Electrocatalytic activity of Cu MOF and its g-C₃N₄-based composites for oxygen reduction and evolution reaction in metal-air batteries

For metal air batteries the synthesis of highly efficient, sustainable, non-precious metal-based electrocatalysts with bifunctional catalytic activity for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are essential. In this work via simple hydrothermal method Cu MOF and its g-C₃N₄ based composites are prepared and characterized via FTIR, XRD, SEM and EDX. The Cu MOF and the g-C₃N₄-based electrode can work synergistically to enhance the electrochemical process. The Cu MOF accepts electrons, and the g-C₃N₄-based electrode donates them. Consequently, improving electron transport between the electrode and oxygen molecule accelerates reaction kinetics. Further, via incorporating g-C₃N₄ in Cu MOF makes the charge transfer between the electrode and electrolyte effective, making it a viable option for electrochemical devices. In stable states, Cu MOF with 5 wt% of graphitic carbon nitride has a low overpotential (389 mV/10 mA/cm²), a Tafel slope of 26.12 mV/dec, and high stability over 3600 s in 1 M KOH. EIS result showed that g-C₃N₄ decreases charge transfer resistance by allowing electroactive species to contact the catalyst. Further, via three-electrode setup under nitrogen and oxygen conditions at different scan speeds ORR analysis is done. The composite Cu MOF (5 wt%) exhibits the maximum current density of 1.31 mA/cm² at 0.05 mV /s scan rate in 1 M KOH, surpassing the original Cu MOF, which produced 1.09 mA/cm².