Recent advances of the key parameters of 3d block transition metal single and dual atoms catalysts: from their synthesis to their practical applications

Single and dual atom catalysts (SACs and DACs) with high catalytic activity have emerged as a new frontier in many sectors owing to their exceptional atom utilization efficiency, excellent selectivity, and long durability. In addition of the synergic effects of two adjacent metals active sites for DACs, and the tailoring of different single-metal center that can stimulate the adsorption-desorption behavior. To promote the catalytic behavior of SACs and DACs many efforts have been devoted for their synthesis. In this review, the recent development and application of 3d transition metal (Fe, Ni, Cu, Mn, Co and Zn) SACs and DACs on various catalytic reaction including oxygen reduction reaction (ORR), water splitting (WS), CO2 reduction reaction (CO2RR), N2 reduction reaction (N2RR) etc. and various devices counting Zinc-air battery, lithium battery, proton exchange membrane fuel cells (PEMFCs) etc. are summarized and discussed. Particularly, we focus on three main parameters including: the relationship between the different dimensional supports (1D, 2D and 3D) on their structure, and strategies to improve the coordination environment and the metal loading. Then we provide a comprehensive summary on their advantages but also shortcomings on their unique structure and final catalytic activity. Finally, the future challenges and prospects are enumerated for the development of SACs and DACs.