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

Abstract

A LaMnO₃/CdS nanocomposite was prepared by a reverse micelle method and examined for its photocatalytic activity for H₂ production from water containing electron donors (Na₂S and Na₂SO₃) under visible light irradiation (λ > 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 H₂; this charge-carrier separation is responsible for the improved activity.