UV-vis spectroscopy studies of H3PMo12−xWxO40 heteropolyacid (HPA) catalysts in the solid state: Effects of water content and polyatom substitution

UV-vis spectroscopy studies of solid state H3PMo12−xWxO40 (x = 0, 3, 6, 9, 12) catalysts were carried out. The solid HPA catalysts were treated at 25 °C (squares) and 330 °C (circles). The absorption edge energies of the H3PMo12−xWxO40 catalysts could be directly correlated with the reduction potentials of the HPA catalysts. The lower absorption edge energy corresponded to the higher reduction potential of the HPA catalyst.