Paired Electrocatalytic Valorization of CO<sub>2</sub> and Hydroxymethylfurfural in a Noble Metal-free Bipolar Membrane Electrolyzer
Philipp Hauke, Sven Brückner, Peter Strasser
Abstract
Direct electrocatalytic valorization of CO 2 in low-temperature electrolyzers is emerging as a new nonfossil, one-step process toward e-fuels and e-chemicals, such as CO. However, Faradaic and energy efficiencies have remained low due to the sluggish 4-electron oxidation of water [oxygen evolution reaction (OER)] at the anode. Replacement of the OER with a thermodynamically and kinetically less-demanding reaction would increase efficiency and overall valorization. This article demonstrates the first full paired implementation of a noble metal-free CO 2 and hydroxymethylfurfural (HMF) valorization in a single cell at industrially relevant current densities. We stepwise design, assemble, test, and analyze the first complete paired low-temperature bipolar membrane (BPM)-based hydroxymethylfurfural oxidation and CO 2 electroreduction electrolyzer cell. The electrolyzer couples a CO 2 -to-CO electrolyzer half-cell to an aqueous HMF-to-2.5-furandicarboxylic acid half-cell via a water dissociation membrane operating in reverse bias. We investigate and compare the bipolar membrane voltage penalties with the single-pass reactant conversion advantages and estimate cell performance benefits due to the more favorable thermodynamic and kinetic processes at the anode. We report successfully suppressing undesired CO 2 loss due to acid–base neutralization with generated alkalinity.