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23 

 

 

 

Article 

Photodecomposition of water\ethanol mixtures 

for the production of hydrogen using as catalysts 

TiO2 fibers 
Luana Góes Soares*1, Maurício de Oliveira Vaz2, Sérgio Ribeiro Teixeira2, Annelise Kopp Alves1  

1Ceramic Materials Laboratory, Federal University of Rio Grande do Sul, Rio Grande do Sul, Brazil 
2Thin Film and Nanostructure Laboratory, Federal University of Rio Grande do Sul, Rio Grande do Sul, Brazil 

A R T I C L E   I N F O 
 

Article history: 
Received 02 August 2022  
Received in revised form 
08 September 2022 
Accepted 14 September 2022 
 
Keywords: 
Energy, Ethanol, Hydrogen,  
Fibers, Water-Splitting 
 
*Corresponding author 
Email address:  
lugoes.soares@gmail.com 

 
 
 
 
DOI: 10.55670/fpll.fuen.2.1.4 

A B S T R A C T 
 

The consumption of hydrogen as an automotive fuel has been growing since 
the 1980s. It can be used both as a gasoline blend and as a pure fuel. All human 
activities involve the use of energy. Some examples are: fuels for transport and 
heating, electricity for various purposes, among others. It is a basic element for 
the production and commercialization of any goods or services and represents 
one of the main expenses of families. Thus, projected future trajectories for 
energy prices are of obvious interest to consumers and producers. The use of 
hydrogen generation and storage technology is an energy generation option to 
replace current fossil fuels, as it offers the opportunity to obtain energy with 
reduced environmental impacts and which does not pollute the environment. 
In this work, TiO2 fibers were obtained by the electrospinning technique and 
used as catalysts in the photodecomposition of water-ethanol mixtures for the 
production of hydrogen. The X-ray diffraction technique (XRD) was used to 
characterize the synthesized catalysts, the BET method provided 
measurements of the specific area, and scanning electron microscopy (SEM) 
analyzed the morphology of the samples. The results indicate that the fibers 
that contain the anatase phase in greater proportion have a high surface area 
and were the most effective in the production of hydrogen. 

 

 
1. Introduction  

The increase in energy demand is related to 

macroeconomic growth, which translates into more 

disposable income for families, allowing for greater 

consumption of fuel, electricity, and other energy uses. With 

this, it is necessary that companies demand more energy, 

aiming to facilitate a greater production of goods and 

services. The literature reports that the elasticity/income 

ratio of energy consumption is around 1, that is, under 

normal conditions, the percentage increase in an economy 

causes a corresponding increase in the demand for energy. 

Countries such as the United States and countries that 

subsidize fuel, as well as oil-producing countries, which 

command the rise and taxation of fuel prices, interfere 

negatively in energy intensity. Currently, energy sources are 

being sought that combine energy efficiency, energy security, 

and the reduction of polluting gas emissions into the 

atmosphere. The generation of energy through H2 creates 

substantial incentives not only for the adoption of efficiency 

measures and technologies to reduce consumption but also 

for the substitution of fossil energy sources. Below we 

highlight some examples of sustainable energy: plug-in 

hybrid electric vehicles, ethanol, biodiesel, and hydrogen [1]. 

Within this context, hydrogen (H2) has attracted the 

attention of researchers, due to some characteristics, such as 

the fact that it can be stored for later consumption, 

converted into electrical energy, serving as a link between 

various forms of energy because of its high energy value, 

among others [2]. Several techniques have been applied for 

the separation of water, such as catalytic reform of organic 

compounds and biological processes, aiming at the 

production of H2. Using these techniques, hydrogen is 

obtained by breaking the water molecule [3]. Some ways to 

produce hydrogen include: primary energy sources (such as 

coal, natural gas, and oil); intermediate sources (chemicals 

such as refinery, ammonia, and ethanol), and alternative 

energy sources (such as biogas, waste gases, and biomass). 
Obtaining hydrogen using photocatalytic processes is still 

low. The main disadvantage of using these processes is the 

possibility of recombination of the electron/hole pair, which 

 

 

Future Energy 

Open Access Journal 

https://doi.org/10.55670/fpll.fuen.2.1.4 

 

 

 

 

 

 

 

 

 

 

 

 

February 2023| Volume 02 | Issue 01 | Pages 23-26 

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LG Soares et al. /Future Energy                                                                                               February 2023| Volume 02 | Issue 01 | Pages 23-26 

24 

 

is generated during the photocatalytic process. Another 

factor that contributes to its low use is because TiO2 has a 

wide band gap (~3.2 eV), which allows its activation only 

under UVA light irradiation. Therefore, this work shows the 

efficient production of hydrogen by water-splitting, using 

TiO2 catalysts and ethanol as a sacrificial agent [4].  

