1. Chemistry Department Seminar

    "Metal-Oxide-Semiconductor (MOS) Photoelectrodes for Efficient Solar Water Splitting"

    Presented by Dr. Daniel Esposito, Postdoctoral Associate at the National Institute of Standards and Technology (NIST)

    Friday, March 8, 2013, 11 am
    Room 300, Chemistry Bldg. 555

    Hosted by: Alex Harris

    Solar-driven water splitting with photoelectrochemical cells is an attractive pathway for renewable production of hydrogen, but the efficiency and stability of semiconducting photoelectrodes must be improved. One promising approach to achieving high efficiency and good electrochemical stability is the metal-oxide-semiconductor (MOS) photoelectrode design. Silicon is a commonly used photovoltaic material that is attractive for use in MOS photo-electrodes, but the performance of Si-based MOS electrodes demonstrated to date has been very poor. In this seminar, I will describe a systematic approach to improving the performance of Si-based MOS photocathodes that is based on studying well-defined arrays of MOS structures with in-situ scanning probe techniques. Specifically, scanning photocurrent microscopy (SPCM) and scanning electrochemical microscopy (SECM) have been combined to simultaneously record images of quantum efficiency and catalytic activity on MOS photocathodes with high spatial resolution. I will show how this powerful combination of techniques can be used as a diagnostic tool, for predicting optimal MOS geometries, and elucidating complex interfacial charge transfer phenomenon. A major focus of this talk will be the use of combined SPCM/SECM in revealing the occurrence of lateral charge carrier collection through inversion layers and a hydrogen-spillover assisted H2 evolution mechanism on MOS photocathodes. These findings have important implications for the optimization and design of MOS photoelectrodes, as well as MOS devices for other applications. I will also discuss several other aspects of this research project, including modeling efforts, interfacial engineering in MOS junctions, and integration of MOS photocathodes into stand-alone water splitting devices. Dr. Esposito received his B.S. in chemical engineering from Lehigh University and his Ph.D. in chemical engineering from the University of Delaware. He is cur