Design And Electrocatalytic Performance Of Metal And Nitrogen Co-Doped Carbon Materials

With the increasingly serious environmental problems and the increasing global energy demand,the oil,natural gas,coal and other fuels energy have been unable to satisfy people’s needs.Therefore,the development of clean and sustainable energy has become the top priority.In recent years,electrolyzed water and metal air batteries in new clean energy technologies have attracted the attention of researchers.However,due to the slow kinetics and high reaction barrier of oxygen reduction reaction(ORR),oxygen evolution reaction(OER)and hydrogen evolution reaction(HER),these energy devices are hindered in practical application.Therefore,accelerating the kinetic reaction and reducing the overpotential of ORR,OER and HER are problems that need to be solved urgently.At present,some noble metals such as Pt have excellent electrocatalytic properties.However,due to the high cost,shortage of resources,poor methanol resistance and other factors,they can not be widely used in practice.In recent years,metal and nitrogen-doped carbon materials have become an attractive high-efficiency electrocatalyst due to their high activity,low cost and high stability.In this paper,two kinds of metal and nitrogen-doped carbon catalysts were studied.The specific work is as follows:1.A triphasic nanocomposite Ag-CoFe@NC with synergetic interfacial structure as trifunctional catalysts toward electrochemical oxygen and hydrogen rections.Three-phase nanocomposite material with Ag-CoFe heterostructure encapulated on graphite carbon shell was synthesized via the electronic control strategy.The combination of Ag,CoFe alloy and carbon layer not only improves chare transfer,but also generates synergistic effect and more active sites at the interface,significantly boosting the electrocatalytic activity.The Ag-CoFe@-700 catalyst exhibits superior electrocatalytic activity,and its potential difference is only 0.72 V.At the same time,it also shows good hydrogen evolution catalytic performance under alkaline conditions,which can be ascribed to the following factors:(1)The combination of Ag,CoFe alloys and N-doped carbon modified the surface electron configuration,which conduces to interfacial electron transfer and reactant/intermediate species adsorption/activation;(2)The synergism among Ag,CoFe alloy and N-doped carbon phase generates more active sites such as the encapsulated metal nanoparticles and M-N moieties,contributing to improve catalytic activity;(3)The N-doped carbon layers is responsible for the stability.2.Preparation and performance analysis of metal alkoxide-derivd Co@NC/NCNS as highly efficient bifunctional oxygen electrocatalysts.A promising bifunctional catalyst integrating with Co@NC units and porous structure carbon nanosheets is in situ prepared by the calcination and acid etching of mixture containing metal alkoxide and melamine.TEM and mapping testresults show that Co@NC,M-N and N-C moieties uniformly disperse on the Co@NC/NCNS surface,providing abundant active sites for ORR/OER.Additionally,the pouous structure of Co@NC/NCNS is favorable to the mass transport and electron transfer.Therefore,originating from the coordination effect of these active sites and porous structure,Co@NC/NCNS catalyst exhibits superior ORR/OER activities.At the same time,the catalyst also showed high stability and methanol resistance.It is calculated that Co@NC/NCNS has a small potential difference(ΔE =0.78 V),indicating that the catalyst has bifunctional activity.