Defect Engineering And Electrocatalytic Performance Of Co₃o₄-based Catalysts

Cobalt-based oxide nanomaterials exhibit excellent electrocatalytic performance for alcohol oxidation reactions under alkaline conditions due to their unique properties,flexible and controllable electronic structure and good stability.It can be used as an economical substitute for precious metal-based catalysts.However,the cumbersome preparation process,low-exposure active sites and insufficient conductivity limit the full display of its catalytic activity and practical application.In this regard,defect-enriched Co3O4-based electrocatalysts were synthesized under mild and controllable conditions.Herein,defect construction and crystal plane engineering were applied to control the nanostructure and surface structure of Co3O4 for high-efficiency electrocatalysis of benzyl alcohol and methanol oxidation electrocatalysis.The main research contents are as follows:(1)A simple one-step low-temperature hydrothermal method was used to synthesize Co3O4 nanosheets(Co3O4/NF)with abundant cobalt and oxygen vacancies on a nickel foam(NF)substrate.EXAFS,XPS,EPR,PL and other characterization combined with theoretical calculation show that the good nanosheet structure and the optimization of electronic structure caused by abundant vacancies make Co3O4/NF have lower alcohol molecular adsorption energy,increased reactive sites and obviouly improved electronic transmission efficiency.The as-prepared Co3O4/NF shows excellent catalytic activity for electrocatalytic oxidation of benzyl alcohol,the peak current density is up to 95 mA cm-2(1.49 V vs.RHE)and it still maintains>99%conversion and selectivity after twenty cycles of catalytic reaction.It has good catalytic stability and can be used as an economical and efficient alcohol electrocatalyst.The Co3O4/NF prepared in one step as a cost-effective BA oxidation electrocatalyst can be applied to the production of carbonyl chemicals and the electrolysis of mixed water electrolysis to produce hydrogen.(2)The acid etching method at room temperature was used to etch the Co3O4 nanosheets grown in situ on the NF substrate to obtain defect-enriched Co3O4 nanoparticles(Co3O4 NP/NF)with preferentially exposed(311)crystal plane.HRTEM,XPS,EPR and other characterization combined with theoretical calculation show that the exposure of highly active crystal plane and the introduction of oxygen vacancy make Co3O4 NP/NF have abundant reactive sites,optimized molecular adsorption performance,good electrical conductivity,higher intrinsic catalytic activity and high CO tolerance.The mass activity and specific activity of Co3O4 NP/NF is up to 710.94 mA·mg-1 and 3.390 mA·cm-2(1.50 V vs.RHE)for methanol electrooxidation reaction(MOR)in alkaline solution and still maintains good catalytic activity after 10000 s of catalytic reaction.The excellent catalytic activity and durability of Co3O4 NP/NF is better than most cobalt-based MOR catalysts,which makes it a good substitute for Ptbased MOR catalysts in alkaline direct methanol fuel cells(DMFC).