Electrodeposition of Trimetallic (Ni, Co, and Fe) Terephtalate Metal–Organic Frameworks Onto Carbon Cloth for Direct Use as Positive Electrode in Aqueous Zn‐Air Batteries

Metal‐air batteries have attracted attention due to their high energy density and low cost compared to conventional ion batteries. One of the primary challenges for metal‐air devices is the development of air electrodes using a fast, easily controlled, and mild‐condition methodology. In this work, bifunctional electrocatalysts for oxygen reduction and evolution reactions (ORR/OER) based on metal‐organic frameworks (MOFs) were prepared using terephthalic acid as ligand and Ni, Co, and Fe as metal centers onto carbon cloths through a quick and easy method, such as electrodeposition. Fe incorporation into Co‐Ni terephthalate drives a remarkable electrocatalytic improvement, decreasing the overpotential for OER (@ 10 mA cm −2 ) and exhibiting a Tafel slope value of 28 mV dec −1 . Meanwhile, incorporating Fe also improves the electrocatalytic behavior towards ORR, achieving a Tafel slope of 157 mV dec −1 and a 4 e − pathway. Introducing Fe modifies the electronic structure, changing the electronic density of neighboring metals (Ni and Co) and promoting these active sites. Finally, an aqueous zinc‐air battery assembled using NiCoFe‐MOF films as the positive electrode exhibited a constant cell voltage of 1.2 V under open‐circuit conditions. The battery remained stable during the galvanostatic charging‐discharging process at 5 mA cm −2 (0.83 mAh cm −2 ) for 9 days with a round‐trip efficiency of around 52%, delivering a maximum energy density of 8 Whm −2 with an energetic efficiency of up to 66%. These results demonstrate the viability of using a fast and economical approach to construct ready‐to‐use oxygen electrodes for metal‐air batteries in 10 min.