Table 3.
The relative free energies for each type of active sites on the monometallic Au4/TiO2 and Ag4/TiO2 cluster bridging row oxygen vacant site shown in Fig. 7a,b, 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: Au4/TiO2, replacing bridging O atoms on the surface with Au4 cluster in vacancy | |||||
| Au | 0.15 | 1.92 | 3.73* | 0.58 V | O* + H2O → HOO* + ½H2 |
| Ti | 0.63 | 2.93* | 4.60 | 1.07 V | HOO* → O2 + ½H2 |
| System: Ag4/TiO2, replacing bridging O atoms on the surface with Ag4 cluster in vacancy | |||||
| Ag | 0.45 | 2.91* | 3.72 | 1.23 V | O* + H2O → HOO* + ½H2 |
| Ti | − 0.13 | 0.67 | 3.55* | 1.65 V | 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.