## 3 Results and Discussion
### Catalytic Activity Tests  
The catalytic performances of the Au/TiO\({}_{2}\), Au/Na-ABen, Au/Ti-Na-ABen, Au-Ti/Na-ABen and Au-Ti-Ce/Na-ABen catalysts for the SRM reaction were evaluated at 250-500 \({}^{\circ}\)C and the results are shown in Figure 5. As shown in Figure 5a, the activity of Au/TiO\({}_{2}\) and Au/Na-ABen is much lower than Au/Ti-Na-ABen, Au-Ti/Na-ABen, and Au-Ti-Ce/Na-ABen, since the BET surface areas and particle size of the Au/TiO\({}_{2}\) and Au/Na-ABen are much smaller than the other samples. In addition, the methanol conversion increases as the temperature rises for Au/Ti-Na-ABen, Au-Ti/Na-ABen, and Au-Ti-Ce/Na-ABen. For Au/TiO\({}_{2}\) and Au/Na-ABen, the methanol conversion increases as the temperature rises at the beginning, and then decreases as the temperature becomes higher. It might be attributed to the Au particles on the Au/TiO\({}_{2}\) and Au/Na-ABen aggregate becoming less active. Since Au-Ti compound as cross-linking agent for Au-Ti/Na-ABen could make the Au nanoparticles move into the interlayer of bentonite clay and be confined in the interspace, the Au-Ti/Na-ABen catalysts show better catalytic activity than Au/Ti-Na-ABen. Au-Ti-Ce/Na-ABen shows the best activity for the SRM reaction and reaches more than 80% methanol conversion at 400 \({}^{\circ}\)C. This could be attributed to the Au-Ti-Ce which can also move into the interlayer space of bentonite and enlarge the d(001) spacing of bentonite. In addition, the Au-Ti-Ce cross-linking agent results in a smaller Au particle for the Au-Ti-Ce/Na-ABen sample, and more Au is defined in the interlayer space of bentonite. It is clear that the cerium obviously promoted the activity of methanol conversion.  
Figure 5b shows that the H\({}_{2}\) selectivity is higher than 95% at 250-350 \({}^{\circ}\)C for all catalysts except Au/TiO\({}_{2}\). The H\({}_{2}\) selectivity decreased as the temperature became higher than 350 \({}^{\circ}\)C for most of the catalysts. This is because the water-gas shift reaction is endothermic. Thus, as the temperature rises, the reaction balance moves and favors the production of CO, and the H\({}_{2}\) selectivity decreases [61]. It should be mentioned that the catalytic performance of the Au-Ti-Ce/Na-ABen catalyst is the best in  
Figure 4: Thermogravimetrc analysis (TGA) curves of ABen, Au-Ti/Na-ABen, Au/Na-ABen, and Au/Ti-Na-ABen in an air atmosphere.  
the present work. However, its activity as well as selectivity is not as good as the reported Cu-Al spinel catalysts, which have been commercialized for industrial methanol reforming [62; 63]. Following the reviewer's suggestions, we also tested the stability and selectivity of the samples at 400 \({}^{\circ}\)C for 120 h (Figure 5c). It was found that all samples show excellent stability without obvious deactivation. The CO and CO\({}_{2}\) selectivities at 400 \({}^{\circ}\)C over Au-Ti-Ce/Na-ABen are 0.2% and 99.7%, respectively. In terms of TOF\({}_{\text{CH3 OH}}\) by counting the surface number of Au atoms in the catalysts (Table 1), it can be seen that the TOF of Au-Ti-Ce/Na-ABen (0.41 s\({}^{-1}\)) is the highest one among those of all catalysts. This indicates that the addition of cerium can remarkably improve the TOF value of the Au-Ti/Na-ABen catalyst.