May 17 2010
Kazuhiro Sayama, Yugo Miseki, et al. of Solar Light Energy Conversion Group, the Energy Technology Research Institute of the National Institute of Advanced Industrial Science and Technology, developed a tungsten oxide (WO3) photocatalyst that provides a significantly higher quantum yield under visible light than conventional photocatalysts.
A photocatalyst-electrolysis hybrid system using this photocatalyst is a hydrogen production system in which solar light is efficiently used. The AIST's original system employs the photocatalyst that generates oxygen by oxidizing water and reducing iron(III) ions (Fe3+) to iron(II) ions (Fe2+). The system also involves low-voltage electrolysis in which water is reduced to generate hydrogen and Fe2+ ions are oxidized to Fe3+ ions.
The high efficiency of the WO3 photocatalyst was achieved using a new method—treatment of the surface of the photocatalyst with Cesium (Cs). The activity of the treated catalyst is more than ten times that of untreated catalysts. The quantum yield of the new photocatalyst is 19% under visible light of wavelength 420 nm and is approximately 50 times the previously reported values (0.4%)*. The use of solar energy can reduce the voltage required for water electrolysis by almost 50%. Hence, the low-cost production of hydrogen is expected.
The details of this technology will be presented on March 19, 2010 at the symposium organized by the Energy and Environment Study Group at the 57th Spring Meeting, 2010, of the Japan Society of Applied Physics to be held at Tokai University.