The electrochemical oxygen reduction reaction is the limiting half-reaction for low-temperature hydrogen fuel cells, and currently costly Pt-based electrocatalysts are used to generate adequate rates. Although most other metals are not stable in typical acid-mediated cells, alkaline environments permit the use of less costly electrodes, such as ​silver. Unfortunately, monometallic ​silver is not sufficiently active for economical fuel cells. Herein we demonstrate the design of low-cost ​Ag–Co surface alloy nanoparticle electrocatalysts for ​oxygen reduction. Their performance relative to that of ​Pt is potential dependent, but reaches over half the area-specific activity of ​Ptnanoparticle catalysts and is more than a fivefold improvement over pure ​silver nanoparticles at typical operating potentials. The ​Ag–Co electrocatalyst was initially identified with quantum chemical calculations and then synthesized using a novel technique that generates a surface alloy, despite bulk immiscibility of the constituent materials. Characterization studies support the hypothesis that the activity improvement comes from a ligand effect, in which cobalt atoms perturb surface silver sites.

http://www.nature.com/nchem/journal/v6/n9/full/nchem.2032.html

Nature Chemistry 6, 828–834 (2014) doi:10.1038/nchem.2032