Nanometer-Thick Hematite Films as Photoanodes for Solar Water Splitting

Photoelectrochemical (PEC) water splitting is one of the most promising sustainable methods for feasible solar hydrogen production. However, this method is still impractical due to the lack of suitable photoanode materials that are efficient, stable, and cost-effective. Here, we present a surprisingly simple fabrication method for efficient, stable, and cost-effective nanometer-thick hematite films utilizing a rapid, ambient annealing approach. In the oxygen evolution reaction, the fabricated hematite films exhibit a Faradaic efficiency of 99.8% already at 1 V versus the reversible hydrogen electrode (RHE), a real photocurrent density of 2.35 mA cm–2 at 1.23 V versus RHE, and a superior photo-oxidation stability recorded for over 1000 h. Considering the active surface area, the measured photocurrent density is higher than any value achieved so far by hematite and other single-material thin-film photoanodes. Hence, we show for the first time that undoped hematite thin films can compete with doped hematite and other semiconductor materials.