Photocatalytic degradation of lignin by low content g-C3N4 modified TiO2 under visible light

Abstract

As the most abundant renewable aromatic resource, the catalytic depolymerization of lignin to obtain high value-added aromatics is very attractive but full of challenges. Photocatalysis is a promising approach in this case. In this research, calcination and solvothermal procedures were used to make TiO₂/g-C₃N₄ heterojunction composites, and XRD, SEM, and TEM characterization methods were used to investigate the structural and morphological properties of TiO₂/g-C₃N₄. Photoluminescence and photoelectrochemical measurements were conducted to confirm the evidence of efficient charge carrier separation by nano-composites. TiO₂/g-C₃N₄ doped with 10 mg of g-C₃N₄ had the best efficacy under simulated sunshine irradiation, with lignin degradation reaching 75%, which was twice as effective as pure TiO₂. Lignin was successfully reduced into tiny molecules, thus according to GC–MS analysis, and TiO₂/g-C₃N₄ showed good application possibilities in the catalytic degradation of lignin. The radical trapping and electron spin resonance outcomes supported the role of oxidative active species and its interaction in the degradation of lignin. The likely mechanism of the photocatalytic reaction was hypothesized, the degradation products were studied, and the various pathways of lignin degradation were addressed based on the experimental data.