Carbon dioxide hydrogenation to methane on hydrogen boride sheet: a density functional theory study

In this study, we employ density functional theory calculations to investigate the reaction pathways of CO₂ conversion to CH₄ on hydrogen-deficient HB sheets, where H-vacancy sites serve as the active centers for CO₂ activation. Our results reveal that the conversion of CO₂ proceeds via a CO-mediated dissociative mechanism. We further consider the effect of O* participation as a reactant following C–O bond cleavage, and show that co-adsorbed OH* lowers the barrier for HCO* formation, making the associative pathway more kinetically favorable than the route proceeding via C*. The rate-determining step is identified as the hydrogenation of CH* to CH₂*, with a barrier of 2.02 eV, consistent with the experimentally observed negligible CH₄ yield under dry conditions. These findings provide mechanistic insight and complement existing experimental observations.