Direct Interfacial Excitation from TiO<sub>2</sub> to Cu(II) Nanoclusters Enables Cathodic Photoresponse for Hydrogen Evolution under Visible‐Light Irradiation
Aufandra Cakra Wardhana, Akira Yamaguchi, Kiyohiro Adachi, Daisuke Hashizume, Masahiro Miyauchi
Abstract
Abstract The titanium dioxide (TiO 2 ) photocatalyst is only active under UV irradiation due to its wide‐gap nature. A novel excitation pathway denoted as interfacial charge transfer (IFCT) has been reported to activate copper(II) oxide nanoclusters‐loaded TiO 2 powder (Cu(II)/TiO 2 ) under visible‐light irradiation for only organic decomposition (downhill reaction) so far. Here, the photoelectrochemical study shows that the Cu(II)/TiO 2 electrode exhibits a cathodic photoresponse under visible‐light and UV irradiation. It originates from H 2 evolution on the Cu(II)/TiO 2 electrode, while O 2 evolution takes place on the anodic side. Based on the concept of IFCT, a direct excitation of electrons from the valence band of TiO 2 to Cu(II) clusters initiates the reaction. This is the first demonstration of a direct interfacial excitation‐induced cathodic photoresponse for water splitting without any addition of a sacrificial agent. This study is expected to contribute to the development of abundant visible‐light‐active photocathode materials for fuel production (uphill reaction).