Effect of operational parameters on gas evolution in electrolyte bulk: possibilities for lowering interelectrode resistance

Gas Bubbles in Electrochemical Gas Evolution Reactions

“…We point out that the theoretical and experimental studies discussed above are based on largely simplified static models and the assumption of a uniform distribution of bubbles in electrochemical cells, both of which can substantially deviate from practical applications. There are numerous studies on the bubble-induced ohmic resistance in specific operating systems. − For example, Vogt built a hydrodynamic model for the ohmic resistance of cells under the assumption that the dispersion of gas bubbles in an electrolyte can be treated as two parts: a stagnant boundary at the electrodes being enriched in gas and flowing bulk in the center region. In following years, he continued to modify this model by considering that only a fraction of the dissolved gas turns into gas bubbles and by treating the flow rates of gas bubbles and electrolyte solution separately .…”

“…There are numerous studies on the bubble-induced ohmic resistance in specific operating systems. − For example, Vogt built a hydrodynamic model for the ohmic resistance of cells under the assumption that the dispersion of gas bubbles in an electrolyte can be treated as two parts: a stagnant boundary at the electrodes being enriched in gas and flowing bulk in the center region. In following years, he continued to modify this model by considering that only a fraction of the dissolved gas turns into gas bubbles and by treating the flow rates of gas bubbles and electrolyte solution separately . Kreysa and Kuhn derived new equations for calculating the gas bubble fraction as a function of the gas bubble velocity by introducing a coalescence barrier model, where gas bubbles in a swarm are separated from each other by a minimum distance due to electrostatic repulsion.…”

Bubble Engineering on Micro-/Nanostructured Electrodes for Water Splitting

“…At the moment of bubble detachment from the electrode surface, the as-formed enhanced localized concentration gradient would facilitate ion diffusion from the bulk solution to the electrode surface and retard the expansion of the Nernst diffusion layer. This is the penetration model developed by Ibl and co-workers (Figure a middle) . When many bubbles are released from the electrode surface, the rising bubble swarm would also induce the free-convective flow of bulk electrolyte, which is also called the hydrodynamic model as proposed by Janssen and Hoogland (Figure a right).…”

“…This is the penetration model developed by Ibl and co-workers (Figure 5a middle). 62 When many bubbles are released from the electrode surface, the rising bubble swarm would also induce the free-convective flow of bulk electrolyte, which is also called the hydrodynamic model as proposed by Janssen and Hoogland 63 (Figure 5a right).…”

Mechanisms of mass transfer of dissolved gas from a gas-evolving electrode and their effect on mass transfer coefficient and concentration overpotential

“…The f~ values differ, the second being larger than the first. And further, due to the fact that the bulk concentration, co, is larger than the gas-liquid interfacial concentration Cb [21][22][23][24][25], desorption continues (to a smaller extent) within the bubble layer remote from the electrode. It is not surprising that the values fc obtained experimentally [18,19] are larger than those calculated for adhering bubbles [3].…”