Ultradurability of metastable β-Fe2O3 photoanodes in highly corrosive seawater

Abstract Durability is one prerequisite for material application. Photoelectrochemical (PEC) decomposition of seawater is a promising approach to produce clean hydrogen by using solar energy, but it always suffers from serious Cl− corrosion. We found that the main deactivation mechanism of the photoanodes is oxide surface reconstruction accompanied by the coordination of Cl− during seawater splitting, and the stability of the photoanodes can be greatly improved by enhancing the metal-oxygen interaction. Taking the metastable β-Fe2O3 photoanode as an example, Sn added to the lattice can enhance the M–O bonding energy and hinder the transfer of protons to lattice oxygen, thereby inhibiting excessive surface hydration and Cl− coordination. Therefore, the Sn/β-Fe2O3 photoanode without any extra electrocatalyst or protective overlayer delivered a record durability for PEC seawater splitting over 1440 h.