Investigation of withdrawal rate effects on the photocatalytic performance of Cu2BaSnS4 for visible-light-induced degradation of organic dyes in aqueous media

Tailoring the properties of semiconductor catalyst materials has emerged as a promising strategy for environmental remediation. In this study, Cu₂BaSnS₄ (CBTS) semiconductor catalyst material deposited using the sol–gel dip-coating technique is investigated, focusing on its photocatalytic degradation efficiency of organic dye pollutants in aqueous solutions under visible light irradiation. By systematically changing the withdrawal rate and characterising the resulting films’ structural, morphological, optical, and electrical properties, a strong correlation is observed between the withdrawal rate and photocatalytic performance. The CBTS films dip-coated at 200 mm/min achieved the highest degradation efficiency of methylene blue (MB) dye at 91.8% in 60 min. This enhancement is attributed to improved light absorption, efficient charge carrier separation, and reduced recombination rates. Additionally, electron spin resonance spectroscopy and radical trapping experiments confirmed that holes are the primary reactive species involved in the photocatalytic process. These findings highlight that CBTS films deposited at a withdrawal rate of 200 mm/min exhibit favourable properties for MB degradation, emphasising the critical role of withdrawal rate in optimising film performance for wastewater treatment and environmental remediation.