Dark and light performance of glass@CuO photocatalyst composites for degradation of methylene blue dye

Nanostructured copper oxide (CuO) was synthesized on two types of waste glass powders: soda-lime and borosilicate, via the thermal dehydration of a Cu(OH) 2 suspension at ⁓ 95 °C, yielding nano-rod and flake-like morphologies. The resulting glass@CuO composites exhibited particle sizes between 300 and 550 nm, as confirmed by Brunauer-Emmett-Teller (BET) analysis and dynamic light scattering (DLS). Band gap measurements revealed that the soda-lime@CuO composite had direct and indirect band gaps of 3.6 eV and 2.8 eV, respectively, while the borosilicate@CuO composite showed slightly higher values of 3.7 eV and 3.0 eV. Under visible light irradiation for 2 h, the borosilicate@CuO composite demonstrated superior photocatalytic activity, degrading 78% of methylene blue (MB), compared to 72% degradation by the soda-lime@CuO composite. Notably, both composites exhibited significant degradation in dark conditions, with borosilicate@CuO achieving ⁓ 62% MB removal after 12 h. A straddling type (Type I) heterojunction was proposed based on the alignment of the conduction and valence bands of the composite components.