ZIF-derived Fe,Co coordinated N/O-codoped three-dimensional tungsten–carbon matrix for the performance-enhanced zinc-air flow battery and water splitting

Constructing efficient and cost-effective electrocatalysts with oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) for the development of zinc-air flow batteries (ZAFBs) and overall water splitting (OWS) is significant, but still challenging. Herein, we have fabricated a heterojunction catalyst (Fe,CoZn₉₊₉-NO/WC) featuring uniformly dispersed Fe and Co coordinated with riched-nitrogen/oxygen codoped into a three-dimensional highly porous tungsten–carbon matrix modified carbon nanotube by a simple stepwise construction route using water as the solvent. The resultant Fe,CoZn₉₊₉-NO/WC exhibits a positive half-wave potential (E_1/2) of 0.889 V for ORR, a low overpotential at 10 mA·cm⁻² for OER (290 mV) and HER (84 mV), and excellent electrochemical durability in alkaline electrolyte, outperforming even benchmark catalysts. Moreover, Fe,CoZn₉₊₉-NO/WC as a bifunctional air cathode for ZAFBs delivers higher open circuit voltage, peak power density (190 mW·cm⁻²), and specific capacity (814 mAh·g⁻¹), lower charge/discharge voltage gap and prolonged operational cycles durability, largely exceeding those of the hybrid Pt/C+RuO₂ bifunctional catalyst. The alkaline OWS electrolyzer is constructed by Fe,CoZn₉₊₉-NO/WC with good stability and requires only 1.556 V cell voltage at 10 mA·cm⁻². Impressively, the self-constructed Fe,CoZn₉₊₉-NO/WC electrodes were applied to practical ZAFBs and OWS devices, demonstrating superior performance to the recently reported ZIF/MOF-derived catalysts in organic solvents. This work offers an economical synthetic strategy to prepare highly efficient multifunctional catalysts with practical potential for commercial production, promising to facilitate the development of clean energy storage and conversion devices.