## 3 Results and Discussion
### Catalyst Reducibility, Acid Properties, and Oxygen Species
In a typical oxidation process, the acid property of the catalysts is another important influencing factor for the 1,2-DCE reaction [48; 49]. The surface acidity of the prepared samples was investigated by NH\({}_{3}\)-TPD measurement, and the resulting profiles are exhibited in Figure 7c. Across all catalysts, the acidic sites identified from the NH\({}_{3}\)-TPD patterns can be classified into three categories, namely, those containing weak acidity (<200 \({}^{\circ}\)C), those with moderate acidity (200-350 \({}^{\circ}\)C), and those with strong acidity (>350 \({}^{\circ}\)C) [38; 50; 51; 52]. For the supporting material \(\gamma\)-Al\({}_{2}\)O\({}_{3}\), only one significant peak at 506 \({}^{\circ}\)C was observed, indicating that \(\gamma\)-Al\({}_{2}\)O\({}_{3}\) belongs to the strong acidity category. When supporting noble metals, the desorption of the strong acidity range of Pt/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) was strengthened significantly, and the Au-, Ir-, and Pd-based materials were also increased extensively. Interestingly, the desorption peaks in the moderate and weak acid ranges emerged in all NM/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) catalysts, especially in those with moderate acidity, suggesting the possible existence of Bronsted  
Figure 7: (a) H\({}_{2}\)-TPR, (b) O\({}_{2}\)-TPD, and (c) NH\({}_{3}\)-TPD profiles of all prepared catalysts. acid sites, where Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) was observed to exhibit more moderate acid emergence than other samples. Strong acid sites generally refer to Lewis acid sites [41]; 1,2-DCE is usually easily trapped on Lewis acid sites, causing the dehydrochlorination effect and inducing the formation of the main by-product (vinyl chloride). On the other hand, the Bronsted acid sites can efficiently promote the desorption of chlorine species from the catalyst surface, further relieving the chlorination effect during 1,2-DCE degradation, as well as hindering the formation of chlorine by-products [25]. As a result, the intensive nature of Bronsted acid sites and the suitable amount of Lewis acid sites may contribute to the excellent performance of Ru/\(\gamma\)-Al\({}_{2}\)O\({}_{3}\) in 1,2-DCE destruction. Moreover, O\({}_{2}\)-TPD was carried out for the determination of the oxygen species (which can be generally divided into three types [53; 54]), as displayed in Figure 7b: the desorption of oxygen species at low temperature \(<\) 300 \({}^{\circ}\)C can be associated with surface physically adsorbed oxygen (O\({}_{2(\mathrm{ad})}\)) and surface chemically adsorbed oxygen (O\({}_{2}\)\({}^{-}\)(ad)). On the other hand, the middle-temperature emergence of desorption peaks in the range of 300 and 700 \({}^{\circ}\)C can be attributed to surface lattice oxygen (O\({}^{2-}\)(ad)). Finally, the adsorption peak overcrossing higher temperature (\(>\) 700 \({}^{\circ}\)C) regions may be related to the lattice oxygen (O\({}^{2-}\)) of the bulk phase. It is shown that only a weak desorption peak at 503 \({}^{\circ}\)C emerged for \(\gamma\)-Al\({}_{2}\)O\({}_{3}\), which is likely associated with the surface lattice oxygen species. When supporting noble metals, for all the prepared materials, there is no adsorption peak in the low- and high-temperature ranges, but only at the temperature range 300-700 \({}^{\circ}\)C, which indicates that surface lattice oxygen represents the main oxygen species in noble metal-based catalysts. In addition, the evolution processes of oxygen species usually convert following the procedures O\({}_{2(\mathrm{ad})}\)\(\rightarrow\) O\({}_{2}\)\({}^{-}\)(ad)\(\rightarrow\) O\({}^{-}\)(ad) \(\rightarrow\) O\({}^{2-}\)(lattice) [55], while the adsorbed oxygen changes for all prepared catalysts in the following manner O\({}_{2(\mathrm{ad})}\)\(\rightarrow\) O\({}_{2}\)\({}^{-}\)(ad) \(\rightarrow\) O\({}^{-}\)(ad), which is attributed to the influence of precious metal oxide species.