Pivotal Role of Surface Holes in Photocatalytic Oxygen Evolution

Taking the rutile TiO₂(110) surface as a prototype, we elucidate the pivotal role of surface holes in the oxygen evolution reaction (OER) through density functional theory simulations. We demonstrate that Yb doping on TiO₂(110) eliminates bulk electron polarons (EPs) while it generates delocalized surface holes. These holes, synergizing with interfacial hydrogen-bond networks, drive the decomposition of adsorbed H₂O into hydroxyl radicals (·OH) and H atoms, underscoring the critical function of surface holes in initiating proton-coupled electron transfer. However, the Yb-doped surface remains inactive for full OER due to insufficient hole density. In contrast, titanium vacancy (V_Ti) defects not only suppress bulk EPs but also produce a higher concentration of delocalized holes. This enhanced hole density facilitates a four-step hole-mediated oxidation pathway for adsorbed H₂O, enabling efficient O₂ evolution via lattice oxygen participation. Our findings provide atomistic insights into hole-regulated OER mechanisms and establish design principles for optimizing photocatalysts for overall water splitting.