Solar-light-driven photocatalysis by Sb2S3/carbon based composites towards degradation of noxious organic pollutants

Heterojunction photocatalysts are quite appealing for the effective removal of pollutants. Herein, we compare the photocatalytic dye degradation of Rhodamine-B (RhB) using pristine Sb2S3 nanoparticles (Sb2S3-NPs), Sb2S3-NPs anchored onto reduced graphene oxide (Sb2S3/rGO), and Sb2S3-NPs coated with porous carbon spheres (Sb2S3@PCS) as heterojunction photocatalysts. The successful fabrication of Sb2S3/C based heterogeneous photocatalysts was confirmed by XRD, FTIR, and Raman spectroscopy. The morphological studies revealed the formation of ~150–500 nm Sb2S3 nanoparticles wrapped with rGO sheets or encapsulated within ~65 nm thick porous carbon spheres. BET surface area analyses disclose that incorporating rGO and PCS improves the sp. surface area and favorable surface properties for effective RhB degradation. The UV–Vis DRS and PL showed that the heterojunction composites had narrow bandgap (~1.6–1.8 eV) and a suppressed recombination rate of photo-generated charge carriers exhibiting excellent photocatalytic activity compared to Sb2S3-NPs. Sb2S3/rGO and Sb2S3@PCS demonstrated RhB degradation-efficiency of ~89% (rate constant~ 0.013 min−1) and 77.65% (0.0091 min−1) after 150 min sunlight irradiation. The effects of catalyst concentration and pH (correlated with pHpzc) on the photodegradation were also examined. The enhanced photocatalytic performance of heterojunction photocatalysts could be ascribed to e−-excitation from the valence to conduction band, and facile electron mediator of π-conjugated porous carbon for Sb2S3/rGO and Sb2S3@PCS, respectively. The efficient photodegradation of colorless thiamethoxam pollutant confirmed indirect photocatalysis. The Sb2S3/rGO composite exhibited ~64% efficiency (rate constant~0.0056 min−1) whereas the Sb2S3@PCS maintained ~62% efficiency (rate constant~0.0064 min−1). Overall, the present study shows that Sb2S3/C-based heterogeneous photocatalysts are promising for wastewater treatment.