Effect of Chloride on PEFCs in Presence of Various Cations

Abstract

The performance and durability of Polymer electrolyte fuel cells (PEFCs) were investigated by separately introducing HCl and five different chloride salts (AlCl 3 , FeCl 3 , CrCl 3 , NiCl 2 , and MgCl 2 ) into the air stream of an operating fuel cell. Under the same operating conditions and at a fixed chloride (Cl − ) concentration of 50 ppm in air stream, it appeared that HCl affected the cell performance faster than the other chloride salts, therefore the presence of the cation in the contaminant solutions slowed and/or reduced the decrease in the cell performance. The overall cell performance degradation was ranked as HCl, AlCl 3 > FeCl 3 > CrCl 3 > NiCl 2 , MgCl 2 . The performance degradation is believed to be due to the adsorption of chloride on the Pt surface reducing active surface area. At lower relative humidity, the contaminant concentration increased in liquid phase and salt precipitated eventually blocking some of the flow channels and the GDL surface and resulted in even lower cell performance. Polymer electrolyte fuel cells (PEFCs) are an attractive source of clean energy in transportation and stationary power sector. Insufficient durability due to performance degradation is one of the key issues in commercialization of PEFC. PEFCs will need to have a durability of 5,000 hours at a cost of $30/kW for automotive applications, and about 60,000 to 80,000 hour durability, at a capital cost of about $1,000-1,500/kW depending on size and application for stationary power generation. 1Impurities present in fuel and air have a severe effect on durability and performance of PEFCs. Impurities may be introduced into the fuel cell from the fuel and air stream or from the corrosion of fuel cell stack and system components, such as bipolar plates, seals, inlet/outlet manifolds, humidifier reservoirs, and cooling loops.2 Chloride (Cl − ) is a contaminant, which can enter through air or fuel stream in various forms. It is commonly present in air near marine environments, and it is also present as a deicer on roads during the winter.3 In addition, Pt-based catalysts are often synthesized from chloride-containing precursors and trace amount of chloride may remain after synthesis. 4 Moreover, to reduce hydrogen production and transportation costs, the direct use of waste or by-product hydrogen from chemical plants (e.g., in the chlor-alkali industry) can also introduce chloride in fuel stream. 5Several ex-situ 4,6,7 and in-situ studies 3,5,[8][9][10][11][12][13] have been carried out to understand the effects of chloride contamination. Schmidt et al. found that the presence of chloride on the Pt surface mainly acted as a site blocking species and reduced the number of active sites for the ORR. 4 It also enhanced the formation of H 2 O 2 . Further, chloride promoted the dissolution of Pt by the formation of soluble chloride complexes near the inlet portion of the MEA and then deposited in the membrane.13 Yadav et al. found a chloride ion concentration of as low as 10 ppm can induce Pt dissolution as chloride complexes...

Distributed effects of calcium ion contaminant on polymer electrolyte fuel cell performance

“…But no Ca/Al is detected in the CCM. These results conform to our previous findings [7,8], which shows that highly hydrophobic nature of the microporous layer (MPL) in GDL acts as a barrier to the transport of contaminant solution into the CCM [11].…”

Thinning of Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells Due to Foreign Cation Contamination

“…[24][25][26][27][28][29][30] The CCMs were GORE PRIMEA Membrane Electrode Assemblies (GORE PRIMEA, W. L. Gore and Associates) with a Pt loading of 0.4 mg/cm 2 for both anode and cathode. Freudenberg C4 gas diffusion layers (Freudenberg FCCT SE & Co. KG, Germany) were used during assembly.…”

“…21 They suggested that these pinholes may have been promoted by the enhanced production of peroxide radicals catalyzed by Fe species through Fenton's reaction. They also reported that Al 3+ reduced ORR kinetics and changed the ORR mechanism from a predominantly 4-electron pathway toward a 2-electron pathway.Our group investigated the effect of different cations (Na [24][25][26][27][28][29][30] as well as modeled the effects of cation contamination on PEFC performance. 9,11 Cation selection was based on several levels of screening: present in the air and water filter samples collected worldwide, contaminants likely to be encountered based on the current and probable future usage, valence state, solubility, toxicity, availability, paucity of scientific or engineering data, and relevance in terms of materials of construction.…”

“…[25][26][27]29,30 Owing to the hydrophobic nature of GDL and low solubility of cationic solutions, most of the salt is preferentially deposited on the GDL and flow channels rather than penetrating through the GDL and the electrode layers to contaminate the polymer membrane.…”

Effect of hydrophobicity of gas diffusion layer in calcium cation contamination in polymer electrolyte fuel cells

“…In our previous studies, we investigated effect of various metal cations (Na + , K + , Mg 2+ , Ca 2+ , Ni 2+ , Ba 2+ , Al 3+ , Cr 3+ , Fe 3+ ) with a combination of various anions ((Cl)ˉ, (OH) -, (ClO 4 ) -, (CO 3 ) 2-, (SO 4 ) 2-) by in-situ injection into the air stream of an operating fuel cell [21][22][23][24][25][26][27] as well as ex-situ contaminating the membrane electrode assembly (MEA) [19,28]. After the screening studies with various cations, one contaminant (Ca 2+ ) was selected for in-depth studies that was not well investigated and abundant in the nature.…”