Structural Analysis of Molybdenum Bronzes

Hydrogen molybdenum bronzes, H0.21MoO3 (type I) and H0.91MoO3 (type II) were characterized by Mo K-edge XAFS spectroscopy. XANES spectra showed that type I has an axially symmetric MoO6 unit which is mainly conncted to each other with vertices sharing and a MoO6 unit in type II are similar to that in MoO2. EXAFS spectra suggested that the MoOx sheet in type I is similar to MoO3 while in type II, a MoOx sheet is similar to that in rutile MoO2 in which MoO6 is conneced to form a chain by sharing the edges of opposite sides. The curve fitting analysis of Mo-O bonds for type I supported the earlier results obtained from diffraction and IR methods ; a MoO6 unit has C4v symmetry. In case of type II, D4h structure is possible and hydrogen is captured by Mo=O bonds resulting in the formation of Mo-OH bonds