Comparison of Nickel Films Electrodeposited from Aqueous and L‐Serine‐Nickel Chloride Deep Eutectic Solvent for Hydrogen Evolution in Alkaline Solution.

Deep eutectic solvents (DES) emerge as an electrolyte alternative to aqueous solutions for metal electrodeposition. In this study, electrodeposition of metallic Ni film is carried out using aqueous solution and using L‐serine‐nickel chloride DES as electrolytes. The deposited Ni films are characterized, and the hydrogen evolution (HER) activity of these films is compared. The Ni film deposited from aqueous solution (Ni‐AQ) exhibits a higher degree of crystallinity, a rougher surface, and a higher electrocatalytic HER activity in 1 M KOH. The overpotential of Ni‐AQ to reach 50 mA cm−2 HER current densities is 140 mV, lower than that of the Ni film deposited from the DES (Ni‐DES). The Ni‐AQ exhibits both a higher number of electrochemically active Ni sites and more facile HER kinetics, which could account for its high HER activity. Both Ni‐AQ and Ni‐DES sustain the long‐term HER test, with Ni‐AQ exhibiting better HER stability. [ABSTRACT FROM AUTHOR]