## 3 Results
In addition, Ag/TiO\({}_{2}\)-5 W-50 s also contained a small amount of silver oxide, and the binding energies of Ag\({}_{2}\)O at approximately 367.2 and 373.2 eV can be assigned to 3d\({}_{5/2}\) and 3d\({}_{3/2}\), respectively [40; 41; 42] in Figure 8b, and the fitting results indicate that the proportion of Ag\({}^{+}\) in all Ag elements is 5.6%, which may be due to the surface oxidation of silver particles caused by exposure to air. Figure 8c shows the XPS spectrum of the Ti 2p of the Ag/TiO\({}_{2}\)-5 W-50 s before the photocatalytic degradation. The spectrum of Ti 2p\({}_{3/2}\) is symmetrical; that is to say, the spectrum of Ti 2p\({}_{3/2}\) is consistent with single-state, the binding energy of the peak is 458.3 eV, and the distance between the peaks of Ti 2p\({}_{1/2}\)(464 eV) and Ti 2p\({}_{3/2}\) is 5.7 eV. The results are the same as the data of a standard XPS of TiO\({}_{2}\)[43; 44]. Consequently, it can be inferred that the titanium ions in Ag/TiO\({}_{2}\) are in the form of Ti\({}^{4+}\), while Ti\({}^{3+}\) is not present in Ag/TiO\({}_{2}\). Figure 8: XPS spectra of Ag/TiO\({}_{2}\)-5 W-50 s film before photocatalytic degradation of MO: (**a**) overall spectrum, (**b**) Ag 3d, and (**c**) Ti 2p; Ag/TiO\({}_{2}\)-5 W-50 s film after the photocatalytic degradation of MO in pure MO solution: (**d**) overall spectrum, (**e**) Ag 3d, and (**f**) Ti 2p; Ag/TiO\({}_{2}\)-5 W-50 s film after the photocatalytic degradation of MO in MO-Na\({}_{2}\)SO\({}_{4}\) solution: (**g**) overall spectrum, (**h**) Ag 3d, and (**i**) Ti 2p. Figure 8d-f show the wide-scan XPS spectra, Ag 3d, and Ti 2p of the Ag/TiO\({}_{2}\)-5 W-50 s XPS spectra after photocatalytic degradation in pure MO solution, respectively. The characteristic peaks of C 1s, Ag 3d, N 1s, Ti 2p, O 1s, and S 2p were detected sequentially in the sample as shown in Figure 8d. Figure 8e shows the XPS spectrum of the amplified Ag 3d of Ag/TiO\({}_{2}\)-5 W-50 s after photocatalytic degradation in pure MO solution. The Ag 3d\({}_{5/2}\) peak at 367.7 eV and the Ag 3d\({}_{3/2}\) peak at 373.7 eV correspond to Ag\({}^{0}\), and the Ag 3d\({}_{5/2}\) peak at 367.2 eV and the Ag 3d\({}_{3/2}\) peak at 373.2 eV correspond to Ag\({}^{+}\). The fitting results indicate that the proportion of Ag\({}^{+}\) in all Ag elements is 9.6%. It can be found that compared with the results in Figure 8b, the increase in Ag\({}^{+}\) is also one of the reasons for the decline in the degradation effect in the cyclic experiment. As the oxidation degree of silver is intensified, the plasma resonance effect is weakened, the ability of bound electrons is reduced, and the recombination rate of photogenerated electron-hole pairs is increased [29; 30]. Figure 8f shows the XPS spectrum of the Ti 2p of the Ag/TiO\({}_{2}\)-5 W-50 s after photocatalytic degradation in pure MO solution. The results are consistent with those in Figure 8c. Figure 8g-i show the wide-scan XPS spectra, Ag 3d, and Ti 2p of the Ag/TiO\({}_{2}\)-5 W-50 s XPS spectra after photocatalytic degradation in MO-Na\({}_{2}\)SO\({}_{4}\) mixed solution, respectively. The characteristic peaks of C 1s, Ag 3d, N 1s, Ti 2p, O 1s, and S 2p were detected in the sample as shown in Figure 8g. Figure 8h shows the XPS spectrum of the amplified Ag 3d of Ag/TiO\({}_{2}\)-5 W-50 s after photocatalytic degradation in the MO-Na\({}_{2}\)SO\({}_{4}\) mixed solution. The Ag 3d\({}_{5/2}\) peak at 367.7 eV and the Ag 3d\({}_{3/2}\) peak at 373.7 eV correspond to Ag\({}^{0}\), and the Ag 3d\({}_{5/2}\) peak at 367.2 eV and the Ag 3d\({}_{3/2}\) peak at 373.2 eV correspond to Ag\({}^{+}\). The fitting results indicate that the proportion of Ag\({}^{+}\) in all Ag elements is 15.5%.