Electrocatalytic Hydrogenation and Oxidation of 5-Hydroxymethylfurfural for Efficient Production of Biobased Monomers: A Paired Electrolyzer Approach

Abstract

Electrochemical conversion of biorenewable compounds is a promising route for sustainable chemical production. Herein, we report a high efficiency for electrocatalytic conversion of 5-(hydroxymethyl)furfural (HMF) to two biobased monomers by pairing HMF reduction and oxidation reactions in a single electrochemical cell. HMF hydrogenation to 2,5-bis(hydroxymethyl)furan (BHMF) was achieved under mild electrolyte conditions (pH 9.2) over a Ag/C catalyst at the cathode. The selectivity and efficiency for Ag-catalyzed BHMF formation were sensitive to cathode potential, owing to competition from HMF hydrodimerization reactions and hydrogen evolution. Moreover, the carbon support of Ag/C was active for HMF reduction and contributed to undesired dimer formation at strong cathodic potentials. As a result, high BHMF selectivity and efficiency was only achieved within a narrow potential range near –1.3 V. At the anode, HMF oxidation to 2,5-furandicarboxylic acid (FDCA) with ~100% efficiency was achieved under the same conditions by a homogeneous redox mediator, 4-acetamido-TEMPO (ACT), together with an inexpensive carbon felt anode. Furtunately, the insensitive selectivity of ACT-mediated HMF oxidation anode potential allows HMF hydrogenation and oxidation reactions to perform together in a single electrochemical cell, which demonstrates high molar yields of BHMF and FDCA (86% and 96%, respectively) and a combined electron efficiency of 187%, which is nearly two-fold enhancement compared to the unpaired cells. Our recent progress in developing porous Ag electrode materials for electrochemical reduction will also be presented.