Study of low concentration CO poisoning of Pt anode in a proton exchange membrane fuel cell using spatial electrochemical impedance spectroscopy

This paper presents experimental and modeling results of the effect of low CO concentration (2 ppm) on the spatial performance of PEMFC as well as its spatial electrochemical impedance spectroscopy (EIS) responses. The cell was operated at constant current using various cathode gases: air, O2 and H2. Due to CO adsorption on the Pt anode and its poisoning, the cell voltage decreased and spatial current redistribution was observed. The steady state voltage losses were 0.089, 0.280 and 0.295 V for the H2/O2, H2/air and H2/H2 gas configurations, respectively. EIS data revealed a pseudo-inductive behavior in the low frequency region for inlet segments of the cell operated under H2/air and H2/H2 conditions. Operation with O2 as an oxidant did not cause any pseudo-inductance. Analysis of the EIS and anode overpotential data suggested that CO oxidation occurred via chemical or electrochemical mechanisms, or a combination of both depending on the selected cathode gas. The spatial EIS data were analyzed using the equivalent electric circuits approach. The distributions of the equivalent electric circuit parameters are presented and discussed. A current distribution model and EIS interpolation technique were successfully applied for detailed analysis of CO effects on the spatial PEMFC performance and EIS.