P-Doped Graphene/Graphitic Carbon Nitride Hybrid Electrocatalysts: Unraveling Charge Transfer Mechanisms for Enhanced Hydrogen Evolution Reaction Performance

Abstract

Recently, hybrid electrocatalyst systems involving an active layer of g-C3N4 on a conductive substrate of N-doped graphene (g-C3N4@NG) have been shown to achieve excellent efficiency for the hydrogen evolution reaction (HER) [e.g., Zheng, Y.; Jiao, Y.; Zhu, Y.; Li, L. H.; Han, Y.; Chen, Y.; Du, A.; Jaroniec, M.; Qiao, S. Z. Nat. Commun. 2014, 5, 3783]. We demonstrate here through first principle calculations examining various hybrid g-C3N4@MG (M = B, N, O, F, P. and S) electrocatalysts that the N-doped case may be regarded as an example of a more general modulation doping strategy – by which either electron donating or electron withdrawing features induced in the substrate can be exploited to promote the HER. Despite the intrinsically cathodic nature of the HER, our study reveals that all of the graphene substrates have an increasingly electron withdrawing influence on the g-C3N4 active layer as H atom coverage increases, modulating binding of the H atom intermediates, the overpotential, and the likely op...