Hydration deactivation mechanism of the 〈100〉 oriented cuprous oxide photocathodes in solar water splitting and the regenerated three-dimensional structure

Abstract

Photocorrosion is the most ticklish problem of cuprous oxide (Cu₂O), and it is widely assumed that the deactivation of Cu₂O photocathodes in solar water splitting is caused by spontaneous oxidation–reduction (REDOX) reactions. However, this work shows that 〈100〉-oriented Cu₂O photocathodes undergo a non-REDOX hydration deactivation mechanism. Briefly, water molecules are embedded in the Cu₂O crystals at low potential under illumination and produce amorphous CuOH, which can be dehydrated at high potential to heal the Cu–O–Cu bonds and regenerate foamed Cu₂O films with a three-dimensional skeleton structure. This study provides a new insight towards the protection and application of Cu₂O photocathodes.