265310 Development of Quantum Confined MoS2 for Enhanced Photoelectrochemical Water Splitting

Wednesday, October 31, 2012: 8:30 AM
316 (Convention Center )
Zhebo Chen, Arnold Forman and Thomas F. Jaramillo, Chemical Engineering, Stanford University, Stanford, CA

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.

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