Nanoparticles of Ag with a Pt and Pd rich surface supported on carbon as a new catalyst for the oxygen electroreduction reaction (ORR) in acid electrolytes: Part 2

In the first part of this work, the feasibility of developing a catalyst with high activity for the oxygen electroreduction reaction (ORR) in acid media and with low Pt loading was demonstrated by over coating a silver (Ag) nanoparticle with a shell of platinum (Pt) and palladium (Pd) [7]. The results show that best activity is not directly related to a higher PtPd loading on the surface of the Ag. The best catalyst in a series of this type of catalyst is found with Ag@Pt_0.3Pd_0.3/C which gives a specific activity for oxygen reduction, j_k (in units of mA cm^-2 of real area), of 0.07 mA cm^-2 at 0.85 V vs. NHE, as compared to 0.04 mA cm^-2 when with a commercial Pt on carbon catalyst (Pt₂₀/C) is used in an identical electrode except for the catalyst. The mass activity, j_m (in units of mA μg^-1 of Pt), for Ag@Pt_0.3Pd_0.3/C is 0.04 mA μg^-1 of Pt at 0.85 V vs. NHE, whereas that for the Pt₂₀/C gives 0.02 mA μg^-1 of Pt, showing Ag@Pt_0.3Pd_0.3/C is a lower-cost catalyst, because using a Ag core and Pd with Pt in the shell gives the highest catalytic activity using less Pt.