(A) Activation energies for various steps during the reduction of Cu2+ species assisted by hydrogen spillover on TiO2 and Al2O3 and (B) experimental temperatures for the reduction of Cu2+ on the catalyst as determined from in situ XAFS data.
| (A) Activation Energy/kcal mol−1 | (B) Reduction Temperature of Cu2+/°C | ||||
|---|---|---|---|---|---|
| H2 cleavage on the Rh5 cluster | H atom transfer from the Rh5 cluster to the support | H atom migration on the support | Cu2+ reduction by spilled H atoms | ||
| TiO2 (101) | 5.9 | 16.5 | 15.0 | 21.7 | 210 (RhCu/TiO2) |
| Al2O3 (100) | 9.3 | 19.4 | 41.7–43.8 | 30.5 | 300 (RhCu/γ-Al2O3) |
| H2 cleavage on the support | Cu–O reduction by H2 vapor | Reduction temperature/°C | |||
| TiO2 (101) | 82.3 | 36.8 | 280 (Cu/TiO2) | ||
| Al2O3 (100) | 89.3 | 44.7 | 310 (Cu/γ-Al2O3) | ||