Influencia del CO2 alimentado en la corriente de combustible en pilas de combustible tipo PEM de baja y alta temperatura

Abstract

Among all the impurities, the study of the influence of C02 on the performance of a Polymer Electrolyte Membrane Fuel Cells (PEMFC) is of considerable interest due to the high concentration of this contaminant in a typical reformate mix. The presence of C02 in the fuel can produce performance losses that cannot be underestimated. An experimental investigation of the performance and contamination of Low and High Temperature PEMFCs operating with different concentrations of C02 at the anode inlet is presented. An analysis of different operating parameters (current density, temperature, relative humidity, catalyst composition and operating time) influence in the contamination process for both low and high temperature operation range are investigated in this work. To reach the main objective, the thesis is divided in the next secondary objectives: 1. Study the effect of different concentrations of H2/C02 mixtures at Low and High Temperature PEMFCs. 2. Researching the current density influence into the contamination process. 3. Evaluate the temperature effect of temperature which is closely related with the ratio �CO production/CO electro- oxidation�. 4. Study the effect of relative humidity in the CO electro-oxidation for LT PEMFCs. 5. Change the composition of catalyst in order to evaluate the impact in the contamination process for LT PEMFCs. 6. Study two different regeneration methods to recover the contaminated electrode, in order to recover initial performance. 7. Develop a new and versatile method to study the effect of contaminants which show an accumulative behavior with time. The results show that the performance loss is larger than expected if only a dilution effect were considered, so that a real contamination process occurs in the cell when C02 is fed to the anode, due to the RWGS reaction. This contamination effect is analysed and quantified by comparing the polarization curves of the contaminated cell with the ones corresponding to the cell operating with pure hydrogen. The oveipotentials for different operating parameters are presented and discussed for both types of fuel cells. Two different regeneration processes (anode feeding with pure H2 and with air) are also presented and discussed. The analysis of the effectiveness of each regeneration strategy also supports that CO produced via the RWGS reaction is adsorbed onto the catalyst.