CoCe-SNC catalyst as well as preparation method and application thereof

Abstract

The invention provides a CoCe-SNC catalyst and a preparation method and application thereof, and belongs to the technical field of hydrogen fuel cell / metal air cell cathode catalysts. The preparation method comprises the following steps: mixing and grinding a metal organic framework ZIF-8 and KSCN, carrying out first pyrolysis, compounding the obtained nitrogen and sulfur-containing co-doped carbon with two metal complexes Co-PM and Ce-PM, and carrying out second pyrolysis to obtain the CoCe-SNC diatomic catalyst. According to the invention, the two-dimensional lamellar structure carbon material and the asymmetric coordination diatomic metal are compounded, so that the catalytic performance of the whole catalyst is improved, and meanwhile, the yield of hydrogen peroxide generated by side reaction is reduced. The catalyst is applied to a hydrogen fuel cell / metal air cell, and the defects that in the prior art, a noble metal catalyst is high in cost, and a non-noble metal catalyst is low in catalytic activity, high in hydrogen peroxide yield, poor in catalyst stability and the like are overcome.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hydrogen fuel cell / metal air battery cathode catalyst, in particular to CoCe-SNC catalyst and its preparation method and application. BACKGROUND

[0002] Hydrogen energy has the advantages of high energy density, wide sources, sustainability and no pollution, hydrogen fuel cells can provide continuous and high proportion of energy with high energy conversion efficiency, and are becoming important electric energy generators in aerospace and automobile industry. However, they are severely limited by slow cathode reaction kinetics. Therefore, designing and constructing a reasonable catalyst to accelerate the oxygen reduction reaction (ORR) is the current top priority. So far, carbon-supported Pt is the most important catalyst for ORR, Pt group noble metals have low overpotential and fast reaction kinetics, and have unique performance advantages in the field of electrocatalysis. However, the scarcity of reserves, high price and unsatisfactory activity and durability seriously limit their large-scale commercial application in energy conversion devices, and improving intrinsic activity and durability and greatly reducing the amount of Pt are the most important means. Now, single-atom catalysts have become the most promising alternative to noble metal electrocatalysts, especially metals anchored on nitrogen-doped carbon substrates (M-N-C), which can improve the utilization of active sites and minimize metal consumption. Among them, Co-N-C has attracted extensive research due to its excellent electrocatalytic activity in ORR.

