Surface state and proton adsorption phenomena on CoRu-based materials during hydrogen evolution reaction in acid conditions

The electrocatalytic activity for hydrogen evolution reaction (HER) of cobalt-ruthenium based nanomaterials (Co₈₀Ru₂₀and Co₈₀Ru₁₅Pt₅) synthesized by high energy mechanical milling was studied in acid medium. The synthesized materials were immersed in a carbon paste electrode matrix (20 wt.%). X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to characterize the synthesized powders. The composition of the nanomaterials was established by means of energy dispersive spectroscopy (EDS). SEM and TEM analysis showed the formation of agglomerates of 1–5 μm, constituted by particles of ca. 20 nm. The electrocatalytic activity of the prepared materials was evaluated in 0.5 M H₂SO₄at 25 °C using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS) techniques. EIS diagrams were obtained in a frequency range from 100 kHz to 10 mHz at selected potentials. Nyquist diagrams showed the presence of two semicircles. The kinetic parameters for HER obtained from analysis of polarization and impedance data showed that both materials exhibit good performance toward HER. According to the electrochemical parameters, the material with the best performance was Co₈₀Ru₁₅Pt₅.