Improved Interfacial Charge Transfer Dynamics and Onset Shift in Nanostructured Hematite Photoanodes via Efficient Ti4+/Sn4+ Heterogeneous Self-Doping Through Controlled TiO2 Underlayers

Abstract

We introduce a simple strategy to unintentional heterogeneous Ti4+/Sn4+ doping and surface passivation of hematite via TiO2 underlayers at high temperature quenching. The effects of the controlled TiO2 underlayer thickness and high temperature quenching process on the interfacial diffusion of Ti4+/Sn4+ and TiO2 passivation of hematite nanorod arrays have been carefully studied. The improved photoelectrochemical water oxidation performance of the TiO2 underlayered hematite nanorod photoanodes after high-temperature quenching (800 °C for 10 min) suggests enhanced interfacial Ti4+ diffusion, blocking of electron back transfer, and reduced interfacial charge recombination. The TiO2 underlayers led to more inclined growth of hematite (α-Fe2O3) nanorods on the fluorine-doped tin oxide (FTO) substrates. Ti4+ and Sn4+ diffusion and formation of the TiO2 passivation layer on the α-Fe2O3 surface are confirmed by HRTEM and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the TU2 photoanode displayed hig...