Electrospun Ag-TiO₂ Nanofibers for Photocatalytic Glucose Conversion to High-Value Chemicals

TiO₂ nanofibers were fabricated by combination of sol-gel and electrospinning techniques. Ag-doped TiO₂ nanofibers with different Ag contents were prepared by two different methods (in situ electrospinning or wetness impregnation of Ag on TiO₂ nanofibers) and heat treated at 500 °C for 2 h under an air or N₂ atmosphere. The obtained catalysts were characterized by field emission scanning electron microscopy, X-ray diffraction, photoluminescence, and N₂ adsorption analyzed by the Brunauer-Emmett-Teller (BET) method. Photocatalytic glucose conversions with electrospun TiO₂ and Ag-doped TiO₂ nanofibers for production of high-value products were carried out. From different doping methods, the results indicated that 1 wt % Ag-TiO₂ nanofibers prepared by an in situ method with calcination under N₂ achieved the highest glucose conversion (85.49%). From several Ag loading contents (i.e., 0, 1, 2, and 4 wt %) in Ag-doped TiO₂ nanofibers, the nanofibers exhibited different glucose conversions [in order of 2 wt % (99.65%) > 1 wt % (85.49%) > 4 wt % (77.72%) > 0 wt % (29.64%)]. Arabinose, xylitol, gluconic acid, and formic acid were found as the high-value chemicals with the photocatalytic reaction of TiO₂ and Ag-doped TiO₂ nanofibers under UVA irradiation. Product yields of each converted chemicals from different photocatalysts from different Ag loading contents showed relatively same trends with the glucose conversion. From all results, it can be concluded that the good characteristics of 2 wt % Ag-TiO₂ nanofibers such as the smallest anatase crystallite size (8.25 nm) and the highest specific surface area (S _BET = 53.69 m²/g) promoted the highest photocatalytic activity. Additionally, TiO₂ and Ag-doped TiO₂ nanofibers exhibited higher photocatalytic performance for glucose conversion than commercial TiO₂ (P25) and synthesized TiO₂ nanoparticles. Finally, Ag-doped TiO₂ nanofibers showed recycling ability with high photocatalytic glucose conversion after four-time use.