Investigation of p-type Ca₂Fe₂O₅ as a Photocathode for Use in a Water Splitting Photoelectrochemical Cell

Ca₂Fe₂O₅ is a p-type oxide that has not been previously investigated as a photocathode for use in a water splitting photoelectrochemical cell. In this study, Ca₂Fe₂O₅ was synthesized as a polycrystalline electrode, and its properties relevant to photoelectrochemical hydrogen production were investigated. Ca₂Fe₂O₅ electrodes were prepared by thermally annealing electrodeposited FeOOH films with a solution of Ca(NO₃)₂ drop-casted onto the electrode surface. The bandgap energy, band edge positions, flatband potential, photocurrent generation, and chemical and photoelectrochemical stabilities of Ca₂Fe₂O₅ were examined. The results showed that Ca₂Fe₂O₅ has an ideal bandgap and band positions that can enable the utilization of visible light for overall solar water splitting. Photocurrent-time measurements were also performed and the changes in morphology, crystallinity, and composition of the Ca₂Fe₂O₅ electrodes before and after the photocurrent measurement were investigated. Furthermore, this made it possible to examine the photostability of Ca₂Fe₂O₅ and elucidate the cause of the observed photocurrent decay.