Plasmon and N-vacancy synergistically enhanced tubular carbon nitride-based S-scheme heterojunction photocatalyst with one stone five birds function: Pathways, DFT calculation and mechanism insight

Abstract

From the perspectives of innovation and broad-spectrum, tubular carbon nitride-based photocatalyst, viz., Ag/AgI/g-C₃N₄ S-scheme heterojunction photocatalyst, with enhancement of nitrogen vacancy and localized surface plasmon resonance (LSPR) effect is reasonably devised and manufactured via combining hydrothermal, calcination and photo-reduction techniques. The optimal specimen displays high photocatalytic activity in removal of dyes [such as crystal violet (CV), 100.00 %/60 min], antibiotics [such as levofloxacin (LEV), 88.72 %/50 min] and Cr(VI) (100.00 %, 30 min), photocatalytic hydrogen evolution (1023.3 μmol h⁻¹ g⁻¹) and H₂O₂ generation (866.2 μmol h⁻¹ g⁻¹), achieving broad-spectrum natures, viz., realizing the function of “one stone five birds”. The broad-spectrum natures are attributed to the synergisms of nitrogen vacancy, LSPR effect of Ag, hollow tube structure and S-scheme heterojunction, which facilitate the separation and migration of photo-generated carriers and inject “hot electrons” generated by Ag into the conduction band of Ag/AgI/g-C₃N₄, increase the specific surface area and broaden the spectral response range. Further, the degraded intermediates of CV and LEV and possible degradation pathways are rationally advanced by the aid of LCMS spectra, the predicted toxicity of degraded intermediates of LEV is assessed by Toxicity Estimation Software (T.E.S.T.), and the biotoxicity of CV, LEV and Cr(VI) solutions after photocatalytic degradation is further assessed by feat of cultivate rice. Synergistically enhanced photocatalytic mechanism of Ag/AgI/g-C₃N₄ hollow tube S-scheme heterojunction is confirmed based upon a series of sound experiments, fs-TA spectra, in-situ XPS and DFT calculation, etc.