Heterostructured ZnO@Ag Nanocatalyst for Photocatalytic Degradation of Atrazine in Aqueous Solution: Kinetics Evaluation, Effect of Hydrogen Peroxide, and Cytotoxicity Assessment.

Herein, photocatalytic efficiency of heterostructured silver-doped zinc oxide (ZnO@Ag) and pure zinc oxide (ZnO) nanocatalysts were assessed for the degradation of atrazine in water. The synthesized nanocatalysts were thoroughly characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), UV-Vis, x-ray diffractometry (XRD), and thermogravimetric analysis (TGA) techniques before being utilized for photodegradation experiments. Characterization results confirmed the synthesis of the photocatalysts, with FTIR spectra showing Zn-O peaks at approximately 500 cm-1 for both catalysts. The UV-Vis spectra for Ag-doped ZnO exhibited an absorption band around 350 nm, typical for ZnO photocatalysts. Photodegradation experiments indicated that silver doping improved the degradation efficiency of atrazine by ZnO. pH studies showed that the highest photodegradation efficiency occurred at pH 5 for both catalysts, with degradation percentages of 95.3% for ZnO@Ag and 84.3% for ZnO. Time-dependent studies revealed that atrazine degradation reached equilibrium within 120 min of photoirradiation. Photocatalytic degradation of atrazine using ZnO@Ag and ZnO in the presence of H2O2 revealed catalyst-dependent performance. Increasing the H2O2 concentration from 10 to 40 mM progressively improved the degradation efficiency of ZnO@Ag, whereas a slight decline in degradation efficiency was observed for ZnO over the same concentration range. Although ZnO exhibited higher degradation efficiencies at lower H2O2 concentrations (10-30 mM), ZnO@Ag outperformed ZnO at 40 mM H2O2, indicating that Ag modification enhances catalyst performance under higher oxidant conditions by improving charge separation and reactive oxygen species generation. Cytotoxicity assessments of the degraded solution indicated nontoxicity (0.00% ± 0%) against the tested cell. These findings highlight that Ag doping should be regarded as a strategy for tailoring catalyst behavior under specific reaction conditions rather than as a universally superior modification.