Toward Chemical-Free Depolymerization of Lignin Surrogate: A Mechanistic Insight into Contact-Electro-Catalysis

Lignin, an abundant natural organic polymer and renewable resource, presents grand challenges in efficient depolymerization into value-added products. Herein, we propose an innovative green mechanochemical (contact-electro-catalysis; CEC) strategy to completely degrade the lignin model compounds (99.98% within 330 min) in a chemical-free, environmentally benign, and highly efficient manner. This is enabled by ultrasound-induced contact electrification to generate electrons and reactive oxygen species (ROS). Comprehensive mechanistic investigations reveal that ROS play a predominant role in lignin depolymerization. Furthermore, the possible thermal effect of CEC on the lignin depolymerization was also considered. Extensive characterization demonstrates the exceptional recyclability of the CEC reagent with a recovery rate of up to 92%. This approach not only exhibits outstanding performance in accelerating lignin depolymerization but also underscores the immense potential of mechanochemistry as a sustainable technology for biomass and lignin valorization.