Functional Group-Directed Adsorption Configurations Govern Alcohol/Ketone Selectivity in Electrochemical Hydrogenation of Biomass Phenolics

We selected guaiacol, mequinol, and o-cresol as representative lignin model monomers to systematically investigate the underlying mechanisms governing alcohol/ketone product selectivity in electrocatalytic hydrogenation (ECH). By combining detailed density functional theory (DFT) calculations, we elucidated the critical role of substituents in steering reaction pathways. Specifically, the ortho-methoxy group promotes a bidentate “boat” adsorption configuration, which enhances alcohol selectivity. In contrast, the para-methoxy or ortho-methyl groups restrict adsorption to a monodentate mode, thereby favoring ketone formation and release. These findings provide atomic-level insight into how distinct functional groups modulate intermediate adsorption geometry and subsequent hydrogenation pathways, offering a theoretical foundation for the rational design of selective electrocatalytic systems for lignin valorization.