Band Gap Narrowing in Nitrogen-Doped La$_{2}$Ti$_{2}$O$_{7}$ with Transient Absorption Spectroscopy for Hydrogen Generation

ORAL

Abstract

Nitrogen doping was found to extend lanthanum dititanate's (LTO), La$_{2}$Ti$_{2}$O$_{7}$, absorption from 380 nm to 550 nm giving a promising 2.3 eV bandgap for solar water splitting. The increased band gap in conjunction with a lack of mid-gap trap states allows for visible light photoactivity. In this presentation, transient absorption spectroscopy with both a supercontinuum and a THz probe confirm N-doping creates a continuum of states slightly above the valence band (VB) of intrinsic LTO without harming carrier lifetimes. Lifetimes are measured for carriers excited from the VB to the CB as well as from the dopant continuum to the CB. The measured lifetimes reveal lifetimes that are comparable to intrinsic LTO due to the minimal density of mid-gap states introduced by the nitrogen dopant. The THz probe confirms the visible light excited carriers are mobile and not trapped by measuring frequency dependent conductivity. Further, by adding reduced graphene oxide (RGO) and gold nanoparticles to the N-doped LTO, carrier extraction is further increased, tripling hydrogen generation.

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Authors

  • Brandon Yost

    West Virginia University

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division

  • Scott Cushing

    National Radio Astronomy Observatory, Jodrell Bank Centre for Astrophysics, New York University Abu Dhabi, Naval Research Laboratory, CSIRO Astronomy and Space Sciences, George Mason University, ASTRON, NASA Goddard Space Flight Center, University of Wisconsin-Milwaukee,, Station de radioastronomie de Nancay, Columbia Astrophysics Laboratory, Max-Planck-Institut fur Physik, West Virginia Univ, West Virginia University, Lehigh University, Fraunhofer Institute for Physical Measurement Techniques, Department of Microsystems Engineering (IMTEK), Pennsylvania State University, Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA, Massachusetts Institute of Technology, University of Minnesota, Pennsylvania State Univ, University of Maryland, Towson University, Department of Physics, Villanova University, University of Virginia, Boston University, Univ of Maryland-College Park, Harvard University, The Pennsylvania State Unversity, University of Wisconsin-Madison, McMaster University, California State University - Long Beach, National Chiao Tung University, National Chiao Tung University, Taiwan, Ohio University, University of Rennes, UMR CNRS 6251, Rennes, France, University of Bordeaux, UMR 5804, Floirac, France, University of Bordeaux, UMR 5255, Talence, France, Sandia National laboratories, Livermore, CA, Department of Chemistry, West Virginia University, Morgantwon, WV, The Pennsylvania State University, University of Toronto, Departamento de F\'isica, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile, Cinvestav-Unidad Queretaro, Queretaro-76230, Mexico, Department of Physics and Astronomy, West Virginia University, Morgantown, WV-26505-6315, USA, The University of Arizona, TU Dortmund, Dortmund, Naval Air Warfare Center - Aircraft Division