Fabrication of N, S co-doped lignin-based hierarchical porous carbon nanocages loaded with binary metal sulfides as high-performance ORR/OER cathode materials for Zn-air batteries

Zinc-air batteries have emerged as a key research focus in the new energy sector in recent years, owing to their high energy density, enhanced safety, and low-carbon environmental protection characteristics. But its limited output power and lower charging and discharging stability have hindered its commercialization applications. In this work, N, S co-doped lignin-based hierarchical porous carbon nanocages loaded with binary metal sulfides (Fe_xNiS_y-TLCs-T) were fabricated firstly using lignin as a carbon source and then using nano-MgO as templates. Meanwhile, lignin was modified by amination via Mannich reaction, and then ligand compounds were formed with metal ions to prepare nano-restricted domain catalysts. The prepared Fe_xNiS_y-TLCs-T not only exhibit bifunctional catalytic activity for oxygen reduction reaction and oxygen evolution reaction (ORR/OER), but also demonstrate a half-wave potential (0.84 V) and overpotential (270 mV) comparable to those of commercial noble metal catalysts. Furthermore, Fe_xNiS_y-TLCs-T also exhibited superior methanol toxicity resistance and stability compared to commercial Pt/C catalysts. This work presents a green and economical approach to construction Zn-air batteries air cathode electrocatalyst, highlighting the potential of biomass-based carbon materials for green energy conversion and offering innovative pathways for high-value lignin utilization.