Photo(electro)catalytic Activity of Cu2+-Modified TiO2 Nanorod Array Thin Films under Visible Light Irradiation

• TiO2 nanorod array thin films were prepared by the hydrothermal method and modified with Cu2+ by an ultrasonic-assisted sequential cation adsorption method.
• I–V curves and photocatalytic activities were investigated.
• The optimum properties were determined in terms of Cu2+ concentration, band gap energy, electron–hole recombination and donor density.

In the present study, a two-step method was applied to synthesise Cu2+-modified TiO2 nanorod array thin films for photocatalytic processes. TiO2 nanorod array thin films were synthesised by a hydrothermal method and then modified with an ultrasonic-assisted sequential cation adsorption method. The samples were characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and inductively coupled plasma mass spectroscopy (ICP-MS) analysis. The photoelectrochemical properties of the samples were evaluated by linear sweep voltammetry and Mott–Schottky analysis; photocatalytic activities were tested by methylene blue degradation under visible light. The photocurrent density of the TiO2/FTO sample modified with 50 mM Cu2+ solution was 26 times higher than that of the unmodified TiO2/FTO sample. Additionally, methylene blue degradation efficiency under visible light was increased 40% with respect to the efficiency of the unmodified sample. The mechanism of the photocatalytic activity enhancement of Cu2+-modified TiO2 nanorod films was discussed.