Cobalt-copper diatom ORR / OER catalyst and preparation method and application thereof

Abstract

The invention relates to the technical field of ORR / OER catalysts, and discloses a cobalt-copper diatom ORR / OER catalyst and a preparation method and application thereof. CeO2 hollow nanospheres are prepared by adopting a hard template method; the preparation method comprises the following steps: adsorbing complex cations of Co and complex cations of Cu on the surface of CeO2 by adopting a strong electrostatic adsorption method to obtain a CoCu precursor coated CeO2; and reducing the CoCu precursor (at) CeO2 in hydrogen to obtain the cobalt-copper diatom ORR / OER catalyst CoCu (at) CeO2. The cobalt-copper diatomic ORR / OER catalyst CoCu-CeO2 prepared by the invention belongs to a diatomic catalyst, and has good activity and stability in the electrochemical oxygen evolution and oxygen reduction reaction process; the preparation process is simple and rapid, and the preparation cost is lower due to the use of non-noble metal.

Description

Technical Field

[0001] The present invention relates to the technical field of ORR / OER catalysts, and in particular to a cobalt-copper diatomic ORR / OER catalyst and a preparation method and application thereof. Background Art

[0002] The electrochemical oxygen evolution / reduction reaction (OER / ORR), as the most promising reaction in sustainable energy conversion technology, is limited in its application in metal-air batteries by its inherently slow kinetics. In order to maximize the overall power output efficiency of these energy conversion devices, the use of electrocatalysts that can reduce the energy barriers in the OER / ORR reactions is essential. To date, iridium / ruthenium and platinum group catalysts are still commonly used OER and ORR catalysts. However, their long-term development is to some extent restricted due to their low crustal abundance, high cost, and poor durability. In view of this, the development of catalysts with abundant earth reserves and significant economic advantages, which can serve as alternatives to precious metals, has become a research focus in the past few decades.

[0003] In recent years, single-atom catalysts (SACs) with multiple well-defined coordination structures have attracted increasing attention due to their high metal atom utilization and unusual catalytic activity. However, in complex reactions such as OER / ORR involving multiple elementary reactions, the single catalytic active center of SACs hinders further improvement of their performance. As an optimization, bimetallic atom catalysts (DACs) have more complex / flexible active sites and may thus exhibit particularly good catalytic performance. Despite the attractive advantages of DACs, the thermal aggregation behavior of metal atoms, restricted mass / charge transfer, and weak bonding to the metal support have to some extent limited their further enhancement of activity and stability in the OER / ORR process. By adjusting the geometric arrangement and electronic properties of the active sites, these limitations of OER / ORR have been significantly improved. This suggests that, despite considerable challenges, the OER and ORR activities of DACs can be maximized by determining the optimal combination of bimetallic-support interactions and metal-metal interactions.

[0004] To date, various types of supported DACs have been developed as ideal models for achieving both bimetallic and metal-metal interactions. Carbon materials, with their high conductivity and large surface area, are generally considered to be the optimal supports for DACs in electrocatalysis. However, carbon-based supports inevitably encounter carbon degradation / corrosion issues in electrocatalysis, especially for reactions with voltages above 0.8 V, which can lead to poor catalyst stability in water splitting reactions. Compared to carbon-based supports, solid oxide supports (including but not limited to MgO, Fe3O4, SiO2, CeO2, and TiO2) exhibit enhanced stability. Metal-support interactions between the metal and the oxide support can induce charge redistribution on the metal oxide surface. Upon H2 reduction treatment, the formation of reduced metal cations affects the support's d orbitals, thereby promoting electron transfer between the metal species and its support. As a key 4f oxide, CeO2 is considered an ideal support for atomic metal active sites, particularly noble metal atoms, due to its ability to anchor and stabilize single metal atoms by binding to surface O / OH groups or by replacing Ce sites. In addition, long-range synergy (LRS) refers to the specific interaction between the two active metal centers in DACs, and the catalytic efficiency and selectivity of DACs are closely related to LRS. Therefore, regulating the type and strength of LRS is crucial to improving the catalytic activity of oxide-supported diatomic catalysts. The focus of this regulation depends on the distance and compatibility between the diatomic centers. Unfortunately, there are few reports on CeO2-supported non-noble metal diatomic catalysts, mainly because this breaks the linear relationship between activity and stability inherent in atomic-level catalysts.

