Carbon-based Materials Support Metal Oxides As High-efficiency Oxygen Reduction And Oxygen Evolution Catalysts

In 2020,the sudden outbreak of locust plague and Antarctic blood snow has seriously threatened human survival.A major cause of such serious environmental problems is the large use of fossil energy and uncontrolled emissions of greenhouse gases.In recent years,it is by change energy sources to replace fossil energy sources for China,improve environmental issues.Metal-air batteries have the advantages of fast start-up,strong environmental adaptability,high portability,simple structure and zero pollution of operation products,etc.,which make them have good competitiveness.In practical applications,metal-air batteries are limited by the development of key components,that is,the cathode/anode catalytic activity limits the overall development.The use of ORR/OER catalysts can improve the catalytic efficiency of the cathode/anode of metal-air batteries.However,most ORR/OER high-efficiency catalysts are precious metals,and the high cost of mining and the use of precious metals has also become a reason that hinders their large-scale use.Therefore,the development of new electrocatalysts with similar catalytic performance to precious metal catalysts can improve the performance of metal-air batteries while reducing the cost of use.In this paper,two kinds of carbon-based materials supported metal oxides are prepared as high-performance ORR/OER catalysts.Their catalytic performance is similar to that of precious metals.X-ray photoelectron spectroscopy(XPS),projection electron microscope(TEM)were used to characterize the structure and composition of two carbon-based materials supported metal oxide catalysts.In terms of catalytic performance research,Linear Sweep Voltammetry(LSV)Rotating Ring Disk Electrode(RRDE)tests were performed what the catalytic performance test of carbon-based materials supported metal oxide catalysts.This paper uses a one-step high-temperature carbonization method,using melamine as the carbon source and nitrogen source,and cobalt ions as the center ion to prepare bamboo-like nitrogen-doped carbon nanotubes coated with cobalt metal oxides Co/Co Ox@BS-NCNTs,as the anode OER catalyst and cathode ORR catalyst for metal-air batteries under normal conditions.The effects of changes in carbonization temperature on the morphology and properties of Co/Co Ox@BS-NCNTs were also explored.Co/Co Ox@BS-NCNTs-700 has the most uniform bamboo structure and the largest surface area after different characterization methods and performance tests.Nitrogen-doped carbon nanotubes give the catalyst satisfactory electron capture and transport capabilities,and the tubular structure protects the internal catalytically active sites and prevents catalyst deactivation.Cobalt ions extend through the chemical surface to gradually produce carbon nanotubes on their surface.The unique hollow tubular structure of carbon nanotubes provides high-speed channels for the transport of active materials;nitrogen atoms are successfully doped into the carbon nanotube skeleton under the catalysis of cobalt ions,and the nitrogen-doped structure formed reduces the adsorption and transfer of electrons activation energy;the presence of a variety of valence cobalt ions can be quickly converted during the catalysis process so that the overall catalytic rate reaches a satisfactory level.Under the synergistic effect,these structures that are beneficial to the catalytic performance make the ORR and OER performance of Co/Co Ox@BS-NCNTs-700 surpass the precious metal catalysts while showing excellent stability.In order to improve the research breadth of carbon-based material-supported metal oxides as high-efficiency oxygen reduction and oxygen precipitation catalysts,we use metal-organic frameworks as the only precursors and adopt a multi-step synthesis to form a semi-metal bismuth-encapsulated dodecahedron porous structure with a double-layered protective structure.Co O@DPNC@SMB with nitrogen-doped carbon embedded Co O as the ORR and OER catalyst for metal-air batteries under alkaline conditions.The test results show that the catalytic performance of ORR and OER of Co O@DPNC@SMB-1 exceeds that of precious metal catalysts,and the current retention rate after the long-term operation is also greater than that of precious metal catalysts.Co O as an active center provides the possibility for efficient catalysis;nitrogen-doped and porous structures provide high-speed channels for the capture and transfer of intermediates;the presence of Bi on the surface protects the internal structure and improves operational stability.And it can increase the oxygen vacancy concentration and improve the overall catalytic reaction kinetics.Through the above synergistic effects,Co O@DPNC@SMB-1 finally showed excellent catalytic activity.The dual-function catalysts for the development of metal-air batteries can improve overall work efficiency and reduce user costs.Meantime,the dual-function catalysts can promote the development of new clean energy,that provide strong support for energy construction and promote the adjustment energy framework for China.