Center National Of Recherches En Science Des Materiaux Cnrsm

Soliman, Tunisia

Center National Of Recherches En Science Des Materiaux Cnrsm

Soliman, Tunisia

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Hamandi M.,Tunis el Manar University | Hamandi M.,CNRS Research on Catalysis and Environment in Lyon | Berhault G.,CNRS Research on Catalysis and Environment in Lyon | Guillard C.,CNRS Research on Catalysis and Environment in Lyon | And 2 more authors.
Applied Catalysis B: Environmental | Year: 2017

The influence on the photocatalytic performance of TiO2 nanotubes (NT) resulting from the addition of graphene oxide (GO) was studied. TiO2 nanotubes (NT) were prepared using alkaline hydrothermal treatment of TiO2 P25 followed by calcination at 400 °C under air. GO-NT composites were then obtained by wet impregnation of the as-prepared TiO2 nanotubes onto graphene oxide before reduction under H2 at 200 °C. In a first step, the influence of the reduction treatment was evaluated on GO alone to determine its role towards the nature of the oxygen-containing functional groups present. GO-NT composites were also characterized considering both the effect of the reduction treatment and of the GO weight loading on textural, structural, electronic, and optical properties of TiO2 nanotubes. The resulting GO-NT composites were finally evaluated for the photocatalytic degradation of formic acid and compared to TiO2 nanotubes alone and to P25. Results emphasize a strong increase of the electron affinity and conductivity of the GO-NT composites if graphene oxide is reduced at 200 °C. These enhanced properties lead to an easier separation of photogenerated charges and to a limitation of the recombination of electron-hole pairs. A dramatic gain in photocatalytic response is observed. Maximum in photocatalytic efficiency is reached at a GO loading of 1.0 wt% while further increase of GO weight loading blocks light penetration and depletes the photocatalytic response. © 2017 Elsevier B.V.


Salem M.,Laboratoire Of Physique Des Materiaux Et Nanomateriaux Appliques A Lenvironnement | Akir S.,Center National Of Recherches En Science Des Materiaux Cnrsm | Massoudi I.,University of Dammam | Gaidi M.,University of Sharjah | Khirouni K.,Laboratoire Of Physique Des Materiaux Et Nanomateriaux Appliques A Lenvironnement
Applied Physics A: Materials Science and Processing | Year: 2017

In this paper, pure and Cr-doped nanostructured Zinc oxide thin films were synthesized by simple and low cost co-precipitation and spin-coating method with Cr concentration varying between 0.5 and 5 at.%. Crystalline structure of the prepared films was investigated by X-ray diffraction (XRD) and Raman spectroscopy techniques. XRD analysis indicated that the films were indexed as the hexagonal phase of wurtzite-type structure and demonstrated a decrease in the crystallite size with increasing Cr doping content. Cr doping revealed a significant effect on the optical measurements such as transmission and photoluminescence properties. The optical measurements indicated that Cr doping decreases the optical band gap and it has been shifted from 3.41 eV for pure ZnO film to 3.31 eV for 5 at.% Cr-doped one. The photoelectrochemical (PEC) sensing characteristics of Cr-doped ZnO layers were investigated. Amongst all photo-anodes with different Cr dopant concentration, the 2 at.% Cr incorporated ZnO films exhibited fast response and higher photoconduction sensitivity. © 2017, Springer-Verlag Berlin Heidelberg.


Akir S.,Center National Of Recherches En Science Des Materiaux Cnrsm | Ghrib T.,University of Dammam | Daoudi K.,University of Sharjah | Gaidi M.,University of Sharjah
Journal of Alloys and Compounds | Year: 2016

In this study, undoped and Fe doped nanostructured Zinc oxide thin films were synthesized by simple and low cost co-precipitation and spin-coating technique. Surface morphology and crystalline structure of the deposited films were investigated by Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) techniques. XRD analysis demonstrated that the films were polycrystalline with the hexagonal phase. From SEM investigations, the surface morphology of the deposited films was found to depend on Fe concentration. The obtained optical measurements indicated that Fe doping decreases the optical transmission and shift the optical gap to 3.08 eV for 0.5 at.% Fe content. An optimum Fe concentration of 0.5 at.% was found to lead to the highest photoconduction sensitivity of the ZnO films. The photocurrent enhancement response was explained by a better charge separation and collection efficiency under visible light illumination. © 2016 Elsevier B.V. All rights reserved.


