Sol-gel synthesis of Cu/Sn-doped TiO2 printed films with calcination-tuned interfaces for visible-light degradation of methylene blue and 4-chlorophenol.

Efficient water treatment requires photocatalytic systems that combine high activity with scalable fabrication. In this work, Cu/Sn-doped TiO2 nanostructured interfaces were developed via a sol-gel method followed by fabrication of printed films to create tailored catalytic surfaces for pollutant removal from water. Since this photocatalyst is printed as a film, it remains fixed on the substrate and can be easily separated from the reaction medium. Co-doping with Sn4+ and Cu2+ modified the electronic structure and charge transfer behavior, as confirmed by photoluminescence, Raman spectroscopy, and EDX analysis. The photocatalytic performance was evaluated using methylene blue under UV irradiation and 4-chlorophenol under visible light. Among the prepared samples, the catalyst calcined at 500 °C exhibited the best performance, achieving approximately 90% degradation of methylene blue under UV light and about 41% degradation of 4-chlorophenol in aqueous solution under visible irradiation. UPLC analysis confirmed the progressive transformation of aromatic intermediates originating from 4-chlorophenol along the oxidative degradation pathway. This enhanced activity is attributed to improved crystallinity and effective dopant incorporation. These results demonstrate that combining dopant engineering with printed nanostructured films provides a promising and scalable approach for developing photocatalytic materials for water purification applications.