[0005] Therefore, the ORR / OER catalysts in the prior art have the following disadvantages:

[0006] 1. Single-atom catalysts with specific configurations have insufficient selectivity for multi-step reactions, resulting in insufficient activity and stability in specific reaction processes;

[0007] 2. The diatoms weakly bound to the support are easily aggregated during high-temperature activation and reaction, so the diatomic catalysts are not active enough for electrochemical oxygen evolution and oxygen reduction reactions;

[0008] 3. The preparation process of diatomic catalysts is very complicated and uses precious metals, resulting in high preparation costs.

[0009] Therefore, there is an urgent need for cobalt-copper diatomic ORR / OER catalysts and their preparation methods and applications to solve the above technical problems. Summary of the Invention

[0010] The purpose of the present invention is to overcome the existing technical problems and provide a cobalt-copper diatomic ORR / OER catalyst and its preparation method and application.

[0011] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0012] The preparation method of the cobalt-copper diatomic ORR / OER catalyst comprises the following steps:

[0013] S1, CeO2 hollow nanospheres were prepared using a hard template method (carbon spheres as templates);

[0014] S2, using strong electrostatic adsorption method to adsorb the complex cations of Co and Cu on the surface of CeO2 hollow nanospheres to obtain CoCu precursor@CeO2;

[0015] S3, the CoCu precursor @CeO2 is reduced in hydrogen to obtain the cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2.

[0016] In the CoCu@CeO2 catalyst prepared by the present invention, Co and Cu exist in the form of non-bonded diatoms.

[0017] Preferably, step S1 includes the following steps:

[0018] Ce(NO3)3·6H2O, hexamethylenetetramine and deionized water are uniformly mixed and then carbon balls are added to obtain a mixture; the mixture is reacted, and the reaction product is separated, washed, dried and heated to obtain hollow CeO2 nanospheres.

[0019] Preferably, in step S1, the ratio of Ce(NO3)3·6H2O, hexamethylenetetramine, deionized water, and carbon spheres is 0.36:0.58:30:0.20, and the comparison unit is g:g:mL:g.

[0020] Preferably, in step S1, carbon spheres are added and then ultrasonically dispersed to obtain a mixture;

[0021] The mixture was reacted under the following conditions: reflux in an oil bath at 60-120°C for 1-4h;

[0022] The heating conditions are: heating at 300-600°C for 1-4h.

[0023] Preferably, the obtained hollow CeO2 nanospheres have a surface potential of zero charge (PZC) of 6.7.

[0024] Preferably, the diameter of the carbon spheres is 150-250 nm.

[0025] More specifically, the average diameter of the carbon spheres is 200 nm.

[0026] Preferably, the preparation process of the carbon spheres is as follows:

[0027] Glucose is dissolved in deionized water to obtain a solution; the solution is placed in an autoclave for reaction, and the product obtained by the reaction is separated and washed to obtain carbon spheres; the mass volume ratio of glucose to deionized water is 8:40, and the unit of comparison is g:mL; the reaction temperature in the autoclave is 160°C, and the reaction time is 3.5 hours.

[0028] Specifically, step S1 includes the following steps:

[0029] S1, glucose (8.0 g) was dissolved in deionized water (40 mL) and stirred to form a clear solution; the solution was transferred to a 50 mL autoclave and maintained at 160°C for 3.5 h. The reaction product was centrifuged and washed to obtain brown carbon spheres;

[0030] In a three-necked flask, 0.36 g of Ce(NO3)3·6H2O, 0.58 g of hexamethylenetetramine, and 30 mL of deionized water were added and stirred vigorously to form a clear solution. 0.20 g of carbon spheres were added to the above solution and ultrasonically dispersed for at least 20 minutes to obtain a mixture.

[0031] The mixture was refluxed in an oil bath at 60-120°C for 1-4 hours, and the obtained white product was collected by centrifugation, washed several times with water and ethanol, and dried at 60°C overnight to obtain a white powder. The obtained white powder was heated at 300-600°C in air for 1-4 hours to obtain hollow CeO2 nanospheres. The zero charge surface potential (PZC) of the hollow CeO2 nanospheres was 6.7. The heating rate was 1°C min -1 .

