Synthesis, physical, optical and electrochemical properties of the ilmenite CrFeO3: Application to photo-reduction of Ni2+. (8th January 2022)

• Record Type: Journal Article
• Authors: Djilali, M.A.; Mellal, M.; Mekatel, H.; Belabed, C.; Mahieddine, A.; Boudiaf, S.; Trari, M.
• Is Part Of: International journal of hydrogen energy. Volume 47:Number 3(2022)
• Page Start: 1589
• Page End: 1604
• Publication Date: 2022-01-08
• Subjects: CrFeO3 -- Hetero-system CrFeO3/TiO2 -- Photo-reduction -- Ni2+ ions -- Visible light -- First order kinetic; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2021.10.134
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: 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 Ni 2+ 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 ( τ ), dissipation factor (tan δ) and optical conductivity are extracted. The forbidden band Eg (= 1.65 eV), was computed and confirmed by different methods. The electrical conductivity (σ) 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 (Efb = −0.38 VAg/AgCl ) and a hole concentration (NA = 5.87 × 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 Ni 2+ reduction of 88% at pH ∼ 7.2 within 4 h irradiation for an initial Ni 2+ concentration of 15 mg/L. A first order kinetic was found from the Ni 2+ 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. Graphical abstract: Image 1 Highlights: The ilmenite CrFeO3, elaborated by nitrate route exhibits p -type behavior with a CB (−1.05 V) above the Ni 2+ level. The gap of 1.65 eV is well suited for the photo-electrochemical conversion. Ni 2+ was successfully reduced onto the novel hetero-system CrFeO3 /TiO2 under visible and solar lights. An optimal mass ratio CrFeO3 /TiO2 (25%/75%) yielding to a Ni 2+ (15 mg/L) reduction of 88% at pH∼7.2 with 4 h irradiation. A first order kinetic was found from the Ni 2+ photoreduction with a half photocatalytic time of 61 min.