Performance of a polymer electrolyte membrane fuel cell exposed to transient CO concentrations

The response of Gore's advanced PRIMEA(R) Series 5561 membrane electrode as sembly (MEA) exposed to transient concentrations of CO in the anode feed wa s studied for a 25 cm(2) laboratory-scale polymer electrolyte membrane fuel cell (PEMFC). The data include relatively high (500 and 3000 ppm) CO level s at 70 degreesC cell temperature, low reactant stoichiometry, and atmosphe ric pressure, conditions that may be typical for stationary PEMFC applicati ons. Poisoning and recovery rates are reported for saturated conditions and these rates are compared for two types of gas diffusion media [single-side d ELAT(R) and CARBEL(TM) CL gas diffusion media (GDM)] and for conditions w ith and without air-bleed treatments, It is shown that a 5% air bleed provi des a current density of 1.0 A/cm(2) at 0.6 V for CARBEL CL GDM exposed to 500 ppm CO/H-2 mixtures. The data show that the transient performance at 0. 6 A/cm(2) with this MEA and relatively high concentrations of CO is a resul t of an interaction of CO kinetics and mass transfer through the GDM. Indir ect evidence of electrochemical oxidation of CO during the transient pulses with 3000 ppm CO is presented. The data discussed in this paper are suitab le for verifying numerical models of a PEMFC and establishing a baseline fo r new recovery schemes using new MEAs with enhanced CO tolerance. In additi on, the results have implications for the design of reformate fuel processi ng systems and the use of effective control schemes to prevent CO transient s. (C) 2001 The Electrochemical Society.