Rational Engineering of Magnetic recyclable S-scheme FeS 2 /TiO 2 heterojunction for photocatalytic destruction of rhodamine B dye under full broad 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 FeS2/TiO2 magnetic heterojunctions containing various proportion of FeS2 [0-10%] are synthesized for expelling rhodamine B dye under solar radiations. Magnetic FeS2 nanoparticles are synthesized through controlled sonochemical route with precise drying under N2-atmosphere to avoid the simultaneous oxidation of Fe2+ to Fe3+ ions. Different compositions of black magnetic FeS2 nanoparticles are deposited sonochemically on TiO2 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 FeS2 nanoparticles are efficiently transfer the absorbability of the heterojunction to deep visible and NIR regions by exceptional reducing the band gap energy of TiO2 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 FeS2/TiO2 outperformed TiO2 and FeS2 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 % TiO2 and 5 wt % FeS2 during two hours of light illumination compared with 97% removal over pristine titania. This extra-ordinary efficiency is ascribed to impulsive role of FeS2 in elevating the electron-hole transportation and separation. A wealth of S-scheme heterojunction charge transportation mechanism is verified through scrubber trapping experiments and PL measurements of terephthalic acid. The hole-electron pair accumulated in the valence and conduction bands of TiO2 and FeS2 nanoparticles, respectively are the spacious charge carriers consumed in the photodegradation process. In conclusion, magnetic S-scheme FeS2/TiO2 heterojunction can convert full solar absorption spectrum into chemical energy dissipated in destruction of toxic organic dye emerged from different wastewater resources.