Kinetics of hydrogen evolution reaction on nickel modified by spontaneous Ru deposition: A rotating disk electrode and impedance spectroscopy approach

• This is a simple and reproducible method to activate nickel electrodes towards HER.
• A deposition of 1800 s originates a decrease on the onset potential of 0.15 V.
• Is observed an enhancement of the catalytic activity after the ageing treatment.
• The RDS is the Volmer reaction and a Langmuir type H adsorption isotherm is observed.
• The catalytic activity loss by nickel hydride formation is avoided by Ru deposition.

The kinetics of hydrogen evolution reaction (HER) was studied on nickel catalysts prepared using a ruthenium spontaneous deposition method. Rotating disk electrode (RDE) and electrochemical impedance spectroscopy (EIS) were used for electrochemical characterization, and the results of the analysis were compared with pure nickel catalysts. Three different deposition times were used to obtain different ruthenium loads and to analyze their impact on the electrocatalytic activity. Kinetic and thermodynamic parameters of the reaction were obtained for freshly synthesized catalysts, and also for catalysts aged using a short chronoamperometric procedure. The presence of ruthenium was found to shift the reaction onset potential up to about 160 mV to lower overpotentials comparing with pure nickel, which not increases after ageing, showing a substantial improvement in catalytic activity. Results of Tafel and Koutecky–Levich (K–L) analysis have shown that the HER rate determining step is the Volmer reaction with Langmuir type adsorption for both, Ni/Ru fresh and aged catalysts.