Pure and modified mesoporous TiO₂ nanoparticles with different loadings of NiO (3–20.0 wt %) were prepared through the surfactant-assisted sol–gel approach with the use of cetyltrimethylammonium bromide as a template. The optical and structural properties of different samples were examined using N₂ adsorption–desorption analysis, energy-dispersive spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence (PL) spectroscopy. X-ray diffraction results confirmed the insertion of Ni²⁺ into the lattice of TiO₂, and the crystallite size reduced remarkably after the addition of NiO. The diffuse reflectance spectroscopy spectra displayed obvious red shift in the absorption edges, and new absorption bands appeared in the visible region when NiO was added, which indicates the formation of surface defects and oxygen vacancies. The optical band gap of TiO₂ reduced sharply when the contents of NiO were increased. The increase in the surface defects as well as oxygen vacancies were examined using PL spectroscopy. The photocatalytic performance of the as-synthesized samples was investigated over photodegradation of brilliant green (BG) and phenol and hydrogen generation under visible light. 10% NiO/TiO₂ exhibited the highest photocatalytic efficiency. The photocatalytic activity was improved due to the creation of a p–n junction at the interface of NiO/TiO₂, which efficiently promotes the separation of photogenerated electron/hole pairs and consequently enhances its photodegradation activity. According to the photocatalytic activity results, NiO contents were considered one of the most important factors affecting the photodegradation of BG and phenol and H₂ evolution. Also, we discussed the mechanism of photodegradation, mineralization (total organic carbon), and photocatalytic reaction kinetics of BG and phenol.

Polyaniline (PANI) has received significant attention in basic and applied studies because it has electrical and electrochemical properties comparable to conventional semiconductors and metals. PANI's electrical and electrochemical properties can be controlled through its preparation methods. Accordingly, in the present work, two different samples of PANI were prepared by the polymerization of aniline monomer via in situ polymerization method using two different oxidizers of dichromate (PANI (1)) and persulphate (PANI (2)). The products were blended with BaTiO₃ (BTO) to form BTO@PANI composites. The composites were characterized by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). SEM illustrated the covering of PANI layers on the BTO nanoparticles. The electrical and electrochemical properties of the prepared composites were studied. The BTO@PANI(2) composite sample showed a conductivity of 1.2 × 10^–3 S/cm higher than that found for each BTO@PANI(1) 9.1 × 10^–4 S/cm and its constituents. The supercapacity showed higher capacity values of 70 F/g, and 76 F/g for BTO@PANI(1), and BTO@PANI(2), respectively, which are higher than its constituents.