When the fate of electrons matters — strategies for correct heterojunction classification in photocatalysis

Composites of semiconductors forming various heterojunctions have become more and more extensively explored in photocatalysis, but the heterojunction classification seems abstruse. This paper aims to present a strategy for correctly elucidating the heterojunction type. The following guidelines are proposed: (I) the determination of band alignment, (II) the thermodynamic analysis of the interface, and (III) the verification of charge fate and charge transfer kinetics under irradiation. The experimental techniques appropriate for particular steps, including novel approaches, are listed, and their limitations are identified. Following the presented strategy, it is possible to conduct the analysis, which explores the intricate dynamics of photoinduced charges within correctly classified heterojunctions. Such a strategy gives a more reliable picture than often presented, oversimplified study.