Electrocatalytic Reduction of Furfural Using Single-Atom Molecular Catalysts

Abstract

The electrochemical conversion of bio-based platform chemicals is an effective way of moving away from a crude oil reliant chemical source. Lignocellulosic biomass such as hemicellulose provides a sustainable chemicals source which can yield important platform chemicals including furfural, which can be upgraded into higher valued chemicals for biofuels, renewable polymers, and pharmaceuticals. In this study, we investigate the electrochemical reduction of furfural using Cu and Co single-atom molecular catalysts on carbon electrodes in a mild basic electrolyte (pH 10) for selective production of hydrofuroin, a promising precursor to sustainable drop-in jet fuels. Using density functional theory, we show that the selectivity of furfural reduction products on transition metals could be generally described by the adsorption energies of furfural and hydrogen (Fig 1a). In particular, we predict that the weak-binding molecular catalysts could give rise to a facile reaction path towards coupling product. Based on theoretical calculations, we synthesized Cu and Co-doped phthalocyanines and show that those single-atom molecular catalysts display up to 92% Faradaic efficiency for hydrofuroin production with suppressed hydrogen evolution in pH 10 at -0.50 V vs. the reversible hydrogen electrode (RHE). Combining experiment and theory, we show that the rate-determining step for hydrofuroin formation on single-atom molecular catalysts is the first proton-coupled electron transfer rather than the chemical coupling step. Furthermore, a single-atom molecular design principle is briefly proposed by tuning the adsorption strength of furfural. Figure 1