Two-Dimensional Biphenylene: A Graphene Allotrope with Superior Activity toward Electrochemical Oxygen Reduction Reaction.

Developing efficient and inexpensive catalysts for the oxygen reduction reaction (ORR) is a key for sustainable development of fuel cell technologies. Herein, by means of density functional theory calculations and microkinetic modeling, we demonstrate that two-dimensional (2D) biphenylene, a recently synthesized allotrope of graphene composed of tetragonal, hexagonal, and octagonal rings, is a metal-free candidate for facilitating the electrochemical ORR. Different from semimetallic graphene, 2D biphenylene is metallic, and carbon atoms of its tetragonal rings are substantially positively charged, resulting in good ORR activity due to the enhanced binding strength with reaction intermediates. In particular, the ORR activity of 2D biphenylene is pH-dependent, and it can be significantly boosted under alkaline conditions. Moreover, 2D biphenylene possesses rather good electrochemical stability, rendering it attractive for alkaline fuel cells.