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Methanol crossover from the anode to the cathode through the polymer electrolyte membrane (PEM) has been one of the detrimental factors affecting the performance of direct methanol fuel cells (DMFCs). Extensive research work has been in progress for developing CH 3 OH crossover tolerant electrolyte membranes. The need for assessing CH 3 OH crossover by an easier and faster method than the conventional CO 2 analysis method has become significant. For this, a potentiometric method has been developed and tested using the Nafion membrane. By recording the potential ( E ) of a PtRu/C electrode in 0.2 M H 2 SO 4 supporting electrolyte during CH 3 OH crossover, it has been shown that the slope (d E /d t ), of E versus t (time) curve, is proportional to the crossover rate. From the time required to reach the equilibrium concentration of CH 3 OH on either side of the polymer electrolyte membrane, CH 3 OH crossover rate has been calculated. This method is expected to be useful in studying polymer electrolyte membranes and also in industry as a quality control technique. The method can also be used to sense methanol concentration.

A composite solid polymer electrolyte (CSPE) consisting of polyethyleneoxide (PEO), LiClO4 and Al2O3 of particle size 24 nm was prepared by a melt-cast method. The differential scanning calorimetry (DSC) data suggested that the CSPE is in an amorphous state due to the presence of nanophase alumina. The specific conductivity versus temperature follows Vogel–Tamman–Fulscher (VTF) behavior and the activation energy has been calculated. By analogy with the Marcus theory of solvent reorganization during electron-transfer reactions, the reorganization energy of the polymer chain has been calculated from the energy of activation of ionic conduction. The ac impedance data was analyzed using a non-linear least square (NLLS) fitting program, and the resistance of the passivating film on Li and the charge-transfer resistance of the Li reaction have been evaluated. The charge-transfer resistance has been shown to follow Arrhenius behavior through the standard rate constant for the reaction. Cyclic voltammograms provided evidence of electrochemical activity at the Li/CSPE interface near ambient temperature.

Several solid electrolytes derived from poly(ethylene oxide) doped with lithium tetrafluoroborate and a high conductivity lithium borosulfate glass were formulated and investigated for their electrochemical performance. The electrochemical characterization included a.c. impedance measurements, the temperature dependence of conductivity, scanning electron microscopy (SEM), cyclic voltammetry (CV), and the charge/discharge cycling of symmetric cells. the ionic conductivities of these electrolytes at ambient temperature were around 10 −7 S cm −1 . Although no significant improvement in conductivity was observed, the cyclic voltammetry, impedance spectroscopy, and cycling data on Li/polymer/Li and Li/polymer/ Ni cells reveal that the electrode reactions are facilitated by the glass incorporation.