Toward a Comprehensive Understanding of Amorphous Photocatalysts: Fundamental Hypotheses and Applications in CO 2 Photoreduction.

In principle, photocatalytic activity can be precisely controlled with crystalline catalysts. However, an amorphous photocatalyst could be a viable candidate for CO 2 photoreduction to form value-added products. The amorphous phase is currently part of the crystalline material in several ongoing CO 2 photoreduction studies. Additionally, no study indicates the amorphous material required for overall CO 2 photoreduction. This perspective review article highlights fundamental assumptions that are necessary to gain insights and understand the effectiveness of amorphous photocatalysts for CO 2 photoreduction. We start with basic ideas and theories about these materials, including light harvesting, variable coordination number, and the interaction of CO 2 molecules with the amorphous catalytic surface. To understand the prospects of the amorphous photocatalyst, we explore machine learning with EXAFS. Furthermore, we discuss product selectivity and regeneration of photocatalysts in detail. Finally, we briefly review the work in progress on amorphous materials and compare it to that on crystalline ones.