Engineering Electrode Rinse Solution Fluidics for Carbon-Based Reverse Electrodialysis Devices

Anetta Platek-Mielczarek; Johanna Lang; Feline Töpperwien; Dario Walde; Muriel Scherer; David P Taylor; Thomas M Schutzius

doi:10.1021/acsami.3c10680

Engineering Electrode Rinse Solution Fluidics for Carbon-Based Reverse Electrodialysis Devices

ACS Appl Mater Interfaces. 2023 Oct 18;15(41):48826-48837. doi: 10.1021/acsami.3c10680. Epub 2023 Oct 9.

Authors

Anetta Platek-Mielczarek¹, Johanna Lang¹, Feline Töpperwien¹, Dario Walde¹, Muriel Scherer¹, David P Taylor², Thomas M Schutzius^{1

3}

Affiliations

¹ Laboratory for Multiphase Thermofluidics and Surface Nanoengineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich CH-8092, Switzerland.
² Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, Zurich 8092, Switzerland.
³ Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California 94720, United States.

Abstract

Natural salinity gradients are a promising source of so-called "blue energy", a renewable energy source that utilizes the free energy of mixing for power generation. One promising blue energy technology that converts these salinity gradients directly into electricity is reverse electrodialysis (RED). Used at its full potential, it could provide a substantial portion of the world's electricity consumption. Previous theoretical and experimental works have been done on optimizing RED devices, with the latter often focusing on precious and expensive metal electrodes. However, in order to rationally design and apply RED devices, we need to investigate all related transport phenomena─especially the fluidics of salinity gradient mixing and the redox electrolyte at various concentrations, which can have complex intertwined effects─in a fully functioning and scalable system. Here, guided by fundamental electrochemical and fluid dynamics theories, we work with an iron-based redox electrolyte with carbon electrodes in a RED device with tunable microfluidic environments and study the fundamental effects of electrolyte concentration and flow rate on the potential-driven redox activity and power output. We focus on optimizing the net power output, which is the difference between the gross power output generated by the RED device and the pumping power input, needed for salinity gradient mixing and redox electrolyte reactions. We find through this holistic approach that the electrolyte concentration in the electrode rinse solution is crucial for increasing the electrical current, while the pumping power input depends nonlinearly on the membrane separation distance. Finally, from this understanding, we designed a five cell-pair (CP) RED device that achieved a net power density of 224 mW m^-2 CP^-1, a 60% improvement compared to the nonoptimized case. This study highlights the importance of the electrode rinse solution fluidics and composition when rationally designing RED devices based on scalable carbon-based electrodes.

Keywords: ERS; RED; blue energy; carbon electrodes; electrode rinse solution; microfluidics; redox electrolyte; reverse electrodialysis; salinity gradient power.