Rational Design of Magnetic Recyclable S-Scheme FeS2/TiO2 Heterojunction for Photocatalytic Degradation of Rhodamine B dye Under Broad Solar Spectrum

Abstract

Precise tunable of heterojunctions with strong redox power is future challenge in photocatalytic treatment of wastewater and energy production. The circuit of the heterojunction must carefully built of two semiconductors aligned in band gap structure with large redox potential difference. Sonicated FeS 2 /TiO 2 magnetic heterojunctions containing various proportion of FeS 2 [0-10%] are synthesized for expelling rhodamine B dye under solar radiations. Magnetic FeS 2 nanoparticles are synthesized through controlled sonochemical route with precise drying under N 2 -atmosphere to avoid the simultaneous oxidation of Fe 2+ to Fe 3+ ions. Different compositions of black magnetic FeS 2 nanoparticles are deposited sonochemically on TiO 2 surface. The nanostructure, crystalline and optical properties of the solid specimens are thoroughly evaluated by HRTEM, BET, Zeta potential measurements, and XRD, PL and DRS techniques. Black magnetic FeS 2 nanoparticles are e ciently transfer the absorbability of the heterojunction to deep visible and NIR regions by exceptional reducing the band gap energy of TiO 2 from 3.22 to 1.47 eV. The electron-hole recombination is effectively depressed by 50 % as elucidated from PL analysis. The photocatalytic reactivity of FeS 2 /TiO 2 outperformed TiO 2 and FeS 2 by 1.4 and 1.6 times in removal of RhB dye. Delightfully, 95 % of RhB dye degrades effectively on the heterojunction containing 95 wt % TiO 2 and 5 wt % FeS 2 during two hours of light illumination compared with 97% removal over pristine titania. This extra-ordinary e ciency is ascribed to impulsive role of FeS 2 in elevating the electron-hole transportation and separation. A wealth of S-scheme heterojunction charge transportation mechanism is veri ed through scrubber trapping experiments and PL measurements of terephthalic acid. The holeelectron pair accumulated in the valence and conduction bands of TiO 2 and FeS 2 nanoparticles, respectively are the spacious charge carriers consumed in the photodegradation process. In conclusion, magnetic S-scheme FeS 2 /TiO 2 heterojunction can convert full solar absorption spectrum into chemical energy dissipated in destruction of toxic organic dye emerged from different wastewater resources.