PUBLICATIONS

Nos Publications 2009

Publications 2009


Publication 1 :

S. Boumaza, A. Bouguelia, R. Bouarab, M. Trari. Physical and photoelectrochemical studies for hydrogen photo-evolution over the spinel ZnCr2O4 . International Journal of Hydrogen Energy. In Press.


The present work deals with the photoelectrochemical hydrogen production over the spinel ZnCr2O4. The photoactivity is dependent on the synthesis conditions and the oxide has been prepared by nitrate way in order to produce homogeneous powder with large active surface. The transport properties indicate p-type conductivity with activation energy of 0.21 eV. A corrosion potential of 0.404 VSCE and an exchange current density of 50 µA cm-2 have been determined from the semi logarithm plot. The photocurrent onset potential, assimilated to the flat band potential, was found to be -0.39 VSCE. ZnCr2O4/S2O32- is a self driven system where absorption of light promotes electrons into the conduction band with a potential (-1 V) sufficient to reduce water into hydrogen. The activity shows a tendency toward saturation whose deceleration is the result of the competitive reductions of end products namely S2O62- and S2O42- with water. A comparative study with CuCr2O4 is reported. © 2008 International Association for Hydrogen Energy.


Publication 2 :

S. Bassaid, M. Chaib, S. Omeiri, A. Bouguelia, M. Trari. (2009) Photocatalytic reduction of cadmium over CuFeO2 synthesized by sol-gel . Journal of Photochemistry and Photobiology A : Chemistry 201 (1), pp. 62-68


The Cd2+ photo-electrodeposition was successfully carried out in air-equilibrated aqueous CuFeO2 suspension. The delafossite CuFeO2 is p-type semiconductor characterized by a low optical gap, properly matched to the sun spectrum, and a long term chemical stability in neutral solution. It has been elaborated by the sol-gel technique where the specific surface area is increased via the surface/bulk ratio. The TG/DSC plots and IR spectra show that the solid phases are formed only at temperatures exceeding 400 and at 700 °C, the system is mixed phases. When fired at 950 °C under nitrogen flow, the delafossite has been identified (CuO + CuFe2O4 ? CuFeO2 + 1/2O2). All the XRD lines index in a hexagonal unit cell with the lattice constants a = 284.2 and c = 169.4 pm. The photocurrent onset potential (+0.35 VSCE) is close to the flat band potential (+0.23 VSCE) determined from the capacitance measurement. CuFeO2/Cd2+ solution is a self photo-driven system, the absorption of light promotes electrons into CuFeO2-CB with a potential (-0.93 VSCE) sufficient to reduce Cd2+. This occurs because of the dark Cd2+ adsorption on the surface powder. The system was optimized with respect to the following physical parameters : pH 6.8, Cd2+ (100 ppm) and a mass concentration Cm (1 mg catalyst/ml solution). The hetero-system CuFeO2/TiO2 has been also reported for a comparative purpose. Prolonged irradiation (>50 min) was accompanied by a pronounced decrease in the rate of Cd-deposition owing to the competitive water reduction. Indeed, the generated bi-functional CuFeO2/Cd particles account for the low over-potential of hydrogen and favour its evolution in aqueous solution. © 2008 Elsevier B.V. All rights reserved.


Publication 3 :

S. Boumaza, R. Bouarab, M. Trari, A. Bouguelia. (2009) Hydrogen photo-evolution over the spinel CuCr2O4 . Energy Conversion and Management 50 (1), pp. 62-68


The photocatalytic H2 evolution over CuCr2O4 has been studied in connection with some physical properties. The black oxide is classified as a narrow band gap semiconductor crystallizing in the normal spinel structure. The photoactivity is dependent on the preparative conditions through the surface area of the powder and CuCr2O4 has been synthesized by nitrate route. The conductivity varies exponentially with temperature indicating an extrinsic conductivity between mixed valences states Cr3+/4+ located in octahedra sharing common corners. The oxide exhibits p-type conductivity with an activation energy of 0.20 eV and a hole mobility of 2.14 × 10-8 cm2/V s thermally activated. CuCr2O4 shows an excellent chemical stability, a corrosion potential of -0.775 VSCE and an exchange current density of 16 µA cm-2 have been determined from the semilogarithm plot. The capacitance measurement (C-2-V), performed in basic electrolyte, exhibits a linear behavior from which a flat band potential of 0.48 VSCE was obtained. CuCr2O4 is photoelectrochemically stable by hole consumption reactions involving X2- (=SO32 - and S2 O32 -) as hole scavengers. The best catalytic performance for H2-photoproduction was obtained in (NaOH 0.5 M, Na2S2O3 0.025 M) with an average rate of 0.013 cm3 h-1 (mg catalyst)-1 and a quantum efficiency of 0.2% under polychromatic light. S2 O32 - is oxidized to SO32 - and subsequently to SO42 - as proven by the dual slopes in the Tafel plot. The system shows a tendency towards saturation whose deceleration is the result of the competitive reductions of the end products namely S2 O62 - and S2 O42 - with the water discharge. © 2008 Elsevier Ltd. All rights reserved.


Publication 4 :

W. Ketir, A. Bouguelia, M. Trari. (2009) NO3- removal with a new delafossite CuCrO2 photocatalyst. Desalination, 244, pp 144-152.


The removal of NO3- by a CuCrO2-mediated catalytic photoprocess was investigated under mild conditions. The delafossite CuCrO2
exhibits an excellent chemical stability over the whole pH range and
relatively a large specific surface area when elaborated by chemical
means. The optical gap was found to be 1.28 eV, close to the optimal
value required for terrestrial applications. The conduction band is
located at -1.06 VSCE and thus lies below the NO3-
level leading to a thermodynamically favorable nitrate reduction under
visible light. The possibility of identifying the reaction products via
the intensity-potential characteristics was explored. The reaction of NO3-
proceeds in competition with the water reduction and seems to be the
major reason in the regression of the photoactivity during prolonged
testing. The complete conversion occurs in less than 4 h with a
quantum efficiency of 2%.


Publication 5 :

L. Djellal, S. Omeiri, A. Bouguelia, M. Trari. Photoelectrochemical hydrogen-evolution over p-type chalcopyrite CuInSe2 . Journal of Alloys and Compounds. In Press.


Photocatalytic H2-production has been realized over active CuInSe2, synthesized by the fusion technique. The material crystallizes in the chalcopyrite structure and exhibits p-type conductivity ascribed to copper deficiency. An optical gap of 0.95 eV was determined from the reflectance diffuse spectrum. The electrical conductivity follows an Arrhenius-type law with activation energy of 23 meV in conformity with polaron hopping. The slope and the intercept of the Mott-Schottky plot gave a holes density NA of 5.9 × 1018 cm-3 and a flat band potential of -0.36VSCE, in perfect agreement with the photo-onset potential Von (-0.35VSCE). Hence, the conduction band, located at -1.29VSCE, allows a spontaneous H2 liberation upon visible light. In aqueous solutions, the material is stabilized by hole consumption involving X2- species (double bond, longS2- and SO32-). H2 formation would become thermodynamically easy in alkaline media and the best photoactivity was obtained in thiosulfate electrolyte (10-2 M S2O32-, 0.5 M KOH) with an evolution rate of 0.009 ml mg-1 h-1. The light induced electron transfer through the interface involves two steps mechanism where S2O32- is oxidized to SO32- and SO42- by successive reactions. Such results are corroborated by the semi logarithmic plots and photocurrent-photopotential characteristics. The influence of pH was studied with S2O32- The tendency towards saturation for prolonged irradiation is attributed to competitive reductions of the end products Sn2- and S2O62- with water and to the yellow color of polysulfide Sn2-. © 2008 Elsevier B.V. All rights reserved.


