Promising single-atom catalysts for environmental energy material applications: overview and perspectives

In recent years, the consumption of renewable energy, utilization of green energy and practicability regarding carbon neutrality have been evidently shown to be dependent on green electrocatalysts. In particular, single-atom catalysts (SACs) stand out among the trending catalysts in the fields associated with the electrical industry, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR), CO₂ reduction reaction (CO₂RR), nitrogen reduction reaction (N₂RR), CO oxidation, zinc-air batteries (ZABs), and lithium-sulfur batteries (LSBs). Advantageously, atomically dispersed metal catalysts, compared with ordinary nanoparticle catalysts, exhibit higher atomic efficiency, resulting in a significant increase in the surface free energy, unsaturated coordination environment, quantum size effect, interaction of metal carriers, and other properties. Therefore, SACs usually show excellent catalytic activity. However, maintaining high reactivity and stability with considerable metal loading still remains a serious challenge. Herein, we reviewed the developments, types, preparation methods, and applications of SACs. Finally, in the summary, the main challenges and ideologically relevant future perspectives are briefly recommended towards the development of SAC-based catalysts.