Based HT-PEM Fuel Cells

Plug Power, working with its European partners PEMEAS (now BASF Fuel Cell GmbH) and Vaillant, is actively pursuing a PBI-based HT PEM fuel cell system as a CHP system with high system efficiency and great CO tolerance. This system demonstration project is jointly sponsored by the U.S. Department of Energy and the European Union, one of the first collaborations of this kind between the U.S. and the EU. 

Table 17.4 Overall degradation rates of PBI-based HT-PEM fuel cells...

Andreasen SJ, Mosbaek R, Vang JR et al (2010) EIS characterization of the poisoning effects of CO and CO2 on a PBI based HT-PEM fuel cell. In ASME 2010 eighth international fuel cell science, engineering and technology conference. New York, p 10... 

Approaches for the Modeling of PBI/H3PO4 Based HT-PEM Fuel Cells... 

Only a few publications have reported the stabihty of Pt/C catalysts for HT-PEM fuel cells, especially PA-doped PBl -membrane-based HT-PEM fuel cells. For example, Liu et al. [52] conducted a 600-hour lifetime test of a PA-doped PBI -membrane-based HT-PEM fuel cell by using commercially available Pt/C as both anode and cathode catalysts. The Pt particle sizes before and after the lifetime test were evaluated by transmission electron microscopy (TEM) measurements. Figure 10.10 shows the TEM images and Pt particle size distribution histograms of the Pt/C catalysts before and after the test. The TEM results reveal that the Pt particle agglomeration occurred at both the anode and the cathode, but more severely on the latter. For the fresh Pt/C catalyst, the Pt particle size distribution was relatively narrow, with a range of 2-5 nm and an... 

Because commercially available Pt/C catalysts show significant degradation during the long-term operation of PA-doped PBI -membrane-based HT-PEM fuel cells, it is necessary to develop highly durable catalysts for these conditions. 

Pan et al. [73] investigated the effect of electrode porosity on the performance of PA-doped PBI-membrane-based HT-PEM fuel cells. They optimized the porosity of the gas diffusion layers by applying different amounts of PTFE, and the porosity of the catalyst layer by adding ammonium oxalate into the catalyst layers, followed by heating to remove the additive and make the pores. They observed that an increase in the porosity of the electrode improved the mass transfer, leading to better cell performance (Fig. 10.16). 

FIGURE 10.16 Polarization curves of PA-doped PBI-membrane-based HT-PEM fuel cells using electrodes with different porosities, and operated with dry gases at atmospheric pressure. The Pt loading of the electrode was 0.5 mg Pt cm and the active area of the electrode was 25 cm Hydrogen and oxygen flow rates were 400 mlmin and the air flow rate was 800 ml min [73]. 

If the proton conductivity of a high-temperature membrane does not rely on water, humidification is unnecessary this simplifies the fuel cell system and lowers its cost. One such system is the PBI-based HT-PEM fuel cell, in which proton conductivity is based on doped H3PO4. 

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