CoSe₂/Co nanoheteroparticles embedded in Co, N co-doped carbon nanopolyhedra/nanotubes as an efficient oxygen bifunctional electrocatalyst for Zn-air batteries

Transition metal selenide-based materials have been demonstrated as promising electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), yet the actual design of a highly efficient and stable electro-catalyst based on these materials still remains a long and arduous challenge. Herein, a predesigned hybrid Zn/Co zeolitic imidazole framework was used to fabricate CoSe2/Co nanoheteroparticles embedded within hierarchically porous Co, N co-doped carbonnanopolyhedra/nanotubes (CoSe2/Co@NC-CNTs) through a facile approach involving controlled carbonization and selenization procedures. As expected, the optimized CoSe2/Co@NC-CNT-1 displayed outstanding electrocatalytic performance for the ORR and OER, with an onset potential of 0.95 V vs. RHE, a half-wave potential of 0.84 V vs. RHE for ORR, and a potential of 1.69 V vs. RHE for OER at 10 mA cm-2. It also exhibited excellent long-term stability and methanol resistance ability, which were superior to commercial IrO2 and the commercial 20 wt% Pt/C catalyst. Notably, the assembled Zn-air battery with CoSe2/Co@NC-CNT-1 showed a low charge-discharge voltage gap (0.696 V at 10 mA cm-2) and a high peak power density (100.28 mW cm-2) with long-term cycling stability. These superior performances can be ascribed to the synergistic effects of the highly active CoSe2/Co nanoheterostructure, hierarchically porous structure with a large surface area, high electrical conductivity and uniform doping of the Co and N.