Ultra‐Narrow Depletion Layers in a Hematite Mesocrystal‐Based Photoanode for Boosting Multihole Water Oxidation
Zhujun Zhang, Hiroki Nagashima, Takashi Tachikawa
Abstract
Abstract Significant charge recombination that is difficult to suppress limits the practical applications of hematite (α‐Fe 2 O 3 ) for photoelectrochemical water splitting. In this study, Ti‐modified hematite mesocrystal superstructures assembled from highly oriented tiny nanoparticle (NP) subunits with sizes of ca. 5 nm were developed to achieve the highest photocurrent density (4.3 mA cm −2 at 1.23 V vs. RHE) ever reported for hematite‐based photoanodes under back illumination. Owing to rich interfacial oxygen vacancies yielding an exceedingly high carrier density of 4.1×10 21 cm −3 for super bulk conductivity in the electrode and a large proportion of ultra‐narrow depletion layers (<1 nm) inside the mesoporous film for significantly improved hole collection efficiency, a boosting of multihole water oxidation with very low activation energy ( E a =44 meV) was realized.