[0032] Preferably, step S2 includes the following steps:

[0033] The hollow CeO2 nanospheres are dissolved in concentrated ammonia water, and the pH of the solution is adjusted so that the surface of the hollow CeO2 nanospheres is negatively charged; Co(NO3)2·6H2O and Cu(NO3)2·6H2O are added to the above solution and stirred to obtain a product containing CoCu precursor@CeO2.

[0034] Preferably, in step S2, the mass ratio of hollow CeO2 nanospheres, Co(NO3)2·6H2O, and Cu(NO3)2·6H2O is 50:25:19; the pH of the solution is adjusted to be greater than 6.7; and ultrasonic dispersion is performed after adjusting the pH of the solution.

[0035] Preferably, in step S2, the pH of the solution is adjusted to 9-13.

[0036] Further preferably, in step S2, the pH of the solution is adjusted to 12.

[0037] Specifically, step S2 includes the following steps:

[0038] Dissolve hollow CeO2 nanospheres (50 mg) in concentrated ammonia water and adjust the pH of the solution to greater than 6.7 (so that the surface of CeO2 is negatively charged); ultrasonic dispersion is performed for 20 minutes; Co(NO3)2·6H2O (0.025 g) and Cu(NO3)2·6H2O (0.019 g) are added to the above solution and stirred for 5-60 minutes to fully adsorb and obtain a product containing CoCu precursor@CeO2.

[0039] Preferably, step S3 includes the following steps:

[0040] The product containing CoCu precursor@CeO2 was centrifuged and dried, and then reduced in hydrogen to obtain the cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2.

[0041] Preferably, in step S3, the reduction process in hydrogen is: annealing at 400-700° C. for 2-6 hours in the presence of hydrogen and argon.

[0042] More preferably, in step S3, the annealing temperature is 600°C.

[0043] More specifically, the hydrogen and argon conditions refer to introducing a mixed gas of hydrogen and argon during the annealing process, wherein the volume percentage of hydrogen in the mixed gas is 10%.

[0044] Specifically, step S3 includes the following steps:

[0045] The adsorbed product CoCu precursor@CeO was centrifuged at 60 °C, vacuum dried for 6 h, and then annealed at 400-700 °C for 2-6 h under H2 / Ar conditions to obtain CoCu@CeO2.

[0046] The present invention also includes a cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2 prepared by the above preparation method.

[0047] The present invention also includes the use of a cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2 in electrochemical oxygen evolution and oxygen reduction reactions.

[0048] Working principle:

[0049] The present invention adopts a strong electrostatic adsorption method to simultaneously adsorb complex cations of Co and Cu on CeO2, and prepares an atomically dispersed Co and Cu diatomic catalyst on CeO2; the catalyst can efficiently and stably catalyze electrochemical oxygen evolution and oxygen reduction reactions.

[0050] The present invention synthesizes a CoCu@CeO2 catalyst through strong electrostatic adsorption and thermal anchoring steps. Using carbon spheres as sacrificial templates, hollow CeO2 nanospheres with high surface roughness are prepared. Subsequently, by adjusting the solution pH to greater than 6.7, the surface of the hollow CeO2 nanospheres is given a negative charge, providing a favorable environment for the adsorption of Co and Cu complex cations. Under the strong electrostatic attraction, a dense and uniformly distributed thin layer of CoCu precursor atoms (CoCu precursor@CeO2) rapidly forms on the CeO2 surface. Ultimately, the thin layer of CoCu precursor atoms on the CeO2 surface is embedded into the CeO2 lattice through thermal reduction, forming a CeO2-supported CoCu diatomic catalyst (CoCu@CeO2). The strong electrostatic adsorption ensures the formation of uniform, dense, and stable bimetallic active sites, endowing CoCu@CeO2 with excellent electrocatalytic performance.

