Key Strategies to Advance the Photoelectrochemical Water Splitting Performance of α-Fe2O3 Photoanode

The last few decades' extensive research on the photoelectrochemical (PEC) water splitting has projected it as a promising approach to meet the steadily growing demand for cleaner and renewable energy in a sustainable and economically viable fashion. Among many potential photocatalysts, hematite (alpha-Fe2O3) emerges as a highly promising photoanode material with favorable characteristics including visible light absorption (a suitable band gap energy), earth abundance, chemical stability, and low cost. A pronounced disadvantage of alpha-Fe2O3 is its low photovoltage together with an extremely short hole diffusion length and a low electrical conductivity, which limit its PEC water oxidation performance. To make alpha-Fe2O3 as a viable photocatalyst for PEC water splitting, one needs to rectify these unfavorable characteristics of alpha-Fe2O3 by elaborated multiple modifications. In this review article, we introduce various modification strategies of hematite with emphasis on surface modifications to achieve low onset potential as well as high photocurrent approaching the theoretical value for solar water splitting.