Publication 6 :

S. Omeiri, B. Bellal, A. Bouguelia, Y. Bessekhouad, M. Trari. Electrochemical and photoelectrochemical characterization of CuFeO2 single crystal . Journal of Solid State Electrochemistry, pp. 1-7. In Press.


CuFeO2 single crystal, synthesized by the flux method, is a narrow band gap semiconductor crystallizing in the delafossite structure with a direct optical transition of 1.63 eV. The oxide exhibits a good chemical stability ; the semi-logarithmic plot gave an exchange current density of 0.60 µA cm-2 in KCl (0.5 M) electrolyte. CuFeO2 shows p-type conductivity ; the origin of acceptors Cu2+ results from oxygen insertion in the layered lattice where most of excess holes are trapped in surface-polaron states. The electrochemical study is confined in the (a,b) plane and reversible oxygen intercalation is evidenced from the intensity potential characteristics. The detailed photoelectrochemical studies have been reported for the first time on the single crystal. The photocurrent is ascribed to the transfer Cu+:3d ?3d. The capacitance measurement (C-2-V) shows a linear behavior from which a flat band potential of +0.54 VSCE and a density NA of 1.60 × 1018 cm-3 were determined. The valence band, located at 5.33 eV below vacuum, is made up of Cu-3d orbital typical of delafossite oxides. The Nyquist plot shows a semicircle attributed to a capacitive behavior with a low density of surface states within the gap. The centre is localized below the real axis with an angle of 16.2° ascribed to a constant phase element (CPE), a single barrier of the junction CuFeO2/electrolyte and one relaxation time of the electrical equivalent circuit. © 2008 Springer-Verlag.


Publication 7 :

W. Ketir, A. Bouguelia, M. Trari. Visible Light Induced NO2- Removal Over CuCrO2 Catalyst . Water, Air, and Soil Pollution, pp. 1-8. In Press.


The delafossite CuCrO2 is a promising candidate for the visible light driven catalysis. The NO2- removal by photoelectrochemical process is studied under mild conditions, close to that encountered in the natural environment. CuCrO2 exhibits a long term chemical stability with a corrosion rate of 0.34 µmol m-2 year-1 in KCl (0.5 M). A forbidden band of 1.3 eV has been evaluated from the diffuse reflectance spectrum. The flat band potential (-0.07 VSCE) determined from the Mott-Schottky plot is close to the photocurrent onset potential (0 VSCE). Hence, the conduction band is positioned at -1.08 VSCE and thus lies below the NO2- level leading to a feasible reduction upon visible illumination. The conversion occurs in less than 5 h with a quantum efficiency of  0.5%. The possibility of identifying the reaction products via the intensity-potential characteristics was explored by using standard solutions. The decrease of the conversion rate over time is attributed to the competitive water reduction. In absence of catalyst, NO2- is oxidized to NO3- in air equilibrated solution and the reaction follows a first order kinetic with a half life of 21 h, NO3- has been identified by iodometry through copper titration. © 2008 Springer Science+Business Media B.V.


Publication 8 :

R. Bouarab, A. Boudjemaa, M. Trari, S. Bennici, A. Auroux. Influence du support sur la structure cristalline, les propriétés acido-basiques et l’activité des systèmes à base de fer en réaction CO + H2O . Comptes Rendus Chimie. In Press.


Effect of support on the crystalline structure, the acid-base properties and activity of iron based systems in the CO + H2O reaction. The water gas shift reaction was studied in the temperature range of 350-450 °C over iron based catalysts exempt of Cr2O3. The basic properties and CO conversion of these catalysts are given in the following sequence : Fe3O4/MgO > Fe3O4/TiO2 > Fe3O4 > Fe3O4/SiO2. The basic catalysts are consequently more active than acid ones. On the other hand, the DRX results showed a strong crystalline fraction of MgO in the Fe3O4/MgO catalyst calcined at 400 °C. Hence, Fe3O4/MgO generates an MgO reservoir able to feed the catalyst surface with formate species during the water gas shift reaction. © 2008 Académie des sciences.


Publication 9 :

A. Boudjemaa, R. Bouarab, S. Saadi, A. Bouguelia, M. Trari . Photoelectrochemical H2-generation over Spinel FeCr2O4 in X2- solutions (X2- = S2- and SO ) . Applied Energy. In Press.


Photocatalytic H2-production has been observed over FeCr2O4, synthesized from Cr(NO3)3 and Fe(NO3)3. The oxide crystallizes in the normal spinel structure and the transport properties exhibit p-type conductivity ascribed to metal deficiency. An optical gap of 1.33 eV is determined from the reflectance diffuse spectrum. From photoelectrochemical measurements, a flat band potential of +0.23 VSCE is found. The valence band, made up of cationic 3d orbital, is located at 5.2 eV (0.45 VSCE) below vacuum. Hence, the conduction band (-0.98 VSCE) allows a thermodynamically feasible H2 liberation under visible light. In aqueous electrolytes, the oxide is stabilized by hole consumption involving X2- species and the best photoactivity for H2-production is obtained in S2- solution with an evolution rate of 8.26 cm3 g-1 h-1. The tendency towards saturation is due to the competitive reduction of the end products namely S and SO with water and to the yellow color of S. On the other hand and for a comparative purpose, the catalytic activity of unreduced FeCr2O4 for the water-gas shift reaction (CO + H2O ? CO2 + H2) is studied in the temperature range 523-723 K. At 723 K, the rate of H2-formation and the degree of CO conversion are respectively 280 µmol g-1 s-1 and 44%. © 2008 Elsevier Ltd. All rights reserved.


Nos Publications 2008

Publications 2008


Publication 1 :

W. Ketir, A. Bouguelia, M. Trari. (2008) Photocatalytic removal of M2+ (Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) over new catalyst CuCrO2 . Journal of Hazardous Materials 158 (2-3), pp. 257-263


The metal ions M2+ (Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Ag+) are potentially toxic. Their electro deposition has been carried out in aqueous air-equilibrated CuCrO2 suspension upon visible illumination. The delafossite CuCrO2 is p-type semiconductor characterized by a low band gap (1.28 eV) and a long-term chemical stability. The corrosion rate is found to be 10-2 µmol m-2 month-1 in aqua regia. The oxide has been elaborated through nitrate route where the specific surface area is increased via the surface/bulk ratio. A correlation exists between the dark M2+ adsorption, the redox potential of M2+/0 couple and the conduction band of CuCrO2 positioned at -1.06 VSCE. Ag+ cannot be photoreduced because of its positive potential located far above the valence band. By contrast, Zn2+ is efficiently deposited due to the large driving force at the interface. The improved photoactivity of copper with a deposition percentage (90%) is attributed to the strong dark adsorption onto the surface catalyst. The results indicate a competitive effect with the water reduction ; it has been observed that the M2+ deposition goes parallel with the hydrogen evolution. Such behavior is attributed to the low H2 over voltage when ultra fine aggregate of M islands are photodeposited onto CuCrO2 substrate. © 2008 Elsevier B.V. All rights reserved.


Publication 2 :

R. Brahimi, B. Bellal, Y. Bessekhouad, A. Bouguelia, M. Trari. (2008) Physical properties of CuAlO2 single crystal. Journal of Crystal Growth 310 (19), pp. 4325-4329


CuAlO2 single crystal elaborated by the flux method is a narrow band gap semiconductor crystallizing in the delafossite structure (SG R3¯m). Oxygen insertion in the layered lattice generates p-type conductivity where most holes are trapped in surface-polaron states. The detailed photoelectrochemical characterization and electrochemical impedance spectroscopy (EIS) have been reported for the first time on the single crystal. The study is confined in the basal plan and reversible oxygen insertion is evidenced from the intensity potential characteristics. The oxide is characterized by an excellent chemical stability ; the semi-logarithmic plot gave a corrosion potential of-0.82 VSCE and an exchange current density of 0.022 µA cm-2 in KCl (0.5 M) electrolyte. The capacitance measurement (C-2-V) shows a linear behavior from which a flat band potential of +0.42 VSCE and a doping density NA of 1016 cm-3 have been determined. The valence band, located at 5.24 eV (0.51 VSCE) below vacuum, is made up of Cu-3d orbital. The Nyquist plot exhibits a pseudo-semicircle whose center is localized below the real axis with an angle of 20°. This can be attributed to a single relaxation time of the electrical equivalent circuit and a constant phase element (CPE). The absence of straight line indicates that the process is under kinetic control. © 2008 Elsevier B.V. All rights reserved.


