Is hydrogen gas in water present as bubbles or hydrated form?

Abstract

When hydrogen gas is bubbled into water, it may well be present as stabilized bubbles rather than hydrated hydrogen molecules, as in the spontaneous emulsification at oil|water interfaces without surfactant. On this prediction, we used dynamic light scattering (DLS) to find bubbles 0.4–0.5μm in diameter, which were stable for more than 9h. The intensity of the scattering light, which was proved to be proportional to concentrations of polystyrene latex suspensions, was also kept in solution in contact with hydrogen gas atmosphere. The bubbles were stable even at 50g (gravity) by centrifugation. Voltammograms of the bubble-included solution had the oxidation peak, of which current was proportional to the intensity of DLS. Concentration of hydrogen in solution was evaluated accurately by comparing voltammetric currents at a regular electrode and a small electrode. The oxidation of hydrogen should be caused by the hydrated hydrogen which was supplied by dissolution of bubbles. Kinetic data of the dissolution were obtained at microelectrodes by using the advantage of extracting kinetics from diffusion currents. Voltammetric currents at microelectrodes were smaller by 10 times than those predicted from diffusion of hydrated hydrogen. Therefore, the oxidation is controlled by the dissolution rate at the high current density. The rate was estimated to be 2×10−8mols−1cm−2, which was converted to the linear transfer rate, 0.4mms−1, at gas|water interface.