Effects of Ethylene Glycol and Caprolactam on the ORR and HOR Performances of Pt/C Catalysts

Abstract

Ethylene glycol (EG) and caprolactam are two representative contaminant species either present in the fuel cell system or released by fuel cell system materials. The contamination effects of EG and caprolactam on the electro-catalytic performances of a Pt/C catalyst toward the oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) were investigated in acid media using the rotating ring/disk electrode (RRDE) technique. The Pt surface coverage increased with EG and caprolactam concentrations. The H 2 O 2 yield also significantly increased because of the effects of the two contaminants. The EG-and caprolactam-derived adsorbates reduce the ORR and HOR rates and modify the rate-determining step (change in Tafel Considering the inevitable depletion of conventional fossil fuels and the release of greenhouse gases into the Earth's atmosphere, it is necessary to look for renewable and clean energy supplies. Proton exchange membrane fuel cells (PEMFCs) are promising as clean energy sources for future automotive applications. However, the performance and durability of PEMFCs can be significantly decreased by the presence of contaminants in air and hydrogen or released by fuel cell system materials.1-3 Such species may adsorb on the Pt catalyst, penetrate into the ionomer and membrane, or compete with the main reactions, which decreases the active surface area, ionic conductivity of the catalyst layer and membrane, and cell performance. 2,4-9In addition, H 2 O 2 , which is a side product of the oxygen reduction reaction (ORR), and its associated yield often increases in the presence of organic contaminants such as acetylene, acetonitrile, propene, naphthalene, and methyl methacrylate. 10-13 A larger H 2 O 2 generation rate exerts an undetermined effect on the performance and durability of PEMFCs. The formation of H 2 O 2 has been linked to the radical attack decomposition of the Nafion ionomer, which is accelerated by the presence of Fe 2+ and Cu 2+ ions. 14,15 The Nafion ionomer is used as an electrolyte membrane and added to the catalyst layer to exploit its binding property and improve catalyst utilization. Consequently, the decomposition of the Nafion ionomer is a significant risk to the PEMFC performance and durability. Therefore, it is necessary to investigate the ORR, hydrogen oxidation reaction (HOR), and H 2 O 2 yield in the presence of contaminants to understand their effects on PEMFCs.This study was initiated with a list of system contaminants identified by the National Renewable Energy Laboratory (NREL).16 These were separated into 2 classes: linear and more structurally complex molecules including cyclic molecules (ring-shaped). One molecule of each class was chosen for these initial studies. Ethylene glycol (EG) is interesting because it is widely used as a coolant, antifreeze agent, and de-icing solution. De-icing of airport runways and airplanes is the primary source of EG in the environment. EG is also dispersed in the environment by the disposal of products that contain it. In addition, 1,6...

Determination of Au(III) and Ag(I) in Carbonaceous Shales and Pyrites by Stripping Voltammetry

“…Figure 4 shows the current-voltage curves for the electrooxidation of gold deposits from the graphite electrode (GE) surface. The sensitivity of gold determination by the SV method can be significantly increased when modifying the GE surface by organic or inorganic modifiers, such as bismuth(III) [29], tosylate salts of aryldiazonium [30], polyethylene polyimine [31], acrylic polyelectrolyte [32], and ε-Caprolactam [33].…”

Determination of Au(III) and Ag(I) in Carbonaceous Shales and Pyrites by Stripping Voltammetry

“…The sensitivity of gold determination by the SV method can be significantly increased when modifying the GE surface by organic or inorganic modifiers: bismuth(III) [29], tosylate salts of aryldiazonium [30], polyethylene polyimine [31] and acrylic polyelectrolyte [32], ε-Caprolactam [33].…”

“…Currently, the graphite electrodes are modified to reduce the LOD and the systematic error of SV-determination of the elements [27]. Various metals [28,29] and organic compounds [30][31][32][33] are used as modifiers.…”

A Scaling Method for Correlating Ex Situ and In Situ Measurements in PEM Fuel Cells and Electrolyzer

“…The contaminants from airborne impurities (SO 2 , H 2 S, CO, NO x , and bromomethane), [3][4][5][6][7][8][9][10][11][12][13] fuel impurities in hydrogen(NH 3 , CO, hydrocarbons, glycols, and alcohols), [14][15][16][17][18][19][20][21] inorganic metal cations(sodium, calcium, potassium, iron, nickel, and silicon etc.) [22][23][24][25][26][27][28][29][30][31][32][33] from gasket, bipolar plates, catalyst alloys, and deicer etc., and also from organic leachates(aniline, toluene, alcohols, glycols, propylene, methyl methacrylate) [34][35][36][37][38][39][40][41][42][43] derived from fuel cell systems including stack, structural plastic materials, and assembly aids.…”