Publication 3 :

B. Hadjarab, A. Bouguelia, A. Benchettara, M. Trari. (2008) The transport and photo electrochemical properties of La-doped stannate BaSnO3 . Journal of Alloys and Compounds 461 (1-2), pp. 360-366


The electrical conductivity and thermoelectric power of polycrystalline Ba0.98La0.02SnO3-d, prepared under O2-free atmosphere, have been measured between 4.2 and 300 K. The existence of onsite bipolaron is due to the tendency to Sn3+ ions to disproportionate into mixed valences Sn2+ and Sn4+ in equivalent sites. The data indicates electron degeneracy like conduction with polaron conductivity and a finite density of states at the Fermi level. The thermal evolution of the conductivity follows an Arrhenius type law with activation energy of 1 meV and electron mobility thermally activated. The conduction mechanism changes to a variable range hopping at low temperatures. From photo electrochemical measurements, the band gap Eg was found to be 3.26 eV and the transition is directly allowed ; further indirect interband transition occurs at 2.82 eV. The valence band edge, located at 7.4 eV below vacuum, is made up from O:2p orbital typical of perovskite oxides. The respective values of the slopes (231 and 1104 mV dec-1) and the exchange current density J (0.339 mA cm-2) in the semi-logarithmic plot predict long-lived material. As expected, the title oxide exhibits a pH-dependent flat band potential Vfb and at pH 13.60 (KOH 1 M), the current-potential characteristic gave a Vfb-value of -0.03 VSCE, close to that obtained from the capacitance measurement (+0.05 VSCE). The C-2-potential plot displays a straight linear part with a positive slope confirming the n-type conductivity and a uniform doping density (Nd = 7.24 × 1020 cm-3). The utilization of BaSnO3 as coating for PEC electrode is suggested. © 2007 Elsevier B.V. All rights reserved.


Publication 4 :

A. Derbal, S. Omeiri, A. Bouguelia, M. Trari. (2008) Characterization of new heterosystem CuFeO2/SnO2 application to visible-light induced hydrogen evolution . International Journal of Hydrogen Energy 33 (16), pp. 4274-4282


Photo-assisted H2 evolution has been realized over the new heterosystem CuFeO2/SnO2 without any noble metal and was studied in connection with some physical parameters. The delafossite CuFeO2 has been prepared by thermal decomposition from various salts. The polarity of generated voltage is positive indicating that the materials exhibit p-type conductivity whereas the electroneutrality is achieved by oxygen insertion. The plot of the logarithm (conductivity) vs. T-1 gives average activation energy of 0.12 eV. CuFeO2 is a narrow band gap semiconductor with an optical gap of 1.32 eV. The oxide was characterized photoelectrochemically ; its conduction band (-1.09 VRHE) is located below that of SnO2 (-0.86 VRHE) at pH 13.5 itself more negative than the H2O/H2 level leading to a thermodynamically favorable H2 evolution under visible irradiation. The sensitizer CuFeO2, working as an electron pump, is stable towards photocorrosion by hole consumption reactions involving the reducing agents X2- (=S2O32- and SO32-). The photoactivity was dependent on the precursor and the best performance (0.026 ml h-1 mg-1) was obtained in S2O32- (pH 13.5) over CuFeO2 synthesized from nitrate with a mass ratio (CuFeO2/SnO2) equal to unity. A quantum yield of 0.5% was obtained under polychromatic light. H2 liberation occurs concomitantly with the oxidation of S2O32- to dithionate and sulfate. The tendency towards saturation, in a closed system, is mainly ascribed to the competitive reduction of the end product S2O62-. © 2008 International Association for Hydrogen Energy.


Publication 5 :

L. Djellal, A. Bouguelia, M. Trari. (2008) Physical and photoelectrochemical properties of p-CuInSe2 bulk material . Materials Chemistry and Physics 109 (1), pp. 99-104


CuInSe2 ingots were elaborated by direct reaction in evacuated quartz ampoule. The material is polycrystalline and crystallizes in the chalcopyrite structure (SG : I over(4, ¯) 2 d). The chemical composition was determined by the energy dispersive spectroscopy and RBS technique. The analysis indicates a stoichiometric compound with small copper deficiency and a uniform bulk composition. A band gap at 0.94 eV was evaluated from the diffuse reflectance spectrum. The electrical properties were investigated and an activation energy of 23 meV was obtained in the heating direction from the Arrhenius type law. The thermal variation of the thermo power indicates p-type conduction with polaron hopping. The compound is stable in aqueous electrolyte with a dissolution rate of 8 µmol cm-2 month-1. A corrosion potential of +0.20 VSCE and an exchange current density of 0.318 mA cm-2 were determined from semi logarithmic plot in KCl (1 M). The current-potential characteristic gave a potential Von of onset photocurrent of -0.60 VSCE, close to the flat band potential (Vfb = -0.58 VSCE), determined by extrapolating the linear part to C-2 = 0 in the Mott Shottky plot. The doping density (NA = 3.8 1017 cm-3) was calculated from the slope. The Nyquist plot shows a semicircular arc whose center is localized below the real axis with an angle of 0.086 rad. This can be attributed to single barrier of the junction SC/electrolyte and single relaxation time of the electrical equivalent circuit. © 2007 Elsevier B.V. All rights reserved.


Publication 6 :

L. Djellal, A. Bouguelia, M. Kadi Hanifi, M. Trari. (2008) Bulk p-CuInSe2 photo-electrochemical solar cells . Solar Energy Materials and Solar Cells 92 (5), pp. 594-600


Dense CuInSe2 of high quality, prepared by the fusion technique in evacuated quartz ampoule from stoichiometric melt, crystallizes in the chalcopyrite structure. Compositional analysis carried out by secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy (EDS) indicates a uniform distribution of elements through the depth and a composition close to the stoichiometry. The diffuse reflectance spectrum gives a band gap at 0.94 eV. The electrical conductivity follows an Arrhenius-type law with activation energy of 23 meV in conformity with polarons hopping. Above  320 °C, CuInSe2 undergoes an irreversible oxidation. The thermal variation of the thermopower indicates p-type behavior attributed to copper deficiency and a hole mobility µ300 K of 0.133 cm2 V-1 s-1, thermally activated. In KCl media, the compound exhibits an excellent chemical stability with a corrosion rate of 8 µmol cm-2 month-1. The photo-electrochemical properties, investigated for the first time on the ingots, confirm the p-type conductivity. From the capacitance measurements, the flat band potential (Vfb=-0.62VSCE) and the holes density (NA=4×1017 cm-3) were determined. The valence band, located at 4.43 eV below vacuum, is made up of mainly Se orbital with little admixture of Cu character. The change of the electrolyte causes a variation in the potential Vfb (dVfb/dpH=-0.058 V pH-1) indicating strong OH- adsorption. The fill factor in S2- media was found to be 0.54 ; such result was corroborated by semi-logarithmic plots. © 2007 Elsevier B.V. All rights reserved.


