Electrocatalytic Valorization of Organosolv Lignin Utilizing a Nickel-Based Electrocatalyst

Lignin is a biopolymer that accounts for up to 30% of biomass and is the most abundant aromatic feedstock in nature. Therefore, extraction of valuable aromatic compounds from lignin is regarded as an attractive way for producing various organic chemicals, which are currently derived from fossil fuels. We report an electrochemical approach for the depolymerization of three ethanol organosolv lignins (EOLs), isolated from sweetgum (SW), aspen (AS), and loblolly pine (LP), utilizing a low-cost nickel foam as the working electrode under alkaline conditions. Gas chromatography–mass spectrometry, two-dimensional (2D) heteronuclear single quantum coherence nuclear magnetic resonance (NMR) spectroscopy, and gel permeation chromatography were employed to analyze and quantify the obtained products after electrolysis. Vanillin and syringaldehyde with a combined maximum yield of 17.5% were produced from the electrochemical depolymerization of EOL-SW. Finally, the difference in oxidized products among these three lignin samples was rationalized from the analysis of their native structures.