## 3 Results and Discussion
### Catalyst Reducibility, Acid Properties, and Oxygen Species  
The redox characteristics of the as-prepared catalysts were determined by H\({}_{2}\)-TPR experiments. First of all, an H\({}_{2}\)-TPR pattern of the supporting material \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) is shown in Figure 7a, where no obvious H\({}_{2}\) consumption appeared for \(\gamma\)-Al\({}_{2}\)O\({}_{3}\), with the exception of a small peak centered at 735 \({}^{\circ}\)C, demonstrating the poor reduction properties of the supporting material \(\gamma\)-Al\({}_{2}\)O\({}_{3}\). For all supported noble metal-based catalysts in this work, the low-temperature range peaks could be recognized as a noble metal reduction action. For instance, a sharp peak located at about 153 \({}^{\circ}\)C in the Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) profile resulted from the reduction of Ru\({}^{4+}\) to Ru\({}^{0}\). As for the Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) sample, the reduction peak at the temperature range 78 \({}^{\circ}\)C was related to the reduction of Rh\({}^{3+}\) to Rh\({}^{+}\), but then the \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Samples** & **S\({}_{\textbf{BET}}\)****a** & **V b** & **D\({}_{\textbf{p}}\)****c** & **Loading****d** & **D (NM Dispersion)****e** \\  & **m\({}^{2}\cdot\)g\({}^{-1}\)** & **cm\({}^{3}\cdot\)g\({}^{-1}\)** & **nm** & **\%** & **\%** \\ \hline \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 207.87 & 0.436 & 4.20 & / & / \\ Ru/\(\gamma\)- & 229.29 & 0.468 & 4.09 & 0.97 & 31.1 \\ Al\({}_{2}\)O\({}_{3}\) & 219.97 & 0.595 & 5.41 & 0.98 & 27.4 \\ Pt/\(\gamma\)- & 227.60 & 0.813 & 7.14 & 1.01 & 25.6 \\ Al\({}_{2}\)O\({}_{3}\) & & & & & \\ Pd/\(\gamma\)- & 226.79 & 0.502 & 4.43 & 1.02 & 29.7 \\ Al\({}_{2}\)O\({}_{3}\) & & & & & \\ Au/\(\gamma\)- & 266.62 & 0.589 & 4.42 & 0.96 & 40.2 \\ Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 230.35 & 0.510 & 4.43 & 0.96 & 33.5 \\ \hline \hline \end{tabular}  
* Specific surface area based on the calculation of \(P\)/\(P_{0}\) = 0.05–0.30;
* Total pore volume tested at \(P\)/\(P_{0}\) = 0.99;
* BJH pore size calculated from the N\({}_{2}\) desorption branch;
* Weight loading of noble metals of prepared materials tested by ICP-OES;
* Calculated from CO chemisorption measurements using average CO-NM stoichiometry of 1:1; \(D\) (%) = N\({}_{\text{surface}}\) of NM/N\({}_{\text{total}}\) of NM.  
\end{table} 
Table 2: Physicochemical properties of synthesized catalysts. Figure 6: (a) N\({}_{2}\) adsorption-desorption isotherms curves and (b) Pore size distribution of all prepared catalysts. second emergence peak centered at 286 \({}^{\circ}\)C was caused by the reduction of Rh\({}^{+}\) to Rh\({}^{0}\). The hydride consumption spike at the temperature of 473 \({}^{\circ}\)C for the Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst can be attributed to the transformation of Pt\({}^{2+}\) to Pt\({}^{0}\). Interestingly, a negative peak occurred at about 44 \({}^{\circ}\)C and can be observed for the Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) material; this represents the decomposition of palladium hydrides [47] due to the superior hydrogen storage capacity of Pd, which might generate partial palladium hydrides during the hydrazine hydrate treatment process. Moreover, the peak centered at 428 \({}^{\circ}\)C resulted from the reduction of Pd\({}^{2+}\) to Pd\({}^{0}\). For the Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) material, the reduction peak at 199 \({}^{\circ}\)C corresponded to the reduction of Ir\({}^{3+}\) to Ir\({}^{+}\), and the following peak located at 417 \({}^{\circ}\)C can be attributed to the reduction of Ir\({}^{+}\) to Ir\({}^{0}\). There is no obvious reduction peak in the profile of the Au/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst, which corresponded to the redox properties of the Au metal. The reduction procedures of the prepared materials result from electron transfer among different metal compositions, which would promote the reaction rate of 1,2-DCE oxidation.