In Situ Synthesized Cobalt Nanocrystal via Bipyridine Ligand Cobaltic Borate Annealing Method for High-performance Zinc-air Battery.

A "butterfly-like" metal templated borate, [Co2(bpy)4(C2O4)]·[B5O6(OH)4]2·py2 (1, bpy = 2,2'-bipyridine, py = pyridine), was synthesized via a solvothermal method. For the first time, the coordination of Co2+ ions with (C2O4)2- ions in borate systems was observed. Notably, upon pyrolyzing precursor compound 1, high-resolution transmission electron microscopy (HRTEM) revealed a catalyst with a carbon-supported Co nanocrystal structure, which significantly enhanced the oxygen reduction reaction (ORR) performance, achieving a half-wave potential comparable to that of Pt/C. More importantly, the catalyst outperformed Pt/C when applied in a zinc-air battery.