Stacking configuration engineering and oxygen vacancy modulation on hydrogen evolution reaction of M′₂M″C₂O₂-MXenes

Two-dimensional transition metal carbides (MXenes) possess inherent advantages, including diverse chemical compositions, tunable layer thicknesses, and facile surface functionalization. These properties make them suitable as promising low-cost, stable and highly active non-precious metal catalysts for hydrogen evolution reaction (HER). However, the complexity of its structure and the lack of descriptors impede the rational design of high-performance HER electrocatalysts. In this work, employing a series of oxygen-terminated double-transition-metal carbides (M′₂M″C₂O₂, where M′ = Ti, V, Cr; M″ = Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W), we propose the reasonable regulation strategy for the improved HER performances of MXene by integrating multidimensional insights from stacking energy, thermodynamic stability, electronic properties and activity descriptors. It is illustrated that ABA stacking configurations with high electron density commonly exhibit the enhanced thermodynamic stability. Six M′₂M″C₂O₂ are screened out exhibiting superior HER activity and robust thermodynamic stability across a wide hydrogen coverage. According to Gradient-Boosted Regression (GBR), the surface O p-band center (ε_p) is identified as a robust activity descriptor for M′₂M″C₂O₂, which can even be extended to defect-containing model (R² = 0.74). Furthermore, we demonstrate a rational design strategy for MXenes with improved HER performance through appropriately modulating ε_p via introducing oxygen vacancies.