4.8 Article

Surface Analysis of Perovskite Oxynitride Thin Films as Photoelectrodes for Solar Water Splitting

期刊

ACS APPLIED MATERIALS & INTERFACES
卷 13, 期 31, 页码 37785-37796

出版社

AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c06974

关键词

oxynitride; thin films; water splitting; surface; low-energy ion scattering; XPS

资金

  1. Paul Scherrer Institute
  2. International Institute for Carbon Neutral Energy Research (WPI-I2CNER)
  3. World Premier International Research Center Initiative (WPI), MEXT, Japan
  4. Swiss Excellence Governmental Scholarship

向作者/读者索取更多资源

Perovskite oxynitride semiconductors have emerged as promising photoelectrode materials for photoelectrochemical water splitting, with their surface characteristics and evolution playing a significant role in their PEC applications.
Perovskite oxynitride semiconductors have attracted huge interest recently as promising photoelectrode materials for photoelectrochemical (PEC) water splitting. Depicted by, the extensive studies of the PEC activity of oxynitride powder-based photoelectrodes and/or deposited thin-film electrodes. High-crystalline-quality, oxynitride thin films grown by physical vapor deposition are ideal model systems to study the fundamental physical and chemical properties of the surface of these materials, including their evolution. In this work, using a combination of high-sensitivity low-energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS), we monitor surface evolution of LaTiOxNy (LTON) and CaNbOxNy (CNON) thin films before and after the PEC characterizations. The as-prepared epitaxial LTON films show a preferential LaO termination at the surface layers, followed by a Tienriched subsurface. Whereas, the polycrystalline CNON thin films exhibit a non-uniform surface, with a mixed surface termination and a significant Ca-segregated subsurface. After the PEC characterizations, additional precipitated LaO species are found on the outer surface of the LTON epitaxial films. However, no significant surface change is observed on the polycrystalline CNON films by LEIS. The XPS analysis shows, an increase of the oxidized Ti and Nb cations (Ti4+ and Nb5+) after the PEC reaction in the LTON and CNON films, respectively. The initial drops in photocurrent for the LTON and CNON films are attributed to the changes in the surface chemical status. This work provides insight into the surface characteristics and evolution of LTON and CNON oxynitride thin films as photoelectrodes for PEC applications.

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