Electronic and atomic structures of gasochromic V_2O5 films

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.