CO desorption kinetics at concentrations and temperatures relevant to PEM fuel cells operating with reformate gas and PtRu/C anodes

Temperature dependence of CO desorption kinetics at a novel Pt-on-Au/C PEM fuel cell anode

“…The relative CO coverage decreases with increasing temperature. This trend is similar to that observed in previous studies for both Pt/C and PtRu/C catalysts under similar experimental conditions [17,18,43]. The relative coverage decreases strongly for temperatures higher than 50 • C. The linear decrease for the relative CO coverage per degree Celsius between 50 and 150 • C is 6.9 × 10 −3 • C −1 .…”

“…The 13 CO desorption kinetics increase with increasing temperature and the area under the exchange curve decreases with increasing temperature across the temperature range investigated. This behaviour is similar to that observed previously for both Pt/C and PtRu/C catalysts for a 12 CO concentration of 1000 ppm under similar experimental conditions [17,18], and to that observed for the PtRu/C catalyst for 12 CO concentrations varying from 100 to 500 ppm [43].…”

“…Knowledge on the dissociative H 2 adsorption behaviour in the presence of CO impurities has also to be obtained, since the balance between the kinetics of CO adsorption and H 2 adsorption is an important factor for the CO tolerance issue. This temperature-dependent kinetics study of the CO desorption process on a novel Pt-on-Au/C PEMFC anode catalyst supplements the literature data obtained previously for the more traditional Pt and PtRu catalysts [17,18,43]. The determination of the CO desorption rate constants on novel PEMFC anode catalysts is believed to be of added value for a better understanding of the CO tolerance issue at PEMFC anodes and if we are to develop novel low cost and CO tolerant catalysts based on the fundamental understanding of the processes involved.…”

“…This dependence on flow rate was already observed extensively in previous similar studies during the desorption measurements. A strong flow rate dependence was observed for both Pt/C and PtRu/C at 1000 ppm CO in argon, for temperatures higher than room temperature and for flow rates higher than 30 ml/min [17,18], as well as for the PtRu/C catalyst at CO concentrations higher than 100 ppm, for temperatures higher than room temperature and for flow rates higher than 90 ml/min [43]. This flow rate dependence was attributed to a significant readsorption of 13 CO during the desorption experiments and consequently the gradients of the plot shown in Fig.…”

“…The fundamental understanding of the CO desorption process involved in improving CO tolerance is expected to help developing novel low cost and CO tolerant PEM fuel cell anode catalysts. A temperature range between 25 and 150 • C has been used for the measurements, since the research community is currently engaged in the development of new PEMFC membranes capable of operating at higher temperatures than the current industry standard, the Nafion membrane, limited by its need for humidification by water to less than 100 • C. The kinetics of CO desorption from the benchmarking commercial Pt/C and PtRu/C catalysts have been investigated at room temperature and as a function of the temperature under dry conditions and in the absence of a potential [17][18][19]43,44]. The measured rates of desorption are high compared with the rates of oxidation measured from polarisation curves obtained with high concentrations of CO in argon.…”