[0003] Co-NC as a catalyst with excellent ORR / OER catalytic performance, the adsorption strength of oxygen Co-N-C active sites oxygen active intermediates is mainly determined by the d-band center of Co atoms, which is highly dependent on their coordination environment and three-dimensional orbital electronic configuration. The coordination environment of metal and its d-band energy level, researchers have proposed a promising strategy: introducing various non-metallic atoms (usually B elements (CHANG B, CAO Z, REN Y, et al. Electronic Perturbation of Isolated Fe Coordination Structure for Enhanced Nitrogen Fixation [J]. ACS Nano, 2024, 18(1): 288-98.), P (LIU M, SUN T, PENG T, et al. Fe-NC Single-Atom Catalyst with Hierarchical Porous Structure and P–O Bond Coordination for Oxygen Reduction [J]. ACS Energy Letters, 2023, 8(11): 4531-9.), S (YUAN M, LIU Y, DU Y, et al. Dual-Shelled Hollow Leafy Carbon Support with Atomically Dispersed (N, S)-Bridged Hydroxy-Coordinated Asymmetric Fe Sites for Oxygen Reduction [J]. Advanced Functional Materials, 2024, 34(29).), O elements (LI Y, SUN H, REN L, et al. Asymmetric Coordination Regulating D-Orbital Spin-Electron Filling in Single-Atom Iron Catalyst for Efficient Oxygen Reduction [J]. Angew Chem Int Ed Engl, 2024, 63(28): e202405334.), F elements (CHANG J, WANG G, WANG M, et al.Improving Pd–N–C fuel cell electrocatalysts through fluorination-driven rearrangements oflocal coordination environment[J].Nature Energy,2021,6(12):1144-53.),Cl element(HU L,DAI C,CHEN L,et al.Metal-Triazolate-Framewor k-Derived FeN(4)Cl(1)Single-Atom Catalysts with Hierarchical Por osity for the Oxygen ReductionReaction[J].Angew Chem Int Ed Engl,2021,60(52):27324-9.)introduced the first or second coordination layer of active metal sites. Due to the unique electronegativity and orbital interaction of these atoms, these atoms effectively destroyed the D4h symmetry of the surface electron distribution, adjusted the d-band energy level, and reduced the adsorption energy of oxygen-containing intermediates, accelerating the oxygen reduction reaction. With the development of the times, the research on single-atom materials as fuel cells and zinc-air batteries gradually turned to the research on diatomic catalysts. For example, Yin et al. (XUE N, XUE X, AIHEMAITI A, et al.Atomically Dispersed Ce Sites Augmenting Activity and Durability of Fe-Bas ed Oxygen Reduction Catalyst in PEMFC[J].Small, 2024, 20(29):e2311034.) introduced Ce into Fe-NC to form FeCe-NC diatomic catalyst, and Fe / Ce-N-C had the most positive ORR peak in 0.1 M perchloric acid solution. As expected, the half-wave potential (E1 / 2) of Fe / Ce-N-C with the reversible hydrogen electrode (RHE) was 0.789 V, and the limiting diffusion current density was 5.49 mA·cm. -2, which is close to the performance of commercial Pt / C (0.792 V vs RHE). Wenxing Chen et al. (WANG X, ZHANG N, GUO S, et al. p-d Orbital Hybridization Induced by Asymmetrical FeSn Dual Atom Sites Promotes the Oxygen Reduction Reaction [J]. J Am Chem Soc, 2024, 146(31): 21357-66.) embedded asymmetrical FeSn dual atom sites on two-dimensional C2N nanosheets (FeSn-C2N), which exhibited excellent oxygen reduction reaction (ORR) performance in alkaline electrolyte with a half-wave potential of 0.914 V. The strong p-d hybridization between p-zone tin and d-zone iron in the FeSn dual atom site made the electrons delocalized, which reduced the energy barrier of *OH protonation, thus improving the ORR activity. In addition, the zinc-air battery based on FeSn-C2N provided a higher maximum power density (265.5 mW·cm -2 ) and a higher specific capacity (754.6 mAh·g -1 ).

[0004] Heteroatom doping on the basis of dual atoms can further optimize the ORR catalytic performance. Bo Wang et al. (SUNC, LIU Y, LV Z, et al. Coordination-environment regulation of atomic Co-Mn dual-sites for efficient oxygen reduction reaction [J]. Nano Research, 2024, 17(8): 6841-8) prepared a dual-atom site catalyst (DASC) with CoN3S-MnN2S2 arrangement for the positive electrode of ZABs. Compared with Co-N-C (without Mn) and CoMn-N-C (without S doping), CoMn-N / S-C exhibited excellent half-wave potential (0.883 V) and turnover frequency (1.54 e · s -1 · site -1 ), which exceeded most of the reported state-of-the-art Pt-free ORR catalysts. ZABs based on CoMn-N / S-C had an extremely high specific capacity (959 mAh·g -1 ) and good stability (350 h @ 5 mA·cm -2 ).

[0005] However, the existing platinum-free diatomic catalyst still has the disadvantages of low intrinsic activity, poor stability, and high byproduct hydrogen peroxide yield. SUMMARY

[0006] The present application aims to provide a CoCe-SNC catalyst, a preparation method and application thereof, which can solve the problems of poor stability, low intrinsic activity, and high byproduct hydrogen peroxide yield of the existing catalyst.

[0007] To achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0008] The present application provides a preparation method of a CoCe-SNC catalyst, comprising the following steps:

[0009] The ZIF-8 is mixed with potassium thiocyanate, and then is subjected to grinding and first pyrolysis in sequence, followed by acid pickling to obtain nitrogen and sulfur co-doped carbon;

[0010] The cobalt source and the o-phenanthroline are mixed with the first solvent to perform a first coordination reaction, thereby obtaining a cobalt-o-phenanthroline complex;

[0011] The cerium source and the o-phenanthroline are mixed with the second solvent to perform a second coordination reaction, thereby obtaining a cerium-o-phenanthroline complex;

[0012] After the nitrogen and sulfur co-doped carbon is compounded with the cobalt-o-phenanthroline complex and the cerium-o-phenanthroline complex, second pyrolysis is performed to obtain the CoCe-SNC catalyst.

