**5. Conclusions**

Black titania nanostructures have attracted extensive interest, and several reductive and oxidative approaches have been established to successfully fabricate the black or coloured titania. A variety of structural and chemical modifications are in practice to impart unique features to black titania, like surface amorphousity, oxygen vacancy/Ti3+, *Perspective Chapter: Black Titania – From Synthesis to Applications DOI: http://dx.doi.org/10.5772/intechopen.110545*

### **Figure 10.**

*a) Upper: Estimated relative band edges of the (101) and (001) facets of the anatase phase of titania, lower: Spin densities around the oxygen vacancy in (101) and (001) slab model of anatase TiO2 under antiferromagnetic alignment. The yellow and cyan isosurfaces refer to up-spin and down-spin densities, respectively. b) CO production over TiO2 and TiO2-x nanocrystals with different exposed facets under visible light. Reproduced with permission [36]. Copyright 2016, American Chemical Society.*

hydroxyl groups and Ti–H bonds. These modifications lead to the change in the electronic structure of titania, for example, decreasing bandgap, which is responsible for the improved visible-light absorption features of black titania. Furthermore, the accompanying charge transport features are enhanced because of the decreased electron-hole recombination. Additionally, the most defective structure of black titania assists the adsorption and dissociation of the reactant on its surface, as well as the consequent charge transfer process. Such a novel optical and electrical features endow the material with enhanced photocatalytic activities as compared to white titania.
