Recent advances on interfacial engineering of hematite photoanodes for viable photo‐electrochemical water splitting

Oxygen evolution reaction (OER) occurring on photoanode is considered as the key step for photo‐electronchemical (PEC) water splitting. Among many potential photoanode materials, hematite (α‐Fe 2 O 3 ) shows high promise considering its ideal band position, long‐term chemical stability, and earth abundance. Unfortunately, its sluggish oxygen evolution kinetics at photoanode/electrolyte interfaces and poor bulk charge transport limit the PEC performance. Herein, the most recent developments on interfacial engineering of hematite photoanode are summarized. We first describe the optical and electronic properties of the α‐Fe 2 O 3 that are related to the PEC performance. Subsequently, we introduce the recent endeavors on the morphological engineering of the hematite photoanode. Then, the effective strategies of interfacial engineering are highlighted to address the limitations of α‐Fe 2 O 3 photoanode at the surfaces and/or interfaces, as well as at the grain boundaries within the film. And the most recent progress of α‐Fe 2 O 3 photoanode‐based tandem cells for self‐assisted overall water splitting is also discussed. Finally, an outlook is presented for future efforts on promoting the interfacial charge transport for boosted PEC performance of hematite‐based photo‐electrodes.