Electronic and atomic structures of gasochromic V₂O₅ films

¹ Institute of Physics, Academia Sinica - Taipei 11529, Taiwan
² National Synchrotron Radiation Research Center (NSRRC) - Hsinchu 30076, Taiwan
³ Department of Mechanical Engineering and Institute of Manufacturing Technology, National Taipei University of Technology - Taipei, 106, Taiwan
⁴ Department of Science, Institute of Technology Tallaght (ITT Dublin) - Tallaght, Dublin 24, Ireland, EU

^(a) clchen@phys.sinica.edu.tw
^(b) dong.cl@nsrrc.org.tw

Received: 29 October 2012
Accepted: 20 December 2012

Abstract

A gasochromic Pt/V₂O₅ film was fabricated by the sol-gel process and it exhibited excellent color change performance from yellow to gray/black upon exposure to hydrogen gas under ambient conditions. X-ray absorption spectroscopy was employed to study the unoccupied electronic states in detail and to explore the gasochromic effect and its coloration mechanism. Upon injection of hydrogen, gashochromism was revealed to correlate strongly with the change of both electronic and atomic structures. Since the hydrogen supplied an extra electron, the hybridization between vanadium 3d and oxygen 2p was modified, reducing the valence state of vanadium from 5 +  to 4.1 + . Linear polarized synchrotron X-rays were utilized to investigate the change in the structural symmetry and the orbital orientation. Along with the electronic structure, the geometric modulation of the VO₆ octahedron is crucial to the gasochromic mechanism, as also revealed in this study.