Table 2.
The relative free energies for each type of active sites on the Au2–Ag2/TiO2 with a cluster on two bridging oxygen rows and bridging row oxygen vacant site shown in Figs. 8c and 9c, respectively, starting from the dissociation of a water molecule (H2O + * ↔ H* + HO*) set as the reference point with zero energy.
| Active site | ΔGOH* | ΔGO* | ΔGOOH* | Overpotential (V) | Rate-determining steps |
|---|---|---|---|---|---|
| System: Au2–Ag2/TiO2 with cluster on two bridging oxygen rows | |||||
| Au | 0.80 | 3.12* | 4.83 | 1.09 | O* + H2O → HOO* + ½H2 |
| Ag | 0.23 | 3.00* | 3.64 | 1.54 | O* + H2O → HOO* + ½H2 |
| Ti | 0.03 | 1.01 | 3.59* | 1.35 | HOO* → O2 + ½H2 |
| System: Au2–Ag2/TiO2 cluster on bridging row oxygen vacant site | |||||
| Au | 1.00 | 2.83* | 4.27 | 0.60 | O* + H2O → HOO* + ½H2 |
| Ag | 1.12 | 3.05* | 4.36 | 0.70 | O* + H2O → HOO* + ½H2 |
| Ti | 0.20 | 0.07 | 3.76* | 2.46 | HOO* → O2 + ½H2 |
The propagating step is denoted as ΔGOH*, ΔGO*, and ΔGOOH* shown together with their overpotentials and rate-determining step. *The rate-determining steps.