| ZnO/MxOy composite | Ratio | Temperature (˚C) | Hydrothermal reaction time duration (hr) |
| ZnO/MnO2 | 1:1 | 180 | 5 |
| ZnO/NiO | 1:1 | 160 | 5 |
| ZnO/Co3O4 | 1:1 | 150 | 6 |
| ZnO/In2O3 | 1:1 | 180 | 8 |