Preparation, characterization and catalytic performance of single-atom catalysts

Supported and colloidal single-atom catalysts (SACs), which possess excellent catalytic properties, are particularly important in both fundamental studies and practical applications. The progress made in the preparation methods, characterization, catalytic performances and mechanisms of SACs anchored to metal oxides, two-dimensional materials and the surface of metal nanoclusters (NCs) are reviewed. The different techniques for SAC fabrication, including conventional solution methods based on co-precipitation, incipient wetness co-impregnation, and the chemical vapor deposition method, as well as the newer atom layer deposition (ALD) and galvanic replacement methods, are summarized. The main results from experimental and theoretical studies of various catalytic reactions over SACs, including oxidation reactions, hydrogenation, water gas shift, photocatalytic H2 evolution and electrochemical reactions, are also discussed. Moreover, the electronic properties of the single atoms and their interactions with the supports are described to assist in understanding the origin of the high catalytic activity and selectivity of SACs. Finally, possible future research directions of SACs and their applications are proposed.