Single step fabrication of CuO-MnO-2TiO2 composite thin films with improved photoelectrochemical response

Abstract

Novel trimetallic composite oxide CuO-MnO-2TiO2 thin films have been deposited on glass substrates, which were coated with fluorine-doped tin oxide (FTO), by aerosol-assisted chemical vapor deposition (AACVD) using a 1 : 1 : 2 non aqueous mixture of copper(ii) acetate monohydrate (Cu(CH3COO)2·H2O), anhydrous manganese(ii) acetate (Mn(CH3COO)2) and titanium(iv) butoxide (Ti(O(CH2)3CH3)4) in the presence of trifluoroacetic acid (TFA). Thin films were characterized by Fourier transform infrared spectroscopy (FT-IR), Raman, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), suggesting the formation of a crystalline mixture of CuO-MnO-2TiO2 composite with well defined and evenly distributed particles. The direct band gap energy of 1.95 eV was estimated by UV-Vis spectroscopy. From its current-voltage characterization, it is evident that the nanostructured CuO-MnO-2TiO2 photoelectrode deposited at 550 °C for 45 minutes displayed enhanced photocatalytic activity in photoelectrochemical (PEC) water splitting and yielded a photocurrent of 2.21 mA cm−2 at +0.7 V vs. Ag/AgCl/3 M KCl using a 0.5 M Na2SO4 electrolyte under AM 1.5 G illumination (100 mW cm−2). The charge transfer dynamics of the thin film were also explored using an electrochemical impedance spectroscopy (EIS) technique.