Stability issues of CO tolerant Pt-based electrocatalysts for polymer electrolyte membrane fuel cells: comparison of Pt/Ti0.8Mo0.2O2–C with PtRu/C

The stability and CO tolerance of a self-made 20 wt% Pt/Ti0.8Mo0.2O2–C mixed oxide–carbon composite supported electrocatalyst was compared to those of a commercial state-of-the-art PtRu/C electrocatalyst by means of cyclic voltammetry and COads stripping voltammetry measurements. On the Pt/Ti0.8Mo0.2O2–C catalyst the oxidation of CO takes place at exceptionally low potential values (ECO,onset = 50 mV); the onset potential is shifted to less positive potentials by 150 mV compared to the PtRu/C catalyst. A stability test involving 500 polarization cycles revealed that the PtRu/C catalyst suffered more significant degradation than the composite supported Pt catalyst. XPS measurements indicated that the degradation is connected to ruthenium dissolution. At the same time, better electrocatalytic stability and increased CO tolerance of the Pt/Ti0.8Mo0.2O2–C electrocatalyst compared to the PtRu/C catalyst was evidenced.