2. Experimental 

For the synthesis of fibers by electrospinning, the 

following reagents were used: Titanium propoxide (Sigma-

Aldrich), glacial acetic acid (Sigma-Aldrich), anhydrous ethyl 

alcohol (Zeppelin), and a 10% solution by weight of 

polyvinylpyrrolidone (PVP – Sigma-Aldrich, 1.300,000 

g/mol). 

3. Methodology 

3.1 Obtaining fibers by electrospinning 

The first step for the synthesis of fibers by 
electrospinning was to prepare the precursor solution that 
contained the mixture of: 2.5 mL of titanium propoxide 
(TiP); 2 mL of glacial acetic acid and 5 mL of an alcoholic 
solution containing 10% by weight of polyvinylpyrrolidone 
(PVP). After completion of the first step, a 5 mL plastic 
syringe was connected to a 1 mm internal diameter stainless 
steel hypodermic needle and filled with the precursor 
solution. The needle was connected to the high voltage 
source. The distance between the needle tip and a rotating 
cylindrical collector covered with aluminum foil was 12 cm. 
A voltage of 13.5 kV was applied between the needle and the 
collector. An infusion pump (KD Scientific) controlled the 
flow of the precursor solution (1.8 mL/h). Fibers were 
collected every 30 minutes for a period of 4 hours daily. 
After obtaining the fibers by electrospinning, they were 
subjected to heat treatment in an electric oven (SANCHIS) at 
temperatures of 650 °C, 700 °C, 750 °C or 800 °C, with 
parameters of 1 hour and a heating rate of 1.4 °C/min in 
order to remove polymeric material and form crystalline 
phases. 

3.1.1 Characterization methods 
To identify the phases formed in the samples, a 

PHILIPS X'PERT diffractometer was used, with CuKα 
radiation, operating with a voltage of 40 kV and a current of 
40 mA, a speed of 0.05°/min, and a step of 1 s in the range of 
5° to 75°. The diffractograms obtained were compared with 
the JCPDS database (Joint Committee on Powder Difraction 
Standards) using the X'Pert HightScore® software. The 
specific surface area was determined using the Brunauer 
Emmett Teller (BET) method. The equipment used was an 
Autosorb Nova 1000e, Quantachrome Instruments. The 
morphology of the samples was observed through the 
technique of scanning electron microscopy (SEM). Band gap 
energy was determined by diffuse reflectance spectroscopy 
(DRS). The equipment used was a dual-beam UV-Vis-NIR 
spectrophotometer Cary Agilent 5000, with an integrating 
sphere in diffuse light reflection mode. The photocatalysis 
process was carried out in a photocatalytic reactor made of 
pyrex glass, where the radiation was provided by 12 black 
light lamps of 8 W each (Fluor BLB T5, Sadokin). After the 
start of the assay, 4 mL aliquots were withdrawn with a 
syringe at 15-minute intervals, filtered through a 0.2 µm 
filter, and transferred to polymethlmethacrylate (PMMA) 
cuvettes. Then, the aliquots were analyzed for their 
absorbance Cary 5000, Agilent, with UMA accessory by 
scanning the wavelength of the radiation λ = 365 nm. The 

determination of photocatalytic activity was performed 
based on the C/Co ratio, where C is the molar concentration 
of the aqueous dye solution with the catalyst at the time of 
analysis and Co is the initial molar concentration of the 
aqueous dye solution without the presence of the catalyst.  

3.2 Hydrogen production 

Hydrogen was produced using a quartz reactor 
consisting of double walls through which the water 
circulated, with a constant temperature of 25 0C. After this 
step, the catalysts, one at a time, were submerged in a 
solution of 7.5 mL of deionized water and 2.5 mL of ethanol. 
Before starting irradiation, analytical argon was bubbled 
through to remove dissolved gases, and the system was 
deaerated through a vacuum line. To simulate sunlight, a 300 
W xenon lamp illuminated the reactor. The gases produced 
were collected using a Hamilton gas syringe at 30 min 
intervals for 4 h and quantified using a GC-Agilent 6820 
chromatograph. The total volume of samples injected into 
the chromatograph was 1.000 μL. 

4. Results and discussion 

Figure 1 depicts the diffractogram of the fibers. The 
samples without heat treatment (WHT) were amorphous. 
The TiO2 catalysts formed anatase (JCPDS 01-078-2486) up 
to 700 ◦ C. From 750 ºC, rutile (JCPDS 01-077-0442) was 
also identified.  The first characteristic peak of the anatase 
and rutile phase appears at approximately 2ө = 25.271º e 
27.294°, respectively. 

