The interaction of 20 wt% 12-tungstophosphoric acid with Ce x Zr 1 − x O 2 solid solutions has been studied by PXRD, FTIR, FT-Raman, H 2-TPR, NH 3-TPD, diffuse reflectance UV-vis-NIR, and 31P MAS NMR techniques. The study indicates that the Keggin anions are attached to Lewis metal ion centres and anion vacancies on Ce x Zr 1 − x O 2 supports through W O terminal bonds. The Keggin units at the interface are chemically perturbed as indicated by non-intrinsic IR bands observed at 958 cm −1 (W O ter bond), and 1052, 1102 cm −1 (P O bond). NH 3-TPD shows that the Keggin anions fixed to Lewis sites and/or oxygen ion vacancies decrease the ammonia uptake on Ce x Zr 1 − x O 2 solid solutions. H 2-TPR shows modified redox behaviour of Ce x Zr 1 − x O 2 solid solutions due to the simultaneous reduction of ceria, decomposition of Keggin anions and the reduction of WO 3. The broadening of 31P MAS NMR and DR-UV-vis-NIR spectra demonstrate the existence of chemical interactions between the Keggin anions and Ce x Zr 1 − x O 2 supports.