The dynamic environment in liquid–phase catalysis plays an important role in controlling the activity and selectivity. Fundamental understanding of the reaction mechanism in this complex media is rather challenging. Here we combine computation and experiments to show the effect of the solvent in liquid–phase conversion of furfural, which possesses conjugated C=C and C=O double bonds, in both electro– and thermal catalysis. Specifically, we find that, when water is used as the solvent, hydrogenation of furfural over a Pd catalyst favors production of furfuryl alcohol, while ring–hydrogenated products dominate in an organic solution. The calculations suggest that the distinct selectivity results from the different hydrogenation routes – one is through a surface–mediated process and the other is via the solution–mediated protonation. In an aqueous phase, hydrogenation of the aldehyde group is significantly enhanced following the latter solution–mediated path. The effect of the water can also be applied in electrocatalytic reduction of furfural. We find that, under negative electrode potentials, methylfuran is the major and primary product on a Cu electrode, while production of furfural alcohol is low. This selectivity is opposite to the reaction in a thermal catalytic process using Cu nanoparticles as the catalysts, where furfural alcohol and its derivatives are the predominant products without producing methylfuran. This distinct selectivity also results from the altered reaction path under the electrode potentials in electrocatalysis as compared to the thermal catalysis.

Furfural conversion in both liquid-phase catalysis and electrocatalysis: The role of the solvent

ACS Fall 2020 Virtual Meeting

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