In this study, two cobalt based catalyst samples were prepared on titania and tita-
nia nanotubes supports using the deposition precipitation method. Their structural con-
figurations were characterized and compared using BET, and TRP analyses. The BET 
analysis showed that the surface area of TiO2 is much higher than that of TNT which 
was due to their structural differences. Analyses of the results obtained revealed that the 
surface area of the 10%Co/TNT catalyst sample is higher than that of the 10%Co/TiO2. 
The TPR analysis showed that it is much easier to reduce 10%Co/TiO2, than 
10%Co/TNT. This is attributed to be due to the fact that the cobalt particles were ad-
sorbed on the surface of the TiO2, and formed covalent bonds with TNT. Therefore 
reduction temperature was higher with TNT than TiO2. The investigation of structural 
changes of these catalysts when they were coated with carbon, using chemical vapour 
deposition method was also conducted. The catalyst prepared on TNT support showed 
better properties in terms of average pore diameter, pore volume and surface area than 
the catalyst sample prepared on TiO2 support when the two samples were exposed to 
carbon environment for the same period of time.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2060

Abdulkareem, A.S.

Afolabi, A.S.

Malose, M.M.

Muzenda, E.

SocioEconomic Challenges Journal (Sumy State University)

Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   93 
 
COMPARISON OF THE STRUCTURAL CONFIGURATION 
OF Co NANOPARTICLES ON TiO2 AND TNT SUPPORTS 
Ayo S. Afolabi1*, Ambali S. Abdulkareem1, Marcus M. Malose1, Edison Muzenda2 
 
1 University of South Africa, Department of Civil and Chemical Engineering, College of Science, 
Engineering and Technology, P/Bag X6 Florida 1710, Johannesburg, South Africa. 
 2 University of Johannesburg, Department of Chemical Engineering, Faculty of Engineering and 
the Built Environment, Johannesburg, South Africa. 
 
ABSTRACT 
In this study, two cobalt based catalyst samples were prepared on titania and tita-
nia nanotubes supports using the deposition precipitation method. Their structural con-
figurations were characterized and compared using BET, and TRP analyses. The BET 
analysis showed that the surface area of TiO2 is much higher than that of TNT which 
was due to their structural differences. Analyses of the results obtained revealed that the 
surface area of the 10%Co/TNT catalyst sample is higher than that of the 10%Co/TiO2. 
The TPR analysis showed that it is much easier to reduce 10%Co/TiO2, than 
10%Co/TNT. This is attributed to be due to the fact that the cobalt particles were ad-
sorbed  on  the  surface  of  the  TiO2, and formed covalent bonds with TNT. Therefore 
reduction temperature was higher with TNT than TiO2. The investigation of structural 
changes of these catalysts when they were coated with carbon, using chemical vapour 
deposition method was also conducted. The catalyst prepared on TNT support showed 
better properties in terms of average pore diameter, pore volume and surface area than 
the catalyst sample prepared on TiO2 support when the two samples were exposed to 
carbon environment for the same period of time.  
 
Key words: catalyst, configuration, TNT, TiO2, support  
 
INTRODUCTION 
A catalyst can either be heterogeneous or homogeneous, depending on 
whether it exists in the same phase as the substrate. Most heterogeneous cata-
lysts are solids that act on substrate in a liquid or gaseous reaction mixture, and 
the total surface area of solid has an important effect on the reaction rate. Thus 
the smaller the catalyst particle size the larger the surface area for a given mass 
of particles and the higher the reaction rate [1]. Supports provide a platform 
from which heterogeneous catalysts, can act to change the rate of a reaction 
without being consumed during the reaction. The support material may or may 
not take part in the catalytic reaction. The support is usually a surface such as a 
metal oxide or carbon material. The support and catalyst may bond together in 
such a way to enhance the reactivity of the catalyst. In other cases, the support 
                                               
