Crystal phase engineering on photocatalytic materials for energy and environmental applications

Crystal phase engineering on photocatalytic materials is a subfield of photocatalysis with intensive research, which has been proven as a versatile approach to maneuver their performance for applications in energy- and environment-related fields. In this article, the state-of-the-art progress on phase-engineered photocatalytic materials is reviewed. Firstly, we discuss the phase engineering on pristine semiconductor photocatalysts, in which the phase-dependent light absorption, charge transfer and separation, and surface reaction behaviors in photocatalytic processes are summarized, respectively. Based on the elucidated mechanisms, the implementation of phase junctions in photocatalytic reactions is then presented. As a focus, we highlight the rational design of phase junctions toward steering the charge kinetics for enhanced photocatalytic and photoelectrocatalytic performance. Moreover, the crystal phase engineering on semiconductor-based hybrid photocatalysts is also introduced, which underlines the importance of choosing a suitable phase for semiconductor components and co-catalysts as well as the synergism of different semiconductor phases for improved photocatalytic performance. Finally, the challenges and perspectives in this research field are proposed. In this review, particular emphasis is placed on establishing a linkage between crystal phase and photocatalytic activity to develop a structure-activity guide. Based on the guide, a framework is suggested for future research on the rational phase design of photocatalysts for improved performance in energy and environmental applications.