Kinetics of Hydrogen Evolution Reactions in Acidic Media on Pt, Pd, and MoS2

Hydrogen evolution reaction (HER) are investigated on Pt, Pd, and MoS₂ in a 0.5 M H₂SO₄ electrolyte in a rotating disk electrode (RDE) configuration in the temperature range of 285-335 K. The reaction is temperature-sensitive on all of the three catalyst surfaces at their respective overpotential ranges. The kinetic parameters (activation enthalpy (ΔH^#), free energy of activation (ΔG^#), and pre-exponential factor (A_f)) toward HER are obtained from the Arrhenius and Eyring relations, and the overall kinetics on the catalyst surfaces is analyzed. ΔH^# for HER is a strong function of the overpotential in the case of both Pt and Pd. On the other hand, the trend in A_f suggests that the electrocatalysis of HER on MoS₂ originates from an increase in entropy factor, perhaps due to the solvent-dipole interaction at the interface. Such analysis is pivotal to the investigation of electrocatalysis of HER, especially on surfaces for which determination of active-site density is not established.