 
Figure 1. Diffractogram of TiO2 fibers 

 

Figure 2 shows SEM illustrations of the microstructure 

of TiO2 fibers. Analyzing these images, the TiO2 fibers do not 

seem to have a preferential orientation, appearing to have an 

elongated and continuous microstructure. 

 

 

Figure 2. SEM illustrations of the microstructure of TiO2 

fibers 

 

 



LG Soares et al. /Future Energy                                                                                               February 2023| Volume 02 | Issue 01 | Pages 23-26 

25 

 

Figure 3 demonstrates the surface area of the TiO2 

fibers. Where it is possible to notice that there is a non-

uniform distribution of fiber diameters obtained by 

electrospinning. This is an undesired characteristic of the 

fibers formed during the process. Finding a way to control 

the uniformity of the diameter becomes difficult since the 

lack of uniformity, apparently, is caused by the inconstancy 

of the jet during the path to the collector and by the non-

uniformity in the division of electrical charges within the 

fluid. 

 

Figure 3. Size distribution of TiO2 fibers 

 

Table 1 shows the band gap values of TiO2 fibers 
synthesized by electrospinning and heat treated at 650 ºC, 
700 ºC, 750 ºC, and 800 °C. It is noted that in relation to the 
TiO2 P25 catalyst, the values obtained for the synthesized 
fibers were lower, which indicates that the synthesized 
materials have a great capacity to act as semiconductors. For 
all TiO2 fibers synthesized by electrospinning were able to 
absorb light in the visible region (400-700 nm) of the 
electromagnetic spectrum. These differences in band gap 
values result from the different phases present in the 
synthesized fibers, from the presence of incomplete bonds 
on the surface of this material, which influence the reduction 
of the band gap, which favors the optical properties of the 
material and also the surface effects on the distribution of 
electronic levels [2]. 

By analyzing the results presented in Figure 4, it is clear 
that the heat treatment temperature benefits the removal of 
the zone of maximum slope of the absorption curve for 
longer wavelengths. These changes in the bands correspond 
to the electron transfer that occurs when the electron passes 
from VB to CB, where the antibonding 2p orbitals of O2 (BV) 
are transferred to the empty 3d orbital of lower energy of 
Ti4+ (BC). The interesting to observe, by comparing the 
percentages of anatase and rutile with the respective energy 
gap values described in Table 1 respectively, that the lowest 
Eg value occurs when the TiO2 fibers are composed of 100% 
of the anatase and without the formation of the rutile phase, 
that is, this is an indication that the reduction in the 
proportion of anatase in the TiO2 fibers influences the “gap” 
value of the TiO2 band. Band gaps in semiconductor 
materials are closely related to the absorbed wavelength 
range, where the gap decreases with increasing absorption 
wavelength, and which can be proven by the gap values 
presented for TiO2 fibers treated thermally at 650 ºC and 
700 ºC, which showed a gap of 2.66 eV and 2.90 eV, and 
absorbed λ= 471 nm and 427 nm, respectively. 

Table 1. Band gap and wavelength values corresponding to 
TiO2 fibers and P25 standard 

 
Figure 5 depicts the catalytic activity of TiO2 fibers in 

the degradation of the methyl orange dye during 135 
minutes of exposure to UV-A light (λ= 365 nm). The most 
photoactive TiO2 samples were those treated at 650 °C and 
700 °C, respectively. Due to the majority presence of the 
anatase phase, proven to be the most photoactive phase of 
TiO2 and for presenting the lowest band gap values, 2.66 eV 
and 2.90 eV, respectively. The presence of anatase in the 
mixture ensures greater absorption of light. The light 
absorption of the rutile phase is lower than that of the 
anatase form, and this lower light absorption results in 
lower photocatalytic activity. As the heat treatment 
temperature increases, the formation of the rutile phase 
occurs, which is the TiO2 phase with the lowest 
photocatalytic activity, and its appearance and the increase 
in the band gap values, 2.94 eV and 2.95 eV, are responsible 
for the decrease in photocatalytic activity of TiO2 fibers 
treated at temperatures of 750 ºC and 800 ºC, respectively. 
 

 
Figure 4. The absorption spectrum of TiO2 fibers and the 
P25 standard. 

