Bifunctional linker-assisted assembly of core-shell TiO2 @In2S3 with enhanced photocatalytic activity for reduction of Cr(VI)

Monodispersed anatase TiO2 microspheres were prepared by a modified sol-gel method. In2S3 nanoparticles (NPs) were loaded on the as-prepared TiO2 to form non-core-shell TiO2/In2S3 and core-shell TiO2 @In2S3 composites through a direct deposition method and a linker-assisted assembly strategy, respectively. The catalytic activity of TiO2/In2S3 and TiO2 @In2S3 for HCOONH4-mediated photoreduction of Cr(VI) was comparatively studied. Based on soft and hard acid-base theory and experimental results, the mechanisms for forming the core-shell TiO2 @In2S3 and enhancing photocatalytic activity were elucidated. Results indicate: i) When TiO2 surface is functionalized by dimercaptosuccinic acid (DMSA), a bifunctional linker, In2S3 NPs can be uniformly and tightly attached onto the TiO2 to form core-shell TiO2 @In2S3 composite via the strong binding force between In3+ ions and thiol groups (-SH), whereas In2S3 NPs can't be evenly and firmly anchored to bare TiO2 due to the weaker affinity of In2S3 NPs for TiO2 and thereby non-core-shell TiO2/In2S3 composite is obtained. ii) TiO2 @In2S3 exhibits superior photocatalytic activity to TiO2/In2S3, which can be attributed to more efficient interfacial electron transfer between In2S3 and TiO2 in TiO2 @In2S3 than that in TiO2/In2S3.

Automated summary

Monodispersed anatase TiO2 microspheres were prepared by modifying the sol-gel method. In2S3 nanoparticles (NPs) were loaded onto the TiO2 to form non-core-shell TiO2/In2S3 and core-shell TiO2@In2S3 composites. The photocatalytic activity of these composites for HCOONH4-mediated photoreduction of Cr(VI) was studied. Results showed that TiO2@In2S3 exhibited higher photocatalytic activity than TiO2/In2S3 due to more efficient interfacial electron transfer between In2S3 and TiO2.