Tailoring band gap and photocatalytic activity of ZnO via Cu doping for enhanced Congo Red degradation

Abstract This paper reports the improvement in the photocatalytic performance of ZnO by substituting Cu with a variable concentration. ZnO and Cu 0.5%, 1.0%, and 2.0% doped ZnO nanoparticles have been synthesized by the sol-gel combustion method. Before measuring photocatalytic properties, we have confirmed the HCP structure and granular nanoparticle morphology of all samples with XRD and SEM analysis. Function groups have been ascertained by FTIR peak assignment. Small variations in structural parameters and ZnO stretching mode indicate substitution of Cu at the ZnO site of the ZnO nanostructure. The band gap engineering with variable Cu concentration successfully reduces the apparent band gap, which helps improve the photocatalytic This research shows that Cu-doped ZnO nanoparticles are better at breaking down Congo red (CR) dye than pure ZnO nanoparticles. Remarkably, ZnO: Cu 2% (also used at a concentration of 120 mg/L) has an outstanding removal efficiency of 97.21%. This accomplishment highlights the substantial impact of pseudo-first-order kinetics, offering a precise and thorough explanation of the photodegradation process.