Rechargeable-Liquid Fuel Cells with a Novel Recharging Method: Exploratory Results with IPA and V II /V III Solutions

Abstract

Rechargeable-liquid fuel cells (RLFCs) have the potential to be utilized in a wide variety of applications, if the performance of RLFCs can be substantially improved. Two of the major historical barriers have been the relatively poor performance of RLFCs compared to conventional polymer electrolyte fuel cells operating on hydrogen and the irreversibility of the oxygen electrode. This work demonstrates a new recharging concept and improved liquid-electrode designs, which help address both of these issues. These two concepts are demonstrated using two different types of rechargeable liquids: 1) an alcohol (isopropanol) that is reversibility dehydrogenated to the corresponding ketone (acetone), and 2) a flow-battery vanadium electrolyte (VII/VIII dissolved in H2SO4). The liquid electrodes utilize interdigitated flow fields, which enable relatively good power densities for a RLFC during discharge with air: 0.14 W/cm(2) at 0.6 V with 2 M IPA and 0.42 W/cm(2) at 0.7 V with 1.5 M V-II/V-III. It is also shown that the liquids can be efficiently recharged using the same cell that was used for the discharge, by supplying hydrogen to the gas electrode to generate protons via the hydrogen-oxidation reaction instead of splitting water, which requires a different catalyst or a bidirectional catalyst. (c) The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.