Construction of S-scheme heterojunction CuFe2O4/α-MnO2 with tuned bandgap for enhanced white light harvesting: Insights of photoluminescence, Raman scattering and photocatalysis

Abstract

Synthesis of MnO2/CuFe2O4 nanocomposites (NCs) was performed by chemical co-precipitation with the assistance of thermal treatment and ultrasonication. Transmission electron microscopic image (TEM) confirmed that CuFe2O4 is embedded over MnO2 with the existence of clear lattice fringes. The SAED pattern attributed to the polycrystallinity of MnO2/CuFe2O4 NCs. Elemental mapping and energy dispersive analysis (EDAX) affirms the existence of elements such as Mn, O, Cu and Fe. XRD confirmed the effective construction of crystalline MnO2/CuFe2O4 NCs with the coexistence of MnO2 and CuFe2O4. The degradation rate constant for MB dye by MnO2/CuFe2O4 NCs-20 under white light irradiation was 0.0011 min−1 which is 2.75 times and 2.2 times higher in comparison with their counter NPs, CuFe2O4 (0.004 min−1) and MnO2 (0.005 min−1) respectively. The current study confessed the insights into the S-scheme photocatalysts which led to retaining of e− and h+ in the CB of reduction photocatalysts (RP) and VB of oxidation photocatalysts (OP) introducing a strong redox potential. Built-in electric filed between MnO2 and CuFe2O4 was substantiated through X-ray photoelectron spectroscopy analysis and free radical assay. Degradation process admits the pseudo-first order kinetics. The mechanism behind the photocatalysis was explained through the application of free radicals scavengers. The significant generation of .OH− by NCs brings forth the degradation of MB dye. The structural stability and reusability of NCs were validated with degradation efficiency by carrying out six cycles of experiments consecutively. There is no difference in the degradation of MB by MnO2/CuFe2O4 NCs-20 until 4th cycle. The efficiency of reusability was found to be 98.91%. The ultimate role of the synthesized MnO2/CuFe2O4 NCs-20 was confessed with the results obtained and it expressed a greater potential to be a photocatalyst to eliminate toxic pollutants from the aquatic resources.