Porous W/N/C nanoframework: A trifunctionally effective cathodic electrocatalyst for rechargeable Zn-Air/iodide hybrid battery

Different from the conventional Zinc-Air batteries which only involves oxygen reduction and evolution (ORR/ OER) in the cathode, the cathode of rechargeable zinc-air/iodide hybrid batteries (ZAIHBs), with the addition of I- species, involves I- electrooxidation (IOR) during charging and oxygen/iodate reduction (ORR and IDR) during discharging. This work reports the synthesis of a hierarchically porous tungsten-based nitrogen-doped carbon framework (W/N/C) with abundant WNx active sites and numerous ultrafine WN nanoclusters and explores their application as a trifunctional IOR/ORR/IDR electrocatalyst for ZAIHBs. The formation mechanism of ZIF-8-derived W/N/C framework as well as its structural and compositional features were investigated. The catalyst demonstrates high trifunctional catalytic activity and robust durability towards IOR/ORR/IDR in alkaline condition, owing to the uniform copresence of the numerous sub-nanometer-sized WN nanoclusters and the abundant single atom WNx sites in the hierarchically structured carbon framework. When applied in homemade ZAIHBs, it revealed a high peak energy density (141.9 mW cm-2) and remarkable cycling stability (65 h), outperforming the commercial Pt/C catalysts. This work demonstrates the multi-functional electrocatalytic activity of tungsten-based non-noble metal electrocatalyst for high-performance ZAIHBs.