Abstract: The invention is based on the preparation of precursor organic solutions of tetravalent metal phosphates and pyrophosphates with composition M(IV)(O3P—H)2, M(IV)[O2P(OH)2]2[O2PO(OH)] and M(IV)P2O7(M=Zr, Hf, Ti). An important property of these solutions is that the said compounds are formed when the solvent is evaporated. This peculiarity allows an easy insertion of the compounds inside the pores of porous membranes, in polymeric membranes and in the electrodic interfaces of fuel cells. The acid properties of their surfaces, the high thermal stability and the insolubility in water make these particles extremely of interest for improving the efficiency of PEMFCs in the temperature range 90-130° C. The peculiar characteristics of non-water assisted proton conductivity of M(IV)[O2P(OH)2]2[O2PO(OH)] compounds open new prospects for their application in PEMFCs at low relative humidity.