Electro-oxidation of furfural on gold is limited by furoate self-assembly

• Published in: Journal of catalysis Vol. 391; pp. 327 - 335
• Main Authors: Román, Alex M., Agrawal, Naveen, Hasse, Joseph C., Janik, Michael J., Medlin, J. Will, Holewinski, Adam
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-11-2020
• Subjects: ATR-SEIRAS; Electrochemical oxidation; Electrolysis flow cell; Furfural; Furoic acid; Electrolysis flow cell; ATR-SEIRAS; Furfural; Furoic acid; Electrochemical oxidation
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2020.08.034

The primary product of furfural electro-oxidation on Au electrodes is furoic acid, which can undergo facile oxidation to surface bound furoate. As this adsorbed furoate accumulates it forms an ordered monolayer and effectively blocks the Au surface, limiting the rate of furoic acid production.
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•Electro-oxidation of furfural on Au/C in acidic electrolyte efficiently produces furoic acid.•Initial furoic acid production is an order of magnitude faster on Au/C than previously seen on Pt/C.•Kinetic studies, ATR-SEIRAS, and DFT show self-inhibition by assembly furoate product.
Processing of biomass-derived compounds with electrocatalysis has shown promise to directly couple the production of valuable feedstocks with the storage of renewably produced electricity. One potential route of electrocatalytic conversion is the partial oxidation of furfural to furoic acid (FA), a precursor to 2,5-furandicarboxylic acid (FDCA). We have utilized differential electrochemical reactor studies along with infrared spectroscopy (ATR-SEIRAS) experiments and density functional theory (DFT) calculations to probe the oxidative reaction pathways of furfural on gold catalysts in acidic electrolyte. We find furfural electro-oxidation activity (~2 µA/cm2Au at 1.0 VRHE) to be an order of magnitude higher than that observed on Pt/C. 96 ± 6% Faradaic efficiency to FA is achieved at 0.8 VRHE. Product desorption is rate limiting, and spectroscopic evidence indicates that the most abundant intermediate is surface furoate. Deeper oxidation products observed with dilution of furfural suggest that self-assembly of the furoate species contributes to selectivity.