Photocatalysis: From Fundamental Principles to Materials and Applications

Photocatalysis represents a unique class of chemical transformations. It utilizes the energy delivered by light and drives reactions that are difficult, sometimes even impossible, to carry out in dark. When used for thermodynamically uphill reactions such as photosynthesis, photocatalysis promises a sustainable solution to large scale solar energy storage. Despite the longstanding interest in this process and research efforts, existing photocatalysis demonstrations are limited to academic laboratory settings. Chief among the reasons for the slow progress is the lack of suitable photocatalyst materials for large scale applications. For the purpose of effective light absorption, charge separation, and charge transfer, a large number of photocatalytic materials, including conventional semiconductors and emerging photoelectronic materials such as nanoscale plasmonic metal particles, quantum dots, and 2D materials, have been studied. This Review is written to summarize these recent efforts from a broad materials perspective and discuss possible strategies to move forward to practical implementations. We start with a discussion on the fundamental principles that govern photocatalysis in general and then move on to discuss the different classes of photocatalytic materials, covering various aspects of their properties, such as efficiency, stability, scalability, and cost. Afterward, we use model photocatalytic reactions including water splitting, CO2 reduction, and N2 fixation to demonstrate the applications of these photocatalysts. Our perspectives concerning where the field of photocatalysis is headed toward are provided at the end.