Hydrogen generation during interaction of oxide covered copper with deoxygenated aqueous solution

Copper is considered to react to a very limited extent with oxygen-free water but detection of hydrogen in amounts beyond those predicted by thermodynamic calculations has been reported. It is thus of importance to explore the influence of different factors on the behavior of copper in deoxygenated aqueous solutions. In the present work, we focus on the role of the surface film and associated cuprous species. Electrochemical impedance measurements, in-situ detection of free soluble cupric ion and dissolved hydrogen are employed. The obtained results are quantitatively described by a kinetic model, its main feature being the formation of a CuOH intermediate at the cuprous oxide film/electrolyte interface both by oxidation of Cu and reduction of free soluble Cu2+. This intermediate is assumed to play a pivotal role in a sequential surface reaction generating hydrogen gas by reduction of water. The model is successfully parameterized using regression of the model equations to in-situ experimental data, and conclusions on the effect of oxide films are reached based on the evolution of kinetic parameters with time and temperature.