“…Figure 3 shows the high-resolution Ti 2p, O 1s, N 1s, and Ni 2p XPS spectra of the N-TiO 2 /1.0 wt% Ni(OH) 2 . As is shown for Ti 2p, peaks at 458.5 and 464.3 eV could be ascribed to Ti 2p 3/2 and Ti 2p 1/2 of TiO 2 , respectively, indicating the existence of Ti 4+ in the sample [24][25][26]; while for O 1s, signals of lattice oxygen (titanium-oxygen-titanium, 529.7 eV) and hydroxyl oxygen (Ti-OH and Ni-OH, 531.4 eV) are observed [27] (Figure 3b). A weak characteristic peak (N1s) at 399.9 eV attributes to the signal combination of weakly charged nitrogen species with C, H, or O atoms [28] (Figure 3c), and demonstrates the successful diffusion of nitrogen into the TiO 2 lattice at interstitial positions [29,30].…”