Paired electrolysis of 5-(hydroxymethyl)furfural in flow cells with a high-performance oxide-derived silver cathode†
Electrocatalytic upgrading of biomass-derived feedstocks driven by renewable electricity offers a greener way to reduce the global carbon footprint associated with the production of value-added chemicals. In this respect, a key strategy is the electrocatalytic hydrogenation (ECH) reaction, which is typically paired with the anodic oxygen evolution reaction (OER) with sluggish kinetics, producing O2 with little value. Here we prepared an oxide-derived Ag (OD-Ag) electrode with high activity and up to 98.2% selectivity for the ECH of 5-(hydroxymethyl)furfural (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF), and such efficient conversion was achieved in a three-electrode flow cell. The excellent BHMF selectivity was maintained over a broad potential range with long-term operational stability. We then considered the oxidation of HMF to 2,5-furandicarboxylic acid (FDCA) and hydrogen (to water) as more efficient and productive alternatives to the OER. In HMF-to-BHMF paired with 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-mediated HMF-to-FDCA conversion, a markedly reduced cell voltage from ∼7.5 V to ∼2.0 V was observed by transferring the electrolysis from the H-type cell to the flow cell, corresponding to more than four-fold increase in energy efficiency in operation at 10 mA. A combined faradaic efficiency of 163% was obtained for BHMF and FDCA. Alternatively, the anodic hydrogen oxidation reaction on platinum further reduced the cell voltage to only ∼0.85 V at 10 mA. These paired processes show the potential for integration of renewable electricity and carbon for green and economically feasible distributed chemical manufacturing.