* e-mail: afolaas@unisa.ac.za, tel: +27(0)11 471 3617; fax: +38(0)11 471 3054 
94                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I            
 
may be inactive and provide a high surface area substrate to increase the colli-
sions of the reactants with the catalysts. For example, in catalytic converters, a 
ceramic  honeycomb acts  as  a  high  surface  area  support  for  a  catalyst  such as  
platinum, rhodium, or palladium for changing pollution gases from the engine 
to environmentally friendly products. In fuel cells, platinum catalysts are locat-
ed on a carbon support, which provides a means for conduction of the electrons 
for the electrocatalytic reactions [2, 3]. 
TiO2 is used in heterogeneous catalysis as a photo catalyst, in solar cells 
for  the  production  of  hydrogen  and  electric  energy,  as  gas  sensor,  as  white  
pigment, as a corrosion-protective coating, as an optical coating, in ceramics, 
and in electric devices such as varistors [4]. TiO2 is not suitable as a structural 
support material, but small additions of titania can modify metal-base catalysts 
in a profound way. A strong-metal support interaction is in part due to encapsu-
lation of the metal particles by a reduced TiOx over layer [5]. The support pro-
vides a high surface area substrate to increase the collisions of the reactants 
with the catalysts which increase the reaction rate; it also gives a good disper-
sion of a catalyst which results in an optimal surface area. Previous studies 
have shown the performances of TiO2 as support for different metal catalysts 
[6]. It has been known that the Co/TiO2 catalyst is considered to have a strong 
metal support interaction (SMSI) and shows a high activity in CO hydrogena-
tion reactions [6,7]. This interaction is an important factor used for determining 
the properties of a Co/TiO2 catalyst such as cobalt dispersion and reduction 
behavior [8]. 
The synthesis of highly dispersed cobalt on a TiO2 support requires the 
strong interaction between cobalt and support. However a too strong interaction 
can produce a Co-support compound as a suboxide at an interface that is highly 
resistant to reduction [9 – 11]. It has been reported that Co-support compound 
formation (Co-SCF) during standard reduction resulted in a lower reducibility 
of a Co/TiO2 catalyst. It has been known that the dominant surface sites of TiO2 
support  consists  of  two  main  sites   Ti4+ and  Ti3+ [6, 12 – 16]. The effect of 
surface sites on the formation of Co-SCF has not yet been investigated.   
This study is therefore aimed at loading cobalt particles on both TiO2 and 
TNT supports using the deposition precipitation method for catalyst prepara-
tion, coating the supports TiO2 and  TNT  with  carbon  (TiO2-C and TNT-C) 
using chemical vapour deposition method and use characterization methods to 
compare the structural configurations of the two supports and catalysts. 
EXPERIMENTAL 
A 2.5 g of a hydrated cobalt nitrate (Co(NO3)2.6H2O) sample was mixed 
with   0.76  g  of  urea  respectively  and  5  ml  of  deionised  water  was  added  to  
dissolve  the  solid  mixture.  A  few  drops  of  deionised  water  were  added  in  a  
beaker with 5 g of the TiO2 support, in an oil bath at 90oC while stirring. A 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   95 
 
solution of urea and (Co(NO3)2.6H2O) was added drop-wise into the support 
using a burette, while stirring until  the mixture was dry. The sample was then 
dried overnight at 120oC in an oven. This catalyst precursor was then calcined 
at 350oC for 6 hours in air. The same procedure was adopted to impregnated Co 
particles on TNT. 
A chemical vapour deposition (CVD) reactor was used to coat the TiO2 
and TNT samples with carbon. The description of this reactor has been reported 
elsewhere [3, 17, 18]. Acetylene was used as a source of carbon for coating 
TiO2 and TNT. About 0.2 g of each sample was placed in a small ceramic boat 
placed at the middle of the quartz tube that is about 80 cm in length. The tube 
was then passed through the ceramic tube of the horizontal furnace. Nitrogen 
gas (Afrox, 99.99%) was introduced while heating the sample at a rate of 
10oC/min to 900oC. This was done to ensure an inert atmosphere in order to 
avoid some side reactions. At 900oC, acetylene was introduced to replace nitro-
gen gas and the process was done for 60 minutes. 
Reducibility behavior of all the calcined catalysts were studied using an 
in-house  designed  TPR.  A  0.2  g  catalyst  sample  was  placed  in  a  U  shaped  
quartz reactor on top of quartz wool which is used as a catalyst bed. Pure nitro-
gen gas (for degassing) was first passed through the quartz reactor while heat-
ing the reactor at the rate of 10oC/ minute from room temperature to 150oC. The 
temperature was kept at 150oC for thirty minutes to ensure that all the moisture 
content was driven off. The reactor was then cooled to room temperature after 
degassing the sample, 5% hydrogen in argon gas was introduced at the rate of 
30 ml/minute and nitrogen gas was then turned off. Temperature was adjusted 
from room temperature to 900oC at 5oC/minute. The temperature profiles were 
collected from a computer.  
TGA analyses were conducted on a Perkin Elmer TGA 4000. After plac-
ing ?20 mg sample  in  a  ceramic  pot  it  was  heated  at  10oC/minute from room 
temperature to 900oC under a constant flow of air (20 ml/minute). The weight 
loss as a function of temperature was monitored on a computer. 
Nitrogen adsorption measurements were performed at -196oC using a Mi-
crometrics Tristar adsorption analyzer. The samples (mass?0.2 g) were loaded 
in the Micrometrics tubes and degassed at 150oC for overnight in nitrogen 
(99.99% purity). The tubes were then attached to the Tristars analysis and run 
overnight.  
RESULTS AND DISCUSSION 
Figures 1a, b show the typical structures of the titania nanotubes and tita-
nia supports respectively. It can be seen that the titania nanotubes have tubular 
structure while the titania has a spherical structural configuration. The titania 
nanotubes also show a well–ordered structure with relatively simple composi-
tions are formed by titania materials [19]. The tubular structure of the titania 
96                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I            
 
