Controllable Urchin-Like NiCo2S4 Microsphere Synergized with Sulfur-Doped Graphene as Bifunctional Catalyst for Superior Rechargeable Zn-Air Battery

Rechargeable zinc-air batteries (ZnABs) are attracting great interest 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 reduction and evolution reactions (ORR/OER). Therefore, it is highly desired to exploit an ideal bifunctional catalyst to endow the obtained ZnABs with excellent ORR/OER catalytic performances. Herein, a new nonprecious-metal bifunctional catalyst of urchin-like NiCo2S4 microsphere synergized with sulfur-doped graphene nanosheets (S-GNS/NiCo2S4) is controllably designed and synthesized by simply tailoring the structure and electronic arrangement, which endow the as-prepared catalyst with excellent electroactivity and long-term durability toward ORR and OER. Importantly, ZnABs constructed by this outstanding catalyst exhibit high power density, small charge/discharge voltage gap, and excellent cycle stability, notably outperforming the more costly commercial Pt/C + Ir/C mixture catalyst. These excellent electrocatalytic performances together with the simplicity of the synthetic method, make the urchin-like NiCo2S4 microsphere/S-GNS hybrid nanostructure exhibit great promise as a superior air-cathode catalyst for high-performance rechargeable ZnABs.