Rational design of Z-scheme PtS-ZnIn2S4/WO3-MnO2 for overall photo catalytic water splitting under visible light

ZnIn2S4/WO3 nanocomposites, with ZnIn2S4 nanosheets loaded on WO3 nanorods, were synthesized by self assembly of hexagonal ZnIn2S4 in the presence of preformed WO3 center dot H2O nanoplates. PtS and MnO2, the co-catalysts for H-2 and O-2 evolution, respectively, were selectively loaded on ZnIn2S4 and WO3 in the nanocomposites. The resultant PtS-ZnIn2S4/WO3-MnO2 nanocomposites show photocatalytic activity for overall water splitting to produce H-2 and O-2 under visible light. An optimum activity was achieved over 0.5%PtS-20%ZnIn2S4/WO3-3.0% MnO2, in which 5.94 mu mol of H-2 and 2.24 mu mol O-2 were evolved in 8 h. The apparent quantum yield (AQY) for H-2 evolution was determined to be ca. 0.50% at 420 nm. The superior photocatalytic activity for overall water splitting over PtS-ZnIn2S4/WO3-MnO2 nanocomposites can be ascribed to an efficient coupling of photocatalytic water reduction over PtS-ZnIn2S4 and photocatalytic water oxidation over MnO2-WO3 via a Z-scheme charge transfer pathway. This study demonstrates a high potential of fabrication of the all-solid Z-scheme photocatalytic systems for overall water splitting.