(786b) Shape Dependence of Oxygen Reduction Activity On Ag Nanoparticles

To mitigate negative economic and environmental consequences arising from our dependence on petroleum, there is a definite need to develop alternative energy systems such as low temperature fuel cells.  Low temperature fuel cells generate electrical energy and water by reacting hydrogen and oxygen gases.  It has been well established that the majority of the energy losses originates from the oxygen reduction reaction at the cathode.  Currently, fuel cells are limited by large kinetic overpotential, limited stability with cycling, and high material cost of platinum electrodes.  With recent advances in anion exchange membranes, cheaper materials have become available as potential cathodes in low temperature alkaline fuel cells. 

In particular, we are investigating Ag nanoparticles as alternative electrocatalysts for oxygen reduction. Different particle geometries have different distributions of surface facets, which have distinct chemical and catalytic properties.  Specifically, we are interested in examining differences in activity between nanoparticles terminated with differing proportions of 100 and 111 facets.  In this work, silver nanoparticles of several geometries are synthesized using several colloidal routes prior to being deposited onto a Vulcan XC72R support.  Kinetic current and electrochemical surface area measurements are obtained using linear sweep and cyclic voltammetry with a rotating disc electrode in a three electrode electrochemical cell.  Silver nanospheres are shown to have slightly higher mass and specific kinetic currents compared to nanocubes.  Our results are consistent with previous work on silver single crystal electrodes, which show the Ag 111 surface is more active than Ag 100.¹

 REFERENCES

1. B.B. Bliznanc, P.N. Ross, and N.M. Markovic, J Phys Chem B 110 (2006) 4735.