Modulation of the photo-response of SrTiO3: influence of surface defects on solid oxide photoelectrochemical cells

Abstract

A type of solid oxide photoelectrochemical cell (SOPEC), where one of the electrodes is made from a photo-absorbing material, has been recently proposed as an innovative approach to enhance the performance of low-temperature energy conversion devices. For the further development of SOPECs, it is crucial to identify the interactions between the photo-response and surface defects in photoelectrodes. Variations in electron density caused by non-stoichiometric defects in photoelectrodes distort the energy band structure, thereby impacting their photo-response. However, the influence of the surface defects induced by electrochemical reactions on the photo-response of photoelectrodes remains poorly understood. Here, we have explored the photo-response of SrTiO₃ (STO) as a photoelectrode in SOPECs during hydrogen–oxygen fuel cell operations. The formation of Sr vacancies on the STO surface induces a positive photovoltage under ultraviolet (UV) irradiation, resulting in a 90% increase in peak power density of the fuel cell. These findings underscore the significant potential of the SOPECs for practical applications.