A Comparative Study of Electrified Oxidation for Valorization of Biomass-Derived Substrates toward 2,5-Furandicarboxylic Acid

Abstract

Electrified oxidation of biomass-derived molecules offers a sustainable route to produce value- added chemicals using renewable electricity, serving as an alternative to traditional methods reliant on stoichiometric oxidants. This thesis presents a comparative study of direct, mediated, and light-assisted oxidation pathways for transforming 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). Additionally, glucose is investigated as a C6 substrate to examine substrate-dependent reactivity. The primary focus is placed on assessing how electrode materials, mediators, and illumination conditions influence conversion efficiency and product distributions across these platforms. Direct electrochemical oxidation on porous nickel foam demonstrated rapid HMF oxidation under alkaline conditions. In contrast, TEMPO-mediated oxidation lowered onset potentials and favored aldehyde and carboxylate formation along defined reaction pathways Building on these comparisons, Zr-doped hematite photoanodes with photoassisted NiOOH overlayers were employed to investigate mediator-free oxidation under illumination. The resulting NiOOH/Zr–Fe2O3 photoanode supported an alcohol-first oxidation route for HMF and enabled operation without soluble mediators, illustrating the potential of semiconductor–catalyst interfaces for light-driven organic oxidation. Application to glucose revealed characteristic multi-site oxidation behavior, highlighting inherent substrate complexity and helping to define the operational boundaries of these electrified systems. Overall, this work provides an integrated experimental evaluation of direct electrochemical (EC), mediated EC, and photoelectrochemical (PEC) approaches for producing FDCA and related C6 products. By comparing their operating characteristics and substrate-dependent outcomes, this thesis offers practical insights into how electrified oxidation strategies can be positioned within renewable- electricity-based biomass upgrading and future electrified biorefinery concepts.