Optimizing hydrogen evolution reaction:Computational screening of single metal atom impurities in 2D MXene Nb_(4)C_(3)O_(2)

MXenes,a novel class of 2D transition metal carbides and nitrides,have recently emerged as a promising candidate in the quest for efficient catalysts for the hydrogen evolution reaction.To enhance the performance of 2D MXenes with modest or poor catalytic efficiency,a particularly prosperous strategy involves doping with transition and noble metal atoms.Taking the Nb_(4)C_(3)O_(2) monolayer as a model,we explore substitutional metallic impurities,which serve as single-atom catalysts embedded within the Nb_(4)C_(3)O_(2) surface.Our findings demonstrate the ability to finely tune the atomic H binding energy within a 0.6 eV range,showing the potential for precise control in catalytic applications.Across different transition and noble metals,the single atoms integrated into Nb_(4)C_(3)O_(2) effectively adjust the free energy of H adsorption at nearby O atoms,achieving values comparable to or superior to Pt catalysts.A comprehensive examination of the electronic properties around the impurities reveals a correlation between changes in local reactivity and charge transfer to neighboring O atoms,where H atoms bind.