C / min in an argon atmosphere (flow rate of 20 sscm), keep it at that temperature for 4 hours, and then cool it naturally to room temperature to obtain a dense Co-La-Ca composite target;

[0095] S5. Fix the PTL sheet in the magnetron sputtering equipment and install the Co-La-Ca composite target on the target holder. Set the sputtering parameters: first evacuate the reaction chamber to 1×10 -6 Torr or less, minimize the interference of impurity gases; then use Ar as sputtering gas, flow rate 20sccm, power mode: DC, sputtering power 100W, substrate temperature 25℃, target temperature 50℃, target-substrate distance 7cm, substrate rotation speed 15rpm, sputtering time 30min, and obtain a LaCa-Co material with a deposition thickness of 2.23μm on the surface of the PTL sheet, namely the PTL-LaCa-Co substrate;

[0096] S6. Rinse the surface of the PTL-LaCa-Co substrate obtained in step S5 three times with deionized water to remove loose sediments, and then place the PTL-LaCa-Co substrate in a vacuum drying oven and dry it at 60° C. for 12 h;

[0097] S7. The dried PTL-LaCa-Co substrate was transferred to an alumina crucible, placed in a muffle furnace, and heated to 500°C at 5°C / min in an air atmosphere. After keeping the temperature for 4 hours, the substrate was naturally cooled to room temperature to obtain a LaCa-Co3O4 catalyst on the surface of the PTL.

[0098] Example 4

[0099] This comparative example provides a method for preparing LaCa-Co3O4 material. The steps are basically the same as those in Example 1, except that:

[0100] In step S2, Co, La and Ca powders with a purity of ≥99.9% are weighed according to a mass ratio of Co:La:Ca=40:40:20 and ball milled, and then prepared into a target material according to step S3 and subjected to subsequent processing.

[0101] Example 5

[0102] This comparative example provides a method for preparing LaCa-Co3O4 material. The steps are basically the same as those in Example 1, except that:

[0103] In step S2, Co, La and Ca powders with a purity of ≥99.9% are weighed according to a mass ratio of Co:La:Ca=20:40:40, and ball milled, and then prepared into a target material according to step S3 and subjected to subsequent processing.

[0104] Comparative Example 1

[0105] This comparative example provides a method for preparing La-Co3O4 material. The steps are basically the same as those in Example 1, except that:

[0106] In step S2, Co and La powders with a purity of ≥99.9% are weighed according to a mass ratio of Co:La=52.34:47.66, and ball-milled. Then, the target material is prepared according to step S3 and subsequently processed.

[0107] Comparative Example 2

[0108] This comparative example provides a method for preparing Ca-Co3O4 material. The steps are basically the same as those in Example 1, except that:

[0109] In step S2, Co and Ca powders with a purity of ≥99.9% are weighed in a mass ratio of 52.34:47.66 and ball-milled. Target materials are then prepared according to step S3 and subsequently processed.

[0110] Comparative Example 3

[0111] This comparative example provides a method for preparing Co3O4 material. The steps are basically the same as those in Example 1, except that:

[0112] In step S2, only Co with a purity of ≥99.9% is ball-milled, and then prepared into a target material according to step S3, and then subjected to subsequent processing.

[0113] Comparative Example 4

[0114] This comparative example provides a commercial IrO2 catalyst purchased from McLean, product number I811643, model I811643-1g.

[0115] Performance testing:

[0116] 1. XRD analysis

[0117] The electrocatalytic materials prepared in Example 1, Comparative Examples 1 and 2 were subjected to XRD analysis. The results are as follows: Figure 1 and Figure 2 shown.

[0118] As can be seen in the figure, all diffraction peaks of LaCa-Co3O4 correspond to the spinel Co3O4 structure. Compared to Co3O4, the overall diffraction peaks of LaCa-Co3O4 shift slightly to lower angles, indicating that the Co3O4 lattice expands due to the incorporation of La atoms with larger ionic radius. This structural change demonstrates the successful La and Ca doping.

[0119] 2. SEM Scanning Electron Microscope Analysis

[0120] The electrocatalytic materials prepared in Examples 1, 4 and 5 were analyzed by SEM. Figures 3 to 5 As shown in the figure, the electrocatalytic material prepared by the present invention presents a hexagonal porous stacked sheet structure, and trace amounts of La and Ca doping do not affect the overall structure of Co3O4.