nanotubes is similar to those of carbon nanotubes and it is expected that they 
will possess exceptional physical, mechanical and electrical properties such as 
the latter.  
 
 
Fig. 1 – Structures of (a) titania nanotubes and (b) titania catalyst supports 
 
The surface area property is very important in the preparation of catalyst 
because it is responsible for the distribution of the catalyst particles on the sup-
port. The larger the surface area of the support, the better it is for good distribu-
tion of the catalyst particles and the better the activity of the resulting catalyst. 
The tubular structure of the titania nanotubes gives it a larger surface area than 
their titania counterpart. This is confirmed by the comparative surface areas 
results of the two structures as shown in Table 1.  
Table 1 shows the BET analysis of the two supports and their respective 
catalyst samples which reveals the pore volume, pore diameter and the surface 
area of the samples. The average diameters of the supports and the Co-loaded 
catalysts exist within the nano–range of the 10.2 and 35.5, which shows that the 
particles are fine enough to give even distribution and subsequent good catalyt-
ic activity for hydrogen oxidation and oxygen reduction reactions [20]. The 
preparation method is also a crucial method in the size of the particles; TNT 
was prepared from the TiO2 and the average diameter of the nanotube material 
is smaller than that of the initial material.  
 
Table 1 – BET analysis of the supports, and 10%Co/TNT & 10%Co/TiO2 catalyst 
samples. 
Sample Average pore 
diameter (nm) 
Pore volume (cm3/g) Surface area 
(m2/g) 
TiO2 
TNT 
10%Co/TiO2 
10%Co/TNT 
35.5 
10.2 
28.2 
12.9 
0.420 
0.370 
0.379 
0.484 
47.2 
231 
53.8 
150 
 
a 
b 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   97 
 
Similar trend is observed in the Co loaded samples of the TiO2 and TNT 
in  which  the  latter  has  a  smaller  size  compared  to  the  former.  It  can  also  be  
observed that the surface area and the pore volume of a 10%Co/TNT sample 
were much higher than that of a 10%Co/TiO2 sample. This can be attributed to 
the structural change of TNT support when it  was prepared from TiO2 of sur-
face area 47.2 m2/g that resulted in a very high surface area of 231.1 m2/g.       
The temperature programmed reduction (TPR) profile (Figure 2) indicates 
the behaviour of a cobalt oxide loaded on TiO2 and TNT supports. These 
catalysts were  both prepared using the deposition precipitation method. Urea is 
used as a cobalt particles precipitator and is believed to be favourable for the 
production of small metal particles as well as acted as a reducing agent during 
the catalyst preparation. The prepared catalyst samples were heated to 1000oC 
at the rate of 5oC, and held at 1000oC for two hours followed by slow cooling in 
static air. The form of heat treatment is an important and necessary step in the 
preparation of the catalysts because it has a significant impact on the Co metal 
particle size and distribution, particle surface morphology, and Co particle 
distribution on the supports [21]. The calcination or thermal treatment, removed 
the volatile compounds contained in the catalysts and removed the undesirable 
impurities resulting from the early preparation stages, to allow a uniform dis-
persion and stable distribution of the Co particles on the supports, and therefore 
improves the electrocatalytic activity of the synthesized catalysts.  
100 200 300 400 500 600 700 800 900
 10% Co/TiO2
Temperature (oC)
-2
0
2
4
 
