Flow-by membraneless electrolyzer designs: A macroporous flow dividing mesh enhances maximum allowable electrode length

• Published in: Fuel (Guildford) Vol. 377; p. 132779
• Main Authors: Borah, Rituraj, Raj A.G., Karthick, Verbruggen, Sammy W.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2024
• Subjects: Electrolysers; Electrolysis; Eulerian Lagrangian, Multiphase flow; Green hydrogen; Membraneless Electrolyzers; Green hydrogen; Eulerian Lagrangian, Multiphase flow; Membraneless Electrolyzers; Electrolysis; Electrolysers
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.132779

[Display omitted] •The maximum electrode length of flow-by membraneless electrolyzers was analyzed.•A flow dividing mesh as a new design elements was introduced.•First, a bubble mass balance approach was implemented.•Next, Eulerian-Lagrangian models (validated with experiments) were employed.•A mesh results in >50 % enhancement of the maximum electrode length. The membraneless electrolyzer design promises a low-cost and robust electrolyzer technology, eliminating the disadvantages associated with the membranes/diaphragms in conventional electrolyzers. Flow-by membraneless electrolyzers exploit the Segré–Silberberg effect, where the electrolyte flow between parallel face-to-face cathode and anode forbids the evolving hydrogen and oxygen bubbles to cross over to the other side, while still allowing ionic currents between the electrodes to pass. The removal of the membrane from traditional electrolyzers, and instead exploiting the electrolyte flow itself to function as a gas separator also imposes certain requirements, namely: 1) upward laminar flow and, 2) vertically aligned electrodes. Given the upper limit of the laminar flow regime (Reynolds number, Re ∼ 1800), the admissible length of both vertically aligned electrodes is constrained by the production volume of H2 and O2 at both electrodes. Beyond a certain production rate the evolving gas plume increases in thickness until it reaches the central line dividing the channel between the electrodes. From that point onwards, flow mediated separation of both gases becomes practically impossible. In this work the design constraints of membraneless electrolyzers are investigated by combined multiphysics modeling and mass-balance analysis. Next, a macroporous flow dividing mesh is introduced in the design that allows seamless ionic flow between the electrodes while facilitating a higher electrolyte velocity in the laminar regime. This in turn enables to increase the maximum electrode length (or height) by >50 %. The model based analysis provides important guidelines for further development of membraneless electrolyzers, significantly reducing future experimental optimization efforts.