Superior photocatalytic degradation of highly photostable R6G dye catalyzed with CuO/ZB-CdS binary heterostructure: catalyst dosage optimization and recyclability for wastewater remediation

Abstract

Cadmium sulphide (CdS) is extensively used as a catalyst for various organic or inorganic pollutant decomposition, heavy metal adsorption, and hydrogen evolution. Continuous efforts are needed to improve its utility by integrating it with appropriate functional materials, such as copper oxide (CuO) with a reduced bandgap that facilitates the charge carrier transition. In this work, copper oxide (CuO) and zinc blende CdS (ZB-CdS) were combined to create a CuO/ZB-CdS binary photocatalyst by a precipitation-impregnation approach. The catalyst dosage was raised to effectively degrade a photostable rhodamine 6G (R6G) dye as a pollutant model under ultraviolet (UV) irradiation. The experimental analysis of XRD, EDS and FTIR confirms the presence of CuO and ZB-CdS in the binary heterostructure. SEM analysis indicates a homogeneous distribution and close interfacial contact of CdS and CuO by preserving their respective morphologies. Absorbance spectra demonstrate a broader band with increased intensity, coupled with bandgap widening, thereby confirming an effective creation and separation of charge carriers in CuO/ZB-CdS. The greatest degradation efficiency accomplished for CuO/ZB-CdS is 94.52 % with a kinetic rate constant of 1.139 × 10⁻² min⁻¹ (R² ≈ 0.913). CuO/ZB-CdS demonstrates a significant breakdown capability after three consecutive recycling cycles, indicating that it might serve as an essential catalyst for future wastewater remediation of diverse hazardous contaminants.