Photocatalytic Co-Dehydrogenation and Hydrogenation of Biomass Derivatives for Coproduction of Value-Added Chemicals and Hydrogen

The increasing demand for renewable energy has spurred significant interest in the photocatalytic anaerobic oxidation of biomass-derived carbohydrates, coupled with water reduction, for the coproduction of value-added organic products and hydrogen (H₂). Nevertheless, the exclusive oxidation of carbohydrates predominantly results in the formation of low-value organics with low C:O ratios such as formate or CO₂. Here, we developed an atomic-scale redox interface by integrating Pd single atoms (PdSAs) and oxidized Mg species onto TiO₂ photocatalysts (Mg/Pd₁/Pd_NP-TiO₂), enabling efficient promotion of both partial dehydrogenation oxidation and partial hydrogenation reduction reactions targeting functional groups in biomass-derived glucose (C₆H₁₂O₆), as opposed to conventional systems that typically facilitate only dehydrogenation oxidation. This dual-functionality design allows for the coproduction of hydrogen and value-added arabinose (C₅H₁₀O₅, C/O = 1:1) under neutral conditions. In situ experiments and theoretical simulations revealed that the oxidized Mg species in PdSAs-loaded TiO₂ not only facilitated both glucose activation and H₂O dissociation but also significantly lowered the energy barrier of the rate-determining surface lattice oxygen regeneration, which governed both the partial oxidation and reduction reactions of glucose. These features endowed Mg/Pd₁/Pd_NP-TiO₂ with a higher H₂ production rate (41.8 μmol cm^–2 h^–1) and greater arabinose yield (14.4 μmol cm–2 h^–1, with a selectivity of 73.8%) compared to conventional Pd₁/Pd_NP-TiO₂ or Pd nanoparticles-loaded TiO₂, a phenomenon also observed in other metal single-atom-loaded TiO₂ systems. Subsequently, an outdoor large-scale experimental system was developed to directly harness natural sunlight for coproducing arabinose (8.2 μmol cm^–2 h^–1 at selectivity of 56.9%) and H2 (23.8 μmol cm^–2 h^–1) from a glucose photoreforming reaction, demonstrating the feasibility of large-scale production. This study presents a striking example of an oxidation–reduction-coupled pathway for the photoreforming of biomass-derived carbohydrates into value-added organic products and hydrogen.

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