Synthesis, properties, and photocatalytic degradation of Brilliant Green dye using Cu2NiSnS4 thin films under ultraviolet irradiation

In this study, Cu2NiSnS4 (CNTS) thin films were synthesized using a novel string pump spray pyrolysis method at varying substrate temperatures (ranging from 300 degrees C to 410 degrees C) to evaluate their structural, optical, and photocatalytic properties. X-ray diffraction (XRD) analysis revealed that all CNTS films exhibited a polycrystalline cubic phase with space group F43m, with preferred orientation along the (111) plane. Increasing the substrate temperature led to a shift in XRD peaks toward higher angles, indicating enhanced crystallinity without the presence of impurity phases. X-ray photoelectron spectroscopy (XPS) showed temperature-dependent changes in elemental composition, notably a significant increase in surface oxidation at higher temperatures, particularly for Sn and O, while Ni and S content decreased. EDS analysis confirmed the presence of all four constituent elements of CNTS. Optical absorption measurements revealed that the CNTS films have a high absorbance in the visible range, with an optimal band gap that increases from 1.1 to 1.7 eV as the substrate temperature rises. Photocatalytic experiments under UV irradiation revealed that the films synthesized at 360 degrees C exhibited the highest photodegradation efficiency, achieving 91.12 % degradation of Brilliant Green dye. The photocatalytic activity followed a pseudo-first-order kinetic model, with the highest rate constant observed for the CNTS film deposited at 360 degrees C. However, further increases in deposition temperature led to a decline in photocatalytic performance, attributed to increased film thickness and consequent charge carrier recombination. These results highlight the critical role of deposition temperature in optimizing the structural and photocatalytic properties of CNTS thin films.