Numerical simulation of hydrogen bubble growth and mass transfer on horizontal microelectrode surface under electrode-normal magnetic field

Based on our previous visual experiments and the volume of fluid (VOF) multiphase model, the growth and detachment characteristics of a single hydrogen bubble on the horizontal microelectrode surface under the electrode-normal magnetic field have been numerically investigated. The mass transfer contributions of supersaturated dissolved hydrogen to the bubble growth from the liquid microlayer under the direct injection model and from the bulk bubble interface under the gas–liquid diffusion-controlled model are adopted. The bubble shapes and diameters predicted from the numerical investigation agree well with experimental results under the same conditions. The simulated results indicate that the supersaturated dissolved hydrogen concentration and the mass transfer source at the wedge-shaped areas adjacent to the bubble foot are obviously higher than those in the wider bulk bubble interface regions. The mass transfer contribution to the bubble growth from the liquid microlayer beneath the bubble base directly plays a dominant role. The higher current density and corresponding Lorentz force mainly appears in the wedge-shaped areas, while the higher rotational electrolyte flow velocity appear at oblique positions of the bubble equator. The bubble detachment behavior makes the rotational electrolyte flows is significantly more complex.