Electrochemical Depolymerization of Lignin in a Biomass-based Solvent

Breaking down lignin into smaller units is the key to generate high value-added products. Nevertheless, dissolving this complex plant polyphenol in an environment-friendly way is often a challenge. Levulinic acid, which is formed during the hydrothermal processing of lignocellulosic biomass, has been shown to efficiently dissolve lignin. Herein, levulinic acid was evaluated as a medium for the reductive electrochemical depolymerization of the lignin macromolecule. Copper was chosen as the electrocatalyst due to the economic feasibility and low activity towards the hydrogen evolution reaction. After depolymerization, high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy revealed lignin-derived monomers and dimers. A predominance of aryl ether and phenolic groups was observed. Depolymerized lignin was further evaluated as an anti-corrosion coating, revealing enhancements on the electrochemical stability of the metal. Via a simple depolymerization process of biomass waste in a biomass-based solvent, a straightforward approach to produce high value-added compounds or tailored biobased materials was demonstrated.

Automated summary

Breaking down lignin into smaller units is crucial for producing high value-added products. However, finding an environmentally friendly way to dissolve this complex plant polyphenol often poses a challenge. Levulinic acid, which is generated during the hydrothermal processing of lignocellulosic biomass, has been found to effectively dissolve lignin. This study demonstrates the reductive electrochemical depolymerization of lignin using levulinic acid as a medium and copper as an electrocatalyst. After depolymerization, lignin-derived monomers and dimers with predominance of aryl ether and phenolic groups were observed. The depolymerized lignin also showed improved electrochemical stability when used as an anti-corrosion coating. This research highlights a simple approach to produce high value-added compounds or tailored biobased materials from biomass waste in a biomass-based solvent.