The effects of surfactant in the sol–gel synthesis of CuO/TiO2 nanocomposites on its photocatalytic activities under UV-visible and visible light illuminations

Abstract

Effective and low-cost CuO/TiO₂ nanocomposite photocatalysts were prepared at room temperature via a surfactant-assisted sol–gel method using titanium(IV) isopropoxide and copper(II) nitrate as precursors. In the current study, a surfactant, namely hexadecyltrimethylammonium bromide, was used in the sol–gel method to reduce the agglomeration of CuO/TiO₂ nanocomposites. The framework substitution of CuO in the TiO₂ nanostructure was established by different characterization techniques, including XRD, TEM and HRTEM, and the results confirmed that CuO and TiO₂ bound one over the other and forming a nanocomposite nature. The optical properties revealed extended tailing of the absorption edge toward the visible region upon CuO doping. CuO serves as the electron reservoir by receiving electrons from TiO₂, which suppresses the recombination of e⁻/h⁺ and transfers the received electrons to split water, resulting in enhanced photocatalytic activity. The concentration of CuO in the TiO₂ nanostructure was fine-tuned to improve the photocatalytic activities. The synergy between CuO and TiO₂ was optimum at a concentration of 0.5 wt% CuO. The optimized product produced a promising hydrogen evolution of 1634 μmol g⁻¹ under illumination from UV and visible light sources. The optimized product also showed promising photocatalytic degradation of Rhodamine B dye and better photochemical reduction of Cr⁶⁺ under sunlight and UV light than those with other CuO ratios.