CO Tolerance and Stability of Proton Exchange Membrane Fuel Cells with Nafion® and Aquivion® Membranes and Mo-Based Anode Electrocatalysts

This work presents a CO tolerance study of PtMo/C (70:30, Pt:Mo) and Pt/MoO2-C anode catalysts on proton exchange membrane fuel cells (PEMFC) with Nafion® and Aquivion® ionomer membranes. Results denote improved activity for the hydrogen oxidation reaction (HOR) in the presence of CO on both anode catalysts at 85 ºC. Experiments of identical location transmission electron microscopy evidenced very good stability of the Pt particles along an accelerate stress test (AST) applied to the Mo-based anode catalysts. However, a crossover of degradation Mo products originated in the anode and going to the cathode takes place along this anode AST, causing a PEMFC performance decay. A very little effect of the nature of the membrane, Nafion® or Aquivion®, is observed over these crossover phenomena. Results also denote that when operating at appropriate high temperatures (105 ºC for Nafion® and 125 ºC for Aquivion®), there is no need of incorporating unstable oxophilic transition metals on Pt to achieve improved CO tolerance on PEMFCs, when the CO level in the hydrogen fed is of the order of 100 ppm.