Heterostructures of MXenes and N-doped graphene as highly active bifunctional electrocatalysts

TL;DR

This paper theoretically designs MXene and N-doped graphene heterostructures as highly active bifunctional electrocatalysts for ORR and HER, demonstrating their potential through first-principles calculations.

Contribution

It introduces a novel class of hybrid MXene/graphene electrocatalysts with enhanced activity, elucidating the electronic mechanisms behind their performance.

Findings

V2C and Mo2C supported heterostructures show low ORR overpotential (~0.36 V).

HER free energies approach zero, indicating high catalytic activity.

Electronic coupling and surface pz band center correlate with catalytic performance.

Abstract

MXenes with versatile chemistry and superior electrical conductivity are prevalent candidate materials for energy storage and catalysts. Inspired by recent experiments of hybridizing MXenes with carbon materials, here we theoretically design a series of heterostructures of N-doped graphene supported by MXene monolayers as bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). Our first-principles calculations show that the graphitic sheet on V2C and Mo2C MXenes are highly active with an ORR overpotential down to 0.36 V and reaction free energies for the HER approaching zero, both with low kinetic barriers. Such outstanding catalytic activities originate from the electronic coupling between the graphitic sheet and the MXene, and can be correlated with the pz band center of surface carbon atoms and the work function of the heterostructures. Our findings screen a novel form of highly active electrocatalysts by taking advantage of the fast charge transfer kinetics and strong interfacial coupling of MXenes, and illuminate a universal mechanism for modulating the catalytic properties of two-dimensional hybrid materials.