 10% Co/TNT
 
Fig. 2 – TPR profile of 10%Co/TiO2 and 10%Co/TNT catalyst samples 
98                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I            
 
The TPR profile shows that the reduction temperature of a 10%Co/TNT 
occurred at  360oC and 650oC while the reduction temperature of 10%Co/TiO2 
occurred at 360oC and 500oC  (Table  2). suggests that it is easier to reduce 
10%Co/TiO2 catalyst sample than 10%Co/TNT catalyst sample. This could be 
due structural metal surface interface (SMSI), because the structural configura-
tion of Co when loaded on TiO2 shows that  the  Co particles  adsorbed on the  
surface of the TiO2, while the structural configuration of Co loaded on TNT 
support indicates a bond between the cobalt oxide and the TNT support.  
 
Table 2 – Reduction temperatures of 10%Co/TNT and 10%Co/TiO2 samples 
Sample Temperature (
oC) 
first peak 
Temperature (oC) 
second peak 
Other peaks 
(oC) 
TiO2 
TNT 
10%Co/TiO2 
10%Co/TNT 
- 
- 
360 
376 
- 
- 
500 
446 
500 – 900 
500 – 900 
- 
- 
 
The height of both peaks was dependent on the consumption of a H2 that 
was measured using the TCD detector that was connected to an amplifier. The 
faster the quantity of H2 consumed the higher the height of the peak. From the 
Figure, the peak of the 10%Co/TiO2 sample is higher than that of 10%Co/TNT 
catalyst sample which can be due to the distribution of cobalt oxide particles on 
the TiO2 support. The reason for the shorter peak of 10%Co/TNT catalyst sam-
ple is attributed to the fact the rate of H2 consumption is slower than that of 
10%Co/TiO2 because the cobalt oxide particles are not close to each other as 
with 10%Co/TiO2. 
On  10%Co/TNT  graph  two  more  peaks  appears  on  the  far  end  of  the  
graph, which was due to the structural change of the TNT support, this is fur-
ther emphasized in Figure 3a. The change occurred at 500oC and 900oC, this is 
the same with a TiO2 Figure 3b.  
 
Fig. 3 – TPR profiles of (a) TNT and (b) TiO2 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   99 
 
Table 3 shows the average pore diameters, the pore volumes and the sur-
face areas of a TNT-C60minutes and TiO2-C60minutes samples coated with carbon for 
60 minutes. The two samples both spent the same period of time (60 minutes) 
in the furnace to obtain carbon coating from acetylene. It can be observed that 
the surface area and the pore volume of TNT-C60minutes sample were higher than 
that of the TiO2-C60minutes sample. This can be attributed to the difference in the 
configurations of the TNT structure the distribution of carbon on the TNT sup-
port left some space in between as the structure has a certain value of length, 
and when it was distributed on TiO2 the carbon particles did not leave some 
space, as it is believed that the TiO2 has a spherical structural configuration as 
previously indicated.  
 
Table 3 – BET analysis of carbon coated TiO2 and TNT supports 
Sample Average pore diameter (mm) 
Pore volume 
(cm3/g) Surface area (m
2/g) 
TiO2-C60minutes 
TNT-C60minutes 
30.4 
12.2 
0.019 
0.026 
2.4 
3.9 
 
CONCLUSIONS 
The loading of 10% cobalt particles on TiO2 and TNT supports using the 
deposition precipitation method was carried out in this investigation. The struc-
tural configurations of the resulting catalyst samples were characterized and 
compared using TGA, BET, and TRP analyses. BET analysis showed that the 
surface  area  of  TNT  is  much  higher  than  that  of  TiO2 which  was  due  to  the  
tubular structure of the nanotubes as compared to the spherical structural con-
figuration of the TiO2. The surface area of the 10%Co/TNT catalyst sample 
also is higher than of the 10%Co/TiO2 catalyst sample. The TPR analysis 
showed that it is easy to reduce 10%Co/TiO2, than 10%Co/TNT. This is due to 
the fact that the cobalt particles were adsorbed on the surface of the TiO2 and 
formed covalent bonds with TNT. Therefore reduction temperature was higher 
in TNT than TiO2 support. The investigation of structural changes of these 
catalysts when they were coated with carbon, using chemical vapour deposition 
method was also conducted. The catalyst prepared on TNT support showed 
better properties in terms of average pore diameter, pore volume and surface 
area than the catalyst sample prepared on TiO2 support when the two samples 
were exposed to carbon environment for the same period of time. 
 
