Synthesis, physical and electrochemical properties of the spinel CoFe2O4: Application to the photocatalytic hydrogen production. (19th February 2022)

• Record Type: Journal Article
• Authors: Benlembarek, M.; Salhi, N.; Benrabaa, R.; Djaballah, A.M.; Boulahouache, A.; Trari, M.
• Is Part Of: International journal of hydrogen energy. Volume 47:Number 15(2022)
• Page Start: 9239
• Page End: 9247
• Publication Date: 2022-02-19
• Subjects: Spinel CoFe2O4 -- Nitrate route -- Semiconductor -- Photo-electrochemical -- Visible light -- Hydrogen; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2021.12.270
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: This research is achieved for the preparation of CoFe2 O4 with a high purity and crystanillity by nitrate route followed by a calcination at 850 °C. The material exhibits a single phase with a cubic symmetry. The electrochemistry performed in Na2 SO4 solution shows a stable semiconductor with a small exchange current density (112 μA cm −2 ). The capacitance-potential measurement indicates p -type behavior, typically related to the metal insertion in octahedral sites. The narrow band gap semiconductor with a direct optical transition of 1.27 eV is due to the lifting of degeneracy of Fe 3+ : 3d orbital in 6-fold coordination, making it attractive for the photo-electrochemical (PEC) conversion. Moreover, its cathodic comportment evidenced from the negative conduction band compared to the potential of the water reduction makes it an ideal candidate for the hydrogen production. The experimental data shows a great activity for the evolution of hydrogen with an average rate of 74 μmol min −1 gcat −1 and a quantum efficiency of 0.34% under visible illumination (23 mW cm −2 ). The use of C2 O4 2− as reducing agent increased substantially the performances by a factor of 57%. Highlights: The spinel CoFe2 O4 prepared by nitrate route is a narrow band gap semiconductor with a crystallite size of 27 nm. CoFe2 O4 with an optical band gap of 1.27 eV is sensitive over the whole visible region. The oxalate C2 O4 2− acting as sacrificial agent enhances the H2 production in NaOH electrolyte. The conduction band (−0.5 V SCE ) derived from Fe 3+ : e g orbital, is more cathodic than the H2 O/H2 level (∼-0.4 V SCE ). H2 evolution rate of 74 μmol min −1 (g catalyst) −1 and quantum yield of 0.34% were obtained under visible light (23 mW cm −2 ).