Numerical Simulation of Hydrogen Bubble Growth at an Electrode Surface

A single hydrogen bubble generated at an electrode surface during water electrolysis is simulated via the volume of fluid (VOF) multiphase flow model to capture the details of the interface evolution and the mass transfer that occurs at the interface. The hydrogen bubble that grows at the electrode is driven by supersaturation of the dissolved hydrogen in the liquid. Two models are used to calculate the gas-liquid interface mass transfer coefficient. The bubble growth from experimental results agrees closely with theoretical predictions. In addition, the mass transfer of dissolved hydrogen from the electrode surface to the bulk liquid is evaluated during the bubble nucleation and growth stages. During the nucleation stage, the mass transfer coefficient is <5.1 x 10(-5)m/s. Once the bubble embryo is formed, the mass transfer greatly increases. Before the bubble releases, the mass transfer coefficient reaches 2.8 x 10(-4) m/s. More detailed information about the bubble growth is presented, including bubble-induced convection and the concentration distribution of dissolved hydrogen around the growing bubble. The results indicate that the VOF method is suitable and reliable for simulating bubble behaviour during electrolysis or other electrochemical reactions that involve gas bubble desorption.