Acetonitrile Contamination and Recovery of Pemfcs
Abstract
The proton exchange membrane fuel cell (PEMFC) is still considered a promising power source for transportation and stationary applications. Electrochemical catalysts and the proton exchange membrane (PEM) are the two key components that determine cell performance. The catalyst promotes fuel cell reactions generating electricity for the external load whereas the PEM completes the circuit by transporting protons. Air pollution is detrimental to both PEMFC performance and durability (1). Acetonitrile, is a critical pollutant that primarily originates from automobile exhausts and manufacturing facilities, where acetonitrile has been used as a solvent for spinning fibers and as an electrolyte in lithium batteries. The acetonitrile concentration in atmospheric air reaches values of up to 3 ppm in some areas (2). During PEMFC operation, acetonitrile is introduced into the cathode compartment by slippage through the air filter. The effects of acetonitrile on a PEMFC were investigated by in-situ operation and ex-situ electrochemical techniques (3,4). The results of in-situ tests showed that a trace amount of acetonitrile close to the atmospheric concentration caused significant short- and long-term damage, especially for MEAs with commercially relevant low Pt catalyst loadings (5,6). The ex-situ analysis indicated that acetonitrile not only impacted the oxygen reduction reaction by adsorbing on the Pt/C catalyst surface, but also affected the proton conductivity of ionomers and PEMs by ion exchange with its conversion products. Acetonitrile reaction products exhausted from an operating PEMFC were also identified by in-situ GC-MS and ex-situ water analysis (7). The acetonitrile reaction intermediates and products assisted the derivation of a contamination mechanism. Acetonitrile is hydrolyzed and reduced to NH3 and CH3CHO, and CH3COOH. Subsequent NH3 hydrolysis forming NH4 + gradually impacted the proton conductivity of the ionomer and PEM by accumulation. The other hydrocarbon products adsorbed on the surface of Pt catalysts competed with the main fuel cell reactions and were successively oxidized to harmless CO2.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 23, 2020
- Source ID
- 10.1149/ma2020-02342194mtgabs
Entities
People
- Jean St-pierre
- Yunfeng Zhai