[0051] Beneficial effects:

[0052] The present invention prepares a cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2, which is a diatomic catalyst and has good activity and stability in the process of electrochemical oxygen evolution and oxygen reduction reaction; the preparation process of the present invention is simple and fast, and the use of non-precious metals makes the preparation cost lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is an SEM image of the carbon spheres prepared in Example 1 of the present invention;

[0054] Figure 2 This is a schematic diagram of the strong electrostatic adsorption principle in Example 1 of the present invention;

[0055] Figure 3 The SEM and TEM images of CoCu@CeO2 obtained in Example 1 of the present invention are shown;

[0056] Figure 4 The XRD pattern, Raman pattern, EPR pattern and XPS pattern of CoCu@CeO2 obtained in Example 1 of the present invention are shown;

[0057] Figure 5 This is the XANES graph of CoCu@CeO2 obtained in Example 1 of the present invention;

[0058] Figure 6 The OER electrocatalytic performance test results of CoCu@CeO2 obtained in Example 1 of the present invention are as follows: Figure 6 a is the LSV curve of OER test, Figure 6 b is the Tafel slope diagram of OER test, Figure 6 c is the impedance diagram of OER test, Figure 6 d is the CV scan of the OER test, Figure 6 e is C for OER test dl picture; Figure 6 f is the stability diagram of the OER test;

[0059] Figure 7 The ORR electrocatalytic performance test results of CoCu@CeO2 obtained in Example 1 of the present invention are as follows: Figure 7 a is the LSV curve of ORR test, Figure 7 b is the Tafel slope diagram of ORR test, Figure 7 c is the CV scan graph of ORR test, Figure 7 d is C of ORR test dl picture, Figure 7 e is the electron transfer number diagram of ORR test, Figure 7 f is the stability diagram of ORR test;

[0060] Figure 8 The XRD spectrum, XPS total spectrum, EPR spectrum and Raman spectrum of Co@CeO2 obtained in Comparative Example 1 of the present invention are shown;

[0061] Figure 9 This is the OER performance diagram of Co@CeO2 obtained in Comparative Example 1 of the present invention;

[0062] Figure 10 This is the ORR performance diagram of Co@CeO2 obtained in Comparative Example 1 of the present invention;

[0063] Figure 11 The XRD spectrum and XPS total spectrum of Cu@CeO2 obtained in Comparative Example 2 of the present invention are shown;

[0064] Figure 12 This is the OER performance diagram of Cu@CeO2 obtained in Comparative Example 2 of the present invention;

[0065] Figure 13 This is the ORR performance diagram of Cu@CeO2 obtained in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0066] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0067] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses industrial purity or conventional purity used in the art.

[0068] The devices used in the present invention are not particularly limited and can be devices commonly used in the art.

[0069] Example 1

[0070] A CoCu@CeO2 diatomic catalyst, the preparation process of which includes the following steps:

[0071] (1) Glucose (8.0 g) was dissolved in deionized water (40 mL) and stirred to form a clear solution. The solution was transferred to a 50 mL autoclave and maintained at 160°C for 3.5 h. The reaction product was centrifuged and washed to obtain brown carbon spheres.

[0072] Ce(NO3)3·6H2O (0.36 g), hexamethylenetetramine (0.58 g), and DI (30 mL) were added to a three-necked flask and stirred vigorously to form a clear solution. Carbon spheres (0.20 g) were added to the above solution and ultrasonically dispersed for at least 20 minutes. Finally, the mixture was refluxed in a 75°C oil bath for 2 hours. The obtained white product was collected by centrifugation, washed several times with water and ethanol, and dried at 60°C overnight. The obtained white powder was heated at 600°C for 2 hours in air at a heating rate of 1°C min -1 , hollow CeO2 nanospheres were obtained;

[0073] (2) 50 mg of CeO2 nanospheres obtained in step (1) were added to 20 mL of concentrated ammonia solution, the pH of the solution was adjusted to 12, and ultrasonic dispersion was performed for half an hour; Co(NO3)2·6H2O (0.025 g) and Cu(NO3)2·6H2O (0.019 g) were added to the above suspension and stirred for 5 minutes to fully adsorb and obtain a product containing CoCu precursor@CeO2;

[0074] (3) The product containing CoCu precursor@CeO2 was centrifuged at 60°C, vacuum dried for 6 h, and then annealed at 600°C for 3 h in an atmosphere of a mixed gas of H2 and Ar (H2 accounting for 10% by volume of the mixed gas) to obtain CoCu@CeO2.

