Bimetallic surface alloys often exhibit enhanced electrocatalytic performance due to ligand, ensemble, and bifunctional effects that arise from the presence of different transition metals along the catalyst surface. Segregation, dealloying, and poisoning events are common modes of catalyst deactivation that are difficult to suppress, limiting the durability of bimetallic catalysts in harsh environments. Efforts to estimate the stability of these novel catalyst formulations under operational conditions via first principles techniques is challenging due to the critical influence of solvation, surface electrification, and finite temperature effects. In this talk, we present a quantum-continuum model of the electrode-solution interface [Weitzner & Dabo, npj Comp. Mater. 3, 1 (2017)] that directly accounts for the influence of the electrochemical environment and pair this model with a recently developed voltage-sensitive cluster expansion technique to perform semi-grand canonical Monte Carlo simulations of the interface [Weitzner & Dabo, Phys. Rev. B (in press)]. We apply this method to study the voltage-dependent stability of Pd-Au(111) surface alloys under realistic electrochemical conditions and discuss the role of environmental effects on the durability of the catalyst.