Porous Ni 3 S 2 -Co 9 S 8 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 Ni 3 S 2 -Co 9 S 8 /carbon aerogels (Ni 3 S 2 -Co 9 S 8 /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 Ni 3 S 2 -Co 9 S 8 /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 Ni 3 S 2 -Co 9 S 8 /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 RuO 2 + Pt/C-based Zn-air batteries. These excellent electrocatalytic properties are mainly attributed to the distinct hierarchical porous structure and interfacial synergy between the Ni 3 S 2 and Co 9 S 8 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.