[0075] The composition, chemical bonds, morphology and microstructure of the CoCu@CeO2 diatomic catalyst obtained in Example 1 of the present invention were systematically studied using modern nano-testing and analysis techniques such as SEM, TEM, XRD and XPS.

[0076] Example 2

[0077] The difference between this embodiment and embodiment 1 is that in step (2), the pH of the solution is adjusted to 9.

[0078] Example 3

[0079] The difference between this embodiment and embodiment 1 is that in step (2), the pH of the solution is adjusted to 13.

[0080] Example 4

[0081] The difference between this embodiment and embodiment 1 is that in step (3), the annealing temperature is 400°C.

[0082] Example 5

[0083] The difference between this embodiment and embodiment 1 is that in step (3), the annealing temperature is 700°C.

[0084] The CoCu@CeO2 diatomic catalysts prepared in Examples 1 to 5 were tested, and the final comparison showed that the product performance was the best when the pH was 12 and the annealing temperature was 600°C in Example 1.

[0085] like Figure 1 Shown is the SEM image of the carbon spheres prepared in Example 1 of the present invention.

[0086] The carbon spheres used in Example 1 of the present invention are produced by thermal polymerization of glucose. The average diameter of the obtained carbon spheres is about 200 nm, ranging from 150 to 250 nm.

[0087] like Figure 2 FIG. 1 is a diagram showing the principle of strong electrostatic adsorption in Example 1 of the present invention.

[0088] Bimetallic CoCu atoms were prepared on CeO2 nanospheres using a strong electrostatic adsorption method in different pH ranges. By adjusting the pH value of the environment, a hydration sheath (i.e., a thin layer of CoCu precursor atoms) of electrostatically adsorbed Co and Cu complex cations was formed on the support surface.

[0089] like Figure 3 As shown, the SEM and TEM images of CoCu@CeO2 obtained in Example 1 of the present invention are shown; Figure 3 As shown in Figure a, the formed CoCu@CeO2 has a spherical structure, which perfectly retains the original morphology and size of the carbon template.

[0090] Depend on Figure 3 As can be seen from Figure b, the surface of the CoCu@CeO2 nanospheres is rough and the average sphere diameter is about 200nm.

[0091] Figure 3 Figure c is a high-magnification TEM image of CoCu@CeO2. The high-magnification TEM image (HRTEM) of CoCu@CeO2 shows obvious lattice fringes with lattice spacings of 0.191 and 0.312 nm, respectively, belonging to the (220) and (111) planes of CeO2. In addition, no obvious metal nanoparticles were found on CeO2, which means that the metal is at the atomic level.

[0092] Figure 3Figure d is the dark field TEM image of CoCu@CeO2. It can be seen from the dark field TEM image of CoCu@CeO2 that the thickness of the hollow sphere is about 31nm.

[0093] Figure 3 Figure e in the figure is the energy dispersive X-ray spectroscopy (EDS) mapping image of CoCu@CeO2, which confirms the uniform distribution of Co, Cu, Ce and O elements on the catalyst surface.

[0094] Figure 3 Figure f is an aberration-corrected high-angle annular scanning transmission electron microscopy image of CoCu@CeO2. Aberration-corrected high-angle annular scanning transmission electron microscopy (HAADF-STEM) was used to verify the formation of isolated bimetallic atoms on CeO2. Since cobalt and copper have lower atomic numbers compared to cerium, the smaller and darker dots under dark field conditions represent single atoms of cobalt or copper ( Figure 3 marked with circles and boxes in f).

[0095] Figure 4 These are the XRD pattern, Raman pattern, EPR pattern and XPS pattern of CoCu@CeO2 obtained in Example 1 of the present invention.

[0096] Figure 4 Figure (a) shows the XRD pattern of CoCu@CeO2. The X-ray diffraction (XRD) pattern shows that the CoCu@CeO2 phase is consistent with pure CeO2 (PDF#34-0394). No diffraction peaks associated with metals or other metal oxides are observed, indicating that the Co and Cu atoms are highly dispersed.

