Investigation of Pd-Ir based alloy catalyst with rare earth elements: comparison of activities towards oxygen reduction reaction

Abstract

To enhance catalyst activity of the palladium (Pd) towards oxygen reduction reaction (ORR), iridium (Ir) and yttrium (Y) and rare-earth elements such as lanthanum (La), and scandium (Sc) were alloyed by polyol method. In the case of Y, it is hard to reduce Y ion completely by polyol method due to the low reduction potential of Y. However, the binding energy of the Pd from the XPS analysis is shifted to a lower value, which indicates the d-electron of Pd is filled by the electron from the Y. Among the catalysts, the Pd4IrY0.1/C showed the best activity towards ORR, which indicates the metallic Y is effective for improving the catalytic activity. Other rare earth elements like Sc and La also showed a similar tendency to Y element. Thus, for further enhancing ORR activity, the novel method for complete reduction of rare earth atoms is demanded.