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Papers by H. Hjuler
Journal of The Electrochemical Society, 1995
Hydrogen oxidation has been studied on a carbon-supported platinum gas diffusion electrode in a p... more Hydrogen oxidation has been studied on a carbon-supported platinum gas diffusion electrode in a phosphoric acid electrolyte in the presence of carbon monoxide and oxygen in the feed gas. The poisoning effect of carbon monoxide present in the feed gas was measured in the temperature range from 80 to 150~ It was found that throughout the temperature range, the potential loss due to the CO poisoning can be reduced to a great extent by the injection of small amounts of gaseous oxygen into the hydrogen gas containing carbon monoxide. By adding 5 volume percent (v/o) oxygen, an almost CO-free performance can be obtained for carbon monoxide concentrations up to 0.5 v/o CO at 130~ 0.2 v/o CO at 100~ and 0.1 v/o CO at 80~ respectively.
This work will provide details on some of the high temperature polymer electrolyte membrane (HTPE... more This work will provide details on some of the high temperature polymer electrolyte membrane (HTPEM) membrane-electrode-assembly (MEA) performance targets most recently achieved by Danish Power Systems. These include (i) MEA performances of >0.67 V at 0.2 A cm À2 using dry H 2 /Air, (ii) MEA lifetime of 17.000 h at 0.24 A cm À2 using dry H 2 /Air with an average degradation rate of 9 mV h À1 , and (iii) an integrated 5 kW stack/reformer system using methanol reformate as fuel. Post mortem SEM, TEM, micro-tomography and XRD showed membrane thinning and catalyst particle growth that is typical for PEM fuel cells. Platinum particles grew from an initial 2e3 nm to 6e8 nm at the cathode and 4e5 nm at the anode, while the membrane showed thinning from an undoped 40 mme18 mm in some areas after testing. Studies using reformate have also led to promising initial results, while the rate of degradation for an MEA supplied with wet H 2 (30 mol%)/Air for 2000 h was found to be very similar to the rate when supplied with dry H 2. In addition to reaching these performance benchmarks, a reduction in the standard deviation for MEA cell voltage at 0.2 A cm À2 to <1% has been achieved through efforts aimed at improving the uniformity of the membrane and catalyst layer thicknesses.
Electrochemical and Solid-State Letters, 2002
On the basis of blend polymer electrolytes of polybenzimidazole and sulfonated polysulfone, a pol... more On the basis of blend polymer electrolytes of polybenzimidazole and sulfonated polysulfone, a polymer electrolyte membrane fuel cell was developed with an operational temperature up to 200°C. Due to the high operational temperature, the fuel cell can tolerate 1.0-3.0 vol % CO in the fuel, compared to less than 100 ppm CO for the Nafion-based technology at 80°C. The high CO tolerance makes it possible to use the reformed hydrogen directly from a simple methanol reformer without further CO removal. That both the fuel cell and the methanol reformer operate at temperatures around 200°C opens the possibility for an integrated system. The resulting system is expected to exhibit high power density and simple construction as well as efficient capital and operational cost.
Journal of The Electrochemical Society, 1995
Hydrogen oxidation has been studied on a carbon-supported platinum gas diffusion electrode in a p... more Hydrogen oxidation has been studied on a carbon-supported platinum gas diffusion electrode in a phosphoric acid electrolyte in the presence of carbon monoxide and oxygen in the feed gas. The poisoning effect of carbon monoxide present in the feed gas was measured in the temperature range from 80 to 150~ It was found that throughout the temperature range, the potential loss due to the CO poisoning can be reduced to a great extent by the injection of small amounts of gaseous oxygen into the hydrogen gas containing carbon monoxide. By adding 5 volume percent (v/o) oxygen, an almost CO-free performance can be obtained for carbon monoxide concentrations up to 0.5 v/o CO at 130~ 0.2 v/o CO at 100~ and 0.1 v/o CO at 80~ respectively.
This work will provide details on some of the high temperature polymer electrolyte membrane (HTPE... more This work will provide details on some of the high temperature polymer electrolyte membrane (HTPEM) membrane-electrode-assembly (MEA) performance targets most recently achieved by Danish Power Systems. These include (i) MEA performances of >0.67 V at 0.2 A cm À2 using dry H 2 /Air, (ii) MEA lifetime of 17.000 h at 0.24 A cm À2 using dry H 2 /Air with an average degradation rate of 9 mV h À1 , and (iii) an integrated 5 kW stack/reformer system using methanol reformate as fuel. Post mortem SEM, TEM, micro-tomography and XRD showed membrane thinning and catalyst particle growth that is typical for PEM fuel cells. Platinum particles grew from an initial 2e3 nm to 6e8 nm at the cathode and 4e5 nm at the anode, while the membrane showed thinning from an undoped 40 mme18 mm in some areas after testing. Studies using reformate have also led to promising initial results, while the rate of degradation for an MEA supplied with wet H 2 (30 mol%)/Air for 2000 h was found to be very similar to the rate when supplied with dry H 2. In addition to reaching these performance benchmarks, a reduction in the standard deviation for MEA cell voltage at 0.2 A cm À2 to <1% has been achieved through efforts aimed at improving the uniformity of the membrane and catalyst layer thicknesses.
Electrochemical and Solid-State Letters, 2002
On the basis of blend polymer electrolytes of polybenzimidazole and sulfonated polysulfone, a pol... more On the basis of blend polymer electrolytes of polybenzimidazole and sulfonated polysulfone, a polymer electrolyte membrane fuel cell was developed with an operational temperature up to 200°C. Due to the high operational temperature, the fuel cell can tolerate 1.0-3.0 vol % CO in the fuel, compared to less than 100 ppm CO for the Nafion-based technology at 80°C. The high CO tolerance makes it possible to use the reformed hydrogen directly from a simple methanol reformer without further CO removal. That both the fuel cell and the methanol reformer operate at temperatures around 200°C opens the possibility for an integrated system. The resulting system is expected to exhibit high power density and simple construction as well as efficient capital and operational cost.