Single-atom heterogeneous photocatalysts

Abstract

Developing highly efficient photocatalysts with low production costs is critical to practical applications. Single-atom photocatalysts (SAPs), in which isolated atoms are anchored on the semiconductor supports, have attracted considerable attention owing to their preeminent catalytic activity, superior selectivity, impressive stability, and maximum atom utilization efficiency. Moreover, they offer a great opportunity to explore photocatalysis on the atomic level. Single atoms stand out from bulk, nanoparticle, and nanocluster counterparts. Herein, we summarize their recent progress, mainly focusing on their properties, geometric structures, synthetic strategies, characterization techniques, and photocatalytic applications. Also, the functions of isolated metal atoms in photocatalytic reactions are discussed. Finally, the challenges and perspectives of designing and fabricating highly active SAPs are presented. Photocatalysis is considered as a promising approach to address the issues of energy crisis and environmental pollution. However, the low efficiency of photocatalysts largely limits their applications. SAPs are one of the most promising candidates due to their maximized atom utilization efficiency, well-defined active sites, and high activities. Herein, we introduce the properties of SAPs, analyze their merits and demerits, and summarize the anchored sites of single atoms. In view of the instability of single atoms, we discuss the main methods for their preparation and characterization. Also, their interaction with supports via chemical bonds and their coordination environments are identified. Furthermore, potential photocatalytic applications are classified according to geometric and electronic structures along with chemical environments. Before long, more efforts will be made to elucidate structure-activity relationships for reactive single-atom centers and underlying photocatalytic mechanisms. Single-atom photocatalysts (SAPs) have been emerging as new and energetic research frontiers in heterogeneous catalysis. Xia et al. introduce the properties of SAPs, analyze the merits and demerits, summarize the anchored sites of single-metal atoms, and discuss the main methods for their preparation and characterization. Also, the interaction with supports via chemical bonds and the coordination environments are also identified. Furthermore, potential photocatalytic applications are classified according to geometric and electronic structures along with chemical environments.