Study On Preparation And Electrocatalytic Properties Of Cobalt-based Nanocomposites Materials

With the continuous development and advancement of clean energy resources technology in China,electrochemical energy storage and conversion technique has become one of the most promising green energy technologies.Among them,the development of efficient,stable,and cheap electrocatalysts is one of the key factors to realize the industrial application of such technology.In this thesis,given the features and advantages of cobalt-based nanomaterials,to resolve the slow kinetic and high overpotential problem occurring in the process of oxygen electrode reaction（including oxygen reduction reaction and oxygen evolution reaction）,using Co-based nanomaterials as model catalysts,we carried out the catalytic performance study of the composition and structure,and examined the influence of the morphology,specific surface area,and the active component on the catalyst activity,and through rational design,eventually realized the enhancement of the catalytic performance.The main research contents are as follows:（1）Zn Co₂O₄/Co_xSe_y nanocomposites with three-dimensional structure were prepared by using Zn Co₂O₄ sub-/micro-nanospheres as templates to grow Co_xSe_y nanosheets by solvothermal reaction.The results show that the Zn Co₂O₄/Co_xSe_y composite catalyst exhibited excellent OER catalytic activity and long-term stability,which was better than the commercial Ir O₂ catalyst.In addition,as the air cathode catalyst for zinc air battery,the as-prepared material showed good battery performances with higher energy density and specific capacity,a small change of the round-trip efficiency and excellent cycling stability,better than that of the Ir O₂/C catalyst.By means of TEM,XPS,XRD and other characterizations,the successful integration of Zn Co₂O₄ sub-/micro-nanospheres and Co_xSe_y nanosheets was proved.The valence state change of Co element before and after integration was analyzed by XPS,and the causes of the enhanced catalytic activity were further clearly elaborated.（2）Three-dimensional porous networked nitrogen doped carbon aerogels supported with cobalt single atoms was successfully prepared by hydrothermal reaction and high temperature pyrolysis,in which cobalt ions were in situ introduced,and then acid etching treatment was carried out to remove cobalt particles and cobalt compounds.The results show that When the mass ratio of CTS to F127 was 1:0.56,Co-NCA@F127-1:0.56 catalyst exhibited an optimal ORR catalytic activity and stability in alkaline condition,as well as good resistance to methanol poisoning,comparable to the commercial Pt/C catalyst.The morphology and structure of Co-NCA@F127-1:0.56 catalyst were characterized by TEM,AC-STEM,XPS,XRD and Raman spectroscopy,and the activity of the catalyst was further analyzed by Raman and XPS,and the relevant reaction mechanism has been comprehensively analyzed.In summary,a series of cobalt-based nanocomposites catalysts with the advantages of high catalytic activity,high stability and low cost were prepared by simple and effective experimental methods in this paper.The relationship between the composition,structure and catalytic activity of electrocatalytic materials was explored and established through various characterization methods.