Design Of Co₃O₄-based Material And Its Electrocatalytic Oxygen Evolution Performance

Splitting water to produce hydrogen（H₂）is an ideal way to obtain hydrogen.This method is not pollution to the environment,high purity of H₂ and rich raw materials.However,the energy conversion efficiency of splitting water is limited by the oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）.Compared with HER,OER involving a multi-step,four-electron transfer process has a slower kinetic behavior and a larger reaction barrier,which becomes a research bottleneck at this stage.Although the noble-metal-based RuO₂ and IrO₂ show the best OER electrocatalyst activity,the scarcity of reserves and high price limit their large-scale application.Therefore,the exploration of low-cost,efficient,stable and environmentally friendly non-noble metal OER electrocatalysts has become a key issue in the research of splitting water hydrogen production technology.And it also has a far-reaching impact on the large-scale promotion and application of fuel cells and metal-air batteries.The thesis aims to obtain an efficient,stable and inexpensive OER electrocatalysts,focusing on the key issue of how to improve the intrinsic conductivity and numbers of active sites.We designed and prepared Co₃O₄-based nanomaterials with special morphology and structure.The impacts of morphology and structure on OER electrocatalyst performance are systematically studied.On the one hand,oxygen vacancy was introduced to improve its numbers of active sites.On the other hand,the OER catalytic activity was greatly improved through the construct of heterogeneous interface and the regulation of electronic structure.The main research contents and research results are as follows:1.The porous Co₃O₄ nano-array on Ni foam substrate was directly prepared by hydrothermal growth and heat treatment method,and the nano-array consist of granular nanowires and nanosheets.The Co²⁺/Co³⁺atomic ratio in Co₃O₄ was adjusted by controlling the atmosphere in the heat treatment process.Then,oxygen vacancies were successfully introduced on the surface of sample,which increased the active site of the catalyst and shown meglio OER catalytic performance.The porous Co₃O₄ nano-array show a low overpotential of 343 mV at a current density of 10 mA/cm² and a small Tafel slope of 79.5 mV/dec in 0.1 M KOH electrolyte.2.Based on the previous work,we successfully prepared Co₃O₄ and MnCO₃co-growth electrocatalyst with porous nano-cactus-like structure on Ni foam by the same method.The morphology and structure characterization showed that the sample formed a Co₃O₄/MnCO₃ heterogeneous interface.We obtained more efficient OER catalyst than single compound by adjusting the electronic structure of the heterogeneous interface.It exhibits a low overpotential of 273 mV at a current density of 10 mA/cm²and a Tafel slope of 62.06 mV/dec,and also shows excellent structure and cycling stability in 1 M KOH electrolyte.In addition,the OER performance of the sample is better than that of most cobalt-based electrocatalytic materials,which provide a new view for the selection of components in interface engineering.