where K p is the partial-pressure equilibrium constant, K p = K/p 0 , K is the true equilibrium constant, and p 0 is the standard state reference pressure of 1 bar. Temperature-programmed desorption (TPD) of CO was used for the transient simulations, using a TPD model from previous work . TPD simulations with the single-crystal surfaces of Pt(111) and Co(0001) were performed with a temperature ramp of 20 K min -1 at ultra-high vacuum condition of 1 × 10 -7 bar. The catalyst surface was initialized with a coverage of 0.6 ML at 300 K. Parameters for the TPD simulation are taken from previous work; we assumed a catalyst surface area of 10.4 m 2 g -1 and a catalyst mass of 0.04 g . The catalyst was flushed with 50 mL N min -1 of N 2 during the TPD.