Turki A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Turki A.,Institute National Of Recherche Et Danalyse Physico Chimique | Kochkar H.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Kochkar H.,Center National Of Recherches En Science Des Materiaux Cnrsm | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2013

The influence of the sodium content on thermal stability and photocatalytic activity of calcined titanate nanotubes (TNT) was herein evaluated by preparing different samples through hydrothermal treatment of TiO2 powder (P25) in a concentrated NaOH solution (11.25M) at 130°C during 20h followed by acid washing steps. Titanate nanotubes samples with sodium (Na-TNT) and sodium-free (H-TNT) were then obtained using different concentrations of HCl aqueous solutions namely 0.1M and 1M respectively. As synthesized nanomaterials with different Na percentages were then calcined at temperatures varying between 400°C and 700°C. Samples were characterized by means of nitrogen adsorption-desorption isotherms at 77K, thermal analysis (DTA, TGA), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance spectroscopy (DRS). The photocatalytic activities of Na-TNT and H-TNT derived nanomaterials were then evaluated through the photocatalytic degradation of formic acid (FA).Results show that the presence of sodium retards the dehydration process during the transformation of titanate into TiO2 shifting the formation of anatase phase to higher temperatures. However, sodium is not necessary to preserve the nanotubular morphology. The presence of sodium after calcination strongly impacts negatively the photocatalytic properties. If sodium is completely removed from the initial titanate orthorhombic phase, calcination leads to TiO2 anatase materials with enhanced photocatalytic properties compared to P25 in the degradation of formic acid, particularly if nanotubular morphology is preserved. The highest activity was therefore achieved for the H-TNT sample calcined at 400°C. The photodegradation activity of formic acid depends on the specific surface areas and TiO2 crystallinity. In pure anatase nanoparticles the activity strongly decreases with coherent crystallographic domains ≥10nm. © 2013 Elsevier B.V.


Mellah B.,Center National Of Recherches En Science Des Materiaux Cnrsm | Lee Y.H.,University of Ulsan | Kim D.I.,Kyungwoon University | Cho J.H.,Kosin University | Kim Y.,Kosin University
Journal of Inclusion Phenomena and Macrocyclic Chemistry | Year: 2015

A first-generation calix-dendrimer 1 suitable as a multidentate ligand for metal-ion binding was prepared from 1,3,5-tris(aminomethyl)-2,4,6-trimethylbenzene as the dendrimer core and p-tert-butylcalix [4] arene monomethyl ester as a repetitive branch, and characterized by spectroscopic techniques. © 2015 Springer Science+Business Media.


Triki M.,Center National Of Recherches En Science Des Materiaux Cnrsm | Ksibi Z.,Tunis el Manar University | Ghorbel A.,Tunis el Manar University | Medina F.,Rovira i Virgili University
Journal of Sol-Gel Science and Technology | Year: 2011

Catalytic wet air oxidation of an aqueous solution of p-hydroxybenzoic acid was conducted over ruthenium catalysts (1 wt%) supported on CeO 2-Al 2O 3 aerogels mixed oxides at 140 °C and 50 bars of air. We study the effect of the amount of CeO 2 in the catalyst. We found that the optimal cerium content in the Al 2O 3 support was 20 wt%. The activity of the Ru/Al 2O 3 and Ru/CeO 2 was also tested for comparison. It was found that the addition of CeO 2 on the alumina support improves the activity of Ru catalysts. The activity of the samples decreases in the following order: Ru/Ce-Al (20) > Ru/Ce-Al (10) > Ru/Ce-Al (5) ≈ Ru/Al 2O 3 > Ru/CeO 2. Samples characterization was performed by means of N 2 adsorption-desorption, XRD, UV-Vis, TPR, SEM and TEM. © 2011 Springer Science+Business Media, LLC.


Mehri A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Kochkar H.,Center National Of Recherches En Science Des Materiaux Cnrsm | Daniele S.,CNRS Research on Catalysis and Environment in Lyon | Mendez V.,CNRS Research on Catalysis and Environment in Lyon | And 2 more authors.
Journal of Colloid and Interface Science | Year: 2012

One-pot deposition of Pd onto TiO 2 has been achieved through directly contacting palladium(II) salt with nanosized functionalized TiO 2 support initially obtained by sol-gel process using titanium isopropoxide and citric acid. Citrate groups act as functional moieties able to directly reduce the Pd salt avoiding any further reducing treatment. Various palladium salts (Na 2PdCl 4 and Pd(NH 3) 4Cl 2·H 2O) and titanium to citrate (Ti/CA) ratios (20, 50, and 100) were used in order to study the effect of the nature of the precursor and of the citrate content on the final Pd particle size and catalytic properties of the as-obtained Pd/TiO 2 systems. Characterization was performed using N 2 adsorption-desorption isotherms, ICP-AES, FTIR, XRD, XPS, and TEM. The as-obtained hybrid Pd/TiO 2 catalysts were tested in the selective hydrogenation (HYD) of an α,β-unsaturated aldehyde, i.e. cinnamaldehyde. Citrate-free Pd/TiO 2-based catalysts present lower selectivity into saturated alcohol. However, citrate-functionalized Pd/TiO 2 catalyst seems to control the selectivity, the particle size and dispersion of Pd NPs leading to high intrinsic activity. © 2011 Elsevier Inc.


