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

Abstract

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 (SBET = 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.