(212d) Mechanistic and Trend Analyses of Selective Furfural Electroreduction on Transition Metals from First-Principles Methods

Furfural is an important biomass-derived platform compound. Electrocatalytic hydrogenation and deep reduction, via the C-O bond cleavage, of furfural on transition metals can be developed into a sustainable strategy to obtain valuable chemicals and fuels. Further, the complex chemical nature of furfural presents challenges to understand the electroreduction pathways and the product selectivity, which are still being debated.

Density functional theory (DFT) calculations were performed on the close-packed (111) facets of Cu, Ag, Pb and Ni to investigate furfuryl alcohol (FA) and 2-methylfuran (MF) formations in acidic conditions. Two FA formation pathways via 2-methoxyfuran (mh6) and 2-hydroxymethylenefuran (mh7), and three MF formation pathways were considered in this study. The computational hydrogen electrode (CHE) model was applied to determine free energies of the reactions under an external applied potential. The energy barriers of elementary reduction steps were estimated using the Brønstedâ??Evansâ??Polanyi (BEP) relationship. On Cu, Ag, Pb and Ni, it has been found that the pathway via mh6 is competitive for FA formation. On Ni, the pathway via mh7 is also competitive. For MF formation, pathways involving mh6 are more competitive on all considered metals. In order to gain insights into the product selectivity, micro-kinetic modeling was performed based on the mechanism derived from DFT calculations. The modeling confirms that FA and MF are formed via parallel pathways. The turnover frequencies of FA and MF formations were also obtained, and Cu is found to be the most active for MF production, which is supported by electrochemical measurements.