Dye-Sensitized Hydrobromic Acid Splitting for Hydrogen Solar Fuel Production

Hydrobromic acid (HBr) has significant potential as an inexpensive feedstock for hydrogen gas (H 2 ) solar fuel production through HBr splitting. Mesoporous thin films of anatase TiO 2 or SnO 2 /TiO 2 core–shell nanoparticles were sensitized to visible light with a new Ru II polypyridyl complex that served as a photocatalyst for bromide oxidation. These thin films were tested as photoelectrodes in dye-sensitized photoelectrosynthesis cells. In 1 N HBr (aq), the photocatalyst undergoes excited-state electron injection and light-driven Br – oxidation. The injected electrons induce proton reduction at a Pt electrode. Under 100 mW cm −2 white-light illumination, sustained photocurrents of 1.5 mA cm –2 were measured under an applied bias. Faradaic efficiencies of 71 ± 5% for Br – oxidation and 94 ± 2% for H 2 production were measured. A 12 μmol h –1 sustained rate of H 2 production was maintained during illumination. The results demonstrate a molecular approach to HBr splitting with a visible light absorbing complex capable of aqueous Br – oxidation and excited-state electron injection.