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 I.E. Pech-Pech a, b , Dominic F. Gervasio b, * , J.F. P  erez-Robles a a Dept. of Materials, CINVESTAV-IPN, Libramiento Norponiente 2000, Fracc. Real de Juriquilla, C.P. 76230 Quer etaro, Qro., Mexico b Dept. of Chemical & Environmental Engineering, University of Arizona,1133 E. James E. Rogers Way #108, Tucson, AZ 85721, USA highlights  Simple oneepot 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. article info Article history: Received 26 May 2014 Received in revised form 14 November 2014 Accepted 15 November 2014 Available online xxx Keywords: Low-cost High-activity Air-cathode catalysts Pt and Pd on Ag nanoparticle core PEM fuel cell abstract 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 0.3 Pd 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 (Pt 20 /C) is used in an identical electrode except for the catalyst. The mass activity, j m (in units of mA mg 1 of Pt), for Ag@Pt 0.3 Pd 0.3 /C is 0.04 mA mg 1 of Pt at 0.85 V vs. NHE, whereas that for the Pt 20 /C gives 0.02 mA mg 1 of Pt, showing Ag@Pt 0.3 Pd 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. © 2014 Elsevier B.V. All rights reserved. 1. Introduction A proton exchange membrane (PEM) is considered the electro- lyte of choice for a portable power source, because a thin solid electrolyte leads to a lighter weight, more compact and more du- rable energy converter, the proton exchange membrane fuel cell (PEMFC). Great efforts have been focused on optimizing the design and performance of the PEMFC, because, compared to combustion engines, a PEMFC power source shows promise for substantially more efficient utilization of fossil fuels as well as fuels derived from renewable alternative sources, like hydrogen made from solar or wind power [1]. There are a few barriers to commercialization of PEMFC power sources, including the need for humidifiers, larger radiators and bulky bipolar plates. Perhaps the greatest barrier to commercialization of the PEMFC is the high cost of catalysts needed to bring the intrinsically sluggish oxygen reduction reaction (ORR) to practical rates. An air cathode is desirable in a PEMFC, because oxygen is sup- plied free from air and its reduction gives favorable thermody- namics for this energy converting device. However, oxygen electroreduction is so slow, that a catalyst is needed to speed up this reaction so practical power levels are available. The best commercial air-cathode catalysts have high surface area platinum (Pt) supported on conducting carbon (C). However, Pt is very costly due to its low natural abundance. So a major challenge for large DOI of original article: http://dx.doi.org/10.1016/j.jpowsour.2014.09.112. * Corresponding author. E-mail address: gervasio@email.arizona.edu (D.F. Gervasio). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2014.11.086 0378-7753/© 2014 Elsevier B.V. All rights reserved. Journal of Power Sources xxx (2014) 1e8 Please cite this article inpress as: I.E. Pech-Pech, et al., Journal of Power Sources (2014), http://dx.doi.org/10.1016/j.jpowsour.2014.11.086