Publication 7 :

L. Djellal, A. Bouguelia, M. Trari. (2008) Structural, optical and photoelectrochemical properties of CuIn 3Se5 . Semiconductor Science and Technology 23 (4), art. no. 045019


The morphology, optical characterization and transport properties of dense material CuIn3Se5 have been reported. CuIn 3Se5 was synthesized by the fusion technique in a sealed quartz ampoule. The ingots were polycrystalline and the phase crystallizes in a P-chalcopyrite structure. The XRD pattern confirms the formation of the ordered vacancy compound. The composition (Cu = 13.3 at%, In = 31.5 at%, Se = 55.2 at%), established by energy dispersive spectroscopy, is close to the stoichiometric formulation. A band gap of 1.19 eV has been obtained from the diffuse reflectance spectrum. CuIn3Se5 exhibits semi-conducting behavior with an activation energy of 0.52 eV. The thermal variation of the thermopower indicates that the charge carriers are electrons and the conduction occurs predominantly by small polaron hopping. The dissolution rate, determined through dissolved copper, was found to be 1.2 ?mol m-2/year in the KCl electrolyte. The results give deeper insights into the photoelectrochemical properties investigated for the first time on the dense material. The capacitance measurement indicates linear behavior from which a flat band potential Vfb of -0.22 VSCE and a doping density N D of 3.75 × 1016 cm-3 were determined. The energy band diagram shows the potentiality for solar energy conversion. The complex impedance pattern is circular in the low frequency region and tends to a straight line in the high frequency one, attributed to the ionic diffusion. © 2008 IOP Publishing Ltd.


Publication 8 :

M. Amara, H. Kerdjoudj, A. Bouguelia, M. Trari. (2008) A combination between membrane selectivity and photoelectrochemistry to the separation of copper, zinc and nickel in aqueous solutions . Journal of Membrane Science 312 (1-2), pp. 125-131


The transport phenomena through ion exchange membrane may be improved by the application of different forces inside or outside the systems. The electrical current, produced by synthetic photo electrode, is applied to enhance the separation of metallic ions. The cation exchange membrane placed between the two compartments permitted the separation and concentration of the ions M2+ (=Cu2+, Zn2+ and Ni2+). The movements of M2+ from the aqueous solution to the membrane and inside the membrane are followed by the flux determinations and the potential measurements. In this study, the three cations are studied alone or as binary and ternary systems. It was observed that the illuminated CdS electrode leads to an increasing of the transport flux at least 10 times more than that calculated in the obscurity. Moreover, in all the cases the potential of the first specie electrode M/M2+ in the feed compartment increases until a maximal value reached at 100 min above which it undergoes a diminution. The membrane is more selective to Zn2+ ; this selectivity decreases in the binary and ternary systems. On the other hand, the photo electrochemical properties of the hexagonal CdS showed strong light absorption of wave lengths shorter than 520 nm. The shape of the intensity potential curve under illumination and the negative flat band potential (-1.02 VSCE) provide unambiguous evidence of n-type conductivity. The conduction band, located at -1.25 VSCE leads to a thermodynamically M2+ reduction under visible light and accentuates the diffusion process. © 2007 Elsevier B.V. All rights reserved.


Publication 9 :

S. Omeiri, Y. Gabès, A. Bouguelia, M. Trari. (2008) Photoelectrochemical characterization of the delafossite CuFeO2 : Application to removal of divalent metals ions . Journal of Electroanalytical Chemistry 614 (1-2), pp. 31-40


The catalytic electrodeposition of a variety of metal ions M2+ (Zn2+, Cd2+, Hg2+, Ni2+, Pb2+, Cu2+, Ag+), all of environmental issue, was performed under visible light in aqueous air-equilibrated CuFeO2 suspensions. The delafossite CuFeO2 was synthesized by nitrate way and the surface/bulk ratio is greatly increased. In the dark, it exhibits a long term chemical stability with a corrosion rate of 1.3 × 10-8 mol m-2 year-1 in KCl (1 M). The black oxide, with a gap of 1.32 eV, determined from the reflectance diffuse spectrum, was characterized by photoelectrochemistry. The flat band potential was found to be 0.16 VSCE and a correlation exists between the redox potential of M2+/0 couple and the conduction band of CuFeO2 located at -1 VSCE. Ag+ is slightly photoelectrodeposited because of its low adsorption and its positive potential. By contrast, Cu2+ and Cd2+ are efficiently reduced owing to the strong dark adsorption and the large driving force at the interface. The quantum yield of M2+ deposition works out to be 0.1% ; the metal deposition proceeds competitively with the water reduction and decelerates over time. The specie showing the high H2-evolution exhibits the lower M2+ reduction and the medium pH should make the M2+ deposition easier. The best photocatalytic H2-evolution (0.18 ml g-1 min-1) was obtained in solution containing Cd2+ (30 ppm). This is a surprising result and merits a more detailed investigation. © 2007 Elsevier B.V. All rights reserved.


Publication 10 :

R. Brahimi, Y. Bessekhouad, A. Bouguelia, M. Trari. (2008) Improvement of eosin visible light degradation using PbS-sensititized TiO2 . Journal of Photochemistry and Photobiology A : Chemistry 194 (2-3), pp. 173-180


PbS was prepared by a simple chemical method for use as a photosensitizer with TiO2. Its physico-chemical characterisation reveals a semiconducting behaviour with a band gap energy of 0.41 eV showing efficient visible light absorption. The valence and conduction band energy levels are
- 0.78 and -1.19 V, respectively. Interparticle electron injection (IPEI) from photoactivated PbS to inactivated TiO2 was demonstrated by the increase of eosin degradation under visible light. Different parameters affecting the photoactivity such as the PbS amount, eosin concentration and initial pH were investigated. Optimal degradation of eosin occurs at a PbS/TiO2 ratio of 10:90, an eosin concentration of 30 mg l-1, a pH 7, and when using a 2× 200 W tungsten lamp. These conditions result in a constant decomposition rate of 0.116 min-1 corresponding to an eosin half-life of 6.4 min. In this case, the rate of degradation of eosin is respectively 20 and 40 times greater than when in contact with pure TiO2 or through direct photolysis. The photoeffeciency of PbS(10%)/TiO2 was compared to that of CdS(10%)/TiO2, Bi2S3(10%)/TiO2, Cu2O(10%)/TiO2 and Bi2O3(10%)/TiO2 using visible and UV-vis light. PbS(10%)/TiO2 has the best efficiency regardless of the wavelength of light used. The contribution of the electromotive force and the band gap of the narrow band gap semiconductor to the photoactivity improvement were discussed. © 2007 Elsevier B.V. All rights reserved.


Publication 11 :

S. Bassaid, M. Chaib, A. Bouguelia, M. Trari. (2008) Elaboration and characterization of poly (acrylic acid-co-crotonic acid) copolymers : Application to extraction of metal cations Pb(II), Cd(II) and Hg(II) by complexation in aqueous media . Reactive and Functional Polymers 68 (2), pp. 483-491


Poly (acrylic acid-co-crotonic acid) copolymers with various compositions of acrylic acid (AA) and crotonic acid (CA), (3.0 = AA = 4.5 g and 0.5 = CA = 2.0 g), were prepared by free radical polymerization using toluene as solvent and azobis-iso-butyro-nitrile (AIBN) as initiator. The average molecular weights were determined from the intrinsic viscosity measurements in NaNO3 (1 M) as supporting electrolyte. The thermal analysis (DSC and TGA) of copolymers indicate a hydrophilic behaviour and a thermal stability in the temperature range (100-220 °C) above which they undergo an irreversible degradation. The synthesized copolymers are good fixation agents that can be used in the recovery of heavy metals, known for their high toxicity in aqueous media. In a second part, we investigated the complexes formation of metal ions M(II) (M = Pb, Cd and Hg) with the copolymer (D) of composition 3.0 g (AA)/2.0 g (CA). The pH titration of the copolymer alone and in presence of M(II) were realized through the batch method to determine the acid-base properties and complex-forming of ligand copolymers. The results show that for Pb(II), the predominant complex specie is PbA2 with a stability constant pK2 = -8.82. On the contrary, with Cd(II) and Hg(II) neither MA nor MA2 becomes predominant and the stability increases as follows : Pb(II)>Cd(II) Hg(II). © 2007 Elsevier Ltd. All rights reserved.