Acknowledgements 
The authors gratefully acknowledge the financial supports of the National 
Research Foundation (NRF) and Universities of South Africa and Johannes-
burg.  
 
100                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I            
 
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English

Comparison of the structural configuration of Cо nanoparticles on Ti02 and TNT supports

Electronic Sumy State University Institutional Repository

Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   93  COMPARISON OF THE STRUCTURAL CONFIGURATION OF Co NANOPARTICLES ON TiO2 AND TNT SUPPORTS Ayo S. Afolabi1*, Ambali S. Abdulkareem1, Marcus M. Malose1, Edison Muzenda2  1 University of South Africa, Department of Civil and Chemical Engineering, College of Science, Engineering and Technology, P/Bag X6 Florida 1710, Johannesburg, South Africa.  2 University of Johannesburg, Department of Chemical Engineering, Faculty of Engineering and the Built Environment, Johannesburg, South Africa.  ABSTRACT In this study, two cobalt based catalyst samples were prepared on titania and tita-nia nanotubes supports using the deposition precipitation method. Their structural con-figurations were characterized and compared using BET, and TRP analyses. The BET analysis showed that the surface area of TiO2 is much higher than that of TNT which was due to their structural differences. Analyses of the results obtained revealed that the surface area of the 10%Co/TNT catalyst sample is higher than that of the 10%Co/TiO2. The TPR analysis showed that it is much easier to reduce 10%Co/TiO2, than 10%Co/TNT. This is attributed to be due to the fact that the cobalt particles were ad-sorbed  on  the  surface  of  the  TiO2, and formed covalent bonds with TNT. Therefore reduction temperature was higher with TNT than TiO2. The investigation of structural changes of these catalysts when they were coated with carbon, using chemical vapour deposition method was also conducted. The catalyst prepared on TNT support showed better properties in terms of average pore diameter, pore volume and surface area than the catalyst sample prepared on TiO2 support when the two samples were exposed to carbon environment for the same period of time.   Key words: catalyst, configuration, TNT, TiO2, support   INTRODUCTION A catalyst can either be heterogeneous or homogeneous, depending on whether it exists in the same phase as the substrate. Most heterogeneous cata-lysts are solids that act on substrate in a liquid or gaseous reaction mixture, and the total surface area of solid has an important effect on the reaction rate. Thus the smaller the catalyst particle size the larger the surface area for a given mass of particles and the higher the reaction rate [1]. Supports provide a platform from which heterogeneous catalysts, can act to change the rate of a reaction without being consumed during the reaction. The support material may or may not take part in the catalytic reaction. The support is usually a surface such as a metal oxide or carbon material. The support and catalyst may bond together in such a way to enhance the reactivity of the catalyst. In other cases, the support                                                * e-mail: afolaas@unisa.ac.za, tel: +27(0)11 471 3617; fax: +38(0)11 471 3054 94                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I             may be inactive and provide a high surface area substrate to increase the colli-sions of the reactants with the catalysts. For example, in catalytic converters, a ceramic  honeycomb acts  as  a  high  surface  area  support  for  a  catalyst  such as  platinum, rhodium, or palladium for changing pollution gases from the engine to environmentally friendly products. In fuel cells, platinum catalysts are locat-ed on a carbon support, which provides a means for conduction of the electrons for the electrocatalytic reactions [2, 3]. TiO2 is used in heterogeneous catalysis as a photo catalyst, in solar cells for  the  production  of  hydrogen  and  electric  energy,  as  gas  sensor,  as  white  pigment, as a corrosion-protective coating, as an optical coating, in ceramics, and in electric devices such as varistors [4]. TiO2 is not suitable as a structural support material, but small additions of titania can modify metal-base catalysts in a profound way. A strong-metal support interaction is in part due to encapsu-lation of the metal particles by a reduced TiOx over layer [5]. The support pro-vides a high surface area substrate to increase the collisions