Noble-metal-free Z-Scheme MoS2–CdS/WO3–MnO2 nanocomposites for photocatalytic overall water splitting under visible light

To fabricate an efficient two-component Z-scheme system for visible light induced overall water splitting, CdS/WO3 nanocomposites, with cubic CdS nanoparticles grown on the surface of hexagonal WO3 nanorods, were prepared via a facile precipitation of Cd2+ with S2− in the presence of pre-obtained hexagonal WO3 nanorods. MnO2 and MoS2, the co-catalysts for O2 and H2 generation respectively, were selectively deposited on WO3 and CdS in the CdS/WO3 nanocomposites. The resultant MoS2–CdS/WO3–MnO2 composites show photocatalytic activity for overall water splitting under visible light, with an optimized performance observed over 2.0%MoS2-0.2 CdS/WO3-1.0%MnO2. The visible light induced overall water splitting over MoS2–CdS/WO3–MnO2 nanocomposites can be attributed to the presence of a Z-scheme charge transfer pathway in the CdS/WO3 nanocomposites, ie, the transfer of the photo-generated electrons from the CB of WO3 to the VB of CdS to recombine with the photo-generated holes through an efficient interface between cubic CdS and hexagonal WO3. The left photo-generated holes in VB of WO3 and the photo-generated electrons in CB of CdS therefore can accomplish the water oxidation and water reduction simultaneously, with the assistance of the surface deposited cocatalysts (MnO2 and MoS2). This work demonstrated the great potential of fabricating the two-component direct Z-scheme photocatalytic systems for overall water splitting from two semiconductors with a staggered band structure.