(418a) Development of Quantum Confined MoS2 for Enhanced Photoelectrochemical Water Splitting

MoS₂ is a layered chalcogenide semiconductor that exhibits unique optical properties at the nanoscale.  Specifically, quantum confinement leads to enlargement of the bandgap and presents an interesting opportunity to engineer a more ideal band structure for photoelectrochemical water splitting.  Yet, nanostructured MoS₂ possesses a higher population of surface defect states that may either serve as highly active sites that enhance catalysis for hydrogen evolution or as centers for photogenerated charge carrier recombination.  By using a progressive in-situ surface state generation approach, we investigate the interplay between these effects on the overall photoelectrochemical activity of bulk crystalline MoS₂.  This unique methodology allows us to simultaneously assess catalytic activity for hydrogen evolution, photoactivity, and Fermi level pinning as a function of surface states.  We also present photoelectrochemical measurements on various morphologies of nanostructured MoS₂, including core-shell nanowires, mesoporous double-gyroid thin films, and quantum confined nanoparticles.  We unite the markedly different properties of bulk vs. nanostructured MoS₂, and discuss strategies for enabling highly active nanostructured MoS₂ photocatalysts.  The implications in this study broadly affect the development of nanostructured materials for photoelectrochemical and photovoltaic applications, and demonstrate how consideration of surface state defects is a critical step towards guiding material development.