Upcycling of waste Ni-MH battery casing into Binder-Free electrode for efficient ethanol Electro-Oxidation

The rapid proliferation of electronic devices has led to a surge in electronic waste, raising significant environmental concerns. In this study, we demonstrate a sustainable and cost-effective approach for converting waste nickel-metal hydride (Ni-MH) battery casings into high-performance electrocatalysts for the ethanol oxidation reaction (EOR) in alkaline media. Upon Hydrothermal treatment, a thin in situ nickel oxyhydroxide layer is generated on the iron-rich battery casing surface, which serves as the electrochemically active phase for ethanol oxidation. Importantly, the metallic casing is preserved and functions as a highly conductive current collector, ensuring efficient electron transport. The enhanced electrochemical performance originates from the strong interfacial coupling between the metallic substrate and the oxyhydroxide layer, which facilitates rapid charge transfer rather than relying on the intrinsic conductivity of the oxyhydroxide itself. In addition, the oxyhydroxide layer passivates the metallic surface, imparting improved corrosion resistance while maintaining effective electronic communication with the underlying metal. The fabricated electrode exhibited outstanding electrocatalytic activity, delivering a high peak current density of 165 mA cm^-2 at 1.70 V and demonstrating an onset potential of 1.36 V with a low overpotential of 1.42 V at 20 mA cm^-2. Additionally, a small Tafel slope of 46 mV dec^-1 indicated favourable reaction kinetics. This study highlights a green strategy to upcycle battery waste for efficient energy conversion, offering dual benefits of environmental protection and energy sustainability.