Corrugation-Induced Active Sites on Pristine Graphene for H2 Activation

Abstract

Pristine graphene is widely considered to be chemically inert, but recent experimental studies have suggested that it can provide frustrated Lewis pairs (FLPs) for activating H2 under mild conditions. Using density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations, we explore in this work the possibility that corrugation in pristine graphene is responsible for the formation of FLPs and thus its observed catalytic activity. Our DFT results demonstrate that the ease of H2 activation is proportional to the degree of corrugation of graphene. For corrugated graphene, the two catalytic para-carbon sites show clear signs of transient Lewis acid/base properties along the reaction coordinate, a pre-requisite for FLPs. Furthermore, the two dissociating H atoms carry opposite charges, suggesting heterolytic activation of H2. This behavior is confirmed by AIMD simulations at room temperature, which show that fluctuations of the corrugated graphene lead to C sites with diverse distances and varying charges. These observations offer a plausible rationalization of the experimental observations and possible design principles for FLP catalysts using homogeneous two-dimensional materials.