Contamination of Pt Catalyst with Carbon Monoxide during Hydrogen Evolution

Abstract

Absorption of carbon monoxide (CO) on the platinum catalyst hampers the hydrogen oxidation and evolution reactions by affecting the reaction kinetics and reducing the electrochemical active surface area [1, 2]. In this paper, we use electrochemical impedance spectroscopy (EIS) to investigate the electrode poisoning on the hydrogen evolution reaction (HER) with the presence of CO. Single cell proton exchange membrane fuel cell (PEMFC) hardware with a low loading catalyst coated membrane (CCM) is operated in electrochemical hydrogen pump (EHP) mode. EIS data is collected every 5 minutes during poisoning with pure H2 or CO-H2 mixture on the anode and cathode. The Nyquist plot shows only one semicircle due to reaction kinetics, and this semicircle diameter increases significantly with time. EIS measurements are performed in galvanostatic and potentiostatic modes. Both methods show that cathode poisoning has significant influence on hydrogen evolution, however, electrochemical surface area is significantly reduced at constant potential compared to constant current. At constant current operation, cell potential tends to increase accelerating the removal of CO. The highest impact on reaction kinetics is observed while both anode and cathode electrodes are poisoned at the same time. Anode electrode poisoning is more effective than cathode electrode poisoning on the rate of oxidation and evolution reactions at constant current. However, both electrodes have similar impacts at constant potential. Moreover, over potential of the anode electrode increases significantly during the CO poisoning at constant current operation compared to over potential of cathode electrode. References G.A. Camara, E.A. Ticianelli, S. Mukerjee, S.J. Lee and J. McBreen, 149(6), A748 (2002).N.R. Elezovic, Lj. Gajic-Krstajic, V. Radmilovic, Lj. Vracar and N.V. Krstajic, Electrochim. Acta, 54, 1375 (2009). Figure 1