Multispectral solar-driven detoxification by S-scheme Ag2S/Co1–xS@ Co9S8@C nanocatalyst of emerging persistent organic pollutant-levofloxacin

Strategic regulation of photogenerated carriers along with efficient utilization of full solar spectrum is a crucial approach in photocatalytic reactions. In this aspect, creating S-scheme heterojunction efficiently promotes the spatial segregation of photogenerated charge carriers for participation in photoreactions. Herein, Ag 2 S/Co 1– x S@Co 9 S 8 @C (A-CCC) S-scheme heterojunction nanocatalysts was synthesized, demonstrating outstanding photocatalytic degradation efficiency under simulated solar light irradiation ranging from ultraviolet to near-infrared owing to strong interfacial electric field. Morphological and structural analyses via scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman, and in-situ -X-ray photoelectron spectroscopy confirmed the retention of the Co-ZIF-67-derived octahedral morphology with uniform Ag 2 S nanoparticle distribution and formation of distinct Co 1– x S and Co 9 S 8 phases embedded in a carbon matrix. Ultraviolet photoelectron spectroscopy and band gap measurements elucidated an S-scheme heterojunction configuration driven by an internal electric field, promoting interfacial charge. A steady-state THz time-domain spectroscopy in transmission mode and multi-exponential time resolved photoluminescence spectra fitting and calculated amplitude-weighted and intensity-weighted lifetimes (~2.38 ns) demonstrated significant interfacial charge separation within the 5A-CCC. The 5 wt% Ag 2 S-CCC (5A-CCC) nanocatalysts endows exceptional photocatalytic activity for environmentally persistent antibiotic levofloxacin (LCN) degrading about 99.7% with an apparent rate constant of 0.0326 min –1 in 40 min reaction duration due to extended light absorption till near infra-red region for effective solar to thermal conversion (13.6%). Radical scavenging and reactive oxygen species probe studies revealed O 2 •– as the dominant active species, participated effectively in LCN degradation. For LCN degradation, fragmentation and intermediate products were observed using liquid chromatography-mass spectrometer. This study features a highly effective photocatalytic system and offers essential insights towards full-spectrum functioning nanocatalysts for environmental detoxification of persistent antibiotics.