Double Transition Metal Carbides MXenes (D-MXenes) as Promising Electrocatalysts for Hydrogen Reduction Reaction: <i>Ab Initio</i> Calculations

Abstract

Double-transition-metal MXenes (D-MXenes) have been widely pursued in the advancement of the renewable energy storage technology in recent years. In this work, the hydrogen evolution reaction (HER) catalytic mechanism of several oxygen-terminated D-MXenes with the chemical formula of M'₂M″C₂O₂ (M' = Mo, Cr; M″ = Ti, V, Nb, Ta) is theoretically studied. For comparison, the corresponding monometallic MXenes (M-MXenes, M'₃C₂O₂) are fairly compared by means of the density functional theory calculations. Based on our theoretical results, the HER performance of M-MXenes can be improved by constructing a "sandwich-like" ordered D-MXene configuration. Moreover, the HER performance of Mo-based D-MXenes (Mo₂M″C₂O₂) is superior to that of Cr-based D-MXenes (Cr₂M″C₂O₂), which highlights that the HER activity of Mo₂VC₂O₂ and Mo₂NbC₂O₂ is better than that of Pt(111). This work not only unravels the HER mechanism of D-MXenes (M'₂M″C₂O₂) but also paves the way in designing emergent MXene-based HER electrocatalysts with high efficiency.