Recent development of active metallic nanostructures-encapsulated carbon hybrid materials for ORR, OER, and HER...

The search for cost-effective, abundant, and efficient alternatives to precious metal catalysts is vital for advancing electrocatalytic performance. Despite various studies on non-precious metal catalysts, their industrial application remains hindered by their inherent reactivity and poor stability. A promising strategy, based on encapsulating non-precious active metal materials within 2D carbon supporting materials, offers distinct benefits, including improved catalytic performance and long-term durability. Such behaviors are attributed to their synergistic effect, which provides ample electrochemically active sites, tunable electronic properties, and an innovative structural design that enhances interaction between the constituents. This review summarizes the recent progress in preparation methods, innovative micro/nano structures, and the widespread applications of nonprecious metal-derived electrocatalysts confined within two-dimensional carbon layers. The main merits and demerits of various synthesis strategies will be critically evaluated to elucidate the relationship between structure and properties, with the aim of improving electrochemical performance. Furthermore, this review highlights the significance of these hybrids for various potential electrochemical processes, including the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR), in the context of relevant fuel cells, metal-air batteries, and water electrolysis. Lastly, the existing issues in the primary study, their practicality, and prospective directions for future development are also briefly emphasized.