Furfural is a significant platform compound derived from biomass. Electrocatalytic reduction of furfural on transition metals emerges as a sustainable approach compared to heterogeneous catalysis to obtain valuable chemicals and fuels, such as furfuryl alcohol (FA) and 2-methylfuran (MF). Although the product selectivity was shown to be strongly depended on the intrinsic properties of the transition metal electrodes, similar as CO₂ reduction, the complex chemical nature of furfural presents challenges to investigate the reaction mechanisms, which are still under debate.

Density functional theory (DFT) calculations have been performed for electrocatalytic reduction of furfural to FA and MF on the close-packed (111) and stepped (211) surfaces of Cu, Ag, Pb, and Ni electrodes. The elementary reaction steps have been evaluated based on computational hydrogen electrode (CHE) model. A novel Brønsted–Evans–Polanyi (BEP) relationship has been established for C-O bond cleavage which is necessary for MF production. On Cu, Ag, Pb, and Ni, at both terrace and stepped sites, the first hydrogenation step of C=O, leading to mh6 or mh7 formation, influences the overall reaction activity and product selectivity. It has been found that the pathway via mh6 is more competitive than that via mh7 for FA formation on Cu, Ag, and Pb, whereas on Ni, both mh6 and mh7 routes are competitive due to strong interactions between the furan ring and the substrate. The C-O bond cleavages of furfural, the partially hydrogenated intermediates (mh6 and mh7) and FA were considered as the parallel pathways to produce MF besides FA formation pathways. It is well-known that solvation can facilitate the hydrogenation reactions involving proton-electron pairs. In this work, solvation was confirmed to decrease the C-O bond cleavage energy barriers, which could boost MF production and potentially tune the product selectivity on transition metal electrodes.