Synergistic Cu/Pt-TiO₂ photocatalysts for enhanced visible-light ROS generation and BPA degradation

Water contamination by toxic organic pollutants remains a major environmental challenge, motivating the development of efficient and sustainable purification technologies. Heterogeneous photocatalysis is a promising approach for degrading persistent organic compounds using solar irradiation as a clean and renewable energy source. Titanium dioxide is one of the most widely studied photocatalysts because of its chemical stability, low toxicity, and excellent resistance to photocorrosion. However, its visible-light activity is limited by its wide band gap and rapid charge-carrier recombination. Surface modification with metallic cocatalysts, particularly bimetallic systems, offers an effective strategy to enhance charge separation, reactive oxygen species (ROS) generation, and photocatalytic activity.

In this study, TiO₂ was modified with mono- and bimetallic Cu, Au, and/or Pt nanoparticles by wet impregnation using either water or ethanol as the impregnation solvent. The prepared photocatalysts were characterised by XRD, N₂ physisorption, UV-vis DRS, PL, and EPR. Metal deposition preserved the crystalline structure of TiO₂ while improving charge separation and suppressing charge-carrier recombination.

Photocatalytic degradation of bisphenol A (BPA) under visible-light irradiation was enhanced for all metal-modified photocatalysts. The Cu/Pt-TiO₂ photocatalyst prepared in ethanol exhibited the highest activity, achieving 33.3% BPA degradation after 180 min, whereas bare TiO₂ showed no measurable degradation under identical conditions. Coumarin probe experiments revealed enhanced hydroxyl radical generation in Pt-TiO₂ and Cu/Pt-TiO₂ systems, with Pt-TiO₂ synthesised in water producing approximately 11-fold higher •OH yields than bare TiO₂. Furthermore, using water instead of ethanol as the impregnation solvent increased the measured •OH yields by 7.5-153%, depending on the deposited metal composition. These findings demonstrate that the choice of impregnation solvent strongly influences ROS generation and photocatalytic performance. Overall, controlling both the metal composition and the impregnation solvent provides a simple and effective strategy for tailoring ROS pathways and improving the visible-light photocatalytic performance of TiO₂.