Synthesis, physical, optical and electrochemical properties of the ilmenite CrFeO3: Application to photo-reduction of Ni2+

During the last decade, there is a growing interest in developing efficient photocatalysts with a visible light sensitivity. Herein, visible-light-driven photoactivity of CrFeO3 prepared by nitrate route was studied. The photocatalysis was evaluated through the Ni2+ reduction. The X-ray diffraction (XRD) is characteristic of a single phase crystallizing in the ilmenite structure with a good crystallinity. It was characterized by the SEM, TEM/HRTEM, FTIR spectroscopy and thermal analysis (TG). The optical and dielectric constants are determined from the diffuse reflectance data. The refractive index (n), extinction coefficient (k), relaxation time (tau), dissipation factor (tan delta) and optical conductivity are extracted. The forbidden band E-g (= 1.65 eV), was computed and confirmed by different methods. The electrical conductivity (sigma) augments exponentially with 1000/T and activation energy of 0.22 eV was calculated. The p-type conduction is evidenced from the capacitance measurements with a flat band potential (E-fb =-0.38 V-Ag/AgCl) and a hole concentration (NA-= 5.87 x 10(18) cm(-3)). The novel hetero-system CrFeO3/TiO2 showed improved efficiency by 47% compared to CrFeO3. An optimal mass ratio CrFeO3/TiO2 (25%/75%) gives to a Ni2+ reduction of 88% at pH 7.2 within 4 h irradiation for an initial Ni2+ concentration of 15 mg/ L. A first order kinetic was found from the Ni2+ photoreduction with a half photocatalytic life of 61 min(-1) and a higher photodegradation under sunlight is obtained. More interestingly, the photocatalyst showed a good stability and recyclability after four runs. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.