Synergistic Fe-Mn-Cu ternary alloys enhance bifunctional activity and stability for alkaline water splitting

Developing cost-effective, high-performance electrocatalysts for water splitting remains a critical challenge for advancing renewable energy technologies. Herein, we present a novel ternary alloy catalyst, 20Fe-80Mn-20Cu, designed and optimized for hydrogen evolution (HER) and oxygen evolution reactions (OER). The catalyst, synthesized via electrodeposition, demonstrates exceptional bifunctional activity and stability, outperforming binary (20Fe-80Mn) and benchmark electrodes, such as Pt and DSA. Linear sweep voltammetry (LSV) revealed that 20Fe-80Mn-20Cu requires a remarkably low overpotential (without iR drop correction) of 172 mV for HER and 147 mV for OER to achieve a current density of 10 mA cm^{- 2}, significantly surpassing the performance of binary alloys and bare substrates. Tafel slope analysis further confirmed the catalytic efficiency, with values of 53 mV dec^{- 1} for HER and 56 mV dec^{- 1} for OER. Electrochemical impedance spectroscopy (EIS) revealed low charge transfer resistance, highlighting the alloy's excellent electron transport properties. Raman and XRD investigations revealed the catalyst's unique structural and compositional features, including extra crystallographic reflections indicating increased surface activity. Stability tests conducted at ± 250 mA cm^{- 2} over 4 days demonstrated excellent durability, with only 7% (HER) and 5% (OER) performance drops. Post-stability characterizations, including XRD and EDX, revealed Mn and Fe redistribution and Cu enrichment on the surface, as well as the formation of stable copper oxides under OER conditions. These findings establish 20Fe-80Mn-20Cu as a promising candidate for scalable water splitting, offering an energy-saving potential of up to 5.5 V per cm² of the electrode surface. This study increases our understanding of alloy-based catalysts and demonstrates a feasible approach for efficient and sustainable hydrogen production.