Synthesis and comparative evaluation of optical and electrochemical properties of Ni+2 and Pr+3 ions co-doped mesoporous TiO2 nanoparticles with undoped Titania

In the present study TiO2-based nanomaterial doped with nickel (Ni) and praseodymium (Pr) ions were prepared using a facile and cost-effective method. Different techniques were used to characterize the nanoparticles. The crystalline nature of nanoparticles was confirmed by X-Rays Diffraction analysis (XRD). The results revealed that with the introduction of Pr and Ni ions in TiO2 lattice the particle size decrease from 18.01 to 9.02 nm accomplished by the enhancement in surface area of the nanoparticles. The results obtained UV–Vis diffused-reflectance (DRS) spectroscopy of co-doped nanoparticles demonstrated a reduction in the bandgap compared with the pure TiO2. The variation in surface defects and oxygen vacancies were evaluated using Photoluminescence (PL) studies, which exhibited a gradual reduction in PL intensity upon the addition of dopants in the TiO2 Lattice. Furthermore, the exciton recombination was also investigated using electrochemical impedance spectroscopy (EIS), which showed the reduction in the recombination rate in doped nanoparticles. The photocatalytic activity of prepared nanoparticles was tested on three azo dyes (reactive blue-19 (RB-19), reactive orange-13 (RO-13), and reactive blue-13 (RB-13)). The experimental results showed that 99.0% of RB-19, 85.0% for RB-13, and 70.0% RO-13 were degraded after a small interval of irradiation. The adsorption of dye on the photo-catalytic support was checked by performing the experiments under different conditions by varying the pH values and temperature. Furthermore, the catalysts also exhibit remarkable activity for the overall water splitting in an alkaline solution with Ni-Pr-3 catalyst being the best, which recorded onset overpotential of 330 mV and a Tafel slope of 76 mV dec−1 for Oxygen evolution reaction (OER). It is also clear that Ni–Pr-3 (with 5% nickel and 3% Pr) content is more active in the OER process showing comparatively lower over-potential value at 10 mA/cm2 than Ni-5 and TiO2.