[0121] 3. TEM analysis

[0122] The electrocatalytic material prepared in Example 1 was subjected to TEM scanning electron microscope analysis. The results are as follows: Figure 6 As shown in Figure 2, the lattice spacing between the (311) planes of LaCa-Co3O4 is 0.251 nm, which is larger than the lattice spacing of pristine Co3O4 (0.244 nm). This increase in lattice spacing can be attributed to the introduction of La and Ca elements with larger atomic radii. This lattice expansion can adjust the band structure, optimize electron transfer, and enhance catalytic activity.

[0123] 4. ICP detection

[0124] The Co, La and Ca elements in the electrocatalytic materials prepared in Examples 1 to 3 were analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES). During the test, a small amount of sample material was taken, weighed, and a solution was obtained after digestion. The treated sample was tested using an inductively coupled plasma optical emission spectrometer. The treated sample was introduced into the nebulizer through a peristaltic pump and atomized and excited in a high-temperature plasma. The light signal emitted by each element at the characteristic wavelength was received by a photodetector and quantitatively analyzed according to the standard curve. To ensure the accuracy of the results, the instrument was calibrated using a variety of standard solutions of known concentrations before the test. At the same time, a blank control was set for each group of samples, and some samples were repeatedly measured to evaluate the test error. The test results showed that the mass ratio of Co, La and Ca was (51.34-52.51): (20.99-21.08): (4.01-4.25).

[0125] 4. OER Testing

[0126] Test Method: A platinum wire (0.5 mm diameter, 10 cm length, purity ≥99.9%) was used as the counter electrode, a mercury-mercuric sulfate reference electrode, and the electrocatalytic material to be tested as the working electrode. Testing was performed on a Gamry Reference 3000 electrochemical workstation. The electrolyte was 0.5 mol / L H₂SO₄ solution, and the scan rate was 5 mV / s.

[0127] The electrocatalytic materials prepared in Examples 1, 4 and 5 and the electrocatalyst materials of Comparative Examples 1 to 4 were subjected to OER tests. The results are as follows: Figure 7 and Figure 8 As shown in Table 1, the results of the cross-point position are shown in Table 1. As can be seen from the figure, the LaCa-Co3O4 prepared in Example 1 has a -2 The lowest overpotential is 260 mV, which is significantly lower than Co3O4 (360 mV) and commercial IrO2 (300 mV), indicating that the OER performance of the catalyst prepared by the present invention is good.

[0128] Table 1

[0129] Overpotential (mV) Example 1 260 Example 2 275 Example 3 280 Example 4 286 Example 5 293 Comparative Example 1 290 Comparative Example 2 325 Comparative Example 3 360 Comparative Example 4 300

[0130] 5. Stability test

[0131] Test method: Fixed target current density 200mA·cm -2 The changes of potential over time were recorded in real time using an electrochemical workstation.

[0132] The OER stability of the electrocatalytic materials of Example 1 and Comparative Example 3 in acidic medium is shown in the following table. Figure 9 As shown. Figure 9The OER stability test results show that the incorporation of Ca and La improves the activity and stability of Co3O4 respectively. LaCa-Co3O4 -2 Under the same conditions, LaCa-Co3O4 can also achieve a service life of 800h without obvious degradation. The catalyst prepared by the present invention has high stability under acidic water electrolysis conditions, and thus can meet the use requirements of full pH water electrolysis.

[0133] 6. Application and Stability Test in PEMWE System

[0134] Test method: Select the PEMWE system, operating temperature 80℃, pressure 1atm, electrocatalyst loaded on PTL to make membrane electrode, circulating water flow rate 25mL / min.

[0135] The electrocatalytic material prepared in Example 1 and the Co3O4 catalyst material of Comparative Example 3 were used in the PEMWE system. Figure 10 The PEMWE system using LaCa-Co3O4 anode only requires a cell voltage of 1.52 V and 1.61 V to achieve 1 and 2 A·cm, respectively. -2 The current density is high and it shows excellent performance in practical applications.

[0136] The stability of the catalyst prepared in Example 1 in the PEMWE system is shown in the following table. Figure 11 As shown in Figure 2, the LaCa-Co3O4 anode of Example 1 has a high thermal conductivity at 1A cm -2 It can operate stably for at least 500 h at a current density of 10.5 μV h-1, and the degradation rate is only 10.39 μV h-1. -1 , indicating its high stability under high current density conditions.

