Enhancing photocatalytic performance: a study of anionic (congo red, orange-g) and cationic (malachite green) dye degradation using WSe2 and WSe2/ZnIn2S4 nanocomposite

In the work, we developed a novel visible-light-driven photocatalyst WSe2/ZnIn2S4 (ZIS) nanocomposite and performed a comparative dye degradation study on cationic (Malachite green, MG) and anionic (Congo red, CR and Orange-g, OG) dyes. WSe2/ZIS nanocomposite was synthesised by the benign chemical aqueous solution method, under low temperature and pressure. The crystal structure and surface morphology of WSe2 and WSe2/ZIS nanocomposite were studied using X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscope (FESEM), respectively. The optical properties of sample were examined using the UV–vis spectrophotometer and the obtained value of band-gap of WSe2 and WSe2/ZIS was about 1.76 and 2.0 eV, respectively. The WSe2/ZIS nanocomposite displays superior photocatalytic activity compared to bare WSe2 due to optimised surface charge and optical appealing characteristics of WSe2 powder, on the incorporation of ZIS. Pseudo-first-order and second-order rate kinetics were also studied and the result revealed that second-order model fitted well and the overall adsorption process is dominated by the chemisorption process. Scavenger tests were conducted to determine the active species ( O2⋅− ) in photocatalysis mechanics, and the reusability of the nanocomposite was evaluated over 5 cycles. The photocatalytic study result demonstrated that WSe2/ZIS nanocomposite might be employed as an efficient, highly stable photocatalyst for the dye degradation application.