Boosting oxygen reduction electrocatalysis of graphene-based bilayer heterojunction

Abstract

Since the successful exfoliation of graphene was reported, the emergence of two-dimensional (2D) materials has inspired the construction of 2D/2D heterostructures for catalytic applications. In this work, a novel strategy is proposed for activity modulation in oxygen reduction electrocatalysis through constructing a heterojunction, which consists of CoN4 embedded graphene and B doped graphene with B concentrations of 3.13 at% and 6.25 at%, termed as BG/B1 and BG/B2 for convenience, respectively. The theoretical results reveal that the B doped graphene alleviates OH poisoning of CoN4 moiety and thereby promotes the activity improvement. As the main indicator of catalytic activity, the overpotential η values are 0.46 V for BG/B1 and 0.38 V for BG/B2, respectively, which are comparable to the benchmark Pt(111). The underlying regulation mechanism involves the electron redistribution, wherein the electron-deficient B dopant causes electron depletion of the CoN4 embedded graphene. More intriguingly, the activity improvement caused by vertical electron transfer is observed for the bilayers with FeN4 moiety. The similarity between CoN4 and FeN4 implies that the electron-mediated mechanism via the 2D/2D coupling might be a universal strategy for material design. Therefore, the proposed graphene-based heterojunction provides a novel insight into activity modulation in electrocatalysis field.