PEM Fuel Cell Contamination: Effects of Operating Conditions on Toluene-Induced Cathode Degradation

Abstract

Toluene, one of many volatile organic compounds existing in the atmosphere, was studied as an impurity or contaminant in the airstream of proton exchange membrane ͑PEM͒ fuel cells. The effects of toluene contamination on fuel cell performance were investigated with constant-current polarization discharge under various operating conditions, including current density, back pressure, and air stoichiometry. The severity of the contamination increased with increasing current density, toluene concentration, and air stoichiometry, but decreased with increasing back pressure. The effect of toluene contamination on current dynamic operation was also studied by cycling the current density from 0.0 to 0.2 A cm −2 and then to 1.0 A cm −2 in the presence of toluene. Cell performance degradation during current dynamic operation was accelerated by the presence of toluene. Electrochemical impedance measurements and analysis revealed that both kinetic resistance and mass transfer resistance were increased as a result of toluene contamination, but the increase in kinetic resistance was dominant.Proton exchange membrane ͑PEM͒ fuel cells are considered promising clean-energy converting devices due to their high efficiency, high power density, and low/zero emissions in portable, residential, and automobile applications. However, major technical challenges, such as high cost and unsatisfactory durability/reliability, are hindering the commercialization of this technology.With respect to the issue of durability/reliability, great efforts have been made in recent years to identify failure modes and develop corresponding mitigation strategies. Fuel cell contamination caused by impurities or contaminants in the feed streams or from fuel cell components has been identified as one of the significant factors contributing to the failure modes of PEM fuel cells. 1-5 Impurities damage the membrane electrode assembly ͑MEA͒ by affecting both anode and cathode catalyst layers ͑CLs͒, the gas diffusion layers ͑GDLs͒, as well as the membrane, causing MEA degradation or even fuel cell failure. Correspondingly, the contamination effects of impurities on a PEM fuel cell fall into three categories: kinetic effect, caused by the poisoning of both anode and cathode catalyst sites; mass transfer effect, due to changes in the structure and hydrophobility of the CLs or GDLs; and conductivity effect, caused by the increase in resistance of the membrane and ionomer.Extensive research has been done on contamination caused by fuel-side impurities, such as CO, H 2 S, and NH 3 . 2,3,6-10 However, there has been much less research on the impact of air-side impurities, including NO x , SO x , CO x , and volatile organic compounds ͑VOCs͒. 11-13 Studying the effect of atmospheric impurities on the durability of the fuel cell is an effort toward overcoming fuel cell contamination problems and developing mitigation strategies to improve the environmental adaptability of the fuel cell system.Our previous paper is the first reported study of the contamination effect of tol...

PEM fuel cell cathode contamination in the presence of cobalt ion (Co2+)

“…This problem, manifested as performance degradation, could be the result of Pt catalyst agglomeration and dissolution, catalyst carbon support corrosion, membrane degradation, and fuel cell contamination caused by feed stream and component impurities [2][3][4][5][6]. These impurities may be present in the fuel (e.g., CO, H 2 S, NH 3 , and hydrocarbons) [7][8][9][10] and/or in the air (e.g., NO x ,S O x ,C O x , and some volatile organic compounds [VOCs]) [11][12][13][14], and may originate from the fuel cell components and system (e.g., Fe 3+ ,Cu 2+ , and Cr 3+ ) or from the alloy catalysts (e.g., Co 2+ ,Ni 2+ , and Fe 3+ ) [15].…”

Influence of toluene contamination at the hydrogen Pt/C anode in a proton exchange membrane fuel cell

“…on the cathode side in a PEM fuel cell was studied by Li et al [15,16]. By constant current polarisation and electrochemical impedance spectroscopy (EIS) measurements, it was revealed that traces of toluene in the air feed cause performance losses in the fuel cell.…”

Effect of Co2+ on oxygen reduction reaction catalyzed by Pt catalyst, and its implications for fuel cell contamination

“…In the last several years, significant progress has been made in identifying impurity sources and understanding their impacts on fuel cell performance [6][7][8][9][10][11][12][13][14]. For example, the primary impurities in hydrogen fuel are CO, H 2 S, NH 3 , and hydrocarbons deriving mainly from hydrogen-rich reformate gas; the major impurities in the air stream include NO x (NO 2 and NO), SO x (SO 3 and SO 2 ), and CO x (CO 2 and CO), as well as some volatile organic compounds (VOCs).…”