Electrochemical depolymerization of Lignin Catalyzed by Biomass-based Magnetic-electrocatalyst

Currently, lignin still remains as a largely underutilized chemical precursor; hence, its electrochemical depolymerization over iron oxide or carbonaceous catalysts presents a promising route to produce value-added aromatics. Herein, this study proposes a novel, cost-effective, and highly efficient electrocatalyst: magnetic biochar (MBC) synthesized via the co-pyrolysis of biomass and red mud (RM). To maximize catalytic performance of the MBC, synthesis parameters were systematically optimized. Linear Sweep Voltammetry (LSV) analysis revealed that the optimal catalytic activity was achieved using maple wood (MW) as the precursor, pyrolyzed at 900 °C, with a MW-to-RM mass ratio of 5: 1 (M-MBC–5/1–900). This optimal composite exhibited a highly graphitized mesoporous skeleton with a specific surface area of 126.95 m 2 /g. M-MBC–5/1–900 demonstrated robust stability throughout a 6-hour continuous electrolysis at a constant current density of 50 mA/cm 2 , alongside highly practical magnetic separability (an average recovery efficiency of ~80.2%). Moreover, its electrocatalytic performance notably outperformed conventional transition metal-based catalysts (Fe 2 O 3 , Fe 3 O 4 , and commercial metallic iron powder) and raw RM. Subsequent characterizations via gel permeation chromatography (GPC) confirmed the successful depolymerization of lignin, evidenced by a drastic 80.8% reduction in the weight-average molecular weight (M w plummeted from 2759 to 530 g/mol). Fourier Transform infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) further verified the cleavage of macromolecular networks into value-added short-chain organic acids and aromatic monomers. This study demonstrates the feasibility of utilizing RM-derived MBC as an electrocatalyst, presenting a sustainable strategy for lignin valorization.