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·H2O nanoplates. PtS and MnO2, the co-catalysts for H2 and O2 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 H2 and O2 under visible light. An optimum activity was achieved over 0.5%PtS-20%ZnIn2S4/WO3-3.0%MnO2, in which 5.94 μmol of H2 and 2.24 μmol O2 were evolved in 8 h. The apparent quantum yield (AQY) for H2 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.