Photo-induced charge separation Z-scheme mechanism in ternary bismuth sulfide coupled SnS/Al2O3 nanostructure

Abstract

The establishment of a solid-state Z-scheme heterojunction photocatalytic system to efficiently tailor photoinduced charge separation is of great significance to water purification. A structure of metal sulfide nanoparticles, tin monosulfide (SnS) and bismuth sulfide (Bi₂S₃) in host alumina (Al₂O₃) was developed by the sol–gel method. FTIR confirmed complete dispersion of SnS and Bi₂S₃ nanoparticles in Al₂O₃ having a cubic structure. The band gap energy (E_g) of the ternary nanocomposite was found to be 1.85, 1.68 and 1.10 eV for 4.0, 8.0 and 12.0% bismuth sulfide coupled SnS/Al₂O₃ respectively. The marked decrease in E_g can be attributed to the tenacious agglomeration among SnS, Bi₂S₃ and Al₂O₃. 99.0% methyl orange (MO) removal was achieved with 12.0% bismuth sulfide coupled SnS/Al₂O₃ due to efficient and quick charge transfer among Al₂O₃ and chalcogenides via Z-scheme electron transfer mechanism. Electrochemical measurements such as those of linear sweep voltammetry and cyclic voltammetry manifested that bismuth sulfide coupled SnS/Al₂O₃ exhibited several times more current density than pristine Al₂O₃ which is very well corroborated with the photocatalytic analysis. Investigation of radical scavengers manifested that O₂˙⁻ and OH˙ have important roles in the degradation of MO. This innovative and uniquely designed hybrid ternary nanocomposite will open new horizons as an economical and effective material for photocatalysis.