Redox-induced structural changes in Keggin-type tungstophosphate investigated by high-energy-resolution fluorescence detection X-ray absorption spectroscopy

T. Matsuyama, S. Kikkawa, N. Kawamura, K. Higashi, S. Yamazoe

Rad. Phys. Chem., accepted.

Redox-active heteropolyanions are widely applied to electron acceptors and redox catalysts and the understanding of their reduced states in solution is essential. In this study, the structural changes of Keggin-type [PW12O40]3- induced by electrochemical reduction were investigated using W L3-edge X-ray absorption near-edge structure (XANES) spectra in high-energy-resolution fluorescence detection (HERFD) mode. W L3-edge HERFD-XANES revealed the changes in the electronic state of W species and local structure of {WO6} units, which were negligible in conventional transmittance mode; the peak intensities of the split two white line peaks were switched by the electrochemical reduction accompanied by enlargement of the splitting width. Our findings suggest that the injected electron was delocalized on whole {WO6} units in [PW12O40]3- and that the improved symmetry of {WO6} units compensated for the change in valence due to the injected electron.