[0013] Preferably, the mass ratio of the ZIF-8 to the potassium thiocyanate is 1-4:0-2 and is not 0.

[0014] Preferably, the temperature of the first pyrolysis is 800-1000℃, the holding time is 1-3h, and the atmosphere is nitrogen, argon, or neon; the temperature rising rate from room temperature to the temperature of the first pyrolysis is 3-8℃ / min.

[0015] Preferably, the acid used for the acid pickling includes dilute hydrochloric acid, dilute sulfuric acid, or dilute nitric acid; the concentration of the acid is 2-4mol / L, the temperature of the acid pickling is 60-80℃, and the time is 12-24h.

[0016] Preferably, the molar ratio of the cobalt source to the o-phenanthroline is 1:2-3; and the temperature of the first coordination reaction is room temperature, and the time is 10-12h.

[0017] Preferably, the molar ratio of the cerium source to the o-phenanthroline is 1:3-4; and the temperature of the first coordination reaction is room temperature, and the time is 10-12h.

[0018] Preferably, the mass ratio of the nitrogen and sulfur co-doped carbon, the cobalt source, and the cerium source is 100:5-25:5-20.

[0019] Preferably, the temperature of the compounding is room temperature, and the time is 10-12h; the temperature of the second pyrolysis is 600-800℃, and the holding time is 1-3h.

[0020] The application provides the CoCe-SNC catalyst prepared by the preparation method.

[0021] The application provides application of the CoCe-SNC catalyst in a hydrogen fuel cell or a metal-air battery.

[0022] The application provides a preparation method of a CoCe-SNC catalyst, which comprises the following steps: mixing and grinding metal organic framework ZIF-8 and KSCN, performing first pyrolysis, and obtaining two-dimensional sheet structure nitrogen and sulfur co-doped carbon (SNC) after acid washing; and then compounding the nitrogen and sulfur co-doped carbon with two metal complexes Co-PM and Ce-PM (a complex of phen and a metal), and performing second pyrolysis to obtain a CoCe-SNC diatomic catalyst. The two-dimensional sheet structure carbon material and the asymmetric coordination diatomic metal are combined and used in the application, which improves the overall catalytic performance of the catalyst, reduces the hydrogen peroxide yield, inhibits the occurrence of side reactions, has the advantages of environmental friendliness, high product utilization, simple preparation method, excellent dual-function electrocatalytic performance and the like. The catalyst is applied to a hydrogen fuel cell / metal-air battery, and the shortcomings of high cost of noble metal catalysts, low catalytic activity of non-noble metal catalysts, low selectivity of 4-electron reaction path, poor stability of catalysts and the like in the prior art are overcome.

[0023] The CoCe-SNC prepared in the application belongs to a diatomic catalyst of a carbon carrier, ZIF-8 and KSCN are mixed and ground and pyrolyzed to prepare two-dimensional sheet carbon material as a carbon carrier, Ce-PM and Co-PM are used as metal sources, and the metal sources are prevented from excessive agglomeration and rapid loss due to high-temperature pyrolysis, the metal source precursor and the carbon carrier are combined closely due to the combination of rigid two-dimensional ligand phen and two-dimensional sheet carbon through π-π stacking, the metal source is prevented from excessive agglomeration during pyrolysis, the preparation method changes the three-dimensional morphology into two-dimensional sheet morphology, improves the charge transport efficiency, the addition of Ce sites is beneficial to maintaining the stability of the structure in the catalytic process, and therefore the overall catalytic activity and stability are more excellent.

[0024] The Co-N4 sites and the Ce-N4 sites are combined and used in the application, which improves the catalytic performance of the overall catalyst, has the advantages of environmental friendliness, high atom utilization, high limiting current density and excellent half-wave potential, and the like. The catalyst is applied to a flexible rechargeable zinc-air battery, and the shortcomings of short cycle life, low specific capacity and low power density of the rechargeable zinc-air battery in the prior art are overcome.