Turki A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Guillard C.,CNRS Research on Catalysis and Environment in Lyon | Dappozze F.,CNRS Research on Catalysis and Environment in Lyon | Berhault G.,CNRS Research on Catalysis and Environment in Lyon | And 3 more authors.
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2014

1D-TiO2 nanomaterials (nanotubes, nanorods, nanoplates, nanospheres and nanoparticles) with tuned structural and textural properties have been evaluated in the photocatalytic degradation of formic acid (FA) under UV conditions. The FA adsorption isotherms follow the model of Langmuir and the kinetic of FA photodegradation shows Langmuir-Hinshelwood model whatever the TiO2 morphologies. TiO2 nanotubes (HTNT-400), nanoplates (HTNW-700) and nanoparticles (HTNT-500 and HTNT-600) show an interesting photocatalytic activities compared to TiO2 nanospheres (P25) and nanorods (TNR). The nanotubular TiO2 (HTNT-400) has a photocatalytic activity 4 times higher than TiO2 P25. The enhanced activity is attributed to the smaller crystallite size of anatase and tuned surface area of the photocatalyst. The pH study showed that the coexistence of HCOO- and HCOOH species at natural pH (ca. 3.5) is favourable for better adsorption on active sites of titanium oxide nanomaterials and consequently to a better photocatalytic activity. © 2014 Elsevier B.V.


Kochkar H.,Center National Of Recherches En Science Des Materiaux Cnrsm | Aouine M.,CNRS Research on Catalysis and Environment in Lyon | Ghorbel A.,Laboratoire Of Chimie Des Materiaux Et Catalyse | Berhault G.,CNRS Research on Catalysis and Environment in Lyon
Journal of Physical Chemistry C | Year: 2011

Shape-controlled silver and palladium nanoparticles were for the first time synthesized by seed-mediated techniques in the presence of β-cyclodextrin (β-CD). Palladium and silver seeds were prepared by reduction of palladium or silver ions with sodium borohydride in the presence of sodium citrate dihydrate as a stabilizer. Seeds were then injected into a "growth" solution containing the same Pd (or Ag) precursor, ascorbic acid (as a weak reducing agent), and β-CD. Using β-cyclodextrin impacts the final morphology of silver nanoparticles through a strong capping effect slowing down the growth regime and shifting it to thermodynamiccontrolled conditions. Adjusting the β-CD/Ag molar ratio can lead to the selective formation of multiply twinned icosahedral particles presenting mainly {111} facets. On palladium, β-cyclodextrin selectively led to the controlled aggregation of primary nanoparticles into nanodendrites or multipods. After deposition on TiO 2, these nanostructured Pd catalysts show excellent activity for the hydrogenation of cinnamaldehyde. © 2011 American Chemical Society.


Turki A.,Tunis el Manar University | Guillard C.,CNRS Research on Catalysis and Environment in Lyon | Dappozze F.,CNRS Research on Catalysis and Environment in Lyon | Ksibi Z.,Tunis el Manar University | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2015

Anisotropic TiO2 nanomaterials (nanotubes, nanorods, nanoplates, nanospheres, and nanoparticles) with controlled structural and textural properties have been evaluated in the photocatalytic degradation of phenol under UV conditions. The kinetic study of phenol adsorption fits well to a quasi-second-order model whereas the adsorption isotherms of phenol over the different TiO2 nanomaterials follow the Langmuir model and the degradation kinetics the Langmuir-Hinshelwood (L-H) model. TiO2 nanomaterials exposing (001) or (101) anatase facets are less active than TiO2 P25 for the phenol degradation. This is related to their tendency to degrade faster intermediates products (organic acids) rather than phenol itself. A good compromise between anatase crystallinity, crystallites sizes, and specific surface area can however improve the photocatalytic activity of the TiO2 nanomaterials. Results also showed that the degradation mechanism follows pseudo-first order kinetics. Pseudo-rate constants were therefore determined and formal mechanism schemes proposed. © 2014 Elsevier B.V.

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