Proton and water transport through polymer electrolyte membrane have great impacts on the cell performance under low relative humicity and high current density operation. In particular, proton transport are strongly related to state of water in the PEM. However, its mechanism is not yet fully understood. In this study, state of water in PEM was evaluated from OH stretching vibration mode obtained by micro-Raman spectroscopy. Density functional theory was adopted for the analysis of micro-Raman results. The results suggested that OH vibration peak around 3200 cm^-1 could be due to water molecule network, which affected proton conductivity under low relative humicity condition.
