Since the discovery of TiO2 as a photocatalyst material, the field of research gained increasing interest.
TiO2 offers several benefits over other photocatalytic materials such as being non-toxic as well as
chemically stable. However, the material only utilizes about 5% of the solar spectrum for photocatalysis
due to its large bandgap. Therefore, bandgap tuning of TiO2 is intensively discussed and several
possibilities are suggested, including doping the material with halogenide elements, carbon,
nitrogen, as well as the modification with hydrogen to obtain black TiO2. During the preparation
of carbon-doped titanate nanotubes for fuel cell applications, our group discovered a carbon doping
method of TiO2 using acetylene/nitrogen gas. The initial approach was modified to work inside a
rotary tube furnace since its publication in 2018. Ever since this discovery, the mechanism of the carbon
doping was not fully understood. To our knowledge, this applies to almost every carbon-doped TiO2, as
several theoretical calculations are available highlighting and discussing the possible opportunities such
as interstitial carbon, substitutional carbon for oxygen or titanium or even combinations with oxygen
vacancies inside the structure.
We are working on solving the mechanism of carbon doping TiO2 for our acetylene/nitrogen gas method
by addressing carbon incorporation via Raman spectroscopy, thermogravimetric measurements, and
diffuse reflectance spectroscopy. Furthermore, we are addressing changes in anatase, and rutile
structure obtained by modifying TiO2 with carbon as well as without the need of dopant elements or
hydrogen by the reduction of TiO2 from sol-gel synthesis. Structural changes were investigated by
Raman spectroscopy as well as by X-ray diffraction. Our obtained carbon-doped samples showed
changes in bandgap structure, structural changes indicating carbon incorporation into the anatase/
rutile structure as well as surface carbon layers.