Carbon quantum dots modified TiO2 composites for hydrogen production and selective glucose photoreforming

Lignocellulosic biomass photoreforming is a promising and alternative strategy for both sustainable H2 production and biomass valorization with infinite solar energy. However, harsh reaction conditions (high alkalinity or toxic organic solvents), with low biomass conversion and selectivity are often reported in literature. In this work, we report glucose photoreforming for coproduction of H2 and arabinose with improved selectivity under neutral condition using carbon quantum dots (CQDs) modified TiO2 composites. We show that the conventional CQDs fabricated by a facile one-step hydrothermal process could be endowed with novel color changing property, due to the particle aggregation under the regulation of incident light. The as-fabricated CQDs/TiO2 composites with certain colored CQDs could greatly improve glucose to arabinose conversion selectivity (~75%) together with efficient hydrogen evolution (up to 2.43 mmolh−1g−1) in water. The arabinose is produced via the direct C1-C2 α-scissions mechanism with reactive oxygen species of O2− and OH, as evidenced by 13C labeled glucose and the electron spin-resonance (ESR) studies, respectively. This work not only sheds new lights on CQDs assisted photobiorefinery for biomass valorization and H2 coproduction, but also opens the door for rationale design of different colored CQDs and their potential applications for solar energy utilization in the noble-metal-free system.