Ryota Doi

Hydrogen production from water and conversion of carbon dioxide to useful chemicals by room temperature photoelectrocatalysis

Abstract A thin film anatase titania photocatalyst having 60% quantum efficiency measured without applied bias potential can produce hydrogen from water at rates of 26 with bias by a mercury lamp as a light source and 0.075 to 0.42 without bias by the sunlight both in units of 1/h/m 2 -irradiation cross section on photocatalyst surface and a single unit photoelectrocatalysis system can be formed with the photocatalyst and an electrocatalyst consisting of zinc oxide and copper which when combined together can stably convert 82% of carbon dioxide to hydrocarbons in terms of current efficiency including 44% for methane and 24% for ethylene without deactivation of the reactions by operating the system under a pulsed bias between the photocatalyst and the electrocatalyst.

Photoelectrocatalytic hydrogen production from wateron transparent thin film titania of different crystal structures and quantum efficiency characteristics

Abstract Quantum efficiency of transparent thin film titania photocatalysts under constant photon irradiation during room-temperature water decomposition reaction without external bias potential was measured for the first time as the wavelength was scanned between 250 and 1200 nm. It decreased as the crystal structure of titania was systematically varied from anatase to mixtures of anatase and rutile and then to rutile. The same trend was observed for photocurrents measured under external bias potential. These results indicate structure sensitivity of the reaction and intrinsic advantage of anatase over rutile. The anatase sample tested in a single unit photoelectrocatalysis (SUPEC) cell produces hydrogen at the rates of 0.42 1 h −1 m −2 without bias under sunlight and 26 1 h −1 m −2 with bias under 500 W mercury lamp wherethe area is the cross-section of light irradiation. Structural analyses of the photocatalysts include atomic force microscopy, laserRaman spectroscopy and X-ray diffraction.