Switchable selectivity to electrocatalytic reduction of furfural over CuO-derived nanowire arrays.

Electrocatalytic reduction of biomass-derived furan compounds provides a green and sustainable approach to produce value-added fuels and chemicals. Despite the achievements in unimolecular transformation, C-C coupling which holds great promise to yield precursors for high-density fuels has not received extensive attention. Herein, we report a CuO-derived nanowire array material with switchable selectivity to electrocatalytic reduction of furfural depending on the electrolyte pH. Besides a high selectivity of 98.4% to furfuryl alcohol hydrogenation at pH 9.5, the CuO-derived array structure also exhibits a high selectivity of 83.5% to hydrofuroin C-C coupling at pH 14. Upon control experiments and detailed characterization of the electrodes, the array architecture is proposed to decrease the diffusion of ketyl radicals which are the key intermediates for C-C coupling. The confined diffusion results in a high local concentration of the radicals in the array and facilitates their collision for enhancing the formation of hydrofuroin.