of the reactants with the catalysts which increase the reaction rate; it also gives a good disper-sion of a catalyst which results in an optimal surface area. Previous studies have shown the performances of TiO2 as support for different metal catalysts [6]. It has been known that the Co/TiO2 catalyst is considered to have a strong metal support interaction (SMSI) and shows a high activity in CO hydrogena-tion reactions [6,7]. This interaction is an important factor used for determining the properties of a Co/TiO2 catalyst such as cobalt dispersion and reduction behavior [8]. The synthesis of highly dispersed cobalt on a TiO2 support requires the strong interaction between cobalt and support. However a too strong interaction can produce a Co-support compound as a suboxide at an interface that is highly resistant to reduction [9 – 11]. It has been reported that Co-support compound formation (Co-SCF) during standard reduction resulted in a lower reducibility of a Co/TiO2 catalyst. It has been known that the dominant surface sites of TiO2 support  consists  of  two  main  sites   Ti4+ and  Ti3+ [6, 12 – 16]. The effect of surface sites on the formation of Co-SCF has not yet been investigated.   This study is therefore aimed at loading cobalt particles on both TiO2 and TNT supports using the deposition precipitation method for catalyst prepara-tion, coating the supports TiO2 and  TNT  with  carbon  (TiO2-C and TNT-C) using chemical vapour deposition method and use characterization methods to compare the structural configurations of the two supports and catalysts. EXPERIMENTAL A 2.5 g of a hydrated cobalt nitrate (Co(NO3)2.6H2O) sample was mixed with   0.76  g  of  urea  respectively  and  5  ml  of  deionised  water  was  added  to  dissolve  the  solid  mixture.  A  few  drops  of  deionised  water  were  added  in  a  beaker with 5 g of the TiO2 support, in an oil bath at 90oC while stirring. A Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   95  solution of urea and (Co(NO3)2.6H2O) was added drop-wise into the support using a burette, while stirring until  the mixture was dry. The sample was then dried overnight at 120oC in an oven. This catalyst precursor was then calcined at 350oC for 6 hours in air. The same procedure was adopted to impregnated Co particles on TNT. A chemical vapour deposition (CVD) reactor was used to coat the TiO2 and TNT samples with carbon. The description of this reactor has been reported elsewhere [3, 17, 18]. Acetylene was used as a source of carbon for coating TiO2 and TNT. About 0.2 g of each sample was placed in a small ceramic boat placed at the middle of the quartz tube that is about 80 cm in length. The tube was then passed through the ceramic tube of the horizontal furnace. Nitrogen gas (Afrox, 99.99%) was introduced while heating the sample at a rate of 10oC/min to 900oC. This was done to ensure an inert atmosphere in order to avoid some side reactions. At 900oC, acetylene was introduced to replace nitro-gen gas and the process was done for 60 minutes. Reducibility behavior of all the calcined catalysts were studied using an in-house  designed  TPR.  A  0.2  g  catalyst  sample  was  placed  in  a  U  shaped  quartz reactor on top of quartz wool which is used as a catalyst bed. Pure nitro-gen gas (for degassing) was first passed through the quartz reactor while heat-ing the reactor at the rate of 10oC/ minute from room temperature to 150oC. The temperature was kept at 150oC for thirty minutes to ensure that all the moisture content was driven off. The reactor was then cooled to room temperature after degassing the sample, 5% hydrogen in argon gas was introduced at the rate of 30 ml/minute and nitrogen gas was then turned off. Temperature was adjusted from room temperature to 900oC at 5oC/minute. The temperature profiles were collected from a computer.  TGA analyses were conducted on a Perkin Elmer TGA 4000. After plac-ing a20 mg sample  in  a  ceramic  pot  it  was  heated  at  10oC/minute from room temperature to 900oC under a constant flow of air (20 ml/minute). The weight loss as a function of temperature was monitored on a computer. Nitrogen adsorption measurements were performed at -196oC using a Mi-crometrics Tristar adsorption analyzer. The samples (massa0.2 g) were loaded in the Micrometrics tubes and degassed at 150oC for overnight in nitrogen (99.99% purity). The tubes were then attached to the Tristars analysis and run overnight.  