[0025] The Ce site is introduced into the Co site to form a heteronuclear diatomic coordination, and has a two-dimensional sheet morphology, which can improve the overall catalytic activity of the original Co-NC catalyst, has excellent stability, low cost, and low hydrogen peroxide yield in a side reaction. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 In Table a, XRD patterns of Co-NC, CoCe-NC and CoCe-SNC in Example 1 and Comparative Examples 1-2; in Table b, Raman spectra of CoCe-SNC in Example 1 and Co-NC in Comparative Example 2 at 800-2000 cm -1 -1

[0027] Figure 2 In Table a, SEM image of CoCe-NC in Comparative Example 1 and its EDS images (b-d);

[0028] Figure 3 In Table a, SEM image of SNC prepared in Example 1, b is a SEM image of CoCe-SNC prepared in Example 1, c is a TEM image of CoCe-SNC prepared in Example 1, and d is a local enlarged view of c;

[0029] Figure 4 In Table a, ORR linear sweep voltammetry curves of different catalysts in 0.1M KOH at 1600rpm in Application Example 2; in Table b, OER linear sweep voltammetry curves of different catalysts in 1M KOH in Application Example 2, c is an EIS graph of different catalysts in Application Example 2, and d is an i-t test comparison graph of Co-NC and CoCe-SNC in Application Example 2;

[0030] Figure 5 In Table a, schematic diagram of a flexible quasi-solid rechargeable zinc-air battery prepared by using CoCe-SNC prepared in Example 1 in Application Example 2, and in Table b, a real object diagram of a lighted LED lamp card. DETAILED DESCRIPTION

[0031] In the present application, if not otherwise specified, the required raw materials or reagents are commercially available goods well known to those skilled in the art.

[0032] The present application provides a preparation method of a CoCe-SNC catalyst, comprising the following steps:

[0033] ZIF-8 is mixed with potassium thiocyanate, and then is subjected to grinding and first pyrolysis in sequence, and then is subjected to acid washing to obtain nitrogen and sulfur co-doped carbon;

[0034] ​​Mixing the cobalt source, o-phenanthroline and the first solvent to carry out a first coordination reaction to obtain a cobalt-o-phenanthroline complex;

[0035] Mixing the cerium source, o-phenanthroline and the second solvent to carry out a second coordination reaction to obtain a cerium-o-phenanthroline complex;

[0036] After compounding the nitrogen and sulfur co-doped carbon, the cobalt-o-phenanthroline complex and the cerium-o-phenanthroline complex, carrying out a second pyrolysis to obtain a CoCe-SNC catalyst.

[0037] In the present application, the preparation method of the ZIF-8 preferably comprises:

[0038] Mixing 2-methyl imidazole, zinc nitrate hexahydrate and methanol, stirring at room temperature for 24 h, centrifuging, washing and drying to obtain the ZIF-8. The molar ratio of the 2-methyl imidazole to the zinc nitrate hexahydrate is preferably 4:1.

[0039] In the present application, the mass ratio of the ZIF-8 to potassium thiocyanate (KSCN) is preferably 1-4:0-2 and not 0, more preferably 1:1.

[0040] The present application does not have special limitations on the grinding, which can be uniformly ground according to the processes well known in the art.

[0041] In the present application, the temperature of the first pyrolysis is preferably 800-1000℃, more preferably 850-950℃, further preferably 900℃, the holding time is preferably 1-3h, more preferably 2h, and the atmosphere is preferably nitrogen, argon or neon; the temperature rising rate from room temperature to the temperature of the first pyrolysis is preferably 3-8℃ / min, more preferably 5-6℃ / min.

[0042] In the present application, the acid used for the acid pickling preferably comprises dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid; the concentration of the acid is preferably 2-4mol / L, the temperature of the acid pickling is preferably 60-80℃, more preferably 70-80℃, the time is preferably 12-24h, and the stirring speed is preferably 3500r / min. The present application adopts acid pickling etching to remove ZnS in the nitrogen and sulfur co-doped carbon.

