Tracking heterogeneous interface charge reverse separation in SrTiO${}_3$/NiO/NiS nanofibers with in situ irradiation XPS

Photocatalytic conversion of H${}_2$O and CO${}_2$ into solar fuels is considered to be a green and renewable technology while photocatalytic performance is hampered by the severe recombination of photogenerated electron-hole pairs. Drawing inspiration from the concepts of the electrons transfer layer (ETL) and the holes transfer layer (HTL) in perovskite solar cells, a multicomponent photocatalyst SrTiO${}_3$/NiO/NiS that incorporates p-n heterojunction and Schottky junction is constructed for converting solar energy into easily storable solar fuels. The NiS and NiO play the roles analogy to the ETL and the HTL which accomplishes the reverse migration of electrons and holes, accordingly, SrTiO${}_3$/NiO/NiS exhibits a noticeable enhancement in photocatalytic performance. However, the lack of direct observation of charge transfer pathways in complex multicomponent photocatalysts makes it challenging to thoroughly investigate their catalytic mechanisms. Herein, the in situ irradiation X-ray photoelectron spectroscopy (ISI-XPS) is employed to track photogenerated charges migration pathways between microscopic heterogeneous interfaces, thereby providing a comprehensive elucidation of the catalytic mechanism and heterojunction formation process by integrating the photoelectrochemical tests. This study not only serves as compelling evidence for the capability of ISI-XPS in directly and accurately tracking charge transfer pathways but also as an intriguing highlight within the catalyst design strategy. (© 2023 Wiley‐VCH GmbH)