The transition state (TS) energy and final energy on the bare Fe(100) surface rise the steepest. They started at the energy vicinity of -5 eV at the potential at -1. Among the three sites, the bare Fe(100) surface is the least favourable due to the rapid increase in both transition state and final state energies compared to the O-hollow site. The Obridged site (Figure ) emerges as the most favourable for water dissociation, as it consistently exhibits lower transition state energy barriers and more stable final state energies across a wide potential range. Due to the shallow energy well for water dissociation, it is suggested that oxygen at the bridge sites of the Fe(100) surface may serve as a catalyst for water dissociation.