Nos Publications 2007

1) Publications 2007


Publication 1 :

Hadjarab, B. Bouguelia, A. Trari, M. (2007) Synthesis, physical and photo electrochemical characterization of La-doped SrSnO3 . JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS 2007 VOL 68 ; NUMBER 8, page(s) 1491-1499 Elsevier Science B.V., Amsterdam.

www.elsevier.com/locate/issn/00223697



The transport properties of Sr0.98La0.02SnO3-d in the system Sr1-xLaxSnO3-d, after which the pyrochlore La2Sn2O7 appears, were investigated over the temperature range 4.2-300K. The oxide was found to be n-type semiconductor with concomitant reduction of Sn4+ into Sn2+. The magnetic susceptibility was measured down to 4.2K and is less than 3x10-5 emu cgs mol-1 consistent with itinerant electron behavior. The electron is believed to travel in a narrow band of Sn:5s character with an effective mass 4mo. The highest band gap is 4.32eV and the optical transition is directly allowed. A further indirect transition occurs at 4.04eV. The electrical conductivity follows an Arrhenius-type law with a thermal activation of 40meV and occurs by small polaron hopping between nominal states Sn4+/2+. The linea...

Publication 2 :

Hadjarab, B. Saadi, S. Bouguelia, A. Trari, M. (2007) Physical properties and photoelectrochemical characterization of SrPbO3 . PHYSICA STATUS SOLIDI A : VOL 204 ; NUMBER 7, page(s) 2369-2380 John Wiley & Sons, Ltd.

www3.interscience.wiley.com/cgi-bin/jhome/40000761



SrPbO3-d is n-type, narrow-bandgap semiconductor crystallizing in a distorted perovskite structure. The electrical conductivity varies with temperature but in a nonmonotonic manner. At high temperatures, the thermal evolution of the conductivity follows an Arrhenius-type law with an activation energy of 0.11 eV attributed to mixed valency states Pb4+/2+ and leading to a dielectric constant of 13.6. The sign of thermopower S is negative, indicating that the mobile carriers are electrons, which is ascribed to oxygen extraction. The electron hopping occurs between similar electronic localized states in the vicinity of the mobility edge with an electron mobility of 10-2 m2 V-1 s-1 that is thermally activated. The variation S (T) suggests a finite density of states at the Fermi level. At low te...

Publication 3 :

Bessekhouad, Y. Gabes, Y. Bouguelia, A. Trari, M. (2007) The physical and photo electrochemical characterization of the crednerite CuMnO2 . JOURNAL OF MATERIALS SCIENCE 2007 VOL 42 ; NUMBER 15, page(s) 6469-6476 Springer Science + Business Media.
www.springer.com/west/home/materials ?SGWID=4-10041-70-35692639-0


CuMnO2 is prepared via Cu+->Li+ exchange in molten copper (I) chloride. It crystallizes in a monoclinic structure (SG C2/m) where the MnO6 octahedra elongation is ascribed to the Yahn-Teller (Y-T) effect of Mn3+ ions. From chemical analysis, the oxide is more accurately formulated as CuMnO2.01. Above 250 °C, it undergoes a reversible transition to spinel Cux Mn3-xO4 and beyond 940 °C it converts back to Cu1.1Mn0.9O2. Extrapolation of high-temperature magnetic data indicates an effective moment of 5.22 uB, and a T-intercept Op of -450 K, consistent with high spin (HS) configuration Mn3+ and strong antiferromagnetism in the basal plans...

Publication 4 :

Koriche, N. Bouguelia, A. Mohammedi, M. Trari, M. (2007) Synthesis and physical properties of new oxide AgMnO2 . JOURNAL OF MATERIALS SCIENCE 2007 VOL 42 ; NUMBER 13, page(s) 4778-4784 Springer Science + Business Media.
www.springer.com/west/home/materials ?SGWID=4-10041-70-35692639-0


A novel oxide AgMnO2 was prepared from LiMnO2 via Ag+->Li+ exchange in the eutectic melt AgNO3-KNO3. It crystallizes in a monoclinically distorted unit cell (SG C2/m) caused by the Jahn-Teller (J-T) ion Mn3+ (3d 4). The structure was refined by isotypy with the crednerite CuMnO2. There are two long axial Mn-O of 264.2(0) pm and four equatorial bonds of 192.7(3) pm and Mn-O-Mn adjoining (83.07°) are bent below the ideal angle. The thermal variation of the magnetic susceptibility (X/T-1) obeys a Curie-Weiss law with manganese in a trivalent, high spin (HS) state accommodated in elongated MnO6 octahedra (14.8%). Direct coupling between Mn3+ involves negative exchange interactions through long-range antiparallel moments with a temperature Op = -436 K and a magnetic mome...

Publication 5 :

Younsi, M. Saadi, S. Bouguelia, A. Aider, A. Trari, M. (2007) Synthesis and characterization of oxygen-rich delafossite CuYO2+x. Application to H2 photo production . SOLAR ENERGY MATERIALS AND SOLAR CELLS 2007 VOL 91 ; NUMBER 12, page(s) 1102-1109 Elsevier Science B.V., Amsterdam.

www.elsevier.com/locate/issn/09270248



Here we report the synthesis and photo electrochemical properties of super oxides CuYO2.50 and CuYO2.25 prepared from the delafossite CuYO2, respectively, by thermal oxidation at 380°C under O2-flow and soft chemistry in NaBrO solution (5N). Their applications as catalysts for H2 evolution upon visible light were investigated. The oxygen insertion was accompanied by partial oxidation of Cu+. For CuYO2.25, the chemical analyses revealed the presence of mixed valent states containing at least formally an equal number of Cu+ and Cu2+. The thermal analysis (TGA) under reducing atmosphere indicates that oxygen is inserted in different crystallographic sites, for CuYO2.25 it exhibits a two-step reduction mechanism with restoration of the parent oxide. In air, CuYO2+x is thermally stable up ...

Publication 6 :

Topfer, J. Trari, M. Doumerc, J. P. (2007) Preparation and physical properties of CuAl1-xMnxO2 (0 < x < 0.2) delafossites . SOLID STATE SCIENCES 2007 VOL 9 ; NUMBER 3-4, page(s) 236-239 Elsevier Science B.V., Amsterdam.

www.elsevier.com/locate/issn/12932558



The formation of a CuAl1-xMnxO2 solid solution for a limited range of x values (0 < x < 0.2). Magnetic studies show that Mn3+ ions are in the HS state and that the predominant interactions are antiferromagnetic. The oxides are semiconductors with an activation energy decreasing with x.

Publication 7 :

Brahimi, R. Bessekhouad, Y. Bouguelia, A. Trari, M. (2007) Visible light induced hydrogen evolution over the heterosystem Bi2S3/TiO2 . CATALYSIS TODAY 2007 VOL 122 ; NUMBER 1-2, page(s) 62-65 Elsevier Science B.V., Amsterdam.

www.elsevier.com/locate/issn/09205861



A new photochemical heterosystem Bi2S3/TiO2 immersed in solutions of X2- (=S2- or S2O32-) as reducing agents for generated minorities is proposed. Bi2S3, synthesized via solvent thermal process, has a good crystallinity and exhibits n-type conduction as evidenced from photocurrent-potential characteristics. The flat band potential of Bi2S3 (-0.83VSCE) is pH-insensitive and shifts negatively with increasing S2- concentration by 53mV/pS. The heterosystem shows a much higher activity than Bi2S3 alone where efficient H2-photoevolution can be realized with concomitant oxidation of X2-. The optimal value of the mass ratio (Bi2S3/TiO2) was equal to unity. In S2O32- electrolyte, the photoactivity peaks at pH 13.7 with an evolution rate of 2.9mmolmg-1h-1 and decreases gradually to zero near pH 7. T...

