Synthesis of novel Cu doped anatase TiO2 catalysts and assessment of the influence of Nb concentration on the photocatalytic and electrochemical properties

In the present study, Cu doped (Ti0.8CuxO2-x/2) and (Cu, Nb) co-doped (Ti0.8Cux-y NbyO2-(x-y/2+y)) TiO2 photocatalysts were fabricated by sol-gel method. The catalysts were polycrystalline in nature with preferential orientation along (101) plane answering to anatase phase of TiO2. Higher Nb concentration results in the formation of secondary phase (Nb2O5). A decrease in average crystallite size was noticed with the addition of Nb concentration in Cu doped TiO2 photocatalyst. The formation of anatase phase was also fixed by Raman spectra. The TEM photograph confirmed the co-doped TiO2 photocatalyst in nanometer range of about 15 nm and the particles were in hexagonal shape. The doping of Nb5+ ions inspired a shift in the absorption threshold towards the visible spectral range (red shift) compared to Cu doped TiO2 catalyst. The photocatalysts have direct bandgaps of 3.253 to 2.974 eV. Semiconducting properties were investigated through electrochemical impedance spectroscopy. The results indicate that the presence of Nb5+ ions into Cu doped TiO2 has enhanced the efficiency of electrochemical conductivity. Photocatalytic performance was assessed from the sample degradation by illuminating methylene blue dye under visible light exposure. It is found that TCN3 photocatalyst bleaches MB much faster than all others. Also it exhibits great improvement of photocatalytic activity (96.86%) within 120 min. The photocatalytic degradation process is explained using the pseudo first order kinetics and it fits well with higher correlation coefficient. All these analyses elucidate that the incorporation of Nb5+ ions might tune the structural, optical, electrochemical and phocatalytic properties of Cu doped TiO2 photocatalysts.