Visible Light Responsive Ni-Doped Hierarchical SnS2 Nanoflowers for Photocatalytic Removal of Atmospheric NOx Gas

초록

Efficient removal of nitrogen oxides (NOx) from urban air is a pressing environmental need. Here, Ni-doped SnS2 nanoflowers are synthesized via a microwave-assisted solvothermal method and their visible-light-driven NOx abatement performance is evaluated. X-ray diffraction and Raman confirm phase-pure hexagonal SnS2, while X-ray photoelectron spectroscopy verifies successful Ni2(+) incorporation without secondary phases. Ni doping slightly distorts the marigold flower-like morphology observed in pristine SnS2 and narrows the bandgap (UV-vis), enhancing visible-light absorption and charge separation. Photoluminescence spectra reveal suppressed carrier recombination, with 5 wt% Ni-doped SnS2 showing the lowest emission intensity. Photocatalytic tests demonstrate that this composition achieves the highest NOx removal efficiency (14.2%) within 60 min, 1.6x higher than pristine SnS2, while maintaining 70% activity after ten cycles. Theoretical calculations reveal Ni-3d/S-p hybridization and the introduction of mid-gap states, which lower the optical transition threshold and support the experimentally observed bandgap narrowing and enhanced light harvesting. A mechanism involving Ni-induced electron trapping and reactive oxygen species generation is proposed to explain the enhanced activity. This work establishes Ni doping as an effective strategy to tailor the structural, optical, and electronic properties of SnS2, delivering a low-cost, stable, and highly active photocatalyst for sustainable NOx mitigation.

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