Promoting the electrochemical hydrogenation of furfural by synergistic Cu0−Cu+ active sites

Electrochemical hydrogenation (ECH) of furfural, which uses the proton from water and avoids the usage of gaseous hydrogen and high pressure, is an efficient way to utilize biomass energy. Cu-based catalysts are promising catalysts for the ECH of furfural. However, their active sites and reaction mechanism have not been fully understood yet. This work unveils the active oxidation state of Cu-based electrocatalysts for the ECH of furfural. The co-existence of Cu+ and Cu0 on the CuO surface under the working potential is confirmed by a series of in situ characterizations. The poisoning experiment shows that the performance decreased heavily after the Cu+ was complexed with SCN−, indicating the decisive role of Cu+. Finally, the density functional theory (DFT) calculation suggests that the Cu0−Cu+ synergistic effect is beneficial to both kinetics and thermodynamics: Cu+ accelerates the second step hydrogenation process of furfural, and Cu0 reduces the energy barrier for the desorption of furfuryl alcohol. This work demonstrates the synergistic effect of Cu0 and Cu+ states for the electrochemical hydrogenation of furfural and provides a deeper understanding of the furfural hydrogenation mechanism.