Supported Zinc Nanoparticle Catalysts for Electrocatalytic Hydrogenation of Furfural

Abstract

Electrocatalytic hydrogenation (ECH) of biomass-derived platform chemicals is a sustainable way to produce value added fuels and chemicals as compared to chemo-catalytic hydrogenation pathway [1,2]. Furfural can be hydrogenated to produce furfuryl alcohol (FAL) and 2-methylfuran (MF) which have applications in pharmaceutical, polymer and fuel industries [1,2].In our prior work, zinc stood out as an efficient metal catalyst in comparison to copper and nickel, achieving 86 % Faradaic efficiency (FE) for the ECH of furfural in neutral pH electrolytes at -0.7 V/RHE [3]. However, the yield of desired products was low compared to fractional conversion, due to electro-dimerization of furfural. Zinc nanoparticles can help to increase the yield of FAL and MF while maintaining the same FE due to high surface area to volume ratio, which will aid in increasing the reaction rate for the conversion of intermediate radicals in ECH of furfural to FAL and MF instead of forming dimerized furfural product. Thus, in this work, we synthesized high surface area zinc nanoparticle catalysts to study their activity for the ECH of furfural. Zinc nanoparticle catalysts were synthesized by electrodeposition using 0.2 M zinc chloride as precursor on bare zinc foil at -2 V/Ag-AgCl for 5 h at 50 C [4]. It was found that current densities in the range of 18-20 mA/cm2 lead to electrodeposited zinc particles, whereas higher current densities (21-26 mA/cm2) give rise to electroplated zinc. SEM analysis revealed the presence of fibrous morphology of zinc particles (Figure 1a). EDS analysis showed that the elemental composition of material was 99 wt% zinc with the remainder oxygen. The BET surface area of the catalyst was found to be 5.6 m2/g with average pore size 10.1 nm. The catalyst exhibited type V isotherm with hysteresis loop of type H3 which signifies plate-like particle aggregates [5]. The differential pore volume vs pore width graph depicts that the zinc catalyst contains both mesopores as well as macropores (Figure 1b). ECH of furfural on these catalysts will be compared to similar results for metallic zinc foil. Post electrolysis characterization will aid in in elucidating reaction mechanism.