[0043] After the acid pickling, the present application preferably sequentially performs suction filtration, anhydrous ethanol washing and drying on the obtained product to obtain a layered nitrogen and sulfur co-doped carbon, which is denoted as SNC.

[0044] In the present application, the first solvent and the second solvent are independently preferably anhydrous ethanol; the present application does not have special limitations on the amount of the first solvent and the second solvent, which can be adjusted according to actual needs.

[0045] In the present application, the cobalt source is preferably CoCl2·6H2O; the molar ratio of the cobalt source to phenanthroline (Phen) is preferably 1:2-3, more preferably 1:2.

[0046] In the present application, the cobalt source and phenanthroline are mixed with the first solvent respectively, and then the two solutions are mixed to carry out the first coordination reaction.

[0047] In the present application, the temperature of the first coordination reaction is preferably room temperature, and the time is preferably 10-12h, more preferably 11-12h.

[0048] In the present application, the cerium source is preferably CeCl3·7H2O; the molar ratio of the cerium source to phenanthroline is preferably 1:3-4, more preferably 1:3.

[0049] In the present application, the cerium source and phenanthroline are mixed with the second solvent respectively, and then the two solutions are mixed to carry out the second coordination reaction.

[0050] In the present application, the temperature of the second coordination reaction is preferably room temperature, and the time is preferably 10-12h.

[0051] After the first coordination reaction and the second coordination reaction are completed, the cobalt-phenanthroline complex (Co-PM) and the cerium-phenanthroline complex (Ce-PM) obtained in the present application are preferably not subjected to any treatment, and are in a solution state for subsequent compounding.

[0052] In the present application, the mass ratio of the nitrogen and sulfur co-doped carbon, the cobalt source and the cerium source is preferably 100:5-25:5-20, more preferably 100:8-20:9-15, and further preferably 100:16:12.

[0053] In the present application, the nitrogen and sulfur co-doped carbon is dispersed in anhydrous ethanol, and then is ultrasonically treated with the cobalt-phenanthroline complex and the cerium-phenanthroline complex for 30min, and then is stirred and compounded. The present application does not have special limitations on the amount of the anhydrous ethanol, and the amount can be adjusted according to actual needs to ensure uniform mixing of the materials.

[0054] In the present application, the temperature of the compounding is preferably room temperature, and the time is preferably 10-12h.

[0055] After the compounding, the obtained product is preferably vacuum dried, and is subjected to a second pyrolysis in a tube furnace to anchor the diatomic metal; the temperature of the vacuum drying is preferably 60℃, and the time is preferably 12h.

[0056] In the present application, the temperature of the second pyrolysis is preferably 600-800℃, more preferably 650-750℃, and further preferably 700℃, the holding time is preferably 1-3h, more preferably 2h, the atmosphere is preferably nitrogen, argon or neon, and the heating rate is preferably 3-8℃ / min, and further preferably 5-6℃ / min.

[0057] After the second pyrolysis is completed, the present application preferably sequentially performs acid washing, suction filtration and drying on the obtained product to obtain the diatomic catalyst CoCe-SNC.

[0058] In the present application, the acid solution used for the acid washing is preferably an HCl solution, the concentration of the HCl solution is preferably 1mol / L, the temperature of the acid washing is preferably 80℃, the time is preferably 5-10h, and more preferably 6-8h, and the temperature of the drying is preferably 60℃, and the time is preferably 12h. The present application removes unstable metal nanoparticles in the CoCe-SNC through acid washing.

[0059] The present application provides the CoCe-SNC catalyst prepared by the preparation method of the above technical solution.

[0060] The present application provides the application of the CoCe-SNC catalyst of the above technical solution in a hydrogen fuel cell or a metal-air battery.

[0061] In the present application, the metal-air battery is preferably a flexible rechargeable zinc-air battery.

[0062] In the present application, the method for using the CoCe-SNC catalyst as an electrode material in a flexible rechargeable zinc-air battery preferably comprises:

[0063] Mixing the CoCe-SNC catalyst, Nafion and anhydrous ethanol to obtain catalyst ink, and dropping the catalyst ink on an electrode carrier to obtain an electrode material.

