A Remarkable Photocatalyst Filter for Indoor Air Treatment

2 (P25) and nitrogen-doped TiO2 samples are shown in 1/2 versus photon energy (hυ) is shown in 2, and PNT, respectively. From this result, it is clearly confirmed that PNT has high photocatalytic activity under visible light. The XPS spectra of PNT nanoparticles are shown in 2 species appear perhaps at 400 eV or even higher. On the contrary, the N1s peak at 398.2 supports the hypothesis that nitrogen is associated into the TiO2 lattice as the N-Ti-O linkage indicates substitutional doping [2 from the same lattice units. The Ti2p spectrum of the PNT sample displayed two distinct energy levels at 458.05 and 463.74 eV, which confirms the Ti2p3/2 and Ti2p1/2, which supports the presence of the Ti4+ species as depicted in 2 bands at 450–800 cm−1, 1610 cm−1, and 3250–3600 cm−1 are present in both P25 and PNT. A broad band at 450–800 cm−1 is attributed to O-Ti-O vibrations, while broad bands at 1610 cm−1 and 3250–3600 cm−1 in PNT are caused due to the adsorption of water and the vibration of the –OH stretching and bending group. As a result of the enlargement of prominent bands of hydroxyl groups caused by the nitrogen incorporation onto TiO2, the catalyst has the capacity to generate more highly reactive hydroxyl radicals during photocatalysis, enhancing their performance. TiO2 doping with nitrogen showed additional vibration bands at 1232 cm−1 and 1160 cm−1 corresponding to Ti-N vibrations.

Diffuse reflectance spectra of TiO(P25) and nitrogen-doped TiOsamples are shown in Figure 1 a. Nitrogen doping extends the light absorption with two characteristic absorption edges with a notable red-shift in the visible region around 400 to 800 nm. The first is due to electron shift from the valence band to the conduction band, while the second comes from new energy levels in the forbidden band of P25 formed by N-doping. Moreover, the Kubelka–Munk function is applied to compute the band gap of the samples [ 31 ]. Data on [F(R)*E]versus photon energy (hυ) is shown in Figure 1 b. The values of band gap energy are found to be 3.22 eV and 2.82 eV for P25 TiOand PNT, respectively. From this result, it is clearly confirmed that PNT has high photocatalytic activity under visible light. The XPS spectra of PNT nanoparticles are shown in Figure 1 c–e for N1s, O1s, and Ti2p energy levels, respectively. In Figure 1 c, it is has been clearly demonstrated that the core level of the Nitrogen 1s peak in PNT occurred at 398.2 eV since the anionic nitrogen present in the O-Ti-N linkage [ 32 ]. It is expected that either simple chemisorbed nitrogen or TiN appears at ≤ 397.5 eV, and NO or NOspecies appear perhaps at 400 eV or even higher. On the contrary, the N1s peak at 398.2 supports the hypothesis that nitrogen is associated into the TiOlattice as the N-Ti-O linkage indicates substitutional doping [ 33 ]. Figure 1 d represents the O1s spectra of PNT with a peak at 530.28 eV that indicates a Ti-O bond [ 34 ]. The PNT sample however shows a broadening on the higher BE side at 531.5 eV. There might be possibilities that PNT has a divergent type of oxygen owing to its characteristic covalent nature. This is such that both oxygen and nitrogen elements are accessible in TiOfrom the same lattice units. The Ti2p spectrum of the PNT sample displayed two distinct energy levels at 458.05 and 463.74 eV, which confirms the Ti2pand Ti2p, which supports the presence of the Tispecies as depicted in Figure 1 e [ 35 ].Thus, a small shift in the binding energy is observed for PNT compared with P25 [ 36 ] due to the interaction between nitrogen and titanium. These results are further supported by FT-IR spectroscopy. Figure 1 f presents the FT-IR spectrum of P25 and PNT photocatalysts. The corresponding TiObands at 450–800 cm, 1610 cm, and 3250–3600 cmare present in both P25 and PNT. A broad band at 450–800 cmis attributed to O-Ti-O vibrations, while broad bands at 1610 cmand 3250–3600 cmin PNT are caused due to the adsorption of water and the vibration of the –OH stretching and bending group. As a result of the enlargement of prominent bands of hydroxyl groups caused by the nitrogen incorporation onto TiO, the catalyst has the capacity to generate more highly reactive hydroxyl radicals during photocatalysis, enhancing their performance. TiOdoping with nitrogen showed additional vibration bands at 1232 cmand 1160 cmcorresponding to Ti-N vibrations.