Building up bimetallic active sites for electrocatalyzing hydrogen evolution reaction under acidic and alkaline conditions

Abstract

The electrocatalytic hydrogen evolution reaction (HER) is one of the major energy conversion processes for clean energy technology. Developing highly efficient and cost-effective electrocatalysts for HER is highly desirable, but it still remains a great challenge. Especially, under alkaline or neutral conditions, HER suffers from the sluggish process of water dissociation. Inspired by dual active sites effect and the tunable electronic structures, we design a series of catalysts with two 3d-transition metal atoms embedded in nitrogen-doped porous graphene (MM’-NPG, M = Fe, Co, Ni and M’=Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and investigate their electrochemical HER activities by employing the density functional theory method. The FeCr-NPG, FeCo-NPG, FeNi-NPG, NiTi-NPG, NiV-NPG, and NiNi-NPG are predicted to exhibit higher HER activities than state-of-the-art Pt under acidic conditions, while under alkaline conditions, FeV-NPG and NiV-NPG are promising HER catalysts with the theoretical overpotential and kinetic barrier of less than 0.37 and 0.16 eV, respectively. It is worth mentioning that the NiV-NPG could work well in all pH values. The detailed mechanistic study indicates that its excellent kinetic behavior for alkaline HER originates from the interaction of d orbital of metals with σ* orbitals of H2O that greatly accelerate the water dissociation, and then the generated H atom and OH radical could be captured by Ni and V atoms, respectively, with a barrierless kinetics process. The present results provide a mechanism-based strategy and evaluation process for developing advanced materials as electrochemical catalysts for HER in a wide pH range.