Design And Application Of Double-carbon Copper-cobalt Spinel Oxosulphide Composite Bifunctional Catalyst

For purpose of coping with the cumulatively serious problems of environmental pollution and energy shortage,electrochemical energy devices have been gradually exploited and further researched in advanced clean energy technologies.Especially,the rechargeable zinc-air batteries（r ZABs）have been investigated due to its obvious advantages of large range of operating temperature（-20 ℃～60 ℃）,high specific energy density,low cost,and friendly environment.The main challenge for r ZABs is the development of the high high-performance bifunctional catalysts to accelerate the kinetics of oxygen evolution reaction（OER）and oxygen reduction reaction（ORR）,which directly determines the process of charge and discharge,respectively.Currently,precious metal-based catalysts such as Pt/C for ORR and Ru O₂ for OER have customarily been used,however,these catalysts are expensive and low reserves,which limit its large-scale development.In addition,the single precious metals cannot provide high activity for both ORR and OER.Thereby,the quest for cheap bifunctional oxygen electrocatalysts based on the abundant-reserves transition metals has become a research hotspot.This paper through the carbon nanotube（CNT）and thiourea after high temperature calcination of C₃N₄ nano as double carbon carrier and carbon and nitrogen sources,and join the vulcanizing agent into sulfur source,using one-step hydrothermal synthesis has the double carbon the cobalt spinel oxygen copper sulfide compound of bifunctional catalyst,and through a series of physical and chemical testing methods for the preparation of the catalyst were materialized and explore its catalytic mechanism.Such as scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray diffraction technology（XRD）,X-ray photoelectron spectroscopy（XPS）and other physical and electrochemical characterization means such as cyclic voltammetry（CV）,linear scanning voltammetry（LSV）,fuel cell active system power test and blue-electric system stability test,etc.The main research contents and achievements of this paper are summarized as follows:N-and S-doped（Cu,CO）₃（O,S）₄ complex and carbon nanotube（CNT）were prepared by one-step hydrothermal method.C₃N₄and 4 different sulfides were used as nitrogen and sulfur sources respectively.The hydrothermal reaction was controlled at120℃,140℃,160℃ and 180 ℃ respectively.The hydrothermal reaction time was 2h,4h,6h,8h and 10h.The sulfurizing agents are sodium sulfide,sodium thiosulfate,sulfur powder,thioacetamide and thiourea.Atomic ratios Co:Cu=1:1,1:2,2:1 and 3:1;The catalyst（Cu,Co）₃OS₃@CNT-C₃N₄ under different conditions was prepared,and the conclusion was reached that the influence of the temperature of hydrothermal reaction was the whole process from cracking to polymerization to cracking.The influence of hydrothermal reaction time makes the catalyst show the whole process from fragmentation to polymerization and then to fragmentation.The effect of the vulcanizing agent is based on the influence of the group it contains on the structure of（Cu,Co）₃OS₃@CNT-C₃N₄ and also on the fragmentation of the C₃N₄ nanosheet.Cu ions(Cu²⁺)can form a catalytic buffer with low lattice basicity due to weakened OH^-coordination properties,which accelerates the OER and ORR dissociation,thus accelerating the dynamics.The optimal reaction conditions obtained by the experiment were as follows:when the hydrothermal reaction temperature was 160℃,the hydrothermal reaction time was 6h,the sulfurization agent was sulfur powder,and the atomic ratio of Co:Cu=2:1,the catalyst structure was the most unique.The ORR half-wave potential E_1/2 was 0.80V,and OER E_j=10 was 1.66V.The performance of the optimal reaction conditions,further synthesized（Cu,Co）₃OS₃@CNT-C₃N₄ and the control group,and to explore its catalytic mechanism,with the Cu S@CNT-C₃N₄ and Co S₂@CNT-C₃N₄ contrast,analysis:by adding C₃N₄ or CNTs as carbon carrier,the unique structure of with large specific surface area of mixed compound（for example,a hierarchical and hollowing out）,can improve the catalytic reactants and electrolytes（OH^-）availability,which is beneficial to mass transfer in the process of ORR and OER.In addition,C₃N₄ provides abundant graphite-N and pyridine-N as ORR and OER active sites to promote the oxygen catalytic process,respectively.As expected,the（Cu,Co）₃OS₃@CNT-C₃N₄ hybrid material showed excellent electro-catalytic activity,with an overpotential(△E=E_j=10-E_1/2)of 0.86 V,exceeding that of the commercial catalyst Pt/C+Ru O₂.The results show that（Cu,Co）₃OS₃@CNT-C₃N₄ catalyst has stable and high efficiency and higher electrocatalytic activity than commercial catalysts.The power,charge and discharge stability and practical application of solid zinc-air battery and flexible zinc-air battery assembled with（Cu,Co）₃OS₃@CNT-C₃N₄catalyst were tested.The results showed that r ZABs using（Cu,Co）₃OS₃@CNT-C₃N₄catalyst had a good power density of 215 m W cm^-2,a very low voltage drop（0.5 V）and a long discharge cycle life of 45 hours.In be used actually,can make the small power bulb light emitting more than 420 h,the flexible zinc-air battery and can make the air conditioning remote control function,series of solid zinc-air battery pile can be multiple led luminous and drive 3 V electric mini cars,and in the process of discharge,the bulb didn’t go out and flashing,mini car didn’t stop,visible zinc-air cells in the efficient and stable discharge process,the results further prove the（Cu,Co）₃OS₃@CNT-C₃N₄ good bifunctional catalytic activity,make its can be used for low power,high power and more demanding devices use conditions.