Interfacial oxygen vacancies yielding long-lived holes in hematite mesocrystal-based photoanodes

Hematite (α-Fe₂O₃) is one of the most promising candidates as a photoanode materials for solar water splitting. Owing to the difficulty in suppressing the significant charge recombination, however, the photoelectrochemical (PEC) conversion efficiency of hematite is still far below the theoretical limit. Here we report thick hematite films (∼1500 nm) constructed by highly ordered and intimately attached hematite mesocrystals (MCs) for highly efficient PEC water oxidation. Due to the formation of abundant interfacial oxygen vacancies yielding a high carrier density of ∼10²⁰ cm⁻³ and the resulting extremely large proportion of depletion regions with short depletion widths (