**Author details**

N is one of the most used non-metals, as doping may be carried out rather simply by thermally

The ultimate effect of N of the light absorption capacity of the sample is however complex and

photocatalytic properties. For instance, by a template-free combustion method, a wormhole

Two photocatalytic reactions were studied, namely, Rhodamine B degradation and *p*-anisyl alcohol oxidation to *p*-anisaldehyde in aqueous solution under direct sunlight. Notwithstanding the high band gap (3.24 eV) of the N-doped sample, the good activity was assigned to a better utilisation of holes due to the low-charge diffusion barrier associated with wormhole mesoporosity along with the occurrence of crystalline NPs, finally confirming the

tures in the 400–800°C range), high crystallinity and Vis light response. The N-doped anatase

P25 for the degradation of phenol under both UV and Vis light irradiation, owing to more oxidising hydroxyl radicals, which were the oxidative species mainly responsible for the degradation of phenol [74]. The authors concluded that the materials might be beneficial to solar-

However, the effect of doping on the photocatalytic performance is not straightforward, as it

but lower UV light-responsive photocatalytic activity. The visible light photocatalytic activity originates from new N 2*p* levels near the valence band. The oxygen vacancies and the associ-

The production of mesoporous titania by template-assisted methods allows obtaining materials characterised by ordered mesoporous structure, controllable crystallinity, high surface

photocatalysts showed much higher photocatalytic activity than N-doped Degussa

g−1) and type-IV H3-mesoporosity.

was obtained, where N doping was due to the presence of urea during combustion

produced in solutions containing a

materials with improved

g−1 for calcination tempera-

occurred as nanocrystalline anatase phase, showing

was prepared via soft-template route by using CTAB as template

atmosphere the calcined samples. The material was char-

shows visible light-responsive photocatalytic activity

/h<sup>+</sup>

, finally reducing

under NH3(g) flow or by heating a M-TiO<sup>2</sup>

(i) Band-gap narrowing due to N2p states close in energy to O2p states

(ii) Formation of impurity energy levels above the valence band

All this notwithstanding, literature reports on N-doped M-TiO<sup>2</sup>

importance of having an ordered mesoporous photocatalyst.

acterised by small crystallite size, large surface area (420–126 m<sup>2</sup>

driven applications in the photodegradation of organic pollutants.

ated Ti3+ species act as the recombination centres for the photoinduced e<sup>−</sup>

photocatalytic activity although contributing to Vis light absorbance [75].

(70%)/N<sup>2</sup>

treating M-TiO2

134 Titanium Dioxide

, urea, etc.).

(iii) Partial doping in oxygen vacancies

[73]. The so-obtained N-doped M-TiO2

has been observed that N-doped TiO2

high surface area (234 m2

N-doped anatase M-TiO2

and by treating in NH3

**4. Conclusions**

may be due to different processes:

N source (NH3

M-TiO2

M-TiO2

Barbara Bonelli1 \*, Serena Esposito<sup>2</sup> and Francesca S. Freyria1,3

\*Address all correspondence to: barbara.bonelli@polito.it

1 Department of Applied Science and Technology, INSTM Turin-Polytechnic Unit, Polytechnic University of Turin, Turin, Italy

2 Department of Civil and Mechanical Engineering, University of Cassino and Southern Lazio, Cassino, Italy

3 Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
