Potential response of single successive constant-current-driven electrolytic hydrogen bubbles spatially separated from the electrode

Raman, Akash; Peñas, Pablo; Meer, Devaraj van der; Lohse, Detlef; Gardeniers, Han; Rivas, David Fernández

doi:10.1016/j.electacta.2022.140691

Cited by 26 publications

(29 citation statements)

References 73 publications

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“…Therefore, we aim to perform interface-resolved direct numerical simulations to account for the various mechanisms at play with electrolytically generated gas bubbles. In particular, we look into the successive processes of bubble growth and rise in the electrolyte solution (van der Linde et al 2017;Raman et al 2022) until an equilibrium state is reached, i.e. the global statistics of the system no longer varies in time.…”

Section: Introductionmentioning

confidence: 99%

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Mass transport at gas-evolving electrodes

Sepahi,

Verzicco,

Lohse

et al. 2024

J. Fluid Mech.

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Direct numerical simulations are utilised to investigate mass-transfer processes at gas-evolving electrodes that experience successive formation and detachment of bubbles. The gas–liquid interface is modelled employing an immersed boundary method. We simulate the growth phase of the bubbles followed by their departure from the electrode surface in order to study the mixing induced by these processes. We find that the growth of the bubbles switches from a diffusion-limited mode at low to moderate fractional bubble coverages of the electrode to a reaction-limited growth dynamics at high coverages. Furthermore, our results indicate that the net transport within the system is governed by the effective buoyancy driving induced by the rising bubbles and that mechanisms commonly subsumed under the term ‘microconvection’ do not significantly affect the mass transport. Consequently, the resulting gas transport for different bubble sizes, current densities and electrode coverages can be collapsed onto one single curve and only depends on an effective Grashof number. The same holds for the mixing of the electrolyte when additionally taking the effect of surface blockage by attached bubbles into account. For the gas transport to the bubble, we find that the relevant Sherwood numbers also collapse onto a single curve when accounting for the driving force of bubble growth, incorporated in an effective Jakob number. Finally, linking the hydrogen transfer rates at the electrode and the bubble interface, an approximate correlation for the gas-evolution efficiency has been established. Taken together, these findings enable us to deduce parametrisations for all response parameters of the systems.

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Section: Introductionmentioning

confidence: 99%

“…2017; Raman et al. 2022) until an equilibrium state is reached, i.e. the global statistics of the system no longer varies in time.…”

Section: Introductionmentioning

confidence: 99%

Mass transport at gas-evolving electrodes

Sepahi,

Verzicco,

Lohse

et al. 2024

J. Fluid Mech.

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“…The studies on the evolution process of hydrogen bubbles and its influencing factors mainly focus on reaction kinetic analysis and experimental analysis. There are existing literatures on visual experimental analysis of hydrogen production by single-electrode, static and alkaline electrolyte [30] , [31] , [32] , [33] , [34] , which are limited in their guidance for practical applications because they do not consider the influencing factors of actual PEM hydrogen production electrolyte, such as flow dynamics, membrane electrode, narrow flow channel and external field. Meanwhile, the electrolysis operating temperature has a great influence on the hydrogen bubble evolution process, which should also be paid attention to.…”

Section: Introductionmentioning

confidence: 99%

Temperature impacts on the growth of hydrogen bubbles during ultrasonic vibration-enhanced hydrogen generation

Su,

Sun,

Wang

et al. 2024

Ultrasonics Sonochemistry

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“…They increase the electrical resistance in electrolyzers by restricting ion conduction pathways in the electrolyte, and by covering portions of the electrode and rendering them inactive [25,50,52,[88][89][90]. However, bubbles can also lower the concentration of dissolved gases, and induce microconvective flows -effects known to have a positive influence on electrolysis [44,46,62,65,91,92]. Despite the sustained interest in electrolytic bubbles, the scientific problem of the optimal bubble management remains open [93].…”

Section: Introductionmentioning

confidence: 99%

“…The study included experiments and a simplified numerical model that allowed a qualitative understanding of the effect of bubble evolution on the concentration, and Ohmic overpotentials. A subsequent analysis of bubble growth and its influence on the half-cell potential in this decoupled electrolysis system was performed with the aid of a simplified numerical model which calculated the change in Ohmic resistance in the system as a function of bubble radius [92]. This combination of experiments and modeling showed the quantitative influence of bubbles on the concentration overpotential.…”

Section: Introductionmentioning

confidence: 99%

Bubbles and membranes : electrolysis at the mesoscale

Raman

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The presence of bubbles in gas-evolving electrolytic processes can heavily alter the mass transport of gaseous products and can induce severe overpotential penalties at the electrode through the action of bubble coverage (hyperpolarization) and electrolyte constriction (Ohmic shielding). However, bubble formation can also alleviate the overpotential by lowering the concentration of dissolved gas in the vicinity of the electrode. In this study, we investigate the latter by considering the growth of successive hydrogen bubbles driven by a constant current in alkaline-water electrolysis and their impact on the half-cell potential in the absence of hyperpolarization. The bubbles nucleate on a hydrophobic cavity surrounded by a ring microelectrode which remains free of bubble coverage. The dynamics of bubble growth does not adhere to one particular scaling law in time, but undergoes a smooth transition from pressure-driven towards supply-limited growth. The contributions of the different bubble-induced phenomena leading to the rich behaviour of the periodic fluctuations of the overpotential are identified throughout the different stages of the bubble lifetime, and the influence of bubble size and applied current on the concentration and Ohmic overpotential components is quantified. We find that the efficiency of gas absorption, and hence the concentration-lowering effect, increases with increasing bubble size and also with increasing current. However, the concentration-lowering effect is always eventually countered and overcome by the effect of Ohmic shielding as the bubble size outgrows and eclipses the electrode ring beneath.

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Potential response of single successive constant-current-driven electrolytic hydrogen bubbles spatially separated from the electrode

Cited by 26 publications

References 73 publications

Mass transport at gas-evolving electrodes

Mass transport at gas-evolving electrodes

Temperature impacts on the growth of hydrogen bubbles during ultrasonic vibration-enhanced hydrogen generation

Bubbles and membranes : electrolysis at the mesoscale

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