Ceria-promoted oxygen reduction reaction in Pd-based electrocatalysts

PdCo-ceria electrocatalyst is synthesized on carbon support in a size of a few nm by colloid method. Enhanced oxygen reduction reaction (ORR) kinetics of PdCo is observed in the presence of ceria similarly as confirmed for PtCo-ceria in a half cell experiment. In addition, there appears a positive shift of the ORR onset potential of PdCo-ceria compared to PdCo while PtCo-ceria shows no such an apparent shift of onset potential. These effects of ceria on the ORR onset potential and the ORR kinetics are more remarkable as temperature increases. To get the most of oxygen storage and supply capacity of ceria, a high temperature proton exchange membrane fuel cell (PEMFC) is fabricated using PdCo-ceria as a catalyst at the cathode. Ceria effects on the ORR of PdCo-ceria catalyst are realized in the form of higher OCV and lower Tafel slope compared to PdCo catalyst in the PEMFC single cell performance. Enhancements in both ORR kinetics and ORR onset potential are very attractive features of ceria as a co-catalyst in the development of a non-Pt ORR electrocatalyst.