Modification of Ti-doped hematite nanowires with a NiOx buffer layer for improved photoelectrochemical performance

Hematite (α-Fe2O3) is a promising photoanode material for photoelectrochemical (PEC) water splitting due to its appropriate bandgap, good stability, and earth-abundance. However, the poor charge transfer property and sluggish kinetics of water oxidation limit the PEC performance of α-Fe2O3 photoanodes. Herein, a thin NiOx buffer layer was introduced between the Ti doped α-Fe2O3 (Fe2O3-Ti) layer and the fluorine-doped tin oxide (FTO) substrate without affecting the nanowire morphology and light absorption property of Fe2O3-Ti. This buffer layer can apparently suppress the charge recombination by mitigating the lattice mismatching between the Fe2O3-Ti film and the FTO substrate. In addition, the good conductivity of the NiOx film from the non-stoichiometric composition is also beneficial to the charge transfer. As a consequence, the photocurrent density was greatly improved by adding the NiOx layer in the Fe2O3-Ti photoanode, reaching 1.32 mA·cm−2 at 1.23 VRHE without any co-catalyst and sacrificial agent. This work gives a detailed analysis of the back contact in the hematite-based photoanode and provides an effective strategy for underlayer interface optimization.