Enhanced photocatalytic degradation of lignin by In2S3 with hydrophobic surface and metal defects

Lignin is difficult to be degraded due to its complex structure and hydrophobicity. Herein, we report an effective strategy to degrade lignin by defective indium sulfide with the hydrophobic surface (InxS3-C). InxS3-C is synthesized by a one-pot hydrothermal method with the assistance of CTAB. The optimal photocatalyst (In0.75S3-C) exhibits great adsorption capacity and degradation efficiency for lignosulfonate. The degradation rate of lignosulfonate achieves 90% after irradiating by visible light for 30 min, representing nearly 80 times higher activity than the commercial photocatalyst (P25). The great photocatalytic performance of In0.75S3-C is ascribed to the enhanced adsorption of lignosulfonate and oxygen, which facilitates intimate contact and mass transfer. Furthermore, TG-DSC, FTIR, UV–vis DRS and TRPL demonstrate that the defects are important for the introduction of CTA+, as well as enhance visible light absorption and the separation of photogenerated carriers. Combined with HPLC-MS analysis, a possible degradation pathway of lignosulfonate is proposed.