Publication 8 :

Saadi, S. Bouguelia, A. Derbal, A. Trari, M. (2007) Hydrogen photoproduction over new catalyst CuLaO2 . JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A 2007 VOL 187 ; NUMBER 1, page(s) 97-104 Elsevier Science B.V., Amsterdam.

www.elsevier.com/locate/issn/10106030



Excellent quality CuLaO2 has been synthesized through solid reaction in evacuated silica tubes and the delafossite structure was refined in the space group Formula Not Shown . The oxide is thermally stable up to 200degreeC, above 610degreeC it converts irreversibly to CuLa2O4. The conduction band (-1.99VSCE) lies below H2O/H2 level leading to a thermodynamically favorable H2-photoevolution with concomitant oxidation of X2- (=S2- or SO32-). The surface platinization improved the activity by increasing the rate constants of X2- oxidation. The redox kinetic is relatively fast with SO32- whereas the electrochemical system S2-/Pt behaves irreversibly and where the polarization is mainly of activation. The charge carriers move in a narrow conduction band made up primarily of Cu 3d orbitals. The ...

Publication 9 :

Brahimi, R. Bessekhouad, Y. Bouguelia, A. Trari, M. (2007) CuAlO2/TiO2 heterojunction applied to visible light H2 production . JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A 2007 VOL 186 ; NUMBER 2-3, page(s) 242-247 Elsevier Science B.V., Amsterdam.

www.elsevier.com/locate/issn/10106030



CuAlO2/TiO2 heterojunction was prepared and studied for its potential application as dispersed photoelectrode capable to generate H2 under visible light. Transport properties of delafossite CuAlO2, i.e. thermoelectric power and electrical conductivity were studied and correlated to an optical and photoelectrochemical characterization to establish energetic diagram of the heterosystem CuAlO2/TiO2. The valence and the conduction bands were estimated to be respectively of -0.05 and of -1.34V/SCE, which permit electron injection from activated CuAlO2 to an activated TiO2. This fact permitted a physical separation of charge carriers. Photocatalytic experiment performed using S2- and S2O32- showed efficiency respectively of 5265 and 60mmol and then after 40min of irradiation by visible light. Th...

Publication 10 :

B. Hadjarab, A. Bouguelia, M. Trari. (2007) Optical and transport properties of lanthanum-doped stannate BaSnO3 . Journal of Physics D : Applied Physics 40 (19), art. no. 006, pp. 5833-5839


BaSnO3, crystallizing in a cubic perovskite structure, is a polaron hopping semiconductor. It can be made conducting by reducing a small fraction of Sn4+ to Sn2+ under O2- free atmosphere. This can be achieved through the solid solution Ba1-xLaxSnO3 which is mixed phase for x> 0.02, a behavior readily understood in term of the lone pair cation Sn2+. The magnetic susceptibility was measured down to 4.2 K and is less than 1.7x10-5 emu cgs mol-1 consistent with collective electron behavior. The Mossbauer spectroscopy at room temperature exhibits a wide unsplit peak with a quadrupole doublet of 3.18 mm sec-1 and an isomer shift of 0.12 mm sec-1 characteristic of Sn4+, corroborating the delocalization of the stereo chemical pair 5s2. The band gap Eg was found to be 3.12 ; further interband transition, indirectly allowed, occurs at 2.85 eV. The transport properties of Ba0.98La0.02SnO3-d, indicate a degenerate n-type conductivity s300K = 4.03 (Ohm cm)-1, little temperature dependent, with an activation energy ?E of 1 meV and an electron mobility µ300K 0.1 cm2 (V s)-1, thermally activated. The conduction occurs by small polaron hopping between mixed valences tin ions. The observed conductivity is greater than that coming from La-substitution with one electron doping implying the existence of oxygen vacancies. The electrons are believed to travel in Sn-5s conduction band with an effective mass of 3.9 mo. A predominant variable range hopping is predicted from the non linearity of Ln s vs T-1 plot. The electron localization may be attributed to the random distribution of lanthanum as well as oxygen vacancies.



Nos Publications 2006

2) Publications 2006


Publication 1 :

Y. Bessekhouad, N. Chaoui, M. Trzpit, N. Ghazzal, D. Robert and J.V. Weber (2006). UV–vis versus visible degradation of Acid Orange II in a coupled CdS/TiO2 semiconductors suspension. Journal of Photochemistry and Photobiology A : Chemistry, 183, pp 218-224.

www.elsevier.com/locate/jphotochem



TiO2, CdS and coupled CdS/TiO2 powders with CdS percentage varied from 5 to 50% (w/w) have been prepared by a sol-gel method. These pure and composite semiconductors were tested for the photocatalytic degradation of an anionic azo-dye, i.e. Orange II in aerated aqueous suspension under UV-vis and visible (l>400nm) illumination. The photocatalytic efficiency of the CdS/TiO2 couples is found to strongly depend on the proportion of CdS. Under UV-vis light, CdS/TiO2 couples containing a low proportion of CdS are found to be as efficient as pure TiO2 which shows the best photocatalytic activity. Under visible illumination, these formers exhibit faster degradation rate than both isolated components of the composite photocatalyst. The results obtained under both illumination conditions are compar...

Publication 2 :

N. Koriche, A. Bouguelia and M. Trari. (2006) Photocatalytic hydrogen production over new oxide CuLaO2.62. International Journal of Hydrogen Energy, 31, pp 1196-1203

www.elsevier.com/locate/issn/03603199



The new oxide CuLaO2.62, synthesized through solid reaction under O2 atmosphere from CuLaO2 at 380°C , crystallizes in a pseudodelafossite structure. The formulation comes from thermal analysis and iodometric titrations. It exhibits a p-type semi-conductivity ; the resistivity p300K (2485 Ohm cm) and the thermopower S300K (93µVK-1) suggest a mechanism conduction by small polarons hopping between Cu2+/3+. The material is thermally stable up to 500°C beyond which it converts irreversibly to CuLa2O4 . Its photocatalytic ability, in contact with S2- and SO32- aqueous solutions for H2 production, has been evaluated in connection with some physical parameters. The title oxide i...

Publication 3 :

B. Hadjarab, S. Bassaid, A. Bouguelia and M. Trari. (2006) On the transport properties of the solid solution Sr1-xLaxPbO3-d (0 < x < 0.15). Physica C : Superconductivity, 439, pp 67-72.

www.elsevier.com/locate/issn/09214534



Mixed valencies system Sr1-xLaxPbO3-d (0x0.15) has been prepared by solid state reaction at 900°C. All solutions crystallize in a distorted perovskite structure and were carefully examined by chemical analysis and X-ray diffraction. The La3+-substitution was checked via the linear dependence of lattice constants on x-value, i.e. Vegard’s law. The expansion of the unit cell volume involves a simultaneous increase of all the parameters. The magnetic susceptibilities are slightly temperature dependent, dominated by core diamagnetism giving an effective mass m* of 9. The transport properties were investigated from 300K down to liquid helium. The resistivity was found to change markedly with the rate substitution x and the oxides behave as degenerate semi-conductors with very weak activati...

Publication 4 :

S. Saadi, A. Bouguelia and M. Trari. (2006) Photocatalytic hydrogen evolution over CuCrO2. Solar Energy, 80, pp 272-280.

www.elsevier.com/locate/solener



We have been studying the technical feasibility of a photochemical H2 evolution based on a dispersion of CuCrO2 powder in aqueous electrolytes containing various reducing agents ( S2-, SO32- and S2O32- ). The title oxide combines a fair resistance to corrosion with an optimal band gap Eg of 1.32eV. The intercalation of a small amount of oxygen should be accompanied by a partial oxidation of Cu+ into Cu2+ implying a p-type semiconductivity. The S2- oxidation inhibits the photocorrosion and the H2 evolution increases parallel to polysulfides Sn2- formation. Most of H2 is produced when p-CuCrO2 is connected to n-Cu2O formed in situ. H2 liberation proceeds mostly on CuCrO2 while the oxidation of S2- takes place over Cu2O surface and the hetero system Cu...

