Electrochemical kinetics of the hydrogen reaction on platinum in concentrated HCl(aq)

•New electrochemical data for the hydrogen reaction on platinum in strong acids•EIS and LSV data fittings provided similar limiting and exchange current densities.•As the concentration of HCl increased, the exchange current density decreased.

The hydrogen reaction in concentrated HCl(aq) solutions is a key reaction for the CuCl(aq)/HCl(aq) electrolytic cell. Here, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were used to obtain new data for the hydrogen reaction on platinum submerged in highly concentrated acidic solutions at 25 °C and 0.1 MPa. LSV and EIS data were collected for Pt in 0.5 mol/L H2SO4(aq), 1 mol/L HCl(aq) and 7.71 mol/L HCl(aq) solutions. It was found that exchange current density (j0) values varied between 1 and 2 mA/cm2. An equivalent circuit model was used to obtain comparable j0 and limiting current density values from EIS data relative to values obtained with LSV data. It was found that as the concentration of acid increased, a noticeable decrease in the performance was observed.