2‐Methoxyhydroquinone from Vanillin for Aqueous Redox‐Flow Batteries

Abstract

We show the synthesis of a redox-active quinone, 2-methoxy-1,4-hydroquinone (MHQ), from a bio-based feedstock and its suitability as electrolyte in aqueous redox flow batteries. We identified semiquinone intermediates at insufficiently low pH and quinoid radicals as responsible for decomposition of MHQ under electrochemical conditions. Both can be avoided and/or stabilized, respectively, using H₃ PO₄ electrolyte, allowing for reversible cycling in a redox flow battery for hundreds of cycles.