Publication 5 :

M. Trari, A. Bouguelia and Y. Bessekhouad. (2006) p-Type CuYO2 as hydrogen photocathode. Solar Energy Materials and Solar Cells, 90, pp 190-202

www.elsevier.com/locate/solmat



A new photochemical system based on a CuYO2 dispersion in aqueous S2- or SO32- solution as hole scavengers is proposed. The delafossite CuYO2, doped with calcium, is a low p-type semiconductor with a hole mobility of 7.3x10-7m2V-1s-1. The band gap is 3.50eV and the transition is directly allowed. The valence band edge, located at 5.23eV below vacuum, is made up from Cu-3d type typical of delafossite oxides. The flat band potential Vfb ( +O.17VSCE ) lies below the H2O/H2 potential permitting a spontaneous H2-formation under band gap illumination in aqueous S2- or SO32- electrolytes. p-CuYO2 loaded with n-Cu2O exhibited a higher performance with a H2 evolution rate of 0.4cm3h-1 in 0.1MS2- (pH 13.4). The decrease of photoactivity over time is due to the formation of yellow polysul...

Publication 6 :

B Hadjarab, A Bouguelia, M Kadi-Hanifi and M Trari. (2006) The physical properties of oxygen-deficient perovskite SrPbO3-d. Journal of Physics : Condensed Matter, 18 (37), pp 8551-8561.

http://www.iop.org/EJ/journal/JPhysCM



The transport properties of oxygen-deficient perovskite SrPbO3-d with mixed lead valency were investigated down to 4.2 K. The small d-value (0.059), determined from iodometry, is due to the inert lone pair Pb2+ that does not enjoy regular octahedral coordination in spite of collective electron behaviour. The oxide exhibits a temperature-independent magnetic susceptibility consistent with itinerant electrons. The sign of carriers like polarons is that of n-type conductivity coming from the balance charge via oxygen extraction. The thermal variation of conductivity and thermopower reveal the existence of an energy gap. The conduction mechanism occurs by polaron hopping in conformity with small activation energy. The metal–insulating transition seems to be of Anderson type, resulting from the disorder of oxygen vacancies. At low temperature, the conductivity was fitted to a variable range hopping . A comparison with SrSnO3 will be reported. The covalency of Sn–O raises the antibonding conduction state of 5s parentage and increases the forbidden gap from 1.78 to 3.30 eV..

Publication 7 :

S. Saadi, A. Bouguelia and M. Trari. (2006) Photoassisted hydrogen evolution over spinel CuM2O4 (M=Al, Cr, Mn, Fe and Co). Renewable Energy, 31, pp 2245-2256

www.elsevier.com/locate/renene



The photocatalytic ability of CuM2O4 (M=Al, Cr, Mn, Fe and Co) crystallizing with spinel-type structure has been evaluated according to the H2-evolution. The oxides are black and displayed a semiconducting behavior where the electronic balance comes from a small over stochiometry (CuCo2O4.016). Electron hopping occurs between similar sites in normal spinel with a low activation energy whereas larger energies were found in inverse spinel. The electrodes were characterized photoelectrochemically and acquired the characteristic of p-type semiconductors. The conduction band edge, determined from intensity-potential curves, is located below the H2O/H2 potential leading to a thermodynamically favorable H2-liberation under visible light. The photoactivity was dependent on preparative conditions a...


Nos Publications 2005

3) Publications 2005


Publication 1 :

M. Trari, J. Töpfer, P. Dordor, J.C. Grenier, M. Pouchard and J.P. Doumerc. (2005) Preparation and physical properties of the solid solutions Cu1+xMn1-xO2 (0 < x < 0.2). Journal of Solid State Chemistry, 178 (9), pp 2751-2758

www.elsevier.com/locate/jssc



Solid solutions of formula Cu1+xMn1-xO2 (0 < x < 0.2) were synthesized by solid state reaction in silica sealed tubes. They crystallize with the monoclinic crednerite structure (space group C2/m). The stability domain in air is quite narrow and a phase diagram is proposed and compared with previous results. Magnetic study confirmed the HS state of Mn3+ ions and revealed that the predominant interactions are antiferromagnetic. Their strength decreases with x, which can be ascribed to a dilution effect, and long-range 3D magnetic ordering observed for CuMnO2, disappears for x>0.05. The crednerite solid solutions are p-type semiconductors. Modeling the thermoelectric power behavior suggests that charge carriers are Cu2+ holes diffusing in Cu layers for small x values and Mn4+ holes d...

Publication 2 :

N. Koriche, A. Bouguelia, A. Aider and M. Trari. (2005) Photocatalytic hydrogen evolution over delafossite CuAlO2. International Journal of Hydrogen Energy, 30 (7), pp 693-699

www.elsevier.com/locate/ijhydene



The small band gap CuAlO2, as prepared, is a p-type semiconductor with a low mobility polarons. Its catalytic ability for H2 production upon visible light was studied in connection with its synthesis method. The potential of the conduction band (-1.63 VSCE) lies below H2O/H2 level leading to a spontaneous H2 -evolution. An enhancement has been made in the preparation of active oxide by coprecipitation. The highest H2 production, with a generation rate of 0.19ml h-1 mg-1 , has been obtained in a 0.1 MS2- solution at pH 13.72 and increases parallel to polysulfide Sn2- formation (nS2-+2(n-1)H2O -> nS2- + (n-1) H2 + 2(n-1) OH-) ; both reactions occur simultaneously and no photoactivity was observed below pH 7 indicating that For...

Publication 3 :

M. Younsi, A. Aider, A. Bouguelia and M. Trari. (2005) Visible light-induced hydrogen over CuFeO2 via S2O32- oxidation. Solar Energy, 78 (5), pp 574-580

www.elsevier.com/locate/solener



The properties of CuFeO2 have been studied according to the catalytic hydrogen production upon visible light. CuFeO2 with a low band gap Eg, a good chemical stability and a suitable flat band potential appears as a suitable candidate. The potential of photoelectrons allows favorably a thermodynamically H2-evolution from alkaline thiosulfate S2O32- solution. There is a major difference between pure and loaded oxide with some metal catalysts. Our best results have been obtained with unloaded CuFeO2 at 50 °C and pH 13.60. Thiosulfate S2O32- ions can be oxidized to sulfite SO32- and subsequently to sulfate SO42- and the electronic exchange occurs via mediation of surface states. The quite high H2-formation at the beginning shows a tendency towards saturation, it competes with SO32- produced by parallel oxidation of S2O32-.

Publication 4 :

Ali Cheknane, B. Benyoucef, J.-P. Charles, R. Zerdoum and M. Trari. (2005) Minimization of the effect of the collecting grid in a solar cell based silicon. Solar Energy Materials and Solar Cells, 87 (1-4), pp 557-565

www.elsevier.com/locate/solmat



The solar cells collecting grids present a serious problem and more particularly under solar concentration. Our contribution in this article is to seek the best compromise between shadow effect and series resistance effect. The cell considered here is of Si (silicon) type, n+p with circular geometry (radius a = 4.9 cm ), a silver metallization (pm = 1.6 x 10-6 Ohm cm), and a contact resistivity of pC = 10-5 Ohm cm. Our calculations are made under the condition of AM1.5 with 1 sun concentration.The various power losses caused by this grid are:losses due to the grid shadow, losses in grain boundaries due to the metal/semiconductor contact,power dissipated in the resistance of layer between bars, andlosses in the grid metallization.We summarize the results of our model by:For a sheet res...

