Bubble Formation at a Gas-Evolving Microelectrode

Abstract

The electrolytic production of gas bubbles involves three steps--nucleation, growth, and detachment. Here the growth of hydrogen bubbles and their detachment from a platinum microelectrode of diameter 125 μm are studied using high-speed photography and overpotential frequency spectrum (noise) analysis. The periodic release of large <800 μm bubbles--gas oscillator behavior--was often observed, with a corresponding periodic oscillation of the overpotential which is reflected as a main peak and a series of harmonics in the power spectral density. The release frequency is inversely correlated with the bubble size and hydrogen production rate. When the coalescence of bubbles at the electrode surface is inhibited, either chemically with a surfactant or ethylene glycol or hydrodynamically by magnetically induced convection, swarms of small ∼50 μm bubbles are released in an aperiodic stream. The abrupt transition from periodic to aperiodic release occurs when the surface tension falls below 70 mN m(-1). Hydrogen bubble growth is also studied on a transparent platinum thin-film electrode, where the bubble coalescence can be observed directly. It leaves sessile droplets of electrolyte within the footprint of the growing bubble, showing that the growth involves scavenging smaller bubbles from solution due to hydrogen generated directly at the electrode. A possible role of nanobubbles in the lift-off process is discussed.

On the Electrolyte Convection around a Hydrogen Bubble Evolving at a Microelectrode under the Influence of a Magnetic Field

“…This is due to a reduction of the active electrode area, leading to a change of the current distribution and an increase of the resistance. 28 At about 60% of the entire residence time of the bubble at the electrode, the absolute value of the current starts to increase again while the bubble continues to grow until it is able to detach from the electrode and the evolution process starts all over again. It was suggested that the increase of the current in the final stages of the bubble growth is associated with a translation of the bubble along the electrode surface 27 or small electrolyte channels 28 forming in the interface between the bubble and the electrode surface, thus increasing the active electrode area.…”

Magnetic fields in electrochemistry: The Lorentz force. A mini-review

“…Electrochemical noise analysis provides a frequency spectrum, [22] and it suggests that bubbles grow by coalescence with much smaller ones, [20,21,23] something that can be observed directly, together with microbubble growth and release, using high-speed photography. [21,24] Magnetic field does modify the bubbling regime, but surface tension appears to be the critical factor.…”

Template-Assisted Electrodeposition of Fe-Ni-Co Nanowires: Effects of Electrolyte pH and Sodium Lauryl Sulfate

“…[34][35][36] In addition to influencing bubble behavior, SLS can also be absorbed on the cathode surface. Gomez et al 37 found that SLS helped to render Zn electrodeposits more crystalline than other additives due to the larger overpotential evident in changes of voltammetry curves attributed to SLS adsorption.…”