Magnetron sputtered TiO2/CuO heterojunction thin films for efficient photocatalysis of Rhodamine B

Abstract

TiO2-based heterojunction nano-thin films are competitive photocatalysts for water pollution treatment due to their abundant availability, non-toxicity, and rapid separation of photogenerated charge carriers. Moreover, the layer thickness, as a vital factor influencing the photocatalytic properties of TiO2-based heterojunction nano-thin films, requires further exploration. Herein, we prepared heterostructured TiO2/CuO nano-thin films by a facile magnetron sputtering approach. The TiO2 nanoparticles were uniformly deposited onto the underlayer CuO to construct heterojunction, and the thickness of the upper TiO2 layer and underlying CuO layer were precisely controlled by simply varying the sputtering time. The samples were described via SEM, XRD, Raman, AFM, and UV–vis DRS analysis. The SEM results exhibited that the optimized heterojunction thin film was composed of the underlying CuO layer with a thickness of 90 nm and the upper TiO2 layer with a thickness of 120 nm. The optical absorption studies of this nano-film showed two band gaps of 1.8 and 3.1 eV. The CuO/TiO2 heterojunction nano-film (1 cm × 1 cm) exhibited superior photocatalytic activity, by degrading 92.94% Rhodamine B (RhB) within 120 min duration under a 300 W high-pressure mercury lamp illumination, which benefited from the better crystalline structure, more active sites, and the effective electrons and holes transfer. Moreover, a possible charge transfer mechanism of TiO2/CuO nano-thin film was proposed based on the results of the capture experiment.