TiO2/Lignin-Based Carbon Composited Photocatalysts for Enhanced Photocatalytic Conversion of Lignin to High Value Chemicals

Upgrading of biomass wastes to be value-added materials has been attempted to apply in various applications. One of the interesting challenges is the effort to utilize biomass wastes to modify metal oxides to form composited photocatalysts to enhance the photoabsorption on the resultant catalysts. In this work, lignin-based carbon was used to modify TiO2 and form the composite photocatalyst (TiO2/lignin). A sol–gel microwave technique was used to prepare these catalysts. The effects of lignin-based carbon modification were investigated on their morphology, crystal structure, surface structure, optical properties, and photocatalytic activity. Characterizations of the obtained catalysts, including field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, UV–visible diffuse reflectance spectroscopy, photoluminescence, N2 adsorption analyzed by the Brunauer–Emmett–Teller method, and UV–vis spectroscopy, were carried out. Here, lignin not only was used as a natural carbon source for modification of TiO2 but also can be used as the biomass resource for green chemical production. Enhancement of photocatalytic performance of TiO2 by carbon from sintered lignin was investigated from conversion of lignin to high value chemicals. It was found that carbon from lignin improved UVA irradiation photocatalytic performance of the TiO2/lignin composite compared with the pristine TiO2. The TiO2/lignin composite with a TiO2 to lignin ratio of 1:0.5 presented good characteristics and showed the highest photocatalytic activity under UVA irradiation for 5 h. After identification by gas chromatography mass spectroscopy, high value chemicals, such as vanillin, were found after photocatalysis.