Electronic structural descriptors for hydrogen evolution and superior catalytic activity of graphene based structures

Abstract

Defect and substrate introduced into catalyst are two feasible routes toward design of heterogeneous catalysts. It is vital to identify and understand the relationships among atomic, electronic structures and adsorbate binding ability of the catalytic surfaces. Herein, hydrogen evolution on different defect graphene with and without two-dimensional (2D) Mo2C substrate are selected as examples to explore the relationships. Three feasible electronic structural descriptors, including p and pz band centers of local atoms, electron transfer to local atoms, and deformation charge densities of composite structures, are exacted from electronic properties of the defect and substrate-supported graphene. It is found that those descriptors could predict the hydrogen binding energy quantitatively, and the hydrogen adsorption order qualitatively. The descriptor of local p and pz band centers originate from hybridization between the site atom and adsorbate. It is believed that the relationship of atomic structure, electronic structure and binding energy may be applied to other surfaces, and shed light on the nature origin of the structure–activity on electrochemistry. By tuning the descriptors by atomic structure of defect or substrate, suitable hydrogen binding ability and superior hydrogen evolution performance of graphene could be achieved. Several structures based on graphene own superior hydrogen evolution activity: the exchange current densities of S3NV1-G, S2NV2-G@Mo2C, N1-G@Mo2C, and N2-G@Mo2C are predicted to be 0.811, 0.963, 0.712, and 1.860 mA/cm2, respectively. Especially the last two ones, their negative interfacial binding energies, and the energy favorability of forming N1 and N2 defects, ensure their stabilities and easy syntheses in experiment, and enhance their potential applications.