Effect of sulfides-TiO2 coupling – pathways to photoanodes for water splitting - research data

Titanium dioxide-metal sulfide heterostructures, TiO2@MSx, based on TiO2 nanotubes, TiO2-NT were successfully fabricated using two straightforward approaches: powdered-assisted anodization of Ti foil in the presence of metal sulfide powders, TiO2@SnS2 and TiO2@MoS2, and SILAR deposition of cadmium sulfide on the surface of TiO2-NT, TiO2@CdS. SEM analysis revealed that the morphology of the SnS2 and MoS2 powders strongly influenced the architecture of the resulting nanotubes, with most heterostructures showing a narrower diameter distribution compared to the pristine TiO2-NT. The EDX analysis detected the presence of sulfides on the nanotube surfaces in all heterostructures. Spectrophotometric studies showed a reduction in the TiO2 optical band gap from 3.46 to 3.33 eV for heterostructures derived from powdered-assisted anodization, while SILAR deposited TiO2@CdS exhibited an additional optical band gap of 2.27 eV, corresponding to CdS. Photoluminescence measurements revealed up to a 30-fold decrease in emission intensity and the presence of point defects in TiO2, SnS2, and MoS2. Photoelectrochemical characterization demonstrated that the heterostructures achieved a photocurrent density up to 4.5 times higher than TiO2-NT at 0 V, highlighting their excellent photoactivity under bias-free conditions. This enhanced performance is attributed to three synergistic effects: reduced charge carrier recombination, increased light absorption, and the presence of point defects, making
these heterostructures highly promising for photocatalytic applications.