The effect of electrolytically evolved gas bubbles on the thickness of the diffusion layer

The thickness, d, of the Nernst diffusion layer depends on the nature of the gas evolved, on the mode of formation of bubbles, on c.d. j, and on the height of the electrode. Pt electrodes of various heights were used at which H, O, or Cl was evolved. d decreases in the sequence H, Cl, O; d decreases with increasing j, this decrease being very marked at j > 200 mA/cm2; it increases with height of the electrode. The no. and the distribution of the sites at which bubbles are formed depend on the nature of the gas evolved and on c.d. The H bubbles are formed at the edges of the electrode at j <40 mA/cm2 but also at the whole surface at j > 150 mA/cm2. The formation of O and of Cl bubbles take place at the whole surface at j > 5 mA/cm2. For an O-evolving electrode log dl = aj + 0.13 log l, where aj depends on j; l is the distance from the lower edge of the electrode. d is detd. by the trajectory, the no., and the size of bubbles. [on SciFinder (R)]