Modification of N-doped TiO₂ photocatalysts using noble metals (Pt, Pd) – a combined XPS and DFT study

Abstract

Nitrogen-doped TiO (N-TiO) is considered as one of the most promising materials for various photocatalytic applications, while noble metals Pd and Pt are known as good catalysts for hydrogen evolution. This work focuses on the determination of structural and electronic modifications of N-TiO, achieved by noble metal deposition at the surface, as a starting indicator for potential applications. We focus on the properties of easily synthesized nanocrystalline nitrogen-doped anatase TiO, modified by depositing small amounts of Pd (0.05 wt%) and Pt (0.10 wt%), aiming to demonstrate efficient enhancement of optical properties. The chemical states of dopants are studied in detail, using X-ray photoemission spectroscopy, to address the potential of N-TiO to act as a support for metallic nanoparticles. DFT calculations are used to resolve substitutional from interstitial nitrogen doping of anatase TiO, as well as to study the combined effect of nitrogen doping and oxygen vacancy formation. Based on the binding energies calculated using Slater's transition state theory, dominant contribution to the N 1s binding energy at 399.8 eV is ascribed to interstitially doped nitrogen in anatase TiO. Given that both structure and photocatalytic properties depend greatly on the synthesis procedure, this work contributes further to establishing correlation between the structure and optical properties of the noble metal modified N-TiO system.

Synergistic Effect of Fluorinated and N Doped TiO2 Nanoparticles Leading to Different Microstructure and Enhanced Photocatalytic Bacterial Inactivation

“…Here, our N-doped P25 samples showed better absorption compared with the P25-UN showing that N doping gives successful visible light absorption. Similar to other studies in the literature, we observed a better light absorption in the visible range for our N-doped [ 27 , 42 ] and F-doped samples [ 28 ]. Moreover, P25-F-HT and P25-F&N-HT showed a similar trend for the same anatase-to-rutile ratio.…”

“…All of these results showed that doped samples changed the electronic structures of P25 that were associated with lower band gap energy. Similar modifications in the adsorption spectra have been previously observed for N and F monodoped anatase nanoparticles [ 42 , 53 ]. However, it was found that F&N modification considerably enhanced the visible light absorption of TiO 2 as observed in our experiments [ 34 , 54 ].…”

“…The highest intensity peak at 400 eV relates to interstitial doping, as stated by different groups [ 38 , 39 , 40 , 41 ]. In addition, this higher binding energy, which was confirmed more recently by Batalović et al using Density functional theory (DFT) calculations, is attributed to interstitial nitrogen located near the lattice oxygen forming a short N–O bond [ 42 ]. The peak at 397.9 eV, despite a poor signal-to-noise ratio and low intensity, can possibly be assigned to atomic nitrogen bonded to titanium, with the N atom replacing the oxygen atoms in the TiO 2 crystal lattice to form a N–Ti–N bond [ 43 ].…”

Photocatalytic Degradation of Bisphenol-A using N, Co Codoped TiO2 Catalyst under Solar Light

“…The peak at 399.1 eV demonstrated that nitrogen is incorporated into the TiO 2 lattice. This considered to be the evidence of the presence of the Ti–N bond 32 .…”

Effect of Synthesis Conditions of Nitrogen and Platinum Co-Doped Titania Films on the Photocatalytic Performance under Simulated Solar Light

“…It has to be pointed out that nitrogen incorporation in the Ns form (BE~396 eV) is only reported for a few instances of nitrogen and metal ions co-modified, titania obtained by the sol-gel method (using urea and RuCl 3 [39], ammonia and Sr(NO 3 ) 2 [43], dodecylamine and Fe(NO 3 ) 3 •9H 2 O [44], tetramethylethylenediamide and Pt 0 /Pt 2+ [45]). Additionally, N1s lines with BE at 397.5 defined by XPS in the samples obtained by the solvothermal method using urea and H 2 PtCl 6 are also reported [46]. Thus, the possibility of N to be incorporated in Ns and Ni forms by means of the sol-gel technique depends on the nature of the co-doped metal ions.…”