[0064] In the present application, the ratio of the use amount of the CoCe-SNC, Nafion and anhydrous ethanol is preferably 2mg:20mL:380mL.

[0065] In the present application, the electrode carrier is preferably carbon cloth, and the loading amount of the catalyst on the electrode carrier is preferably 0.5-1mg / cm 2 , and more preferably 1mg / cm 2 .

[0066] The present application does not have special limitations on the source of the electrode carrier, and any corresponding carrier known in the art can be used.

[0067] The specific embodiments of the present application are described in detail below, but the scope of protection of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0068] The experimental methods described in the embodiments of the present application are all conventional methods unless otherwise specified; the reagents and raw materials described below are all commercially available unless otherwise specified.

[0069] Example 1

[0070] Dissolve 6 mmol of zinc nitrate hexahydrate in 20 mL of methanol, dissolve 24 mmol of 2-methylimidazole in 20 mL of methanol, mix the two solutions, stir at a stirring speed of 3500 r / min at room temperature for 24 h, centrifuge, wash with anhydrous ethanol, and dry the product to obtain ZIF-8;

[0071] Weigh 250 mg of ZIF-8 powder and mix with 250 mg of KSCN, then grind and place in a tube furnace, heat to 900℃ at a heating rate of 5℃ / min, pyrolyze for 3 h in a nitrogen atmosphere, cool to room temperature, then acid wash the product with 2 mol / L HCl solution at a stirring speed of 3500 r / min at 80℃ for 24 h, then filter, wash with anhydrous ethanol, and dry at 60℃ for 12 h to obtain SNC powder;

[0072] According to a molar ratio of cobalt salt to o-phenanthroline of 1:2, dissolve 16 mg (0.067 mmol) of CoCl2·6H2O in 5 mL of anhydrous ethanol, add 25 mg (0.138 mmol) of o-phenanthroline (Phen) to 5 mL of anhydrous ethanol, mix the cobalt salt solution and the o-phenanthroline solution, stir at room temperature for 12 h, and obtain a Co-PM complex solution;

[0073] According to a molar ratio of cerium salt to o-phenanthroline of 1:3, add 12 mg (0.03 mmol) of CeCl3·7H2O to 5 mL of anhydrous ethanol, add 18 mg (0.09 mmol) of Phen to 5 mL of anhydrous ethanol, mix the cerium salt solution and the o-phenanthroline solution, stir at room temperature for 12 h, and obtain a Ce-PM complex solution;

[0074] The 100 mg SNC powder was dispersed in 20 mL anhydrous ethanol, mixed with the Co-PM complex solution and the Ce-PM complex solution described above, and after 30 min of ultrasonic treatment, magnetic stirring for 12 h, and vacuum drying at 60 °C for 12 h, the collected powder was transferred to a tube furnace and pyrolyzed at 700 °C for 2 h at a heating rate of 5 °C / min. The obtained product was acid washed with 1 mol / L hydrochloric acid solution at 80 °C for 5 h, and then suction filtered, washed, and dried at 60 °C for 12 h to obtain the CoCe-SNC catalyst.

[0075] Example 2

[0076] The difference from Example 1 is only that the amount of KSCN is changed, and 62.5 mg, 83.3 mg, and 125 mg of KSCN are mixed and ground with 250 mg of ZIF-8 to obtain SNC powder; the remaining steps are the same as in Example 1.

[0077] Example 3

[0078] The difference from Example 1 is only that the mass ratio of the Co source to the Ce source is kept unchanged, and the amount of the metal source is changed, and the amounts of the Co source and the Ce source in the four groups are 8 mg:6 mg, 12 mg:9 mg, 20 mg:15 mg, and 24 mg:18 mg, respectively; the remaining steps and conditions are the same as in Example 1.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that a methanol solution containing 24 mmol of 2-methylimidazole, a methanol solution containing 6 mmol of zinc nitrate hexahydrate, and a methanol solution containing 0.2 mmol of cobalt nitrate hexahydrate are mixed and stirred for 24 h, centrifuged and dried to obtain ZnCo-ZIF;

[0081] The ZnCo-ZIF is mixed with the Ce-PM complex solution in Example 1 and stirred for 12 h, and then centrifuged with anhydrous ethanol at 5000 r / min for 10 min, and vacuum dried at 60 °C for 12 h. The obtained ZnCo-ZIF@Ce-PM is ground, moved to a tube furnace, and pyrolyzed at 900 °C for 3 h, and then acid washed, suction filtered, washed, and dried to obtain the CoCe-NC catalyst.

