| Budget Amount *help |
¥49,270,000 (Direct Cost: ¥37,900,000、Indirect Cost: ¥11,370,000)
Fiscal Year 2007: ¥7,540,000 (Direct Cost: ¥5,800,000、Indirect Cost: ¥1,740,000)
Fiscal Year 2006: ¥7,540,000 (Direct Cost: ¥5,800,000、Indirect Cost: ¥1,740,000)
Fiscal Year 2005: ¥34,190,000 (Direct Cost: ¥26,300,000、Indirect Cost: ¥7,890,000)
|
|---|
| Research Abstract |
There is an increasing understanding that the reserves of fossil fuels, such as oil, coal and natural gas, are limited and the transition to renewable energies is necessary and urgent. In view of the global and regional environmental issues such as global warming and air pollution, it is generally considered that hydrogen would become an important supplement to oil, even though basic practical problems still need a solution. In spite of the rapid technological advance in the development of fuel-cell cars based on H_2 and 1/2O_2, the means of generating and storing hydrogen gas has not been well established as yet. In this context, the electrochemical decomposition of water into H_2 and 1/2O_2 is regarded as one of the candidates as a method of generating hydrogen, where wind power stations or solar batteries are considered as the source of electricity. Nevertheless, the energy return on energy invested in such systems still does not meet the criteria for the practical use. On the other
… More
hand, hydrogen is also known to be generated upon the treatment of methane with steam, which also leads to the emission of greenhouse gas (CO_2) as a byproduct. Moreover, this process requires the energy to produce the steam. Consequently, great attention has been paid to the studies on the photocatalytic systems promoting the solar-light-induced splitting of water into H_2 and 1/2O_2, because water and sunlight are abundant and such systems are free of the CO_2 emission.
Since the original discovery in the H_2-evolving activities of amidate-bridged Pt(II)_2 dimers having a relatively strong metal-metal interaction, considerable efforts have been made to develop the 'photo-hydrogen-evolving (PHE)' molecular devices (MDs) that are made up of photosensitizing Ru(bpy)_3^2+ derivatives and H_2 evolving Pt(II) catalysts. Such PHEMDs are expected to serve as an efficient photocatalyst' towards the visible-light-induced reduction of H_2O by EDTA into H_2. As a result, we discovered that one particular molecular device consisting of a [Ru(bpy)_2(5-amino-phen)]^2+ unit and a PtCl_2(bpy) unit evolves H_2 in the presence of EDTA under the visible light illumination. Several other related compounds have also been prepared and evaluated to better understand the factors affecting the PHE activities of such PHEMDs. These studies suggested the following key factors: (i) destabilization of the HOMO corresponding to the filled Pt(II) d_Z^2 orbital enhances the PHE activity; (ii) steric hindrances around the axial site of the square-planar Pt(II) coordination sphere lower the PHE activity; (iii) an appropriate aromaticity is needed to enhance the intramolecular electron transfer processes; (iv) EDTA forms an adduct with a PHEMD before undertaking the H_2 generation; (v) the H_2 formation undergoes via a bimolecular process of the PHEMD. In addition to these results, the electrochemical studies, stopped flow experiments looking at the reactions between the Pt(II) complexes and a radical cation generated from methylviologen, and DFT MO investigations have been examined. Less
|
