Dynamic Reconfiguration and Induced Symmetry Switching in Iron Carbide Surface by Adsorbed Hydrogen

Adsorbate-induced surface reconstruction and symmetry switching critically impact reaction dynamics and surface reactivity. We show that hydrogen adsorption on the Fe 2 C(100) surface drives a reversible transformation from p4g(2 × 2) to c(2 × 2), triggered by the conversion of carbon from sp 2 to sp 3 hybridization and consequent reduction in electron delocalization. Annealing to 298 K restores the p4g(2 × 2) structure as hydrogen desorbs, underscoring adsorbate-controlled reversibility. Systematic analysis elucidates the underlying mechanism governing this dynamic surface modification.