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

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.

N‐Doped Graphene Supported on Metal‐Iron Carbide as a Catalyst for the Oxygen Reduction Reaction: Density Functional Theory Study

“…The relation between the deeper valence orbital levels of the graphene sheet with the larger binding strength with the reaction intermediate has been reported and explained previously by Zhou et al. using extended Hückel theory . Additionally, the interaction between the N‐doped graphene surface and the adsorbates seems to be a delocalized interaction.…”

Surface Modified MXene‐Based Nanocomposites for Electrochemical Energy Conversion and Storage

“…Zhao and co‐workers studied the HER activity of N‐doped graphene supported by the M 2 CT m (M = Ti, V, Nb, or Mo) MXene monolayer by first‐principles calculations . Due to the strong electronic coupling between the graphene and MXene monolayer, the graphene band profile and band center were pushed to the Fermi level.…”

Surface Modifications of Ti2CO2 for Obtaining High Hydrogen Evolution Reaction Activity and Conductivity: A Computational Approach

“…The layered metal carbide/nitride MXenes have triggered considerable research interest since they were successfully obtained by etching A from MAX phase in 2011 . Owing to their high electronic conductivity and hydrophilic nature,, these MXenes exhibit potential applications in the areas of lithium battery,, supercapacitors, heterogeneous catalysts and newly discovered electrocatalysts for the oxygen evolution reaction (OER), HER and photocatalyst for CO 2 reduction . The hydrophilic terminated‐O after etching MAX phase was recently found to efficiently drag Δ G H to approach zero, e. g. Δ G H values for HER on Ti 2 CO 2 or Mo 2 CO 2 are calculated to be −0.04 eV and 0.05 eV at low hydrogen coverage ,…”

“…[8][9][10][11] Owing to their high electronic conductivity and hydrophilic nature, [12,13] these MXenes exhibit potential applications in the areas of lithium battery, [14,15] supercapacitors, [16] heterogeneous catalysts [9] and newly discovered electrocatalysts for the oxygen evolution reaction (OER), [17] HER [18][19][20][21][22][23][24][25][26][27][28][29][30] and photocatalyst for CO 2 reduction. [31] The hydrophilic terminated-O after etching MAX phase [32] was recently found to efficiently drag DG H to approach zero, e. g. DG H values for HER on Ti 2 CO 2 or Mo 2 CO 2 are calculated to be À0.04 eV and 0.05 eV at low hydrogen coverage. [18,32] However, in addition to DG H , HER performance is also related to conductivity and the number of active sites in electrocatalysts.…”