MOF derived Trimetal (Fe Mn and Co) based efficient bifunctional electrocatalyst for oxygen electrode in zinc-air batteries/

Abstract

Rechargeable Zinc-air batteries (RZABs) have gained significant recognition in renewable energy due to their exceptional safety, cost- effectiveness, enhanced energy density (1084 Wh·kg⁻¹), and environmental sustainability. The sluggish rate of oxygen electrolysis requires noble metal-based electrocatalysts for Re-zinc-air batteries (RZABs), but these are expensive and exhibit instability issues. This requires the development of efficient, highly stable, and economical non-noble metal dual functional electrocatalysts for oxygen evolution (OER) and oxygen reduction (ORR) reactions. We introduce an easy strategy to synthesize trimetallic nitrogen-containing nanoporous carbon (FeMnCo/N-C) electrocatalyst. By combining Fe/Mn-MOF with ZIF-67, followed by pyrolysis, we obtain FeMnCo/N-C. The prepared materials are characterized by using XRD for phase confirmation, SEM for studying the morphology and surface properties. Raman spectroscopy was utilized for identification of functional groups. The electrochemical techniques like cyclic voltammetry, Linear Sweep Voltammetry and Electrochemical Impedance Spectroscopy were utilized to test the electrochemical performance of the material. FeMnCo/N-C an electrocatalyst, featuring a high surface area, reveals exceptional bifunctional activity, with potential at 10 mA/cm2 (Ej (10) = 1.60 V) for the oxygen evolution reaction (OER) and half-wave potential (E1/2 = 0.83 V) for the oxygen reduction reaction (ORR), which results in a potential gap of 0.77 V, exceeding Fe/Mn-C and Co/N-C. A zinc-air battery containing FeMnCo/N-C electrocatalyst has exhibited specific capacity of 721.7 mAh/g , Power density of 87.2 mW/cm2 and stable charge- discharge 60 cycles in 3.8 hrs. The bifunctional activity of an electrocatalyst is due to the combined effects of the tri-metals, nitrogen-doped carbon, and their porous nature, offering FeMnCo/N-C a notable candidate for wider application in electrochemical energy devices.