Photosensitization of TiO₂ nanofibers by Ag₂S with the synergistic effect of excess surface Ti³⁺ states for enhanced photocatalytic activity under simulated sunlight.

ABSTRACT: TiO₂ nanofibers, with mean diameter ~200?nm, were fabricated by electrospinning and successfully photosensitized with low bandgap Ag₂S nanoparticles of 11, 17, 23 and 40?nm mean sizes, with corresponding loading of 4, 10, 18 and 29?wt.% Ag₂S, respectively. 17?nm Ag₂S@TiO₂ nanofibers exhibited optimal activity in the photodegradation of methylene blue under simulated sunlight with pseudo-first order rate constant of 0.019?min^-1 compared to 0.009?min^-1 for pure TiO₂ nanofibers. In spite of greater visible-light absorption and reduced bandgap, larger than 17?nm Ag₂S nanoparticles exhibited sluggish photodegradation kinetics probably due to less photo-induced carriers generation in TiO₂ and reduced electron injection rates from the larger sized Ag₂S into TiO₂. Furthermore, a UV-O₃ surface treatment induced excess Ti³⁺ surface states and oxygen vacancies which synergistically enhanced the photodegradation rate constant to 0.030?min^-1 for 17?nm Ag₂S@TiO₂ sample which is ~70% better than the previously reported for Ag₂S/TiO₂ hierarchical spheres. This was attributed to the efficient charge separation and transfer driven by increased visible-light absorption, bandgap narrowing and reduced electron-hole recombination rates. The present study demonstrate the potential utilization of Ag₂S@TiO₂ nanofibers in filtration membranes for removal of organic pollutants from wastewater.

SUBMITTER: Ghafoor S 

PROVIDER: S-EPMC5428275 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature