Precise Synthesis of Dual-Atom Catalysts for Better Understanding the Enhanced Catalytic Performance and Synergistic Mechanism

ConspectusDual-atom catalysts (DACs), featuring two catalytic sites in close proximity, have emerged as a new frontier in energy-related catalysis. Compared with single-atom catalysts (SACs), DACs have more space to optimize the catalytic performance by changing the dual-atom catalytic sites and their coordination environments. Through adjusting the compositions and coordination environments of the metal sites in DACs, it is possible to finely tune the electronic and geometric properties of active centers, and then the synergistic effects for facilitating substrates activation and intermediates stabilization can be strengthened or optimized, consequently tailoring diverse reaction pathways and achieving various challenging catalytic reactions. The most important yet challenging task in DACs studies is the precise synthesis of DACs, which is crucial to understand the relationship between the catalytic performance and structure at the atomic level. In most cases, DACs were synthesized via the pyrolysis of a mixture of metal salts and organic ligands, in which two metals are randomly distributed in DACs, and it was difficult to control the M···M distance (M = metal ion) and uniform dispersion of DACs. Hence, developing innovative strategies for the precise synthesis of DACs with definite structures and high-efficiency catalytic performance is urgently needed.In this Account, we tentatively summarize the strategies for the precise synthesis of DACs and their applications in activation and conversion of small molecules such as H2O, CO2, and so on. Focusing on the precise synthesis of DACs, three types of synthesis strategies have been put forward and systematically introduced. Based on the precise synthesis strategies, the applications of the resulting DACs with high purity in synergistically activating and converting small molecules have concurrently been discussed, including the cleavage of C-C bonds, activation and reduction of CO2 and H2O, and so on. Attempts have been made to explain why the catalytic performance of DACs for these functions is much higher than what SACs have achieved. Efforts have been made on revealing the influences of dual-metal site types, the separations between dual metals, their geometry configurations and coordination environments, as well as the ligand structures on the catalytic performance. Emphasis has been placed on the analysis of the structure-reactivity relationship and revealing the synergistic mechanism at the molecular level. Finally, perspectives on the current challenges and future development of DACs have been put forward. We anticipate and believe that this Account will provide profound insights into the synthesis of structurally defined DACs and give new insights of synergistic catalytic effects in DACs.