heterogeneous catalysis

Accounts of Materials Research

ConspectusRecent decades have witnessed the rapid development of catalytic science, especially after Taylor and Armstrong proposed the notion of the “active site” in 1925. By optimizing reaction paths and reducing the activation energies of reactions, catalysts appear in more than 90% of chemical production reactions, involving homogeneous catalysis, heterogeneous catalysis, and enzyme catalysis. Because of the 100% efficiency of active atom utilization and the adjustable microenvironment of metal centers, single-atom catalysts (SACs) shine in various catalytic fields for enhancing the rate, conversion, and selectivity of chemical reactions. Nevertheless, a solo active site determines a fixed adsorption mode, and the adsorption energies of intermediates from multistep reactions linking with a solo metal site are related to each other. For a specific multistep reaction, it is almost impossible to optimally adjust the adsorption of every intermediate on the solo site simultaneously. This phenomenon is termed the scaling relationship limit (SRL) and is an unavoidable obstacle in the development of pure SACs.Dual-atom catalysts (DACs), perfectly inheriting the advantages of SACs, can exhibit better catalytic performance than simple SACs and thus have gradually gained researchers’ attention. Depending on the dual-metal structure, dual-metal sites (DMSs) in DACs can be divided into two separated heterometal sites, two linked homometal sites, and two linked heterometal sites. Two separated heterometal sites prescribe a distance limit between two metal sites for electron interaction. Currently, the active origins of DACs can be summarized in the following three points: (1) electronic effect, in which only one metal center serves as active site and the other plays an electronic regulatory role; (2) synergistic effect, in which two metal centers separately catalyze different core steps to improve catalytic performance together; (3) adsorption effect, in which offering additional sites changes the adsorption structures to b...

Breaking the Scaling Relationship Limit: From Single-Atom to Dual-Atom Catalysts