Hematite (α‐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 α‐Fe2O3/electrolyte interface. Herein, an insulative metal oxide, hafnium dioxide (HfO2), is deposited on the surface of α‐Fe2O3 to engineer the photoelectrode/electrolyte interfacial electronic structure. With the conformal HfO2 overlayer coating, the surface defects of α‐Fe2O3 are effectively passivated, whereas the charge migration from α‐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 α‐Fe2O3 but are also promptly injected into the electrolyte for water oxidation, due to the reconfigurated surface electronic structure. Consequently, the HfO2 nanoparticles‐decorated α‐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 α‐Fe2O3. An alternative approach to engineer the photoelectrode/electrolyte interfacial electronic structure to improve the PEC performance for water splitting is demonstrated herein.
