NiCo₂Se₄ Nanowires as a High-Performance Bifunctional Oxygen Electrocatalyst

Rechargeable zinc-air batteries are attracting great attention due to their high theoretical specific energy, safety, and economic viability. However, their performance and large-scale practical applications are largely limited by poor durability and high overpotential on the air-cathode due to the slow kinetics of the oxygen evolution and reduction reactions (OER/ORR). Therefore, it is highly desired to develop new bifunctional catalysts to improve the OER and ORR kinetics. In this paper, NiCo₂Se₄ nanowires were uniformly grown on carbon fiber paper (CFP) for the first time. With an overpotential for OER of 327 mV, NiCo₂Se₄ nanowires show a better performance than RuO₂ (350 mV) and a high stability. Moreover, their half-wave potential of 0.77 V and limiting current density of 3.75 mA•cm^-2 make it a promising non-precious-metal catalyst for ORR, with performance close to Pt/C (0.87 V, 3.7 mA•cm^-2). The excellent performance is attributed to the nanowire morphology with efficient 1D electronic pathways, high conductivity of NiCo₂Se₄ and an enhanced electronic structure, thanks to a mixed valence of nickel and cobalt ions.