Anatase bandgap energy

Catalyst Anatase, % BET surface area, m2/g Panicle size, nm Purity as TiQ2, % Bandgap energy, eV... 

Absorption of a photon with an energy hv greater or equal the bandgap energy Eg of the semiconductor (i.e., 3.2 eV for titanium dioxide in its anatase modification) generally leads to the formation of an electron/hole pair in the semiconductor particle (reaction (7.1) and Fig. 7.1). 

The bandgap energy for the anatase form of Ti02 is close to 3.2 eV which corresponds to the onset of absorption around 390 nm, whereas Ti02 with crystal structure of rutile (the bandgap is about 3.0 eV) should absorb light with wavelength shorter than 412 nm. 

The most serious problem however relates to the relatively large bandgap of titanium dioxide. Titanium dioxide (anatase) has a bandgap energy of... 

Fig. 3.5 Band position of anatase Ti02, bandgap = 3.2 eV, in the presence of a pH = 1 aqueous electrolyte. The energy scale is indicated in electron volts (eV) using either normal hydrogen electrode (NHE) or vacuum level as reference showing the condition for water splitting.

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