Enhanced surface electron transfer by fabricating a core/shell NiiO cluster on TiO sub(2) and its role on high efficient hydrogen generation under visible light irradiation

A NiiO core/shell cluster was fabricated on TiO sub(2) surface (NiiO/TiO sub(2)) and its roles on surface electron transfer and the enhancement on hydrogen evolution under visible light irradiation were investigated. For a comparison, the Ni/TiO sub(2) and NiO/TiO sub(2) catalysts were fabricated, respectively. By photosensitization using Eosin Y as an antenna molecule, (1.6 wt%)NiiO/TiO sub(2) exhibited the highest activity (364.1 mu mol h super(-1)) in comparison with (1.6 wt%)Ni/TiO sub(2) and (1.6 wt%)NiO/TiO sub(2) and the corresponding apparent quantum efficiency reached 28.6% at 460 nm. The photoluminescence spectra and photoelectrochemical characterization results confirmed that the NiiO core/shell structure could promote the photogenerated electrons transferring from TiO sub(2) conduction band to NiiO clusters, resulting in the quicker separation of electron-hole pairs. In addition, part of NiO shell can be reduced into metallic Ni during the photoreaction and vice versa. Cyclic voltammogram characterization verified that the transformation between Ni and NiO was a dynamic balance process, which can not only provide reacting channels for electrons and protons but also ensure the photocatalytic hydrogen evolution proceeding continuously. This study discloses structure-dependent effect of non-noble metal cocatalyst on semiconductor photocatalysts in photocatalytic water reduction, and gives an insight into designing high-efficient non-noble metal/semiconductor hybrid photocatalysts.