The microkinetic models used the NASA 7-coe cient polynomial parameterization to describe heat of formation H, entropy S, and temperature-dependent heat capacity C p at low and high temperature ranges. The polynomial parameters can be determined from heat of formation at 0 K and vibrational frequencies through partition functions. The routine reported by Blondal et al. was used in this study to generate the parameters. For the cases where the first 2 frequencies are less than 100 cm 1 , a 2D gas model was applied instead of the harmonic oscillator approximation. To calculate heat of formation at 0 K of an adsorbate, the energy of its gas-phase precursor is calculated and corrected to align with Active Thermochemical Tables (ATcT), and the zero-point corrected adsorption energy is added on top of the ATcT corrected energy of the gas-phase precursor. As reported by Klippenstein et al., a reference reaction should be used to reduce the error introduced by di↵erent wave functions. Therefore, a similar hypothetical reaction shown in Eq. 3, was used to describe the heat of formation of any species formed by a combination of H, C, N, and O.