[0097] Figure 4 Figures b, e, f, g, and h are XPS images of CoCu@CeO2; Figure 4 Figure c is the EPR graph of CoCu@CeO2; Figure 4 Figure d is the Raman image of CoCu@CeO2.

[0098] X-ray photoelectron spectroscopy (XPS) was used to measure the surface chemical states of the elements on CoCu@CeO2. Figure 4 b). The XPS spectra of Co 2p and Cu 2p show that Co and Cu in CoCu@CeO2 are both in oxidized states (Co is between 0 and 3+; Cu is between 1+ and 2+), and no zero-valent Co and Cu are detected ( Figure 4 c and 4d). Compared with CeO2, the position of Ce 3d peak shifts toward the direction of low binding energy, which indicates that there is a stronger interaction between the diatoms and the support ( Figure 4 e). The XPS results of O 1s are shown in Figure 4 f.

[0099] like Figure 5 Shown is the XANES graph of CoCu@CeO2 obtained in Example 1 of the present invention.

[0100] In order to study the chemical state and coordination environment of Co and Cu atoms in CoCu@CeO2, X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements were performed from XANES spectra ( Figure 5 a) It can be seen that the absorption edge of Co K-edge in CoCu@CeO2 shifts to higher energy compared with that of Co foil, which indicates that the valence state of Co in CoCu@CeO2 is located at the Co 0 and Co 3+ In addition, from Figure 5 In the EXAFS spectrum in b, it can be observed that CoCu@CeO2 and Co3O4 There is an obvious peak at , which is usually assigned to the Co-O bond, elucidating the clear Co-O coordination environment in CoCu@CeO2. Similarly, the Cu K-edge XANES adsorption edge position of CoCu@CeO2 ( Figure 5 c) shows that Cu in Cu 0 and Cu 2+ The average price between Figure 5 As shown in d, the Cu K-edge FT-EXAFS spectrum of CoCu@CeO2 is There is a main peak at , which is attributed to Cu-O coordination. It is worth noting that there are no typical Co-Co or Cu-Cu bonds, which also proves that there is no atomic Co-Cu configuration.

[0101] like Figure 6 As shown in the figure, the OER electrocatalytic performance test results of CoCu@CeO2 obtained in Example 1 of the present invention are shown. Figure 6 a is the LSV curve of OER test, Figure 6 b is the Tafel slope diagram of OER test, Figure 6 c is the impedance diagram of OER test, Figure 6 d is the CV scan of the OER test, Figure 6 e is C for OER test dl picture; Figure 6 f is the stability diagram of the OER test.

[0102] The OER performance of CoCu@CeO2 was evaluated in a standard three-electrode system under 1.0 M KOH conditions. Figure 6 In a, CoCu@CeO2 obtained a 10 mA cm-2 overpotential of 235 mV. -2The current density is better than RuO2 (255mV). The Tafel slope ( Figure 6 b), the small Tafel value of CoCu@CeO2 indicates that its reaction kinetics is more favorable. Figure 6 The electrochemical impedance spectroscopy (EIS) curve shown in c further shows that CoCu@CeO2 has a small charge transfer resistance (R ct ) and more favorable OER kinetics. From the non-Faraday region cyclic voltammetry test ( Figure 6 d) Obtained double layer capacity (C dl ) is a measure of the electrochemically active surface area (ECSA). The calculation results are as follows Figure 6 As shown in d, the C dl The value is 14.9mF cm -2 , CoCu@CeO2 has a larger ECSA and has more active sites during the reaction. In addition, the stability of the catalyst was characterized by chronopotentiometry ( Figure 6 f). A 200-h stability test was conducted under 1.0 M KOH conditions, and the results showed that the catalyst had good OER stability.

[0103] like Figure 7 As shown in the figure, the ORR electrocatalytic performance test results of CoCu@CeO2 obtained in Example 1 of the present invention are shown. Figure 7 a is the LSV curve of ORR test, Figure 7 b is the Tafel slope diagram of ORR test, Figure 7 c is the CV scan graph of ORR test, Figure 7 d is C of ORR test dl picture, Figure 7 e is the electron transfer number diagram of ORR test, Figure 7 f is the stability diagram of ORR test.

