Silver and Polyvalent Cobalt Encapsulated in N-Doped Carbon Nanomaterials as an Efficient Bifunctional Electrocatalyst for Zn-Air Battery.

Abstract

Rational design of nonprecious bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR/OER) is essential for rechargeable zinc-air batteries. Here, a nitrogen-doped carbon-coated catalyst incorporating silver and mixed-valence cobalt species is synthesized via a low-temperature strategy followed by molten salt-assisted pyrolysis and chemical reduction. The approach modulates the crystallization of ZIF-67 and embedded KCl, which upon melting creates a hierarchical porous structure beneficial for mass transport and active site exposure. The introduced Ag nanoparticles enhance electrical conductivity and facilitate electron transfer. The resulting catalyst, Ag/Co/Co₃O₄@NC-5, exhibits outstanding ORR (E_1/2 = 0.853 V) and OER (E_j = 10 = 330 mV) performance. A zinc-air battery based on this catalyst demonstrates excellent stability over 160 h with only 0.076 V decay after 150 cycles. This work offers a novel synthesis route for efficient bifunctional electrocatalysts.