Single-molecule mapping of catalytic reactions on heterostructures

Due to the synergistic effect, heterostructure-based nanocatalysts usually possess higher catalytic performance; therefore, much attention has been attracted in this filed. To understand the charge transfer and reaction mechanism on these heterostructures, in situ techniques with high temporal and spatial resolutions need to be introduced. This review summarizes and discusses the employment of single-molecule fluorescence microscopy (SMFM) in heterostructure-catalyzed chemical reactions. First, the working principle of SMFM, especially in catalysis imaging, is introduced, demonstrating its role in the mapping of active sites and acquisition of reaction kinetics. Then, nanoscale imaging of the chemical reactions on heterostructures is summarized and discussed in five categories: carbon-supported metal nanocatalysts, metal nanocatalysts coated with mesoporous silica, bimetal nanocatalysts, semiconductor-based heterostructures, and zeolite homostructures. It is found that there is a strong synergistic effect between the two components in heterostructures. The active site distribution, reaction kinetics, and reaction mechanisms are fully discussed based on the results from SMFM measurements. Finally, further perspectives and remaining challenges in this field are presented. This review will be helpful not only for deep understanding of the catalytic reactions on surface of heterostructures, but also for design and fabrication of more efficient and stable nanocatalysts based on heterostructures.