Coupled Effects of Carbon Monoxide Poisoning, Platinum Loading, and Membrane Degradation on the Performance of High-Temperature PEM Fuel Cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are promising energy-conversion devices owing to their simplified water management and improved tolerance to carbon monoxide in reformate H2. However, their practical performance and durability are constrained by anode carbon monoxide (CO) poisoning, cathode catalyst utilization, and long-term degradation of phosphoric-acid-doped polybenzimidazole (PBI) membranes. In this study, a three-dimensional, non-isothermal numerical framework was established to investigate the coupled effects of CO contamination at the anode, cathode platinum loading, and phosphoric acid doping level degradation on HT-PEMFC performance. The proposed model explicitly describes the competitive CO/H₂ adsorption and electrochemical oxidation processes on anode platinum sites, employs an agglomerate-based formulation to represent oxygen reduction kinetics and oxygen transport in the cathode catalyst layer, and incorporates the conductivity decay of PBI membranes associated with phosphoric acid loss during prolonged operation. The model predictions were validated against experimental polarization curves obtained under CO-containing anode fuel conditions. The results indicate that CO poisoning causes pronounced performance deterioration, particularly at elevated CO concentrations, lower operating temperatures, and medium-to-high current densities, while increasing the temperature partially alleviates the anode poisoning effects. A higher cathode platinum loading improves the cell output by enhancing the electrochemical reaction kinetics, but concurrently strengthens the oxygen transport limitations within the catalyst layer. Moreover, progressive phosphoric acid depletion leads to a substantial reduction in the membrane ionic conductivity and a corresponding increase in ohmic losses, and after approximately 6,000 h of operation, severe doping loss renders the fuel cell nearly inoperable. These results demonstrate that coordinated optimization of the operating temperature, cathode platinum loading, and membrane durability is essential for achieving stable and efficient HT-PEMFC operation with CO-containing fuels.