 
Figure 6 the evolution of H2 production by the TiO2–P25 

(reference) and TiO2 fibers. All synthesized samples 
produced H2. The highest H2 production was achieved by the 
catalysts of TiO2-650 ºC, with approximately (86.6%) H2 
production capacity. These results confirmed that the heat 
treatment temperature associated with bandgap mitigation 
contributed to the formation of a larger number of oxygen 
vacancies. The conduction occurs through consecutive leaps 
of O2 vacancies within the TiO2 crystal structure in almost all 
oxygen ion conductors. The joint action of these factors gave 
titanium structural phase stability. Rising heat treatment 
temperatures allowed O2 vacancies to acquire the mobility 
required to move in a disordered state inside the anionic 

Fibers 
Samples 

Band gap (eV) λ (nm) 
Anatas

e % 
Rutile 

% 
TiO2 P25 
Evonik 

3.20 
387.5 80 20 

650o C 2.66 
471.0 100 - 

 700o C 2.90 
427.0 100 - 

 750o C 2.94 
422.7 50 50 

 800o C 2.95 
420.5 30 70 



LG Soares et al. /Future Energy                                                                                               February 2023| Volume 02 | Issue 01 | Pages 23-26 

26 

 

subnet [5]. In an investigation using ethanol and Pt-doped 
TiO2 for H2 production, it was found that the solution pH 
impacts the gas production rate. It was indicated that either 
neutral or basic reaction media H2 production because OH is 
absorbed on the catalyst surface, which possibly increases 
the gas production rate. The OH groups on the catalyst 
surface might participate in two processes: (1) trapping the 
holes and (2) transferring charge between the 
semiconductor and the electrolyte solution. Participation in 
these two processes mitigates the recombination rates 
between the electron-hole pairs. Therefore, greater pH in the 
synthesis of samples could have contributed to enhanced OH 
groups on the catalyst surface [5]. 

 

 
Figure 5. Photocatalytic activity of the fibers and the P25 
standard in the degradation of the MO dye 

 

Figure 6. Evolution of hydrogen production using TiO2 
fibers as catalysts and commercial TiO2 (P25) was presented 
for comparison 

 
 

5. Conclusion 
With This study showed that the water-splitting 

technique is a promising route to synthesize TiO2 catalysts 
since all synthesized samples demonstrated photocatalytic 
capacity for the production of H2, applying ethanol molecules 
as sacrificial reagents, which functioned as electron donors 
for H2 photogeneration in photocatalytic reactions. Among 
all the synthesized samples, the TiO2 catalysts heat-treated 
at 800 ºC had the lowest hydrogen production capacity, 
probably because TiO2 in pure water has the highest rate of 
recombination of the electron/hole pair. The samples heat 

treated at 650 ºC were the most effective in hydrogen 
production, reaching 86.6% effectiveness in hydrogen 
generation. Due to the reduction of sample bandgap, an 
increase in heat treatment temperature, which increased the 
concentration of O2 vacancies (point defects) that played a 
fundamental role in the movement of the TiO2 crystal lattice. 
Which caused a greater photocatalytic capacity and to 
absorb visible light, which trapped the electrons, thus 
preventing the recombination of electron/hole pairs. 

Acknowledgment 
The authors are grateful for the financial support of the 

Federal University of Rio Grande do Sul (UFRGS), the 
Coordination for the Improvement of Higher Education 
Personnel, and CNPq. 

Ethical issue 
The authors are aware of and comply with best practices 

in publication ethics, specifically with regard to authorship 
(avoidance of guest authorship), dual submission, 
manipulation of figures, competing interests, and 
compliance with policies on research ethics. The authors 
adhere to publication requirements that the submitted work 
is original and has not been published elsewhere in any 
language. 

Data availability statement 
Data sharing is not applicable to this article as no 

datasets were generated or analyzed during the current 

study. 

Conflict of interest 

The authors declare no potential conflict of interest. 

References 

[1] E. and Y. Terco, Sustainable Brazil, 2011. 

https://cuadrivio.net/Publication/vwLUAssets/Sustai

nable_Brazil_-_World_Cup/_FILE/copa_2014.pdf 

[2]  L. Silva, Correlação entre as propriedades fotocrômicas 

e atividade fotocatalítica dos óxidos de titânio e 

tungstênio, 2018. 

 [3]  L. Soares, M. Vaz, S. Teixeira, A. Alves, Absorbance 

determination and photocatalytic production of 

hydrogen using tungsten and TiO2 oxide 

nanostructures as catalyst, 2021. 

[4]  C. Rangel, R. Silva, T. Paiva, B. Charrasse, Produção de 

hidrogénio solar com simultânea mineralização de 

poluentes orgânicos, 2014. 

[5]  A. Garcia, W. Guaglianoni, D. Garcia, L. Soares, M. Vaz, S. 

Teixeira, M. Pereira, T. Basegio,  F. Clemens, A. Alves, 

Fabiano S. Rodembusch, C. Bergmann, Facile synthesis 

by peroxide method and microwave-assisted 

hydrothermal treatment of TiO2 with high 

photocatalytic efficiency for dye degradation and 

hydrogen production, 2018. 


