Phase Transformation Dynamics in Sulfate-Loaded Lanthanide Triphosphonates. Proton Conductivity and Application as Fillers in PEMFCs.

Phase transformation dynamics and proton conduction properties are reported for cationic layer-featured coordination polymers derived from the combination of lanthanide ions (Ln) with nitrilo-tris(methylenephosphonic acid) (HNMP) in the presence of sulfate ions. Two families of materials are isolated and structurally characterized, i.e., [Ln(HNMP)(HO)](HSO)·HO (Ln = Pr, Nd, Sm, Eu, Gd, Tb, Er, Yb; = 4-5, ) and [Ln(HNMP)]SO·2HO (Ln = Pr, Nd, Eu, Gd, Tb; ). Eu/Tb bimetallic solid solutions are also prepared for photoluminescence studies. Members of families and display high proton conductivity (10 and 10 S·cm at 80 °C and 95% relative humidity) and are studied as fillers for Nafion-based composite membranes in PEMFCs, under operating conditions. Composite membranes exhibit higher power and current densities than the pristine Nafion membrane working in the range of 70-90 °C and 100% relative humidity and with similar proton conductivity.