The Impact of Impurities on Long-Term PEMFC Performance

Abstract

Electrochemical experimentation and modeling indicates that impurities degrade fuel cell performance by a variety of mechanisms. Electrokinetics may be inhibited by catalytic site poisoning by sulfur compounds and CO and by decreased local proton activity and mobility caused by the presence of foreign salt cations or ammonia. Cation impurity profiles vary with current density, valence and may change local conductivity and water concentrations in the ionomer. Nitrogen oxide and ammonia species may be electrochemically active under fuel cell operating conditions. The primary impurity removal mechanisms are electrooxidation and water fluxes through the fuel cell.

Understanding of Correlation between Electronic Properties and Sulfur Tolerance of Pt-Based Catalysts for Hydrogen Oxidation

“…Hydrogen produced from renewable powers is one of the critical enablers for reconstructing low-carbon energy systems. − The distribution of green hydrogen via a natural gas network to fuel-cell end users is considered a cost-effective way to decarbonize the transportation and residential sectors. , However, a trace amount of sulfur compounds derived from natural gas can act as inevitable poisoners for proton-exchange membrane fuel cells (PEMFCs) of vehicle propulsion systems and residential power generators by suppressing the output performance and reducing the reliability . Currently, the total sulfur amount in hydrogen for fuel cell vehicles is limited to a rather low value of 4 parts per billion (ppb), which leads to relatively high cost of hydrogen separation and purification.…”

“…4,5 However, a trace amount of sulfur compounds derived from natural gas can act as inevitable poisoners for proton-exchange membrane fuel cells (PEMFCs) of vehicle propulsion systems and residential power generators by suppressing the output performance and reducing the reliability. 6 Currently, the total sulfur amount in hydrogen for fuel cell vehicles is limited to a rather low value of 4 parts per billion (ppb), 7 which leads to relatively high cost of hydrogen separation and purification.…”

Recent Developments in Sensor Technologies for Enabling the Hydrogen Economy

“…The various effects of impurities in hydrogen on the performance of PEMFCs have been studied in depth over the years. [65][66][67][68][69][70][71][72][73][74] The mechanism of poisoning typically involves the adsorption of impurities onto the anode's platinum (Pt) electrocatalyst, thus blocking sites for the hydrogen oxidation reaction (HOR) and lowering the PEMFC's performance. 66 Moreover, impurities are also known to infiltrate the membrane as ions, decreasing its conductivity.…”

Operatable and Efficient Mitigation Strategies for H2S Poisoning in Proton Exchange Membrane Fuel Cells: Releasing Pt Reactive Sites for Hydrogen Oxidation

“…3,4 Among these contaminants, H 2 S is regarded one of the most sensitive impurities for PEMFCs, having a serious detrimental effect on the output cell performance and durability. 5 The total sulfur limit in hydrogen is determined to be stringent for the application of PEMFCs with the limit level of 0.4 ppb according to the ISO standard (14687: 2019), 6 so the limit value of H 2 S may be equivalent or smaller, which is remarkably stricter than that of CO (0.2 ppm) and other impurities (e.g., total halide (0.05 ppm) and total hydrocarbons (2 ppm)), indicating that the poisoning extent of H 2 S on PEMFCs is the most serious among all hydrogen impurities. 7−9 Previously reported literatures have shown that the rate of H 2 S poisoning on PEMFCs is much higher than that of CO under the same operation conditions (4.5 and 19% loss of cell voltage at the current density of 600 mA cm −2 after anode exposure to 30 ppm CO/H 2 and 30 ppm H respectively), 10 showing a strongly relation of H 2 S concentration and current density.…”

“…Among these contaminants, H 2 S is regarded one of the most sensitive impurities for PEMFCs, having a serious detrimental effect on the output cell performance and durability . The total sulfur limit in hydrogen is determined to be stringent for the application of PEMFCs with the limit level of 0.4 ppb according to the ISO standard (14687: 2019), so the limit value of H 2 S may be equivalent or smaller, which is remarkably stricter than that of CO (0.2 ppm) and other impurities (e.g., total halide (0.05 ppm) and total hydrocarbons (2 ppm)), indicating that the poisoning extent of H 2 S on PEMFCs is the most serious among all hydrogen impurities. − …”