Visible-Light-Active Photoelectrochemical Z‑Scheme System Based on Top 5 Clarke-Number Elements

Visible-light-sensitive photoelectrochemical Z-scheme systems are developed based on the stable metal oxides consisting of the ubiquitous elements, those are ranked in the top 5 in the Clarke number. Iron-based metal oxides, that is, n-type α-Fe2O3 and p-type CaFe2O4 semiconductors are used as the photoanode and photocathode materials, respectively, in the present study. High-quality thin films made of these materials are fabricated by pulsed laser deposition on electroconductive substrates, and postannealing is carried out to achieve a high photocurrent performance. By using these two pristine metal oxide electrodes, the Z-scheme system is constructed in a photoelectrochemical separate H-type cell. The present visible-light-active Z-scheme system is working even under the zero bias condition without any addition of sacrificial agent. These iron-based electrodes exhibit long-term stability in aqueous media under continuous photon irradiation