RESULTS AND DISCUSSION Figures 1a, b show the typical structures of the titania nanotubes and tita-nia supports respectively. It can be seen that the titania nanotubes have tubular structure while the titania has a spherical structural configuration. The titania nanotubes also show a well–ordered structure with relatively simple composi-tions are formed by titania materials [19]. The tubular structure of the titania 96                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I             nanotubes is similar to those of carbon nanotubes and it is expected that they will possess exceptional physical, mechanical and electrical properties such as the latter.    Fig. 1 – Structures of (a) titania nanotubes and (b) titania catalyst supports  The surface area property is very important in the preparation of catalyst because it is responsible for the distribution of the catalyst particles on the sup-port. The larger the surface area of the support, the better it is for good distribu-tion of the catalyst particles and the better the activity of the resulting catalyst. The tubular structure of the titania nanotubes gives it a larger surface area than their titania counterpart. This is confirmed by the comparative surface areas results of the two structures as shown in Table 1.  Table 1 shows the BET analysis of the two supports and their respective catalyst samples which reveals the pore volume, pore diameter and the surface area of the samples. The average diameters of the supports and the Co-loaded catalysts exist within the nano–range of the 10.2 and 35.5, which shows that the particles are fine enough to give even distribution and subsequent good catalyt-ic activity for hydrogen oxidation and oxygen reduction reactions [20]. The preparation method is also a crucial method in the size of the particles; TNT was prepared from the TiO2 and the average diameter of the nanotube material is smaller than that of the initial material.   Table 1 – BET analysis of the supports, and 10%Co/TNT & 10%Co/TiO2 catalyst samples. Sample Average pore diameter (nm) Pore volume (cm3/g) Surface area (m2/g) TiO2 TNT 10%Co/TiO2 10%Co/TNT 35.5 10.2 28.2 12.9 0.420 0.370 0.379 0.484 47.2 231 53.8 150  a b Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   97  Similar trend is observed in the Co loaded samples of the TiO2 and TNT in  which  the  latter  has  a  smaller  size  compared  to  the  former.  It  can  also  be  observed that the surface area and the pore volume of a 10%Co/TNT sample were much higher than that of a 10%Co/TiO2 sample. This can be attributed to the structural change of TNT support when it  was prepared from TiO2 of sur-face area 47.2 m2/g that resulted in a very high surface area of 231.1 m2/g.       The temperature programmed reduction (TPR) profile (Figure 2) indicates the behaviour of a cobalt oxide loaded on TiO2 and TNT supports. These catalysts were  both prepared using the deposition precipitation method. Urea is used as a cobalt particles precipitator and is believed to be favourable for the production of small metal particles as well as acted as a reducing agent during the catalyst preparation. The prepared catalyst samples were heated to 1000oC at the rate of 5oC, and held at 1000oC for two hours followed by slow cooling in static air. The form of heat treatment is an important and necessary step in the preparation of the catalysts because it has a significant impact on the Co metal particle size and distribution, particle surface morphology, and Co particle distribution on the supports [21]. The calcination or thermal treatment, removed the volatile compounds contained in the catalysts and removed the undesirable impurities resulting from the early preparation stages, to allow a uniform dis-persion and stable distribution of the Co particles on the supports, and therefore improves the electrocatalytic activity of the synthesized catalysts.  100 200 300 400 500 600 700 800 900 10% Co/TiO2Temperature (oC)-2024  10% Co/TNT Fig. 2 – TPR profile of 10%Co/TiO2 and 10%Co/TNT catalyst samples 98                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I             The TPR profile shows that the reduction temperature of a 10%Co/TNT occurred at  360oC and 650oC while the reduction temperature of 10%Co/TiO2 occurred at 360oC and 500oC  (Table  2). suggests that it is easier to reduce 10%Co/TiO2 catalyst sample than 10%Co/TNT catalyst sample. This could be due structural metal surface interface (SMSI), because the structural configura-tion of Co when loaded on TiO2 shows that  the  Co particles  adsorbed on the  surface of the TiO2, while the structural configuration of Co loaded on TNT support indicates a bond between the cobalt oxide and the TNT support.   