CO tolerance and CO oxidation at Pt and Pt-Ru anode catalysts in fuel cell with polybenzimidazole-H3PO4 membrane

Abstract CO tolerance of H 2 –air single cell with phosphoric acid doped polybenzidazole (PA–PBI) membrane was studied in the temperature range 140–180 °C using either dry or humidified fuel. Fuel composition was varied from neat hydrogen to 67% (vol.) H 2 –33% CO mixtures. It was found that poisoning by CO of Pt/C and Pt–Ru/C hydrogen oxidation catalysts is mitigated by fuel humidification. Electrochemical hydrogen oxidation at Pt/C and Pt–Ru/C catalysts in the presence of up to 50% CO in dry or humidified H 2 –CO mixtures was studied in a cell driven mode at 180 °C. High CO tolerance of Pt/C and Pt–Ru/C catalysts in FC with PA–PBI membrane at 180 °C can be ascribed to combined action of two factors—reduced energy of CO adsorption at high temperature and removal of adsorbed CO from the catalyst surface by oxidation. Rate of electrochemical CO oxidation at Pt/C and Pt–Ru/C catalysts was measured in a cell driven mode in the temperature range 120–180 °C. Electrochemical CO oxidation might proceed via one of the reaction paths—direct electrochemical CO oxidation and water-gas shift reaction at the catalyst surface followed by electrochemical hydrogen oxidation stage. Steady state CO oxidation at Pt–Ru/C catalyst was demonstrated using CO–air single cell with Pt–Ru/C anode. At 180 °C maximum CO–air single cell power density was 17 mW cm −2 at cell voltage U  = 0.18 V.