[0104] The ORR performance of CoCu@CeO2 catalyst was measured in a three-electrode system with a rotating ring disk electrode (RRDE) as the working electrode at a speed of 1600 rpm under O2 saturation conditions with 0.1 M KOH. Figure 7 As shown in a, CoCu@CeO2 exhibits strong ORR activity, and its onset potential (E onset ) is as high as 1.05V, close to Pt / C (1.02V). The LSV curve shows that the positive half-wave potential (E 1 / 2 ) is the highest, which is 0.878V, 22mV higher than Pt / C (0.845V). CoCu@CeO2 (79mV dec -1 ) has a lower Tafel slope, indicating that CoCu@CeO2 has superior ORR kinetics ( Figure 7 b). Figure 7 As shown in c, C in the ORR process dl 16.1mF cm -2 , confirming that the long-range synergistic effect between Co and Cu atoms enhances the intrinsic activity of CoCu@CeO2. Figure 7 The EIS curve in d confirms that the charge transfer resistance of CoCu@CeO2 is small, indicating that the charge transfer rate at the interface is fast. The ring-disk electrode (RRDE) test further confirmed the four-electron reaction pathway ( Figure 7 e). The results show that CoCu@CeO2 has a highly selective ORR catalytic performance for direct four-electron transfer. In addition, the catalyst has been subjected to 5000 accelerated durability tests, and the ORR polarization curve E of CoCu@CeO2 is 1 / 2 The value shows a small negative shift of 8mV ( Figure 7 f), showing its excellent stability.

[0105] Comparative Example 1

[0106] The difference between Comparative Example 1 and Example 1 is that Cu(NO3)2·6H2O is not added in step (2), and the rest is the same as Example 1 to obtain Co@CeO2 single-atom catalyst.

[0107] Comparative Example 2

[0108] The difference between Comparative Example 2 and Example 1 is that Co(NO3)2·6H2O is not added in step (2), and the rest is the same as Example 1 to obtain a Cu@CeO2 single-atom catalyst.

[0109] Comparative Example 1 The preparation process of Co@CeO2 is the same as that of Example 1, except that Cu(NO3)2·6H2O is not used during strong electrostatic adsorption.

[0110] Figure 8-10 Characterization and performance diagram of Co@CeO2:

[0111] like Figure 8 The following are the XRD spectra, XPS total spectra, EPR spectra, and Raman spectra of Co@CeO2 obtained in Comparative Example 1 of the present invention; Figure 8 a is the XRD spectrum; Figure 8 b is the XPS total spectrum; Figure 8 c is the EPR spectrum; Figure 8 d is the Raman spectrum.

[0112] like Figure 9 Shown is the OER performance diagram of Co@CeO2 obtained in Comparative Example 1 of the present invention. Figure 9 a is the LSV curve; Figure 9 b is the Tafel slope plot; Figure 9 c is the impedance diagram; Figure 9 d is the electrochemically active surface area diagram.

[0113] like Figure 10 Shown is the ORR performance diagram of Co@CeO2 obtained in Comparative Example 1 of the present invention. Figure 10 a is the LSV curve; Figure 10 b is the Tafel slope plot; Figure 10 c is the impedance diagram; Figure 10 d is the electrochemically active surface area.

[0114] Comparative Example 2 The preparation process of Cu@CeO2 was the same as that of Example 1, except that Co(NO3)2·6H2O was not used during strong electrostatic adsorption.

[0115] Figure 11-13 Characterization and performance diagram of Cu@CeO2:

[0116] like Figure 11 Shown are the XRD spectrum, XPS total spectrum, EPR spectrum, and Raman spectrum of Cu@CeO2 obtained in Comparative Example 2 of the present invention; Figure 11 a is the XRD spectrum. Figure 11 b is the XPS total spectrum; Figure 11 c is the EPR spectrum; Figure 11 d is the Raman spectrum.

[0117] like Figure 12 Shown is the OER performance diagram of Cu@CeO2 obtained in Comparative Example 2 of the present invention. Figure 12 a is the LSV curve; Figure 12 b is the Tafel slope plot; Figure 12 c is the impedance diagram; Figure 12 d is the electrochemically active surface area.

