Electrocatalytic Upgradation of Bio-Oil to Biofuel

Abstract

Electrocatalytic hydrogenation (ECH) represents a transformative pathway for converting biomass derivatives, especially furfural (FF), into high-value renewable biofuels. In this comprehensive study, three distinct types of electrocatalytic nanoparticles, molybdenum-cobalt (NMoCo) and tantalum-tungsten-boron (TaWB), both anchored on date seed-activated carbon (DSAC), were synthesized and utilized to explore their capabilities in ECH of furfural to furfuryl alcohol (FA). Concurrently, palladium-nickel-boron (PdNiB) electrocatalytic nanoparticles on various carbon supports (carbon black – CB, reduced graphene oxide – rGO and DSAC)), were prepared, demonstrating superior conversion rates of FF to furfural alcohol (FA) and 5-hydroxymethylfurfural (HMF) to 2,5-dihydroxymethyltetrahydrofuran (DHMTHF). These hybrid tandem electrocatalysts (HTEC) have high structural stability and exhibit high electrocatalytic activity in the reduction of biomass derivatives, i.e., furfural (FF), to furfural alcohol (FA). Product yields were fine-tuned by altering the elemental composition of the electrocatalysts during synthesis. Characterization by XRD and EDS showed that all catalysts incorporated metals and their oxides into the unique graphite-like structure of date seed-derived activated carbon. Catalysts with optimized metal ratios, especially MC3/DSAC with Mo:Co ratio of 3:1, TW75/DSAC with Ta:W ratio of 3:1, and PN25/rGO with Pd:Ni ratio of 1:3, exhibited the highest conversions with significant faradaic efficiencies. The incorporation of boron into the catalysts reduced the competing hydrogen evolution reaction (HER), increasing the Faradaic efficiency of FF ECH. Experimental factors, including applied potential, electrolyte molarity, temperature, and time, were optimized to improve the conversion of furfural and selectivity toward FA. The hydrogenation of FF on the MoCoO4 – (010) surface – over the graphite – (001) surface – to form FA, 2-methylfuran (2-MF), furan, tetrahydrofuran, and tetrahydrofurfuryl alcohol has been investigated thoroughly using the Density Functional theory (DFT). Based on the minimum energy path, the hydrogenation of FF results in the formation of FA (FCHO + 2H → FCHOH + H → FCH2OH) subsequently leading to the generation of 2-MF through the hydrodeoxygenation reaction. The transition of FF to furan is kinetically unfavorable due to high energy barrier present. Electrochemical impedance spectroscopy studies elucidated the reaction mechanism for the conversion of FF to FA to be electrocatalytic hydrogenation for NMoCo and PdNiB catalysts, while electroreduction mechanism for the TaWB catalyst. In conclusion, this study highlights the potential of bio-derived feedstocks as a cornerstone for future sustainable energy production driven by novel and environmentally friendly electrocatalytic processes.

Date of Award	18 Dec 2023
Original language	American English
Supervisor	Fawzi Banat (Supervisor)