Preparation And Electrocatalytic Performance Of Iron Oxide Nanocomposite Arrays

As important fundamentals for the sustainable energy system,electrochemical energy storage and conversion technology have received extensive attention and research in recent years.Among them,the development of electrocatalytic technology represented by oxygen reduction/evolution and nitrogen reduction plays an important role in promoting the future metal-air battery,electrochemical ammonia synthesis and other emerging fields.The research and development of electrocatalysts with excellent performance and low cost is the core content of electrocatalytic technology.As a potential non-noble metal catalyst,iron oxide has been widely studied because of its low cost and abundant resources.However,the intrinsic catalytic activity of iron oxide-based catalysts is usually low,requiring more active sites to be exposed through micro-nano structure design,or in collaboration with other components to achieve the high catalytic activity.Therefore,in this paper,nanorods array structure is used to fully expose the catalytic activity of iron oxide,and high catalytic activity is achieved through the coordination of iron oxide and other catalysts.In this paper,the study of high catalytic activity of nanoarray structure in coordination with the properties of multiple nano-functional components provides a new idea for the preparation of low-cost multifunctional catalysts.The main research contents and conclusions are as follows:（1）A series of characterization methods such as XRD,SEM and XPS proved that the composite array of Fe₂O₃ nanorods and Mn O₂ nanosheets（Fe₂O₃-Mn O₂@CC）was successfully prepared on conductive carbon cloth by hydrothermal method and electrodeposition method,and a three-dimensional nanocomposite array structure was constructed.As oxygen catalytic electrode,the Fe₂O₃ nanoarray structure of Fe₂O₃-Mn O₂@CC can fully express the catalytic activity of Mn O₂,thus achieving low charge and discharge polarization of lithium oxygen battery.The excellent conductivity of carbon cloth and three-dimensional nanoarray structure can provide more active sites and material diffusion channels to achieve high charge-discharge capacity.Finally,Fe₂O₃-Mn O₂@CC with the largest electrochemically active area showed a reversible charge-discharge capacity of 2.44 m A h cm^-2 and a stable cycle of 116 cycles with a capacity cutoff of 0.15 m A h cm^-2.Further mechanism study shows that the discharge of Fe₂O₃-Mn O₂@CC follows the solvent-mediated mechanism,and it is easier to induce the formation of bulk discharge product Li₂O₂,thus providing a high charge-discharge capacity.（2）A series of characterization methods such as XRD,TEM and XPS proved that Fe₂O₃@Au/CC nanocomposite arrays was successfully prepared by loading Au nanoparticles on Fe₂O₃ nanorods by chemical reduction method,and a nanocomposite array structure was constructed.In addition,the effect of Au loading on the catalytic performance of electrochemical nitrogen reduction（NRR）of composite electrodes was also studied.The results show that the catalytic activity of Fe₂O₃@Au/CC is significantly improved compared with Fe₂O₃/CC,and the catalytic activity gradually increases with the increase of Au loading.The mechanism study shows that Au nanoparticles have weak hydrogen evolution（HER）ability,and at the same time,Au nanoparticles increase the NRR catalytic active site of catalyst,thus improving the efficiency of ammonia production.In addition,the loading of Au nanoparticles further improves the conductivity of the catalyst,which is conducive to electron transfer.Finally,Fe₂O₃@Au/CC obtained the highest ammonia production rate of 39.14μg h^-1cm^-2 at-0.6 V vs.RHE and the highest Faraday efficiency of 2.12%at-0.2 V vs.RHE.