[0082] Comparative Example 2

[0083] The difference from Comparative Example 1 is only that no Ce-PM complex is added, and the other steps are the same as in Comparative Example 1 to obtain the Co-NC catalyst.

[0084] Comparative Example 3

[0085] The only difference from Example 1 is that ZIF-8 in Example 1 was pyrolyzed at 700℃ for 2 hours with a heating rate of 5℃ / min, and then dried after acid washing according to Example 1 to obtain the NC catalyst.

[0086] Characterization and performance testing

[0087] Figure 1 In Figure a, the XRD patterns of Co-NC, CoCe-NC, and CoCe-SNC in Example 1 and Comparative Examples 1-2 are shown. Figure 1 It can be seen that no obvious metallic characteristic peaks were detected because the atomically dispersed metal atoms exist in an amorphous state within the graphitic carbon. This not only improves the utilization rate of atoms but also enhances the catalytic activity of the oxygen reduction reaction.

[0088] Figure 1 In the middle b, CoCe-SNC in Example 1 and Co-NC in Comparative Example 2 are compared at 800cm. -1 ~2000cm -1 Raman spectra at the location, from Figure 1 As can be seen from c, I D / I G The values ​​are 1.13 and 1.24 respectively, indicating that both the prepared CoCe-SNC and Co-NC have high defects. The CoCe-SNC prepared by the method in the example has slightly fewer defects than Co-NC.

[0089] Figure 2 The SEM image (a) and EDS images (b-d) of CoCe-NC in Comparative Example 1 clearly show the collapsed rhombic dodecahedral structure. It can be seen that Co and Ce elements are evenly distributed without obvious aggregation, but the collapsed rhombic dodecahedral exposes limited active sites.

[0090] Figure 3 Image a is a SEM image of the SNC prepared in Example 1, image b is a SEM image of the CoCe-SNC prepared in Example 1, image c is a TEM image of the CoCe-SNC prepared in Example 1, and image d is a magnified view of a portion of image c. Figure 3 As can be seen, SNC exhibits a distinct layered porous carbon structure, while CoCe-SNC also exhibits a stacked layered structure. Furthermore, no obvious nanoparticles are present, which corroborates the XRD findings, confirming the successful preparation of CoCe-SNC.

[0091] Application Example 1

[0092] 2 mg of the different catalysts prepared in Example 1 and Comparative Examples 1-3 were taken and ultrasonically mixed with 20 mL of Nafion and 380 mL of anhydrous ethanol to obtain catalyst ink.

[0093] The catalyst ink was dropped on the carbon cloth, and the loading area was 2 x 4 cm 2 , the mass of the catalyst after drying was controlled to be 8 mg, and the catalyst was placed in a 60°C oven for drying to obtain an electrode material, and the loading amount of the catalyst on the electrode carrier was 1 mg / cm 2 .

[0094] Application Example 2

[0095] The flexible solid-state ZAB was composed of carbon cloth, polyacrylic acid (PAA) film and zinc foil, which were used as air electrode, quasi-solid-state electrolyte and anode, respectively. The air electrode had a cross-sectional area of 2 cm x 4 cm. The loading amount of the catalyst was determined to be 1 mg·cm -1 .

[0096] Preparation of PAA gel electrolyte: 1 g of N,N-methylenebisacrylamide was used as a crosslinking agent and 5 g of acrylic acid was quickly poured into 6M KOH under continuous stirring, and then 0.2M Zn(Ac)2 was dissolved, after stirring for 2 h, an aqueous solution of K2S2O8 (0.12 g dissolved in 20 mL of DI water) was added as an initiator to the above solution in a square mold, and then shaken vigorously to form a PAA gel.

