Multiway Analysis of the Electrochemical Oxidation Pathway of a Lignin Model Compound, Benzyl Phenyl Ether, with Chemometrics

Abstract The economics of electrochemical depolymerization of lignin are most likely unfavorable without having control over the oxidation mechanism because many unwanted compounds are generated during depolymerization. Control over the depolymerization process can lead to high-yield chemical products like aromatic phenols and carboxylic acids. While previous literature has reported the formation of hydroxyl radicals ( · OH) during electrochemical oxidation, the studies have not proved whether · OH or electrocatalysis depolymerizes lignin. This study addresses a critical question: whether · OH radicals or direct electrochemical routes drive depolymerization using a well-studied lignin model compound benzyl phenyl ether. Electrochemical oxidation was performed using a nickel–cobalt (Ni–Co) electrocatalyst at varying electrode potentials. Analysis of oxidation products was conducted using headspace solid-phase micro-extraction (SPME) gas chromatography-mass spectrometry (GC–MS). Factor analysis (FA) was applied to the two-way GC–MS data, facilitating a statistical and visual assessment of the variations between samples treated with the radical quencher dimethylsulfoxide (DMSO) and those untreated. This work successfully revealed that · OH radicals primarily contribute to the electrochemical depolymerization of lignin, with direct oxidation occurring to a much lesser extent. This study advances our understanding of the electrochemical oxidation process and underscores the pivotal role of integrating chemometrics, a novel approach to unraveling complex electrochemical reaction mechanisms. These insights are crucial for steering the design of efficient and sustainable lignin depolymerization strategies in biomass valorization.