Electronic and atomic structures of gasochromic V ₂ O ₅ films

A gasochromic Pt/V 2 O 5 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 3 d and oxygen 2 p 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 VO 6 octahedron is crucial to the gasochromic mechanism, as also revealed in this study.