Surface engineering and electronegativity effects on the catalytic performance of Hf2CO2 MXene: An ab initio study

In this work, we systematically examine the stability and catalytic performance of functionalized Hf${}_2$COT MXenes using density functional theory, with a special focus on the impact of breaking the symmetry on the structure due to the presence of chalcogen or halogen T atoms. Our findings indicate that functionalized Hf${}_2$COT MXenes are generally stable; however, the Cl- and Br-terminated structures show positive binding, indicating a certain thermodynamic instability. The modification of the surface electronic environment promotes increased activity. Charge density analysis reveals that Janus MXenes, particularly Hf${}_2$COI, exhibit pronounced charge redistribution and stronger attractive interactions with adsorbed hydrogen, in contrast to their symmetric counterparts like Hf${}_2$CO${}_2$. This unique behavior is attributed to the intrinsic dipole moment and the asymmetric charge distribution induced by the Janus configuration.