[0137] In summary, the present invention uses Pt-coated titanium mesh (PTL) as a substrate and working electrode, and uses a homemade target to deposit a Co-LaCa film on its surface by magnetron sputtering; the obtained PTL sheet is then washed, dried and calcined to obtain a catalyst, achieving uniform doping of La and Ca, constructing a hydrophilic-hydrophobic coupling structure on the surface of the catalyst, optimizing the water / catalyst interface microenvironment at the atomic level, and the catalytic material has excellent electrocatalytic activity and long-term stability, inhibiting lattice oxygen dissolution, and the stable lattice oxygen skeleton significantly improves the acid OER corrosion resistance of LaCa-Co3O4 at high current density, and significantly improves the acid OER stability. At the same time, the introduction of Ca produces highly active unsaturated Co sites, balances activity and stability, promotes interfacial water interaction, and accelerates the formation and conversion of reaction intermediates. The preparation method of the present invention is simple and easy to operate, has mild reaction conditions, and is low in cost. The obtained catalyst has good performance, solves the problems of low catalytic performance and poor stability of cobalt-based catalysts, and has broad application prospects in the field of water electrolysis (especially in the field of hydrogen production by water electrolysis).

[0138] It should be noted that the electrocatalyst and substrate material prepared in the performance test are a whole and are not separated.

[0139] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A La and Ca doped Co3O4 electrocatalyst, characterized in that: La partially replaces Co in Co3O4 3+ ions, Ca partially replaces Co in Co3O4 2+ ions, the mass ratio of Co, La and Ca elements is 100:(30~200):(5~200).

2. The electrocatalyst according to claim 1, characterized in that In the electrocatalyst, the mass ratio of Co, La and Ca is 100:(35-40):(5-15).

3. A method for preparing the La and Ca dual-doped Co3O4 electrocatalyst according to any one of claims 1 to 2, characterized in that: The following steps are involved: A Co-La-Ca composite target is used to deposit Co, La, and Ca elements on a substrate material by a magnetron sputtering method. The mass ratio of Co, La, and Ca in the composite target is 100:(30-200):(5-200), and the deposition thickness is 2.1-2.3 μm, thereby obtaining a substrate with La-Ca-Co deposited on the surface. The substrate with La-Ca-Co deposited on the surface is calcined at 300-500° C. for 3-5 hours in an air atmosphere, and after cooling, the La and Ca dual-doped Co3O4 electrocatalyst is obtained on the surface of the substrate.

4. The method according to claim 3, characterized in that The magnetron sputtering parameters are: argon flow rate 20-30 sccm, background vacuum ≤ 1×10 -6 Torr, chamber working pressure 1×10 -3 ~5×10 -3 Torr, sputtering power adopts DC sputtering: 80~120W, substrate temperature 15~25℃, target temperature 25~150℃, target-substrate distance 6~8cm, substrate rotation speed 10~20rpm, sputtering time 20~30min.

5. The method according to claim 3, characterized in that The base material is a platinum-plated titanium felt sheet with a thickness of 100 to 400 μm.

6. The method according to claim 3, characterized in that The preparation method of the Co-La-Ca composite target material comprises: cold-pressing uniformly mixed Co, La and Ca powders into a mold, performing heat treatment under a protective atmosphere, and obtaining the composite target material after cooling.

7. The method according to claim 6, characterized in that Also includes any of the following technical features: A. The cold pressing is performed at a pressure of 400 to 600 MPa for 10 to 30 minutes; B. The heat treatment is performed at a heating rate of 2-5°C / min and a temperature holding time of 900-1200°C for 3-5h.

8. The method according to claim 6, characterized in that The Co, La and Ca powders are mixed by ball milling.

9. The method according to claim 6, characterized in that The purity of the Co, La and Ca powders is not less than 99.9%, and the particle sizes are 1-10 μm, 5-20 μm and 10-30 μm respectively.

10. Use of the La and Ca doped Co3O4 electrocatalyst according to claim 1 or 2 in electrocatalytic hydrogen evolution, characterized in that: The electrocatalyst is prepared according to the preparation method according to any one of claims 3 to 9.

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