[0097] The catalyst ink prepared in Application Example 1 was used for electrochemical performance test, the ORR test electrolyte was 0.1M KOH solution, the OER test electrolyte was 1M KOH solution, the ring disc electrode was the working electrode, the graphite rod was the counter electrode, and the saturated calomel electrode was the reference electrode. The commercial catalysts Pt / C were purchased from Tianzhong, and RuO2 were purchased from Maikelin.

[0098] The ORR and OER catalytic performance is shown in Figure 4 , wherein a is the ORR linear sweep voltammetry curve of different catalysts in Application Example 2; b is the OER linear sweep voltammetry curve of different catalysts in Application Example 2; c is the EIS graph of different catalysts in Application Example 2; d is the i-t test comparison graph of Co-NC and CoCe-SNC in Application Example 2. As can be seen from a in Figure 4 , CoCe-SNC has the highest half-wave potential, from b in Figure 4 , CoCe-SNC has the lowest overpotential of 10 mA·cm -2 , from c in Figure 4 , CoCe-SNC has the smallest impedance, representing excellent conductivity, and from d in Figure 4 , CoCe-SNC has good stability, the introduction of Ce sites improves the stability of the catalyst, reduces the hydrogen peroxide production rate, enhances the 4-electron reaction path selectivity, the two-dimensional sheet porous structure is more conducive to mass transfer, and the conductivity of the catalyst is enhanced, which overall improves the oxygen reduction reaction rate.

[0099] Figure 5 A schematic diagram of the flexible quasi-solid rechargeable zinc-air battery prepared in application example 2 using the CoCe-SNC prepared in example 1 and a practical diagram of lighting LED lamp board. Among them, a represents the schematic diagram of the flexible quasi-solid rechargeable zinc-air battery, b represents the practical diagram of lighting LED lamp board; it can be seen that the prepared flexible quasi-solid rechargeable zinc-air battery has the function of lighting LED and other electronic devices.

[0100] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing a CoCe-SNC catalyst, characterized by, The preparation method comprises the following steps: mixing ZIF-8 and potassium thiocyanate, grinding and first pyrolysis in sequence, acid washing to obtain nitrogen and sulfur co-doped carbon; mixing a cobalt source, o-phenanthroline and a first solvent to perform a first coordination reaction to obtain a cobalt-o-phenanthroline complex; mixing a cerium source, o-phenanthroline and a second solvent to perform a second coordination reaction to obtain a cerium-o-phenanthroline complex; compositing the nitrogen and sulfur co-doped carbon, the cobalt-o-phenanthroline complex and the cerium-o-phenanthroline complex to perform second pyrolysis to obtain a CoCe-SNC catalyst.

2. The production method according to claim 1, characterized by, The mass ratio of the ZIF-8 to the potassium thiocyanate is 1-4:0-2 and not 0.

3. The production method according to claim 1 or 2, characterized by, The temperature of the first pyrolysis is 800-1000℃, the holding time is 1-3h, the atmosphere is nitrogen, argon or neon, and the temperature rising rate from room temperature to the temperature of the first pyrolysis is 3-8℃ / min.

4. The method of claim 1, wherein, The acid used for the acid washing comprises dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid, the concentration of the acid is 2-4mol / L, the temperature of the acid washing is 60-80℃, and the time is 12-24h.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the cobalt source to the o-phenanthroline is 1:2-3, the temperature of the first coordination reaction is room temperature, and the time is 10-12h.

6. The method of claim 1, wherein, The molar ratio of the cerium source to the o-phenanthroline is 1:3-4, the temperature of the first coordination reaction is room temperature, and the time is 10-12h.

7. The production method according to claim 1 or 5 or 6, characterized by, The mass ratio of the nitrogen and sulfur co-doped carbon, the cobalt source and the cerium source is 100:5-25:5-20.

8. The method of claim 1, wherein, The temperature of the composition is room temperature, the time is 10-12h, the temperature of the second pyrolysis is 600-800℃, and the holding time is 1-3h.

9. The CoCe-SNC catalyst prepared by the preparation method in any one of claims 1-8.

10. The application of the CoCe-SNC catalyst in claim 9 in a hydrogen fuel cell or a metal-air battery.

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