A comparative study of PtCo/C Alloys and Pt/C as cathode catalysts for fuel cell applications

Commercialisation of fuel cells for automotive applications requires catalysts with both improved activity, particularly for the cathodic oxygen reduction reaction (ORR), and stability over commercial platinum only catalysts. This requires a detailed understanding of both desirable catalyst structure and mechanistic activity. In this work a comparative study is made between commercial Pt/C catalysts and developmental PtCo/C catalysts, with the aim of increasing understanding of the desirable characteristics of improved activity and stability demonstrated for PtCo catalysts. To explore the origins of activity and stability enhancement for Pt3Co/C catalysts over Pt/C, the mechanisms of catalyst deactivation have been investigated. In addition, four new PtCo3/C catalyst materials have been prepared and evaluated for ORR activity before and after activation by electrochemical dealloying. Structural changes occurring during these processes have been characterised using cyclic voltammetry, Transmission Electron Microscopy (TEM) and X-ray absorption spectroscopy (XAS). XAS has also been used to explore the relationship between catalyst activity and structure. This has been achieved by building and validating a specially adapted fuel cell, enabling study of fuel cell catalysts in situ under realistic operating conditions. Findings from time resolved potential step experiments with 12 s and 0.1 s time resolution will be presented for catalysts operating at OCV and under load with oxygen cathode gas. In addition, studies have been conducted with nitrogen cathode feed gas to investigate the effect of potential and temperature on the processes of oxide formation and removal on both Pt/C and PtCo/C catalysts.EThOS - Electronic Theses Online ServiceGBUnited Kingdo