Preparation Of Fe-N-C Catalyst And Its Electrocatalytic Performance For Oxygen Reduction Reaction

At present,the environmental problems caused by the overuse of fossil fuel resources have become increasingly prominent.In order to alleviate these problems,the development of sustainable and efficient energy conversion equipment has become an urgent need.Fuel cells and metal air cells have become the most promising energy technologies because of their sustainability,environmental friendliness and high efficiency.These new technologies are limited by the slow kinetics of some key reactions,such as oxygen reduction reaction（ORR）.Therefore,it is necessary to develop efficient and stable electrocatalysts to reduce the energy barrier and accelerate the reaction rate.Currently,platinum group noble metals are widely used in catalytic ORR.However,the high cost and low natural abundance of precious metals seriously hinder the wide application of these technologies.Based on these reasons,many advanced noble metal free electrocatalysts have been discovered,including transition metal macrocyclic compounds,metal oxides and transition metal catalysts with M-N_X structure.Among them,transition metal-based carbon and nitrogen materials（M-N/C,M=Fe,Co,Ni,etc.）are considered as the most promising substitutes for platinum based catalysts.In this paper,a series of Fe-N-C catalysts with different structures were designed and synthesized,and characterized by SEM,TEM,XRD,XPS,BET and electrochemical tests.The details are as follows:（1）Fe-Phen complex was formed by the coordination of Fe³⁺and1,10-Phenanthroline hydrochloride（Phen）,which was supported on graphene oxide（GO）by hydrothermal reaction.After calcination at high temperature,Fe-N-G catalyst was obtained by calcination at high temperature.Through the characterization of HAADF-STEM,XRD and XPS,it was found that a single iron atom was successfully doped into the defect layered graphene.The half wave potential of Fe-N-G is 0.881 V,which is 30 m V higher than that of 20 wt.%Pt/C.In addition,in the durability test,after 15000 s,it still maintains 82%of the current density,indicating that it has good stability.Similarly,in the methanol resistance test,Fe-N-G has better methanol resistance than Pt/C after adding methanol.（2）First of all,a single molecule complex iron dicyandiamide was synthesized,which was used as a metal nitrogen precursor,and then GO with rich functional groups（hydroxyl,carboxyl,carbonyl,etc.）was used as a carbon precursor.Under hydrothermal conditions,Fe₃O₄ based nanoparticles were firmly bound in the layered graphene oxide.Fe₃O₄/N-r GO was further analyzed by XRD,XPS,BET and other characterizations.In the electrochemical performance test,the half-wave potential of Fe₃O₄/N-r GO can reach 0.876 V,which is 25 m V higher than that of 20 wt.%Pt/C.In addition,Fe₃O₄/N-r GO also has excellent stability and methanol resistance,and can be used as an efficient ORR electrocatalyst.