Porous Ni3S2–Co9S8 Carbon Aerogels Derived from Carrageenan/NiCo-MOF Hydrogels as an Efficient Electrocatalyst for Oxygen Evolution in Rechargeable Zn–Air Batteries

Herein, we fabricate N-doped porous Ni3S2-Co9S8/carbon aerogels (Ni3S2-Co9S8/NCAs) using carrageenan/NiCo-metal-organic framework (MOF) hydrogels as the precursor via the high-temperature carbonization route with excellent electrocatalytic properties for the oxygen evolution reaction (OER). The electrochemical measurements indicate that the Ni3S2-Co9S8/NCA as a quintessential electrocatalyst exhibits excellent OER performance, which has outperformed most transition metal sulfide (TMS) catalysts in alkaline environments, as attested with a lower overpotential of 337 mV at 10 mA cm-2 and a smaller Tafel slope of 77 mV dec-1. Meanwhile, a Zn-air battery based on Ni3S2-Co9S8/NCA + Pt/C achieves a large power density of up to 256 mW cm-2 (and 193 mW cm-2), small charge/discharge voltage gap, and good cycling stability, notably better than the conventional RuO2 + Pt/C-based Zn-air batteries. These excellent electrocatalytic properties are mainly attributed to the distinct hierarchical porous structure and interfacial synergy between the Ni3S2 and Co9S8 nanoparticle structure with rich defects, facilitating the mass transport and high graphitization degree beneficial for electron mobility. It is envisioned that the research provides a novel approach for the exploration of marine biomass as an electrocatalyst.