Enhanced electrocatalytic activity of Ni-Mn-Co-Fe alloys for efficient hydrogen and oxygen evolution reactions: A study on the effects of electrodeposition parameters

The synthesis of high-performance and cost-effective electrocatalysts for water splitting and fuel cell processes is crucial for hydrogen energy production and is considered one of the most significant challenges. This work produced a Ni‒Mn‒Co‒Fe electrocatalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) via electrodeposition, which is a highly efficient and cost-effective method for synthesizing electrodes. The operating deposition parameters for Ni-Mn-Co-Fe were investigated, including the bath composition; scan rates of 5, 10, and 50 mV/s; pH values of 1.5, 3.5, and 7.5; bath temperatures of 25, 40, and 60 °C; and applied potentials ranging from −0.5 to −1.4 V vs. Ag/AgCl. The electrocatalytic activity of the electrocatalyst was evaluated at various temperatures and KOH concentrations. Linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were employed to estimate the electrocatalytic activity. The electrocatalytic performance of various electrodes for the HER and OER in alkaline environments, including Ni, Ni‒Mn, Ni‒Co, Ni‒Mn‒Co, Ni‒Mn‒Fe, and Ni‒Mn‒Co‒Fe, was examined. The results indicate that the Ni‒Mn‒Co‒Fe electrode required overpotentials of 436 mV and 447 mV to achieve a current density of 100 mA/cm² for the HER and OER, respectively, demonstrating outstanding electrocatalytic activity. Moreover, after 20 h of electrolysis at a current density of 100 mA/cm², the overpotential changes were minimal (less than 4 %), indicating exceptional electrochemical stability. As a bifunctional electrode in the overall water-splitting system, a cell voltage of 1.57 V vs. RHE is required to deliver a current of 10 mA/cm².