Heterolayered TiO2@layered double hydroxide-MoS2 nanostructure for simultaneous adsorption-photocatalysis of co-existing water contaminants

The highly ordered heterolayered-nanostructure TiO2@Layered double hydroxide/Molybdenum disulfide (TiO2@LDH/MoS2; T@L/M) is formed by electrostatically-driven self-assembly of positively charged TiO2-dispersed-LDH layers (T@L) and negatively charged MoS2 nanosheets. TiO2 are incorporated in-situ across the LDH during synthesis yielding exfoliated TiO2-dispersed-LDH layers (T@L). Prior to MoS2 assembly, its interlayer spacing is enlarged and defects are created in basal-plane exposing sulfur-rich sites. Visible-light-active MoS2 and TiO2 synthesized heterostructure extending the T@L/M photoactivity in visible spectrum (2.92 eV) for enhanced degradation capacity. This enables a strong adsorptive-photocatalytic dual modality removal of both cationic and anionic organic dyes (97-99%) that usually cannot be achieved using one material facilitating visible-light-driven self-regeneration of exhausted adsorption sites. While dye removal efficiency varies within (4-7) % of the first cycle over 5 repeated uses, it simultaneously enables excellent affinity and selectivity for heavy metal ions (distribution coefficient similar to 10(7) mL/g for Ag+, Pb2+) with enormous adsorption capacity for single metal ion 421.8 mg/g (Ag+) which is at the top of materials known for such removal. It rapidly lowers toxic Pb2+ (from 10 mg/L to <= 0.8 mu g/L) well below the standard drinking water limit. The self-regenerating heterostructure for targeting and removing multiple water pollutants of diverse physicochemical properties has not been reported until now.

Automated summary

The study reports the formation of a highly ordered heterolayered-nanostructure TiO2@Layered double hydroxide/Molybdenum disulfide. The combined MoS2 and TiO2 materials demonstrate efficient removal of organic dyes and heavy metal ions pollution.