Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-V-19A PHOTOCATALYTIC REACTOR FOR SEPARATE HYDROGEN ANDOXYGEN EVOLUTION FROM WATER SPLITTINGGian Luca Chiarello, Elena Selli, Lucio ForniDipartimento di Chimica Fisica ed Elettrochimica, Università degli Studi di Milano,Via Golgi 19, 20133 Milano, fax: +39 02 503 14300, e-mail: gianluca.chiarello@unimi.itThe photocatalytic splitting of water into hydrogen and oxygen using solar energy is achallenging research topic which has received much attention in recent years for its potentialto provide clean and renewable H 2 as an energy resource. Almost all photocatalytic watersplitting systems described so far imply the evolution of a mixture of hydrogen and oxygen;of course, a separation step would be required prior to any use of hydrogen.A Plexiglas cell [1] has been set up, which6H 2 SO 4NaOHallows the separate evolution of the two gases,solutions, separated by a 10 cm 2 hνtitanium disk13(1); a thin titanium dioxide layer had beenPt TiO 2resulting in streams of hydrogen and oxygen57O 2that do not need any further purification. Thetwo cell compartments (see Fig. 1) were filledwith NaOH (side A) and H 2 SO 4 (side B) waterH 2 4deposited by radio frequency magnetron2Side BSide Asputtering on the irradiated disk face in contactwith the basic solution, while platinum wasFig. 1 Sketch of the cell for photocatalytic waterdeposited on the opposite side. TiO 2 depositionat 600°C led to the formation of a layer of purerutile phase, whereas deposition at 450°C led tosplitting, with separate H 2 and O 2 evolution:1 titanium disk;2 cation exchange membrane;3 glass filter;4 burette;5 stopcock;the formation of a mixture of almost equal6 rubber septum;amounts of rutile and anatase phases. A cation 7 reservoir.exchange membrane (2) was mounted below the photoactive titanium disk, in the frameseparating the two cell compartments. Upon illumination of side A of the cell (Fig. 1) througha square window, in which different cut off glass filters could be inserted (3), water splittinginto molecular hydrogen and oxygen occurs at almost constant rate. The evolved gases can becollected in the two upside down burettes (4) surmounting the two cell compartments.The rates of H 2 and O 2 evolution under irradiation with differently filtered light (cut offfilters at 300, 350 and 400 nm) were evaluated by taking into account the effective204