Surface Electronic Structure Reconfiguration of Hematite Nanorods for Efficient Photoanodic Water Oxidation

Hematite (alpha-Fe2O3) is a promising candidate as a semiconducting photoanode for photoelectrochemical (PEC) water splitting. However, its PEC performance is much limited by the sluggish charge transfer kinetics at the alpha-Fe2O3/electrolyte interface. Herein, an insulative metal oxide, hafnium dioxide (HfO2), is deposited on the surface of alpha-Fe2O3 to engineer the photoelectrode/electrolyte interfacial electronic structure. With the conformal HfO2 overlayer coating, the surface defects of alpha-Fe2O3 are effectively passivated, whereas the charge migration from alpha-Fe2O3 to the electrolyte is blocked by the continuous HfO2 overlayer, leading to a moderate PEC enhancement. In contrast, with HfO2 nanoparticles deposited, the photogenerated holes are not only effectively extracted from the bulk of alpha-Fe2O3 but are also promptly injected into the electrolyte for water oxidation, due to the reconfigurated surface electronic structure. Consequently, the HfO2 nanoparticles-decorated alpha-Fe2O3 photoanode achieves an onset potential cathodic shift by 180 mV and a 460% photocurrent density enhancement, reaching up to 1.20 mA cm(-2) at 1.23 V versus reversible hydrogen electrode as compared with pristine alpha-Fe2O3. An alternative approach to engineer the photoelectrode/electrolyte interfacial electronic structure to improve the PEC performance for water splitting is demonstrated herein.