LaTiOxNy Thin Film Model Systems for Photocatalytic Water Splitting: Physicochemical Evolution of the Solid–Liquid Interface and the Role of the Crystallographic Orientation |
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| Authors: | Markus Pichler Wenping Si Fatima Haydous Helena Téllez John Druce Emiliana Fabbri Mario El Kazzi Max Döbeli Silviya Ninova Ulrich Aschauer Alexander Wokaun Daniele Pergolesi Thomas Lippert |
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| Affiliation: | 1. Neutron and Muon Research Division, Paul Scherrer Institut, Villigen‐PSI, Switzerland;2. Electrochemical Energy Conversion Division, International Institute for Carbon‐Neutral Energy Research (I2CNER), Kyushu University, Fukuoka, Japan;3. Energy and Environment Research Division, Paul Scherrer Institut, Villigen‐PSI, Switzerland;4. Ion Beam Physics, ETH Zurich, Zurich, Switzerland;5. Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland;6. Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Zurich, Switzerland;7. Molecular Photoconversion Devices Division, International Institute for Carbon‐Neutral Energy Research (I2CNER), Kyushu University, Fukuoka, Japan |
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| Abstract: | The size of the band gap and the energy position of the band edges make several oxynitride semiconductors promising candidates for efficient hydrogen and oxygen production under solar light illumination. Intense research efforts dedicated to oxynitride materials have unveiled the majority of their most important properties. However, two crucial aspects have received much less attention: One is the critical issue of compositional/structural surface modifications that occur during operation and how these affect photoelectrochemical performance. The second concerns the relation between electrochemical response and the crystallographic surface orientation of the oxynitride semiconductor. These are indeed topics of fundamental importance, since it is exactly at the surface where the visible‐light‐driven electrochemical reaction takes place. In contrast to conventional powder samples, thin films represent the best model system for these investigations. This study reviews current state‐of‐the‐art oxynitride thin film fabrication and characterization, before focusing on LaTiO2N, selected as a representative photocatalyst. An investigation of the initial physicochemical evolution of the surface is reported. Then, it is shown that after stabilization the absorbed photon‐to‐current conversion efficiency of epitaxial thin films can differ by about 50% for different crystallographic surface orientations, and be up to 5 times larger than for polycrystalline samples. |
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| Keywords: | oxynitride thin films photoelectrochemical water splitting pulsed laser deposition solar water splitting |
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