TDLAS-based water vapor monitoring in narrow channels of polymer electrolyte fuel cells using a single-ended fiber-optic sensor.

The dehydration of electrolyte membranes in polymer electrolyte fuel cells (PEFCs) operating under low-humidity conditions is a critical issue for achieving their high efficiency and high power density. To reduce the membrane dryout, it's necessary to investigate and control the water transport within working fuel cells. This study developed a single-ended fiber-optic sensor based on tunable diode laser absorption spectroscopy (TDLAS) and applied it to the real-time monitoring of the water vapor concentration in the narrow flow channel of a PEFC. The newly proposed wavelength modulation spectroscopy (WMS) technique enabled to quantify the mole fraction of water in the channel over the wide concentration range with high accuracy. The in-situ TDLAS measurement in the PEFC during a low-humidity and load-change operation revealed that the dynamic change of cell voltage is strongly correlated to the dry-wet transition in the anode channel.

Buffer-gas pressure broadening for the (3 0(0) 1)III <-- (0 0 0) band of CO2 measured with continuous-wave cavity ring-down spectroscopy.

Buffer-gas pressure broadening for the (3 0(0) 1)(III)<--(0 0 0) band of CO(2) in the 1600 nm region was investigated with continuous wave cavity ring-down spectroscopy within the temperature range 263-326 K. The measured absorption profiles were analyzed with Voigt functions. Pressure broadening coefficient, gamma(gas), and the temperature dependent parameter (broadening exponent), n, were determined for a variety of buffer gases: N(2), O(2), He, Ne, Ar, Kr and Xe. gamma(air) values estimated subsequently are 0.096(2) for R(0), 0.085(5) for P(8), 0.075(2) for P(16), 0.070(4) for P(26), and 0.069(2) for P(38) in units of cm(-1) atm(-1), where numbers in parentheses are one standard deviation in units of the last digits quoted. n(air) values are 0.77(4) for R(0), and 0.73(11) for P(8).