Spray-Deposited TiO₂-CuO Heterostructured Thin Films for Rifampicin Degradation and Solar Cell Application

TiO₂, CuO, and TiO₂-CuO heterostructures are commonly synthesized using hydrothermal or furnace-based methods, which often lack precise control over the thickness of the film. Moreover, their photocatalytic applications have mostly been limited to the degradation of conventional dyes such as methylene blue, methyl orange, and rhodamine B. Their use in degrading pharmaceutical pollutants remains largely unexplored. In this study, we report the synthesis of TiO₂-CuO thin films via the spray pyrolysis method for the photocatalytic degradation of rifampicin (RMP), a pharmaceutical contaminant. The effects of varying the concentrations of TiO₂ and CuO oxides in the sprayed solution at ratios (100:00, 75:25, 50:50, 25:75, and 0:100) on the thin films were explored and characterized with XRD, XPS, PL, and UV-vis Spectroscopy. TiO₂ and CuO exhibited band gaps of 3.4 and 1.44 eV, respectively, while the optimized TiO₂-CuO composite (T50C50) showed a slightly increased band gap of 1.47 eV, indicating strong interfacial coupling between the two oxides. Photoluminescence (PL) spectra indicated all samples' emissions in both the UV and visible regions. The optimal ratio of TiO₂ to CuO was determined to be 50:50 (referred to as T50C50). The photocatalytic degradation of RMP, a well-known antibiotic, under sunlight illumination demonstrated a high degradation rate of nearly 99% after 3 h. The influence of real operational parameters, such as pH, presence of scavengers, and catalyst dosage, has been investigated. Furthermore, simulations of solar cells utilizing TiO₂-CuO absorber layers yielded a promising efficiency of approximately 22.5%. These findings indicate that TiO₂-CuO heterostructured thin films have significant potential for optoelectronic applications and photocatalytic processes.