Influence on the electrolyte resistance of the contact angle of a bubble attached to a disk electrode

• We calculate the ER increment due to bubble of any contact angle on disk electrode.
• The ER increment is up to 40% of that of a perfect sphere near the electrode edge.
• We developed a technique to measure the ER increment due to a truncated sphere.
• Despite low values, the ER increments could be experimentally measured.
• We obtained an excellent agreement between the theoretical and experimental results.

In a previous work, the analysis of the electrolyte-resistance (ER) increment due to the presence of an insulating sphere above or in contact with a disk electrode, simulating a spherical particle, drop, or gas bubble close or attached to an electrode has been reported (Bouazaze et al., 2010) [17]. In the present work, the influence on the ER of the contact angle with the electrode surface, which plays for example a major role in the size of bubbles on gas-evolving electrodes, is quantitatively determined. The mathematical collocation method used in the previous work was improved to account for the change in geometry of the electrode-sphere system. The theoretical results show that the ER increment due to the presence of the sphere depends on its size, position, and contact angle. For a given size and position of spheres of aspect ratio less than 0.4, the ER increment due to the contact angle varies roughly between −45% and +35% of the increment due to a perfect sphere, depending on the interplay of the surface and volume competing effects influencing the ER. Despite their low values, the ER increments could be experimentally measured for spheres of different contact angle placed at the electrode centre, owing to a high-precision motorized translation stage and a specific low-noise ER measurement device. An excellent agreement was obtained between the theoretical and experimental results.