Nb-Doped Cobalt Pentlandite Catalysts as a High-Performance Electrocatalyst for the Rechargeable Zinc-Air Batteries.

Abstract

In the commercialization process of zinc-air batteries (ZABs), the sluggish kinetics of the oxygen evolution reaction (OER) at the air cathode is one of the major bottlenecks. To address this issue, we have successfully fabricated a series of niobium-doped (FeCoNi)9S8 (Nb-FCNS) catalysts via a two-step solvothermal method. Systematic characterizations confirm that the incorporation of Nb5+ induces lattice contraction, optimizes the valence states of transition metals, and enhances the ordering of M-S bonds. The optimized Nb-FCNS-2 exhibits exceptional OER performance in 1 M KOH electrolyte, with an overpotential of 278 mV at 10 mA cm-2 (η10) and a Tafel slope of 80.94 mV dec-1, both of which outperform the commercial IrO2 benchmark. The assembled ZABs deliver a low charge overpotential (ΔE = 0.912 V), a high-power density of 154.12 mW cm-2, and excellent cycling stability (over 350 h). In situ Raman spectroscopy reveals that Nb doping suppresses the excessive oxidation of sulfur species to SO 4 2 - , thus achieving a well-controlled surface reconstruction process. This work not only provides valuable design insights for constructing high-performance transition metal sulfide electrocatalysts, but also offers new perspectives for the design of low-cost, highly stable air cathode catalysts for ZABs.

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