Synthesis, characterization and application of TiO2-Bi2WO6 nanocomposite photocatalyst for pretreatment of starch biomass and generation of biofuel precursors

This study explores a novel photocatalytic approach for the conversion of complex biomass into smaller molecular units for their utility in generation of biofuel precursors. Following hydrothermal method, TiO2/Bi2WO6 nanocomposite photocatalyst for different ratio of TiO2 viz. 15% and 25% by weight have been synthesized. The efficiency of photodegradation of organic molecule is determined. Composite loaded with 25% TiO2 found to represent maximum photocatalytic efficiency of 99.9%. The structural and optical properties of the synthesized photocatalyst nanomaterial were characterized. A band gap of 2.7 eV was observed for 25% TiO2 composition which displayed an excellent visible light photoactivity, examined by removal of Rhodamine B. We further observe a four-fold higher photocatalytic activity in this composite compared to pristine Bi2WO6. Using this composite, solar energy is harvested to perform photocatalytic fragmentation of a biopolymer, namely starch, to derive smaller molecule precursors. Colorimetric analysis of reducing sugars from the degraded biomass quantifies the monomarization of starch. The linear chain molecular fragments thus formed were further analyzed by Raman, FTIR and ESI-MS. The results demonstrate photocatalytic pretreatment of starch by nanocomposite of TiO2/Bi2WO6 resulted in the formation of organic precursors that are common feedstock for the microbiota of anaerobic methanation and ethanol fermentation. We therefore conclude that photocatalytic pretreatment of biomass can be utilized for hydrolysis and partial acedogenesis of biomass in biofuel conversion processes. Such an approach represent environmentally benign way to convert biomass waste to biofuel.