Eco-Friendly Synthesis of CdO Photocatalyst: Tuning Structural, Morphological, and Optical Characteristics via Calcination Temperature.

The resistance of azo dyes to degradation in wastewater, together with the limitations of conventional treatment technologies and the limited availability of green-synthesized cadmium oxide nanoparticles (CdO NPs) with tunable properties, represents a major environmental concern. To address these issues, CdO NPs were synthesized at various calcination temperatures (300°C-500°C) through a simple and cost-effective method using Ficus carica leaf extract as a reducing, capping, and stabilizing agent. Structural analyses revealed a calcination-induced phase transition from cadmium hydroxide (Cd(OH)2) to crystalline CdO accompanied by a reduction in surface -OH groups, which can influence the surface properties and photocatalytic activity of the nanoparticles. The photocatalytic activity of CdO NPs, assessed via methyl orange degradation. The sample calcined at 500°C exhibited the highest efficiency, achieving 41% degradation in the absence of H2O2, which markedly increased to 95% upon H2O2 addition. Furthermore, the reusability test over 5 cycles showed only a minimal decrease in photocatalytic activity, demonstrating the stability of the CdO NPs.