Currently our work is focused on understanding the effect of surface species including their interaction between each other and with the catalysts surface that influence the activity and selectivity of the electrocatalyst.  For example, highly efficient Pt-based catalysts are now able to deliver higher currents at lower overpotential.  In the case of the oxygen reduction reaction (ORR), catalysis at low ORR overpotential happens at a potential range where dynamic oxide growth is occurring on the underlying Pt and Pt alloy surfaces resulting in the catalyst becoming oxidized over periods of prolonged use which alters both the catalytic activity and selectivity with time.  In this paper, we report our recent analysis on decoupling electrochemical contributions from oxide growth vs. catalytic ORR.