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 TiO2 or SnO2/TiO2 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 mu mol 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.