Calculations on surface-supported clusters were performed using plane-wave DFT in VASP, using the PBE exchange-correlation functional, PAW pseudopotentials, and a plane-wave cut-off of 500 eV. Unit cells were constructed from a 5-layer 3x3 supercell of Al 2 O 3 with a 15 Å vacuum gap. Transition states were calculated using the climbing-image nudged elastic band (CI-NEB) method implemented in VTST. QTAIM analysis was performed using the Bader code developed by the Henkelman group. Global optimizations were performed with a BLDA approach 50 to generating chemicallyreasonable initial structures, both for cluster structure sampling, and adsorbate binding sampling. The in-house codes PGOPT and GOCIA were used to run the optimizations.