报告人：Yiyang Sun (Department of Physics, Rensselaer Polytechnic Institute, New York, USA）

时间地点：2014年5月29日(周三)上午 11:00 田家炳楼-南205

联系人：董正高

Abstract: We elucidate the molecular mechanism of the oxygen-evolution reaction (OER) using first-principles calculations that employ an explicit interface of TiO2 crystals and liquid water. We find that during the formation of an O-O species, such as HO-OH and O-OH, an occupied molecular orbital with anti-bonding character evolves from the valence band and increases into the conduction band of TiO2. This occupied high-energy orbital results in a high reaction barrier that renders the OER forbidden in the dark. The presence of photocatalytic hole formation in the presence of light depletes the anti-bonding orbital, which significantly reduces the reaction energy and influences the reaction barrier in the rate-limiting step. We propose a novel reaction mechanism, termed nucleus-coupled electron transfer (NCET), that emerges from our calculations. In this mechanism, the oxidation of a pair of hydroxyl groups, which is an electron transfer reaction is enabled by the movement of the nuclei (i.e., the two O atoms moving towards O-O bond formation) that drives the reactive orbital (the 2p orbital in the present case) to become the frontier orbital (i.e., above the valence band maximum of TiO2). Based on the NCET mechanism, for the first time, we identify a reaction pathway of the OER that exhibits a kinetic barrier that is surmountable at room temperature.