Shouichi Somekawa

Visible-light induced hydrogen production using a polypeptide–chlorophyll complex with α-helix conformation

Hydrogen production was accomplished under visible-light irradiation by using a system consisting of a biomolecule (chlorophyll a), methylviologen, ethylenediaminetetraacetic acid disodium salt and Pt-loaded poly(L-glutamate) (Poly(Glu)), in aqueous decylammonium chloride (DeAC) solution. Spectroscopic studies revealed that chlorophyll a is solubilized in the hydrophobic clusters of Pt-loaded Poly(Glu)–decylammonium chloride. In the Poly(Glu)–DeAC complex, the electron transfer occurred between chlorophyll a and methylviologen leading to hydrogen production. The most noticeable result is that the rate of hydrogen evolution depends on the change from the random coil to the α-helix in conformation of Poly(Glu) induced by the cooperative binding with DeAC.

Photocatalytic Hydrogen Production from Diacids and Their Decomposition Over Mixtures of TiO2 and Single Walled Carbon Nanotubes

Abstract The photocatalytic hydrogen production from aqueous solutions of two diacids, i.e., oxalic acid and fumaric acid, was performed using the mixtures of TiO2 and single walled carbon nanotubes (SWNTs) under UV light irradiation. The highest hydrogen evolution rates from aqueous oxalic acid and fumaric acid were found to be 15.7 and 2.6 μmol h-1, respectively. In the absence of SWNTs, however, a negligible amount of hydrogen gas was observed. The content of SWNTs was changed from 1 to 20 wt% and the optimum hydrogen production was observed around 5 wt% for fumaric acid and 7 wt% for oxalic acid. The experiment was also performed to find the pH effect on the hydrogen production. The highest hydrogen evolution rate was observed around pH 3.5 for both acids. The influence of added inorganic anions on the hydrogen production was also studied.

A Novel Type of Solar Cell Based on Visible-Light Responsive Photocatalyst Films

We present a novel attempt to replace a Dye/TiO2 composite film in dye-sensitized solar cells (DSC) by a visible-light responsive photocatalyst film. A two-layer Fe2O3 film was prepared by the laser ablation and the squeegee methods. This novel type of solar cell using Fe2O3 gave a short circuit current such as 0.45 mA cm-2 and an open circuit voltage such as 0.15 V. The durability test was also performed by long time continuous irradiation (ca. 5 sun containing both UV and visible light, while the surface temperature was 50-60 °C). Even after 5 days irradiation, a stable I-V curve was found with our novel cell (Fe2O3, water solvent), whereas performance of DSC (N719/TiO2, organic solvent) decreased sharply under the same conditions. A Ni-doped InTaO4 film was also used to prepare a novel type of solar cell.

Enhancement Effect of Laser Ablation in Liquid On Hydrogen Production Using Titanium(Iv) Oxide and Graphite Silica

Photocatalytic hydrogen production from methanol solution containing mixture of TiO2 and graphite silica (GS) was enhanced by the laser ablation in liquid. Addition of TiO2 to lased GS increased the amount of hydrogen gas evolved two times as large as that of GS-TiO2 mixture. This may be attributed mainly to the aggregation of TiO2 and GS fined by the laser ablation.