Se prepararon membranas de Polivinil Difluoruro y Acido Hipofosforoso (PVDF/H3PO2) con diferentes concentraciones de ácido. Los resultados de calorimetría diferencial de barrido (DSC), presentan un escalón característico de la transición vítrea alrededor de 250 K. También se observan dos anomalías endotérmicas: una cercana a 357 K debido a la evaporación de agua, y otra cerca a los 422 K atribuida a la fusión de la fase cristalina del PVDF. Los análisis de Espectrometría de masas (MS) acoplado con Termogravimetría (TGA), revelan la posible presencia de moléculas de (C2H2O) y ácido fluorhídrico (HF), esto plantea la posibilidad de que el H3PO2 perdió un átomo de hidrógeno y se enlazó a la cadena polimérica del PVDF desplazando un átomo de flúor. Se evidencia la presencia de moléculas de agua a diferentes temperaturas, que sugiere la formación de agua superficial, interna y estructural en el sistema polímero-acido. Esta característica, hace que el sistema PVDF/H3PO2 sea propuesto como electrolito solido en celdas de combustible.
Polyvinylidene fluoride (PVDF) and hypophosphorous acid (H3PO2) are combined to synthesize solid polymer electrolyte membranes using the solution cast method. Electrochemical impedance spectroscopy measurements are used to find the conductivity, and those values are plotted as a function of relative humidity (% RH) to which the membranes are kept. In agreement with the modified Onsager, the results show growth in conductivity as % RH increases, which states that ionic mobility of a polar polymeric phase increases as levels of absorbed water by the polymeric membrane increase. The high values of conductivity observed at high concentrations of H3PO2 (σ = 9.83 × 10−3 S cm−1 for x = 60% wt) are attributed to the increase of charge carriers and the dissociation of ions in an aqueous phase. The synthesized membranes are tested as electrolytes in a fuel cell and the voltage and power density plotted as a function of the current density with maxim values of the power density of 2.88 mW cm−2 for a 30% wt membrane.
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