Biosynthesis of Ag2S/TiO2 nanotubes nanocomposites by Shewanella oneidensis MR-1 for the catalytic degradation of 4-nitrophenol

Biosynthesized nanocomposites are attracting growing interests because they are environmentally friendly. Ag 2 S nanoparticles (Ag 2 S NPs) are deposited in situ on the surfaces of TiO 2 nanotubes (TNTs) via Shewanella oneidensis MR-1 to form Ag 2 S/TNT nanocomposites. The prepared Ag 2 S/TNTs nanocomposites are characterized using high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray spectroscopy. The results show that Ag 2 S NPs smaller than 8 nm are successfully synthesized and fabricated on the TNT surfaces with relatively uniform distribution. The catalytic performance of the Ag 2 S/TNT nanocomposites is evaluated for catalytic reduction in the presence of NaBH 4 and the photocatalytic degradation of 4-nitrophenol (4-NP) under visible light. The Ag 2 S/TNT nanocomposites show excellent catalytic activity and good stability in the 4-NP reduction process. The 4-NP degradation ratio reaches 98.3% in 50 min, and 87% conversion was achieved after eight cycles. The Ag 2 S/TNT nanocomposites also exhibit excellent photocatalytic activity for 4-NP at a rate of 0.69 h −1 , and the complete degradation of 4-NP was observed within 5 h. Therefore, this study offers an environmentally friendly approach to synthesize nanocomposites for practical applications.