A nucleus-coupled electron transfer mechanism for TiO2-catalyzed water splitting

Abstract

Based on first-principles calculations, we reveal that in the photocatalytic oxygen evolution reaction (OER) at the TiO₂/water interface, the formation of an O–O bond always involves the anti-bonding σ_2p* state elevated from the valence band into the conduction band of TiO₂ regardless of a detailed reaction pathway. The role of photoholes is to deplete this anti-bonding state once it emerges into the band gap. The reaction barrier is thus determined by the onset where photoholes enter the reaction. This process represents a new reaction mechanism, termed nucleus-coupled electron transfer (NCET), where electron transfer is enabled by the movement of nuclei that promotes the reactive orbital to become the frontier orbital. The NCET mechanism for the OER is shown to exhibit an overall kinetic barrier surmountable at room temperature.