All-in-one visible-light-driven water splitting by combining nanoparticulate and molecular co-catalysts on CdS nanorods

Abstract

Full water splitting into hydrogen and oxygen on semiconductor nanocrystals is a challenging task; overpotentials must be overcome for both half-reactions and different catalytic sites are needed to facilitate them. Additionally, efficient charge separation and prevention of back reactions are necessary. Here, we report simultaneous H2 and O2 evolution by CdS nanorods decorated with nanoparticulate reduction and molecular oxidation co-catalysts. The process proceeds entirely without sacrificial agents and relies on the nanorod morphology of CdS to spatially separate the reduction and oxidation sites. Hydrogen is generated on Pt nanoparticles grown at the nanorod tips, while Ru(tpy)(bpy)Cl2-based oxidation catalysts are anchored through dithiocarbamate bonds onto the sides of the nanorod. O2 generation from water was verified by 18O isotope labelling experiments, and time-resolved spectroscopic results confirmed efficient charge separation and ultrafast electron and hole transfer to the reaction sites. The system demonstrates that combining nanoparticulate and molecular catalysts on anisotropic nanocrystals provides an effective pathway for visible-light-driven photocatalytic water splitting. While the two individual half-reactions involved in visible-light-driven water splitting are well studied, producing H2 and O2 simultaneously on a single particle remains challenging. Here, the authors achieve this by decorating CdS nanorods with both Pt nanoparticles and molecular Ru complexes to catalyse the evolution of H2 and O2, respectively.