## 3 Results and Discussion
### Catalyst Activity Performance
The \(E_{\rm a}\) indexes of the synthesized catalysts can be ordered as follows: Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (47.89 KJ\(\cdot\)mol\({}^{-1}\)) \(>\) Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (36.11 KJ\(\cdot\)mol\({}^{-1}\)) \(>\) Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (35.90 KJ\(\cdot\)mol\({}^{-1}\)) \(>\) Au/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (28.89 KJ\(\cdot\)mol\({}^{-1}\)) \(>\) Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (27.45 KJ\(\cdot\)mol\({}^{-1}\)) \(>\) Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) (21.29 KJ\(\cdot\)mol\({}^{-1}\)), suggesting that Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) boasts the lowest light-off temperature and expresses the highest 1,2-DCE conversion activity at low temperatures. At the same time, the TOFs were also estimated at a low conversion efficiency range (200 \({}^{\circ}\)C was used in this case) and listed in Table 1. Of course, the TOF value of NM/Al\({}_{2}\)O\({}_{3}\) catalysts for 1,2-DCE oxidation at 200 \({}^{\circ}\)C can be ordered as follows: Ir/Al\({}_{2}\)O\({}_{3}\) \(>\) Pd/Al\({}_{2}\)O\({}_{3}\) \(>\) Ru/Al\({}_{2}\)O\({}_{3}\) \(>\) Rh/Al\({}_{2}\)O\({}_{3}\) \(>\) Au/Al\({}_{2}\)O\({}_{3}\) \(>\) Pt/Al\({}_{2}\)O\({}_{3}\), indicating the superior low-temperature activity of the Ir- and Pd-based catalysts and poorest performance of the Pt-based sample. However, a slightly different trend is found with that of \(E_{\rm a}\), where the Ru- and Rh-based catalysts exhibited higher TOF values compared to that  
Figure 1: (**a**) 1,2-DCE conversion curves of NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts; (**b**) Arrhenius plots of active samples for 1,2-DCE catalytic oxidation over NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts; (**c**) CO yield and CO\({}_{2}\) yield over NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts; (**d**) Distribution of by-products over NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts during 1,2-DCE oxidation. of Au, which is the opposite of the \(E_{\text{a}}\) tendency, suggesting an intrinsic potential activity of Ru/Al\({}_{2}\)O\({}_{3}\) and Rh/Al\({}_{2}\)O\({}_{3}\) in the 1,2-DCE oxidation reaction [20]. The organic by-products were further evaluated during 1,2-DCE destruction. As shown in Figure 1d, all by-products in the process of 1,2-DCE destruction over the NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts were acetaldehyde (C\({}_{2}\)H\({}_{4}\)O), dichloromethane (CH\({}_{2}\)Cl\({}_{2}\)), trichloromethane (CHCl\({}_{3}\)), tetrachloromethane (CCl\({}_{4}\)), trichloroethylene (C\({}_{2}\)HCl\({}_{3}\)), 1,1,2-trichloroethane (1,1,2-C\({}_{2}\)H\({}_{3}\)Cl\({}_{3}\)), and tetrachloroethylene (C\({}_{2}\)Cl\({}_{4}\)). The amounts of by-products increased gradually with the elevating temperature first, and then decreased slightly with the temperature at 50% conversion of 1,2-DCE over the Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), and Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts. For the other catalysts, the amounts of by-products increased gradually with the increase in temperature over the Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\), and Au/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts until the highest test temperature of 400 \({}^{\circ}\)C. Summarily, the amounts of organic by-products of the prepared catalysts can be ordered as follows: Au/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)\(>\) Ir/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)\(>\) Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)\(>\) Pd/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)\(>\) Rh/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\)\(>\) Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\). Along with the analysis of the CO\({}_{\text{x}}\) yield tendency, it was observed that although the Au- and Ir-based catalysts obtained a higher 1,2-DEC conversion efficiency at lower temperatures, the conversion just stops at the point of \"degradation\" at higher temperatures, with higher organic compound generation and lower mineralization efficiency.