Electrochemical Strategies for Lignin Valorization: Advancing Biomass Utilization.

Lignin is the most abundant renewable source of aromatic carbon, and yet it remains a mostly underutilized byproduct of the biorefinery and paper industries. Factors such as complexity and a heterogeneous structure make lignin recalcitrant to conventional valorization, the utility of which often requires harsh conditions and expensive catalysts. Electrochemical conversion has emerged as a highly promising, sustainable alternative due to the use of electricity produced by renewable sources to drive depolymerization under mild, ambient conditions. This review summarizes recent progress in this field and provides a comprehensive overview of the primary electrochemical pathways used to promote the valorization of lignin. Herein, we critically examine oxidative strategies that include both direct electrooxidation at the anode surface and indirect oxidation using redox mediators, and provide details of the key challenges of electrode deactivation and product overoxidation. We then discuss reductive strategies with a focus on electrocatalytic hydrogenolysis for C-O bond cleavage. Furthermore, we explore advanced integrated systems that combine electrochemistry with microbial, enzymatic, and photochemical processes to enhance selectivity and efficiency. Finally, this review addresses persistent challenges and offers future perspectives and suggests opportunities with an emphasis on the critical need for innovations in electrocatalyst design, green electrolytes, and integrated reactor engineering to unlock the full potential of lignin as a renewable feedstock for a circular carbon economy.