Enhancing photocatalytic cleavage of C[sbnd]C bonds in lignin model substrates by ternary nanocomposite of g-C3N4/rGO/CdS using rGO as electronic mediators

Abstract

Depolymerizing lignin into aromatic monomers with high yield and selectivity via photocatalysis remains a challenging task. Herein, we introduced reduced graphene oxide (rGO) nanosheets as solid electronic mediators and successfully synthesized g-C3N4/rGO/CdS ternary nanocomposites using a simple multi-step assembly strategy. The photocatalysts can efficiently break the CC bond of lignin under simulated sunlight conditions. The characterization results demonstrate that the loading of CdS effectively enhances the light absorption range and accelerates the transfer of photogenerated charge carriers. Simultaneously, the introduction of rGO inhibits the recombination of electron-hole pairs. When using the β-O-4 model substrate, a 95% conversion rate could be achieved with yields of 71% benzaldehyde and 69% phenyl formate, which are 3.09 times and 3.63 times higher than that of pure g-C3N4, respectively. Our research highlights the importance of energy band structure engineering and electronic mediator design in developing efficient photocatalysts for breaking CC bonds of lignin.