Superior photocatalytic activity of Mn-doped CoFe2O4 under visible light irradiation: Exploration of hopping and polaron formation in the spinel structure

• Published in: Materials science & engineering. B, Solid-state materials for advanced technology Solid-state materials for advanced technology, 2021-08, Vol.270, p.115222, Article 115222
• Main Author: Srinivas, M.
• Format: Article
• Language: English
• Subjects: Catalysts; Catalytic activity; Cobalt ferrites; Electron transport; Energy value; Hopping; Light irradiation; Manganese; Oxidation; Photocatalysis; Polaron; Polarons; Semiconductor; Sol-gel processes; Spinel; Valence
• ISSN: 0921-5107; 1873-4944
• DOI: 10.1016/j.mseb.2021.115222

Depiction of Mn-doped CoFe2O4 catalyst showing the generation of super oxide, oxyhydroxyl and hydroxyl free radicals under illumination of visible light. [Display omitted] •Structural changes taking place in CoFe2O4 lattice on incorporation of Mn2+ ions.•Influence of hopping and polaron formation on the rate of degradation using Mn doped CoFe2O4 is rarely attempted.•Jumping or hopping process takes place because of valence states of two ions get interchanged at octahedral site.•Trapping/detrapping is vital for assessing semiconducting electron transport mechanism correlated with photocatalytic activity. CoFe2O4 and MnxCo1-x Fe2O4 (x = 0.5 atom %) samples were synthesized by sol–gel combustion method. XPS spectra confirms the presence Mn and Co is in + 2 oxidation state. Binding energy values suggests Fe in + 3 oxidation state in MnCoFe2O4 catalyst. Mn0.5Co0.5Fe2O4 sample shows best fit to the Langmuir adsorption isotherm. Quantitative prediction of the carrier trapping/detrapping energy is essential for the assessing the semiconducting electron transport mechanism and formation of small-Polaron hopping correlated with photocatalytic activity. Higher photocatalytic activity is observed for Mn doped CoFe2O4 due to unique characteristic Mn2 + ion which can exist in different oxidation states. The Fe2+ ions intern get reoxidised to Fe3 + state through the multi electron reduction of oxygen. To the best of our knowledge the influence of hopping and Polaron formation in the spinel lattice for degradation of Methyl Violet by using Mn doped CoFe2O4 catalyst is rarely attempted.