Efficient and selective glucose conversion in a low temperature photocatalysis-assisted hydrothermal process over TiO2-few layer graphene and Ta-doped TiO2 (photo)catalysts

The study reports significantly enhanced glucose conversion under coupled low temperature hydrothermal-photocatalytic conditions with TiO₂ nanoparticles (NPs) catalysts and the formation of various high-value-added chemicals such as gluconic acid, arabinose, erythrose and presumably levulinic acid (LevA) isomer, referred to single activation mode. TiO₂ NPs, TiO₂ combined with few layer graphene (FLG/TiO₂) and TiO₂ doped with tantalum catalysts with different physicochemical features, including surface acidity properties are investigated (Lewis acid sites in the catalysts are assessed by dihydroxyacetone (DHA) transformation and pyridine adsorption by FTIR). The doping with Ta is beneficial in the photocatalytic conversion, while the FLG integration has a positive impact in photo-, and especially in thermal- and coupled process. On the other hand, the coupled process reveals the synergetic effect of the photo and thermal mode with doubled/tripled conversion of glucose, particularly for FLG/TiO₂ (1 wt% of FLG). The improved properties of this original catalyst are related to high density of jaggy FLG edges as significant acid sites, sites for glucose adsorption and TiO₂ efficient surface and interface formation, along with high charge transport and heat transfer via the conjugated C = C lattice. The results pave the way for ongoing engineering of catalysts and processes for efficient and selective biomass valorization at low thermal energy.