Synthesis, characterization and application of tetragonal BaTiO3-δ in adsorption and photocatalysis of congo red

Abstract

The synthesis by a simple approach of the deficient Barium Titanate BaTiO3-δ (BTO) crystallizing in a perovskite structure is reported along with the physicochemical properties. Thermal analysis (TG/DSC) was performed to elucidate the synthesis process. The X-ray diffraction (XRD), BET analysis, scanning electron microscopy (SEM-EDS) and electrochemistry were investigated. The catalyst revealed a single phase with a tetragonal symmetry obtained by treatment at 650 °C. The direct band gap (3.34 eV), obtained from diffuse reflectance spectroscopy (DRS), is assigned to the charge transfer O2-: 2p-Ti4+: 3d. The electrical characterization indicated a non-degenerate conductivity due to oxygen vacancies with an activation energy of 0.33 eV. The capacitance measurements indicated n-type behavior with a flat band potential (Efb) of − 0.43 V and a carrier concentration (ND) of 3.90 1018 cm−3. The photocatalytic process was elucidated by the electrical impedance spectroscopy (EIS). The performance of BTO was assessed by a combination of the adsorption of Congo Red (CR) followed by its degradation under UV light. The photodegradation kinetic was well fitted by a pseudo-first-order model with an abatement of 50% and 91% under UV and solar lights respectively. Different scavengers were used to evaluate the reaction mechanism and the radicals O2•- are the main reactive species of the CR oxidation. Four regeneration cycles demonstrated the catalyst stability. A degradation mechanism was established based on the scavengers effect