## 3 Results and Discussion
### Crystalline and Morphology  
Figure S1 shows the XRD pattern of supporting material \(\gamma\)-Al\({}_{2}\)O\({}_{3}\), in which the typical diffraction peaks of 2\(\theta\) at 32.0\({}^{\circ}\), 37.7\({}^{\circ}\), 45.7\({}^{\circ}\), and 66.6\({}^{\circ}\) are well agreed with PDF card # 97-003-9014. Figure 3 showed the XRD patterns of all prepared materials. Of course, all NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts have similar diffraction peaks at 2\(\theta\) = 45.7\({}^{\circ}\) and 67.1\({}^{\circ}\), which can be attributed to the presence of \(\gamma\)-Al\({}_{2}\)O\({}_{3}\). The Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst exhibits three obvious diffraction peaks at 2\(\theta\) of 27.9\({}^{\circ}\), 34.8\({}^{\circ}\), and 54.2\({}^{\circ}\), suggesting the formation of RuO\({}_{2}\) phase [36]. No crystalline phase related to rhodium oxide can be identified with Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), suggesting that the rhodium species exhibits a high level of dispersion on the surficial framework of the \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) support [41]. A diffraction peak can be identified at 2\(\theta\) = 39.7\({}^{\circ}\) over Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst, attributed to the Pt (111) plane of metallic Pt [42]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Samples**} & \multicolumn{2}{c}{**Conversion**} & \multicolumn{2}{c}{**\(E_{\text{a}}\)a**} & \multicolumn{2}{c}{**TOF b**} \\ \cline{2-5}  & \(T_{\text{50}}\) (\({}^{\circ}\)C) & \(T_{\text{50}}\) (\({}^{\circ}\)C) & kJ mol\({}^{-1}\) & 10\({}^{-3}\) s\({}^{-1}\) \\ \hline Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 289 & 337 & 30.90 & 3.19 \\ Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 220 & 349 & 36.11 & 2.89 \\ Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 228 & 361 & 35.89 & 0.84 \\ Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 227 & 361 & 27.45 & 4.75 \\ Au/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 267 & 373 & 40.89 & 2.12 \\ Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) & 230 & 380 & 31.29 & 7.16 \\ \hline \hline \end{tabular}  
* Apparent activation energy: calculated by Equation (6). b Turnover frequency: calculated by Equation (7) at 200 \({}^{\circ}\)C.  
\end{table} 
Table 1: Catalytic activity of synthesized catalysts. There are three small diffraction peaks for the Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst at 2\(\theta\) = 34.3\({}^{\circ}\), 54.9\({}^{\circ}\), and 61.2\({}^{\circ}\), which can be attributed to the PdO phase [43]. The Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalyst exhibits two small diffraction peaks at approximately 35.1\({}^{\circ}\) and 53.1\({}^{\circ}\), suggesting the appearance of IrO\({}_{2}\) phase [44]. No crystalline phase can be found for Au/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), which suggests the Au species was dispersed well on the surface of the \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) support [45]. Figures 4 and 5 show the typical SEM images and the EDS elemental mapping of the prepared samples. As displayed, the FE-SEM photos in Figure 4a,g,m suggest that precious metal species are well-distributed, especially for Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\). Meanwhile, Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) and Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) exhibit a slight reunion, which is also reflected by the sharp peak in the XRD patterns. Figure 4d-fj-l,p-r and Figure 5d-fj-l,p-r depict the EDS images of all prepared materials. It also can be recognized that Al, O, Ru, Rh, Pt, Pd, Ir, and Au were dispersed homogeneously over each catalyst. Figure 3: XRD patterns of prepared catalysts. Figure 4: FE-SEM images of (**a**) Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), (**g**) Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), (**m**) Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\); EDS elemental mapping of (**b**,**d**–**f**) Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), (**h**,**j**-**I**) Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), (**n**,**p**–**r**) Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) derived from the SEM images of (**c**), (**i**), and (**o**), respectively.