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

Abstract

Biosynthesized nanocomposites are attracting growing interests because they are environmentally friendly. Ag2S nanoparticles (Ag2S NPs) are deposited in situ on the surfaces of TiO2 nanotubes (TNTs) via Shewanella oneidensis MR-1 to form Ag2S/TNT nanocomposites. The prepared Ag2S/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 Ag2S NPs smaller than 8nm are successfully synthesized and fabricated on the TNT surfaces with relatively uniform distribution. The catalytic performance of the Ag2S/TNT nanocomposites is evaluated for catalytic reduction in the presence of NaBH4 and the photocatalytic degradation of 4-nitrophenol (4-NP) under visible light. The Ag2S/TNT nanocomposites show excellent catalytic activity and good stability in the 4-NP reduction process. The 4-NP degradation ratio reaches 98.3% in 50min, and 87% conversion was achieved after eight cycles. The Ag2S/TNT nanocomposites also exhibit excellent photocatalytic activity for 4-NP at a rate of 0.69h-1, and the complete degradation of 4-NP was observed within 5h. Therefore, this study offers an environmentally friendly approach to synthesize nanocomposites for practical applications.