Physical, spectroscopic and electrochemical information on the potentiostatically synthesized hybrid material polypyrrole/PW12O403- was obtained by means of electron microscopy, W-vis spectroscopy, in situ UV-vis absorption -reflection spectroelectrochemistry, FTIR spectroscopy, EDX and cyclic voltammetry. The hybrid shows a very flat morphology and a two-layer structure after its generation. By reduction, the external layer, 76% weight of the material, is electrodissolved. This fraction contains PW12O403- anions and pyrrole oligomers. Continuous potential cycling of the insoluble hybrid adhered to the electrode gives rise to an increasing concentration of polyoxometalate in the background solution, thus proving that phosphotungstate anions were gradually rejected from the film. Films before and after electrodissolution of the soluble fraction show similar flat morphology. The insoluble fraction undergoes a strong morphological change during potential cycling, keeping almost constant both weight and stored charge. The oxidized state of the electrosoluble layer is partially soluble in DMSO and in mixtures of PC and EC, thus opening new ways for processing those materials. The two-layer structure of polypyrrole-based hybrid materials was also observed for other polyoxometalates, synthesized in different electrolytic media.