Tailoring the properties of SnS thin films deposited at room temperature by varying the amount of complexing agent for enhanced photocatalytic activity

Abstract

This work examines how the characteristics and photocatalytic efficacy of modified SILAR-deposited SnS thin films are affected by the addition of a complexing agent. Stannous chloride dihydrate and sodium sulphate were used as tin and sulphur sources, respectively, while triethanolamine (TEA) served as a complexing agent in film deposition. The modified SILAR method facilitated the formation of well-adhesive thin films on the glass substrate at room temperature. The formation of SnS was demonstrated using EDAX and XPS analysis. XRD analysis proved that all the films are polycrystalline in nature with an orthorhombic crystal structure. The presence of chlorine as an involuntary dopant was observed in all the films prepared with TEA. Optical studies employing UV–visible spectroscopy found that all of the films have good visible absorption, with bandgap values ranging from 1.58 eV to 2.2 eV. Even though the films were deposited at room temperature, all films exhibited good thermal stability as per TGA analysis. The introduction of TEA caused improvements in the adhesion of the film to the substrate, a decrease in the band gap, a change in the morphology and composition, and an increase in the crystallinity and crystallite size. Due to their suitable bandgap corresponding to the visible region, SnS thin films exhibited good photocatalytic efficiency in degrading various types of dyes. The SnS thin film catalyst reduced 97% of methylene blue in 90 min at room temperature without using any reducing agent. The LCMS analysis validated the photocatalytic degradation of dye, whereas the UV–visible spectroscopic analysis gave a quantitative measure of the degradation efficiency. The reduction in photodegradation efficiency in the presence of OH radical scavengers confirmed the role of OH radicals in the degradation process. The terephthalic acid test further demonstrated the generation of OH radicals during the dye degradation process. The observed increase in photocatalytic activity of SnS thin films with TEA addition could be due to TEA-induced bandgap reduction, crystallinity increase, and crystallite size increase. The catalyst was reusable, stable, easy to recover after use, and effective against various kinds of dyes. The study emphasizes the use of complexing agents as a useful tool for modifying the characteristics and, consequently, the photocatalytic efficiency of modified SILAR-deposited SnS thin films.