Binary Metal SulfideNanoparticles as a BifunctionalElectrocatalyst for Durable Zn-Air Batteries

Transition metal sulfides (TMSs) have gradually become the major catalysts for bifunctional electrocatalytic processes of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) applied in rechargeable Zn-air batteries (ZABs). In this article, by epitaxially growing a Ni complex onto Co-based ZIF-67 as a precursor, an optimal catalyst (abbr. Co₉S₈/Ni₃S₂@NC-800) incorporating N-doped carbon matrices encapsulated binary Co₉S₈ and Ni₃S₂ nanoparticles was constructed by high-temperature pyrolysis, which can efficiently drive bifunctional ORR/OER activity (Δ<i>E</i> = 0.62 V). Notably, the catalyst exhibits remarkable 4e^– ORR activity, characterized by a high half-wave potential (<i>E</i>_1/2 = 0.96 V), exceeding the performance of benchmark Pt/C. It demonstrates commendable OER activity, requiring a modest operating overpotential of only 325 mV (<i>E</i>_J=10). Moreover, a ZAB assembled with Co₉S₈/Ni₃S₂@NC-800 as the air cathode has a substantial power density (213.17 mW·cm^–2), an elevated specific capacity (771.10 mAh·g_Zn^–1), and exceptional cycle stability (1421 h, 2842 cycles), which is potentially applied in various energy-related devices. The favorable ORR/OER performance may be due to the synergistic interaction of the N-doped carbon matrix and binary Co₉S₈ and Ni₃S₂ TMSs in the catalyst.