Abstract
The effect of NH3 in H2 and in air was investigated at various concentrations ranging from 1.0 ppm to 100 ppm in air and ranging from 0.25 ppm to 10 ppm in fuel. The effect of NH3 on cathode caused an instantaneous decrease in cell voltage which dropped from 0.734 V to 0.712 V in 30 h and drop rates was 0.73 mV/h for 1 ppm; however, the cell voltage dropped to 0.415 V in 1 h for 100 ppm of NH3. The voltage could not be recovered after the polarization test (V-I test) but could be recovered to 84.4% after operation with neat air for 1.5 h and 98.4% after cycle voltammogram (CV). It was found that the voltage drop was obvious, and the drop rate increased with the NH3 concentration in H2. The voltage drop rates at 500 mA/cm2 were 0.54 mV/h for 0.5 ppm of NH3, 0.8 mV/h for 1 ppm, and 2 mV/h for 10 ppm. The voltage could be recovered from 70.6% to 77.3% after discharged with high purity H2 for 24 h, to 92.8% after being purged with clean air for 10 h and to 98.4% after CV scan. The tolerance concentration of NH3 in H2 for 1000 h was 40 ppb, for 2000 h was 20 ppb, and for 5000 h was 9 ppb.
Highlights
The effect of NH3 in H2 and in air was investigated at various concentrations ranging from 1.0 ppm to 100 ppm in air and ranging from 0.25 ppm to 10 ppm in fuel
At least four different research groups have published papers regarding the ammonia contamination of Proton exchange membrane fuel cell (PEMFC) [13,14,15,16]
F.A et al [13] found that the cell resistance measured by high frequency resistance (HFR) was more than doubled when the cell was exposed to 30 ppm NH3 in H2 for 15 h
Summary
The effect of NH3 in H2 and in air was investigated at various concentrations ranging from 1.0 ppm to 100 ppm in air and ranging from 0.25 ppm to 10 ppm in fuel. The voltage could not be recovered after the polarization test (V-I test) but could be recovered to 84.4% after operation with neat air for 1.5 h and 98.4% after cycle voltammogram (CV). It was found that the voltage drop was obvious, and the drop rate increased with the NH3 concentration in H2. Ammonia (NH3 ) is a common contaminant in the hydrogen-rich fuel stream [12] and in ambient air in some special places, such as heavy traffic tunnels and the livestock industry. Exposure to 30 ppm ammonia for about 1 h resulted in performance loss, which was recoverable in about 18 h. Extended exposure to 30 ppm NH3 for 17 h was not fully recoverable within 4 days of operation on pure H2. It was suggested that the observed performance loss was due to a loss of proton conductivity in the anode catalyst layer
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