Regulation Of The Carbon Based Materials Catalysis Performance On The Fuel Cell Cathode

Fuel cell is a promising candidate for application in green energy.However,the high cost of catalyst prevents its wide application.Therefore,finding a cheap and reli-able catalyst is the key.Furthermore,the scaling relations between adsorption energies of different reaction intermediates on a variety of surfaces simplify the catalyst design,but they also make it difficult to achieve the optimal catalyst.The oxygen reduction reaction(ORR)at the cathode of fuel cells,for instance,cannot attain the ideal effi-ciency even with the nowadays best-performed pt catalysts,due to the correlation be-tween the adsorption energies of O,OH and OOH.In this work,based on the nitrogen doped graphene,we compare the ORR reaction on active sites with different defor-mation while in similar structural and chemical environments.Since both the tensile strain and the adsorption of O tend to stretch and even break the NC*bond,tensile strain enhances the adsorption strength of O atom while leaving that of OH and OOH approximately unchanged.In contrast,the local curvature cannot uncouple the corre-lation between the adsorption strength of O,OH and OOH.The results suggest that it is possible to improve the catalytic performance by tuning the structure of catalyst to be in selective resonance with adsorption of a specific intermediate,which provides a new way to design optimal catalysts.The details are summarized as follow:In chapter one,we introduce the background.The review of the development of the Oxgyen reduction reaction and the scaling relations in catalysis are presented.With these summaries,it demonstrates that we must break the scaling relations in ORR if we want further improve the efficiency of ORR catalysis.In chapter two,we introduce the research methods.The origin of ORR catalysis,the methods of simulation and the influence of scaling relation on ORR are presented.In chapter three,we introduce the mechanical properties of graphene in external stress.Furthermore,we demonstrate the influence of tensile and rippling deformation on nitrogen doping in the graphene.In chapter four,we introduce the research details.The influences of the ten-sile strain and the rippling deformation on the ORR catalytic efficiency of N-doped graphene have been theoretically studied by first-principles calculations.Since both the tensile strain and the adsorption of O tend to break the NC*bond,the adsorption strength of O atom is resonantly enhanced by the tensile strain,while those of OH and OOH remain unchanged.The underlying mechanism for tensile deformation is con-sistently confirmed from different aspects,including the variation of the N-C*bond length,the PDOS and the magnetic moments upon adsorption of different intermedi-ates.In contrast,the linear relations among the adsorption energies of the three in-termediates still hold for the active sites with different local curvature,stronger bonds forming at the sites of larger positive curvature due to the redistribution of the electronic charge.The results strongly suggest that it is possible to uncouple the well-known linear correlation between the adsorption energies of the reaction intermediates,if the cata-lyst is tailored to be selectively in resonance with the adsorption of the intermediates by suitable ways.