Engineering MXene Surface via Oxygen Functionalization and Au Nanoparticle Deposition for Enhanced Electrocatalytic Hydrogen Evolution Reaction

Abstract MXene, a family of 2D transition metal carbides and nitrides, presents promising applications in electrocatalysis. Maximizing its large surface area is key to developing efficient non‐noble‐metal catalysts for the hydrogen evolution reaction (HER). In this study, oxygen‐functionalized Ti ₃ C ₂ T _x MXene (Ti ₃ C ₂ O _x ) is synthesized and deposited gold nanoparticles (Au NPs) onto it, forming a novel composite material, Au‐Ti ₃ C ₂ O _x . By selectively removing other functional groups, mainly ‐O functional groups are retained on the surface, directing electron transfer from Au NPs to MXene due to electronic metal‐support interaction (EMSI), thereby improving the catalytic activity of the MXene surface. Additionally, the interaction between Au NPs and ‐O functional groups further enhanced the overall catalytic activity, achieving an overpotential of 62 mV and a Tafel slope of 40.1 mV dec ⁻¹ at a current density of −10 mA cm ⁻² in 0.5 m H ₂ SO ₄ solution. Density functional theory calculations and scanning electrochemical microscopy with ≤150 nm resolution confirmed the enhanced catalytic efficiency due to the specific interaction between Au NPs and Ti ₃ C ₂ O _x . This work provides a surface modification strategy to fully utilize the MXene surface and enhance the overall catalytic activity of MXene‐based catalysts.