The Influence of Ti Doping on Morphology and Photoelectrochemical Properties of Hematite Grown from Aqueous Solution for Water Splitting

Hematite (alpha-Fe2O3) is a promising material for photoelectrochemical (PEC) water splitting. However, the poor conductivity and short hole diffusion length have limited its energy conversion efficiency. Nanorod structure could improve the transport of charge carriers and increase the reaction sites. Herein, we have investigated the influence of Ti doping on the morphology change and find that insufficient precursor concentration is the main reason for the morphology deviation from the optimized nanorod structure. The photoelectrochemical performance of the Ti-doped nanorod hematite was investigated and optimized. Analysis shows Ti plays a crucial role in improving both the bulk charge separation and surface charge transfer. We have also analyzed the limiting factor of the performance and the corresponding solution. Our systematic investigation indicates that the electron transport is still a limiting factor for the PEC performance of hematite. Further improvement can be obtained through replenishing the Ti source during the nanorod growth, and by subsequent nitrogen treatment.