Magneto-Electrocatalysis of Co-Ni Alloy Electrodeposits for Hydrogen Evolution Reactions

Abstract Co–Ni alloy with various compositions were fabricated through a one-step electrodeposition process and evaluated as electrocatalysts for the hydrogen evolution reaction (HER). The electrocatalytic behaviour of the deposited alloys were systematically investigated under both conventional electrocatalytic and magneto-electrocatalytic (0.3 T magnetic field strength) conditions. The Co–Ni alloy exhibited excellent HER activity, which was further enhanced upon the application of an external magnetic field. The magnetic field significantly improves the electron-transfer kinetics, reducing the HER overpotential from 141 mV to 114 mV and increasing the current density from 511 to 533 mA.cm-2. Electrochemical impedance spectroscopy (EIS) further confirmed the magnetic-field-induced enhancement by showing a decrease in charge-transfer resistance (Rct) from 30.5 Ω.cm-2 to 17.1 Ω.cm-2. Field-emission scanning electron microscopy (FESEM) revealed composition-dependent surface morphologies, transitioning from micro-conical and rough architectures in Co-rich alloys to smoother surfaces in Ni-rich compositions. X-ray photoelectron spectroscopy (XPS) provided insights into the surface chemistry, demonstrating composition-dependent shifts in Co and Ni binding energies. This study highlights the effectiveness of magneto-electrocatalysis in boosting the HER performance of electrodeposited Co–Ni alloys and emphasizes the potential of integrating external magnetic fields to achieve superior electrocatalytic activities.