| Summary: | Titanium dioxide (TiO2) is a metal oxide semiconductor that is widely
used in solar energy application because its highly thermal and chemical stability,
inert, non toxic, high specific surface area and easy to prepare. However, the
intrinsic wide band gap nature of TiO2 (3�3,4 eV) impairs TiO2 from playing such
important role since it provides less respond to visible light. In order to increase
the efficiency of solar energy utilization based on TiO2, it is a need to improve its
activity in visible region mainly focusing on nitrogen doping. In this research, the
synthesis of anatase type N-doped TiO2 mesopore was done through one step sol
gel technique, where the pore formation process and nitrogen doping process were
done in one step. Dodecylamine was used as pore template agent and nitrogen
source, whereas titanium tetraisopropoxide (TTIP) as titania precursor. The
improvement of TiO2 with respect to visible light response was then tested as
catalyst material in methylene blue photodegradation and as semiconductor
material in dye-sensitized solar cells (DSSC) system.
The one step sol gel synthesis of N-doped TiO2 begins with formation of
dodecylamine micelle structure before the addition of titanium precursor. The
mixed precursor solution was then refluxed to facilitate the coordination between
dodecylamine and TTIP. In order to control the hydrolysis rate, the acid was
added to the mixed precursor solution after reflux treatment. Hydrolysis process
was achieved by adding aquadest gradually to prevent particle agglomeration and
fast formation of TiO2. Calcination treatment was done to eliminate the template
from the resulted solid to form the pore and crystal structure of TiO2. The result
showed that acidic condition, mole ratio of N/Ti precursor, H2O content in
hydrolysis process influenced the crystal structure and porosity of resulting N-
doped TiO2. Acidic condition influenced the N-doped TiO2, where the low acidic
condition lead to raise rutile type crystalline formation. The acidic condition also
influenced the porosity of N-doped TiO2, where the high acid condition did not
support the mesostructural formation. The pH range of 5 � 7 provided the
optimum formation of N-doped TiO2 mesostructure. The mole ratio of N/Ti
precursor showed a significant effect on the porosity of the N-doped TiO2 and
nitrogen content but only a little influence on the crystal structure. H2O content on
hydrolysis process affects both the porosity and the crystallinity of N-doped TiO2
because the content of H
+
ions regulates the interaction between TTIP and
dodecylamine. While the variation of the calcination temperature affects the phase
and crystal size and also the amount of nitrogen doped. The presence of nitrogen
doped in TiO2 provides a response to visible light.
Application of N-TiO2 as a photocatalyst on methylene blue degradation
reactions is influenced by the physicochemical and adsorption characters of N-
doped TiO2. The reaction rate constant of methylene blue degradation using N-
doped TiO2 catalysts is related to the specific surface area, pore volume, amount
of nitrogen doped, maximum adsorption capacity and adsorption equilibrium
constants. The adsorption characters of N-doped TiO2 are also strongly influenced
by its physical character, i.e. the specific surface area and amount of nitrogen
doped. N-doped TiO2 has higher adsorption equilibrium constant and maximum
adsorption capacity values than pure TiO2
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