[0118] like Figure 13 Shown is the ORR performance diagram of Cu@CeO2 obtained in Comparative Example 2 of the present invention. Figure 13 a is the LSV curve; Figure 13 b is the Tafel slope plot; Figure 13 c is the impedance diagram; Figure 13 d is the electrochemically active surface area.

[0119] This study uses a strong electrostatic adsorption strategy to construct a uniformly distributed and isolated cobalt-copper dual-site catalyst on the surface of CeO2 hollow spheres. The cobalt and copper active sites with specific spacing can synergistically catalyze the dual-function OER and ORR. The nano-hollow structure not only shortens the mass / charge transfer distance during the reaction, but also significantly expands the catalyst-electrolyte interface contact area. The cobalt-copper dual-site catalyst (CoCu@CeO2) exhibits a high electrostatic adsorption rate at 10 mA cm -2 The catalyst exhibits an OER overpotential of 235 mV and an ORR half-wave potential of 0.878 V at a current density of 0.878 V, demonstrating significantly superior bifunctional reaction activity compared to single-site catalysts. The long-range synergistic effect between the two active metal centers plays a significant role in regulating chemical reaction rates. Optimizing this long-range synergistic effect effectively modulates the interfacial electronic configuration and optimizes the adsorption / desorption energies of reaction intermediates, thereby enhancing the catalyst's OER / ORR performance.

[0120] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. Any technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a cobalt-copper diatomic ORR / OER catalyst, characterized in that: The following steps are involved: S1, preparation of CeO2 hollow nanospheres using hard template method; S2, using strong electrostatic adsorption method to adsorb the complex cations of Co and Cu on the surface of CeO2 hollow nanospheres to obtain CoCu precursor@CeO2; S3, the CoCu precursor @CeO2 is reduced in hydrogen to obtain the cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2.

2. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 1, wherein: The step S1 comprises the following steps: Ce(NO3)3·6H2O, hexamethylenetetramine and deionized water are uniformly mixed and then carbon balls are added to obtain a mixture; the mixture is reacted, and the reaction product is separated, washed, dried and heated to obtain hollow CeO2 nanospheres.

3. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 2, characterized in that: In step S1, the ratio of Ce(NO3)3·6H2O, hexamethylenetetramine, deionized water, and carbon spheres is 0.36:0.58:30:0.20, and the comparison unit is g:g:mL:g; In the step S1, carbon spheres are added and then ultrasonically dispersed to obtain a mixture; The mixture was reacted under the following conditions: reflux in an oil bath at 60-120°C for 1-4h; The heating conditions are: heating at 300-600°C for 1-4h.

4. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 2, wherein: The diameter of the carbon spheres is 150-250 nm.

5. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 1, characterized in that: The step S2 comprises the following steps: The hollow CeO2 nanospheres are dissolved in concentrated ammonia water, and the pH of the solution is adjusted so that the surface of the hollow CeO2 nanospheres is negatively charged; Co(NO3)2·6H2O and Cu(NO3)2·6H2O) are added to the above solution and stirred to obtain a product containing CoCu precursor@CeO2.

6. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 5, characterized in that: In the step S2, the mass ratio of hollow CeO2 nanospheres, Co(NO3)2·6H2O, and Cu(NO3)2·6H2O is 50:25:19; the pH of the solution is adjusted to be greater than 6.7; and ultrasonic dispersion is performed after the pH of the solution is adjusted.

7. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 1, characterized in that: The step S3 comprises the following steps: The product containing CoCu precursor@CeO2 was centrifuged and dried, and then reduced in hydrogen to obtain the cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2.

8. The method for preparing the cobalt-copper diatomic ORR / OER catalyst according to claim 1, characterized in that: In step S3, the reduction process in hydrogen is: annealing at 400-700° C. for 2-6 hours in the presence of hydrogen and argon.

9. A cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2 prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the cobalt-copper diatomic ORR / OER catalyst CoCu@CeO2 according to claim 9 in electrochemical oxygen evolution and oxygen reduction reactions.

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