The CBH methodology for adsorbates can only be applied for molecules that can be broken down into isodesmic reactions. Thus, the method cannot be used for small adsorbates like *O, *H, or *CO. In this work, we can use experimental ∆ f H for the parameterization of the microkinetic model (see Table ). Alternatively, it is possible to perform higher-level of theory calculations for these adsorbates to determine accurate ∆ f H. The CBH approach integrates available experimental data for the reference adsorbates, accurate gas-phase species from the ATcT, and DFT energies into a global thermochemical network as shown in Fig. . Additionally, systematic error cancellation provides a more accurate ∆ f H of adsorbates from DFT. Kreitz et al. obtained a ∆ f H for *OCH 3 and C 3 H * 8 that is within chemical accuracy of the experimental value using BEEF-vdW DFT energies. However, isodesmic reactions do not necessarily have the maximum degree of error cancellation 199,201 , e.g., the degree of error cancellation for CO * 2 is rather low. Conserving only the bond types does not always conserve the correct hybridization and the molecular orbitals. A good indicator for the effectiveness of the error cancellation is the reaction enthalpy of Eq. 208 . High reaction enthalpies indicate a low degree of error cancellation, and climbing to the next highest rung would be preferable. Unfortunately, this depends on the size of the target adsorbate. Additionally, independent and accurate reference ∆ f H are needed to populate the fragments for the hypohomodesmotic level. Yet, the approach provides a way to leverage a relatively small number of strategically selected highly accurate reaction enthalpies from experiment or wavefunction theories and use these to elevate the accuracy of other reaction enthalpies by maximizing cancellation of error.