Table 2 – Reduction temperatures of 10%Co/TNT and 10%Co/TiO2 samples Sample Temperature (oC) first peak Temperature (oC) second peak Other peaks (oC) TiO2 TNT 10%Co/TiO2 10%Co/TNT - - 360 376 - - 500 446 500 – 900 500 – 900 - -  The height of both peaks was dependent on the consumption of a H2 that was measured using the TCD detector that was connected to an amplifier. The faster the quantity of H2 consumed the higher the height of the peak. From the Figure, the peak of the 10%Co/TiO2 sample is higher than that of 10%Co/TNT catalyst sample which can be due to the distribution of cobalt oxide particles on the TiO2 support. The reason for the shorter peak of 10%Co/TNT catalyst sam-ple is attributed to the fact the rate of H2 consumption is slower than that of 10%Co/TiO2 because the cobalt oxide particles are not close to each other as with 10%Co/TiO2. On  10%Co/TNT  graph  two  more  peaks  appears  on  the  far  end  of  the  graph, which was due to the structural change of the TNT support, this is fur-ther emphasized in Figure 3a. The change occurred at 500oC and 900oC, this is the same with a TiO2 Figure 3b.   Fig. 3 – TPR profiles of (a) TNT and (b) TiO2 Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I                   99  Table 3 shows the average pore diameters, the pore volumes and the sur-face areas of a TNT-C60minutes and TiO2-C60minutes samples coated with carbon for 60 minutes. The two samples both spent the same period of time (60 minutes) in the furnace to obtain carbon coating from acetylene. It can be observed that the surface area and the pore volume of TNT-C60minutes sample were higher than that of the TiO2-C60minutes sample. This can be attributed to the difference in the configurations of the TNT structure the distribution of carbon on the TNT sup-port left some space in between as the structure has a certain value of length, and when it was distributed on TiO2 the carbon particles did not leave some space, as it is believed that the TiO2 has a spherical structural configuration as previously indicated.   Table 3 – BET analysis of carbon coated TiO2 and TNT supports Sample Average pore diameter (mm) Pore volume (cm3/g) Surface area (m2/g) TiO2-C60minutes TNT-C60minutes 30.4 12.2 0.019 0.026 2.4 3.9  CONCLUSIONS The loading of 10% cobalt particles on TiO2 and TNT supports using the deposition precipitation method was carried out in this investigation. The struc-tural configurations of the resulting catalyst samples were characterized and compared using TGA, BET, and TRP analyses. BET analysis showed that the surface  area  of  TNT  is  much  higher  than  that  of  TiO2 which  was  due  to  the  tubular structure of the nanotubes as compared to the spherical structural con-figuration of the TiO2. The surface area of the 10%Co/TNT catalyst sample also is higher than of the 10%Co/TiO2 catalyst sample. The TPR analysis showed that it is easy to reduce 10%Co/TiO2, than 10%Co/TNT. This is due to the fact that the cobalt particles were adsorbed on the surface of the TiO2 and formed covalent bonds with TNT. Therefore reduction temperature was higher in TNT than TiO2 support. The investigation of structural changes of these catalysts when they were coated with carbon, using chemical vapour deposition method was also conducted. The catalyst prepared on TNT support showed better properties in terms of average pore diameter, pore volume and surface area than the catalyst sample prepared on TiO2 support when the two samples were exposed to carbon environment for the same period of time.  Acknowledgements The authors gratefully acknowledge the financial supports of the National Research Foundation (NRF) and Universities of South Africa and Johannes-burg.   100                   Nanomaterials: Applications and Properties (NAP-2011). Vol. 2, Part I             REFERENCES [1] Sabatier P. and Senderens J. B. C.R. Acad. Sci. Paris 134, 514, 1962. [2] Diebold U. 2002, Appld Physics A Vol. 76, P 1 - 7  [3] Afolabi A.S. 2009, PhD thesis, University of the Witwatersrand, Johannesburg South Africa. [4] Haller G. L. and Resasco D. E. 1989, Adv. in Catalysis Vol. 36, P 173-235. [5] Dubrovinsky L. S., Dubrovinskaia N. A., Swamy V., Muscat J., Harrison N. M., Ahuja R., Holm B., Johansson B. 2001, Nature Vol. 410, P 653-654. 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Comparison of the structural configuration of Cо nanoparticles on Ti02 and TNT supports

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