Electrocatalytic activity on single atoms catalysts: Synthesis strategies, characterization, classification, and energy conversion applications

Due to ever compounding environmental issues, the energy future is based on sustainable energy conversion technologies. Electrocatalytic activities drive the functionality of these technologies. The full commercialization of sustainable energy conversion technologies thrives on developing low-cost and highly efficient electrocatalysts. In recent years, it has been a run to develop single-atom catalysts (SACs). These atomic level electrocatalysts dispersed on a substrate enable high metal utilization, a road to low-cost catalyst engineering coupled with high catalytic activity. This possibility necessitates the elucidation of the correlation between the atomic structure, properties, and mechanistic perception of the innovative synthesis notion. Thus, these SACs possess the ability to bridge the gap between homo- and heterogeneous catalysis. Herein, we give a brief introduction to SACs, followed by a readable account of the synthetic routes and SACs classification and a summary of clean energy catalytic reactions: Oxygen reduction reaction (ORR), Water splitting {Hydrogen evolution reaction (HER), and Oxygen evolution reaction (OER)}, Carbon dioxide reduction reaction (CO₂RR), Nitrogen reduction reaction (N₂RR), Methanol oxidation reaction (MOR), and Ethanol oxidation reaction (EOR). We present a concise summary fostered with futuristic perceptions. Finally, we hope to provide more insights on the advancement in SACs development for electrochemical energy conversion. Moreover, the opportunities and challenges in this emerging field are offered based on its current development.