Solvent-free synthesis of Co/CoNx encapsulated by N-doped, sucrose-derived porous carbon as bifunctional air cathode catalyst for high-energy rechargeable zinc-air batteries

Rechargeable zinc-air batteries have a substantial theoretical energy density while potentially being manufactured at a minimized cost. Hence, developing low-cost bifunctional electrocatalysts is of crucial importance. Herein, the synthesis of an electrocatalyst containing zinc/cobalt species encapsulated in a nitrogen-doped carbon matrix modulated with a large number of carbon nanotubes (ZnCo@CN) was developed through a facile thermal method under solvent-free conditions. Using bio-based sucrose in the presence of inorganic catalysts (Zn/Co) resulted in a Zn/Co carbon foam-like structure. Subsequently, the high-temperature treatment with the addition of 2-methylimidazole resulted in a unique material (ZnCo@CN). The incorporation of highly active species dispersed in hierarchical porous carbon presented an excellent bifunctional electrocatalyst for ORR (half-wave potential of 0.85 V) and OER (overpotential of 327 mV). The assembled zinc-air battery with ZnCo@CN as a bifunctional air cathode exhibited an excellent power density of 206 mW cm -2 and an astonishing energy density of 983 Wh Kg -1 .