Single Atom Engineering for Electrocatalysis: Fundamentals and Applications.

The global transition to sustainable energy production revolves around innovations in electrocatalysis, the cornerstone of energy conversion technologies. Over the years, catalysts have evolved from bulk materials to nanoparticles (NPs) and nanoclusters (NCs), culminating in single-atom catalysts (SACs), which represent the peak of catalyst engineering. SACs have revolutionized electrocatalytic processes by maximizing atom efficiency and offering tunable electronic properties, lowering the energy barrier associated with the absorption and desorption of key reaction intermediates, thus promoting specific reaction pathways. This review delves into the synthesis, characterization, and theoretical modeling of SACs, offering a comprehensive analysis of state-of-the-art methodologies. It highlights recent breakthroughs in diverse electrocatalytic reactions, including the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting, the oxygen reduction reaction (ORR) for Zn-air batteries and fuel cells, the CO reduction reaction (CORR), and green ammonia synthesis. The discussion emphasizes the unique mechanisms that drive the exceptional performance of SACs, shedding light on their unparalleled activity, selectivity, and stability. By integrating experimental insights with computational advances, this work outlines a path for the rational design of next-generation SACs tailored to a broad spectrum of electrocatalytic applications. While summarizing the current landscape of electrocatalysis by SACs, it also outlines future directions to address the energy challenges of tomorrow, serving as a valuable resource for advancing the field.