Photocatalytic hydrogen production from water over a LaMnO3/CdS nanocomposite prepared by the reverse micelle method

A LaMnO3/CdS nanocomposite was prepared by a reverse micelle method and examined for its photocatalytic activity for H-2 production from water containing electron donors (Na2S and Na2SO3) under visible light irradiation (lambda > 420 nm). The prepared LaMnO3/CdS nanocomposite of 10-20 nm particle size showed 6 times higher photocatalytic activity than that of CdS; on the other hand, LaMnO3 showed no photocatalytic activity. It was also found that LaMnO3/CdS can continuously produce hydrogen from water in the presence of electron donors for more than 200 h. In order to account for the improvement in the activity, the valence edge potentials of CdS and LaMnO3 were investigated by photoemission yield measurements. The proposed energy band scheme for the LaMnO3/CdS composite suggests that photogenerated holes in the valence band of CdS can move to that of LaMnO3 and react with Na2S while photogenerated electrons remain in the conduction band of CdS and react with water to produce H-2; this charge-carrier separation is responsible for the improved activity.