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

• Simple one–pot synthesis for making platinum (Pt) electrocatalysts supported on carbon.
• Catalysts for oxygen electroreduction reaction (ORR) in acid media with low Pt loading.
• Optimization of Pt and palladium (Pd) on silver (Ag) core for catalyzing ORR in acids.
• Higher ORR activities with Pt, Pd, Ag than Pt, Pd catalysts with same Pt, Pd loadings.

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@Pt0.3Pd0.3/C which gives a specific activity for oxygen reduction, jk (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, jm (in units of mA μg−1 of Pt), for Ag@Pt0.3Pd0.3/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@Pt0.3Pd0.3/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.