The Dealloying Critical Potential

Abstract

This paper reexamines the concept of the dealloying critical potential by considering the critical potential to be a kinetically controlled morphological transition dependent not only on extensive system parameters such as alloy and electrolyte composition, but also on the rate of application of an intrinsic parameter such as the potential ramp rate. In the limit of a quasi-static potential sweep rate, an expression for the critical potential is derived which considers both compositional and morphological fluctuations on the alloy surface at the incipient point of either stability (passivation) or instability (bulk dealloying). In addition, we present detailed critical potential results for the entire range of Ag-Au alloy compositions in xMAgClO4+1MHClO4xMAgClO4+1MHClO4 and xMAgNO3+1MHNO3xMAgNO3+1MHNO3 (x=10−4,(x=10−4, 10−3,10−3, 10−2,10−2, 10−1,10−1, and 1). These results are shown to be consistent with the expression for the critical potential. Finally, we present and discuss ancillary experiments examining the effect of potential sweep rate on the determination of the critical potential. © 2002 The Electrochemical Society. All rights reserved.