Hydrogen evolution reaction (HER), occurring on platinum rotating disc electrode (RDE) in aqueous solutions containing dissolved CO2 in different pressures was investigated. This system was modeled by taking into account the two dissociation reactions of CO2 and using a numeric finite difference method (FDM). Moreover, in the high potential range where the current plateau starts to increase, a new reaction (water reduction) was proposed. A satisfactory agreement between the experimental data and the model was obtained. The model-building article did not take into account any additional cathodic reactions attributed to CO2. (C) 2019 The Electrochemical Society.