Photoredox Cascade Catalyst for Efficient Hydrogen Production with Biomass Photoreforming
Atsushi Kobayashi
Abstract
Abstract Biomass photoreforming is a promising method to provide both a clean energy resource in the form of hydrogen (H 2 ) and valuable chemicals as the results of water reduction and biomass oxidation. To overcome the poor contact between heterogeneous photocatalysts and biomass substrates, we fabricated a new photoredox cascade catalyst by combining a homogeneous catalyst, 2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPO), and a heterogeneous dual‐dye sensitized photocatalyst (DDSP) composed of two Ru(II)‐polypyridine photosensitizers ( RuP 6 and RuCP 6 ) and Pt‐loaded TiO 2 nanoparticles. During blue‐light irradiation (λ=460±15 nm; 80 mW), the DDSP photocatalytically reduced aqueous protons to form H 2 and simultaneously oxidized TEMPO • radicals to generate catalytically active TEMPO + . It oxidized biomass substrates (water‐soluble glycerol and insoluble cellulose) to regenerate TEMPO • . In the presence of N ‐methyl imidazole as a proton transfer mediator, the photocatalytic H 2 production activities for glycerol and cellulose reforming reached 2670 and 1590 μmol H 2 (g TiO2 ) −1 h −1 , respectively, which were comparable to those of state‐of‐the‐art heterogeneous photocatalysts.