Publication 5 :

Y. Bessekhouad, D. Robert and J.-V. Weber. (2005) Photocatalytic activity of Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions. Catalysis Today, 101 (3-4), pp 315-321

www.elsevier.com/locate/cattod



Cu2O/TiO2, Bi2O3/TiO2 and ZnMn2O4/TiO2 heterojunctions were studied for potential applications in water decontamination technology and their capacity to induce an oxidation process under VIS light. UV-vis spectroscopy analysis showed that the junctions-based Cu2O, Bi2O3 and ZnMn2O4 are able to absorb a large part of visible light (respectively, up to 650, 460 and 1000nm). This fact was confirmed in the case of Cu2O/TiO2 and Bi2O3/TiO2 by photocatalytic experiments performed under visible light. A part of the charge recombination that can take place when both semiconductors are excited was observed when a photocatalytic experiment was performed under UV-vis illumination. Orange II, 4-hydroxybenzoic and benzamide were used as pollutants in the experiment. Photoactivity of the junctions was f...


Nos Publications 2004

4) Publications 2004


Publication 1 :

Y. Bessekhouad, D. Robert, J-V Weber and N. Chaoui. (2004) Effect of alkaline-doped TiO2 on photocatalytic efficiency. Journal of Photochemistry and Photobiology A : Chemistry, 167 (1), pp 49-57

www.elsevier.com/locate/jphotochem



Alkaline (Li, Na, K) modified titanium dioxide nanoparticles were prepared by sol-gel route and by impregnation technology. XRD analysis showed that the crystallinity level of catalysts is largely dependent on both the nature and the concentration of alkaline. Indeed, the best crystallinity is obtained for Li-doped TiO2 and is lowest for K-doped TiO2. In general, it was found that the anatase phase is stabilised by the alkaline. pH of zero charge has been found to be in the range 6.6-7.9. Depending on the alkaline concentration, the charge compensation may occur at the surface of the catalyst in acidic and basic environment. For photocatalytic test, Malachite green oxalate, 4-hydroxybenzoic acid and benzamide were used as representative organic pollutants. The catalysts prepared by the imp...

Publication 2 :

Y. Bessekhouad, D. Robert and J. V. Weber. (2004) Bi2S3/TiO2 and CdS/TiO2 heterojunctions as an available configuration for photocatalytic degradation of organic pollutant. Journal of Photochemistry and Photobiology A : Chemistry, 163 (3), pp 569-580

www.elsevier.com/locate/jphotochem



Bi2S3/TiO2 and CdS/TiO2 heterojunctions were prepared by direct mixture of both constituents and by precipitation of the sensitizer with commercial TiO2 at different concentrations. UV-Vis spectroscopy analysis showed that the junctions-based Bi2S3 and CdS are able to absorb a large part of visible light (respectively up to 800 and 600nm). This fact was confirmed by photocatalytic experiment performed under visible light. A part of charge recombination that can take place when both semiconductors are excited was observed when photocatalytic experiment was performed under UV-Vis illumination. Orange II, 4-hydroxybenzoique acid (4-HBZ) and benzamide (BZ) were used as pollutants. Photoactivity of the junctions was found to be strongly dependent on the substrate. The different phenomena taking...


Nos Publications 2003

5) Publications 2003


Publication 1 :

Y. Bessekhouad, M. Trari and J. P. Doumerc. (2003) CuMnO2, a novel hydrogen photoevolution catalyst. International Journal of Hydrogen Energy, 28 (1), pp 43-48

www.elsevier.com/locate/ijhydene



Photocatalytic hydrogen production induced under illumination using a new oxide CuMnO2 has been studied. The applied catalyst was without noble metal. The hydrogen was generated from aqueous solution containing either S2- or SO32-. The conduction band of CuMnO2, with a value of -0.88V/SCE, allows a spontaneous hydrogen formation. The highest hydrogen evolution rate was 0.95x10-2mlmg-1h-1 on the crednerite CuMnO2-E obtained by exchange reaction with SO32- as hole scavenger. When S2- was used, the hydrogen production reaches a saturation attributed to the competitive reduction of yellow polysulfides Sn2- as well as their strong light absorption in the visible region. There was no photoactivity observed below pH 12...


Publication 2 :

Yassine Bessekhouad, Didier Robert and Jean Victor Weber. (2003) Synthesis of photocatalytic TiO2 nanoparticles : optimization of the preparation conditions
Journal of Photochemistry and Photobiology A : Chemistry, 157 (1), pp 47-53

www.elsevier.com/locate/jphotochem



Nanosized titanium oxide (TiO2) powders were prepared by sol-gel route. The preparation parameters are optimized by means of Malachite green oxalate degradations. All catalysts were analyzed by X-ray diffraction (XRD) and BET technique. The best catalyst was compared to TiO2-P25 using two other types of pollutant, 4-hydroxy benzoic and benzamide (BZ) and their performance was found to be strongly dependant on the pollutant’s type...


Publication 3 :

Y. Bessekhouad, D. Robert, and J. V. Weber. (2003) Preparation of TiO2 nanoparticles by Sol-Gel route. International Journal of photoenergy ; 5 (3), pp 153-158

www.hindawi.com/journals/ijp/



Nanosized titanium oxide (TiO2) powders were prepared by emulsification-gelation technology, hydrolysis and reflux process. Starting precursor ( Tetraisopropylorthotitanate Ti(OC3H7)4 ) was modified by 1,4 cyclohexane diol (C6H14O2), hydrogen peroxide (H2O2) and Triethanol amine (C6H15NO3). Titanium tetrachloride was also used as precursor. The effect of methanol on ethanol solvent was also investigated. The powders were analyzed by X-ray diffraction (XRD) and BET technique. Scanning electron microscopy observation was used for agglomerate observations. The photoactivity of the products obtained was taken as efficiency of Benzamide photodegradations.


Nos Publications 2002

6) Publications 2002


Publication 1 :

Y. Bessekhouad and M. Trari. (2002) Photocatalytic hydrogen production from suspension of spinel powders AMn2O4(A=Cu and Zn). International Journal of Hydrogen Energy, 27 (4), pp 357-362

www.elsevier.com/locate/ijhydene



Two narrow band gap-semiconductors AMn2O4 (A=Cu and Zn) with p-type semiconductivity and crystallising in the spinel structure have been studied for photoassisted hydrogen production by visible light in aqueous solution containing sulfide S2- or sulfite SO32-. The highest H2 evolution rate, obtained under illumination with platinized Cu-oxide, was found to be 0.26×10-2 mlmg-1 h-1 in a 0.1 M SO32- alkaline solution and does not depend on specific area. H2 evolves over oxide whereas oxidation of S2- and/or SO32- occurs on platinum that behaves as a counter electrode. When sulfide is used as hole scavenger, the hydrogen production decreases over time and reaches a zero value after 3 h because of the formation of coloured polysulfides Sn2-, which acts as an optical filter and compete with water reduction...

Publication 2 :

Y. Bessekhouad, M. Mohammedi and M. Trari. (2002) Hydrogen photoproduction from hydrogen sulfide on Bi2S3 catalyst. Solar Energy Materials and Solar Cells, 73 (3), pp 339-350

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Films of polycrystalline Bi2S3 have been prepared onto bismuth and platinum substrates by electrodeposition from an aqueous sulfide bath. The films were thin, uniform and well adhered. Bi2S3 is a direct band gap semiconductor with a value of 1.28 eV optimally matched with the solar spectrum. The photoelectrochemical study was undertaken for the generation of hydrogen by using illuminated n-Bi2S3 particles ; it was found that hydrogen evolution depends highly on the synthesis method of powder. Impregnation of platinum onto Bi2S3 shows a production enhancement of about 25%. The most active photocatalyst, prepared by a solvent thermal process and loaded with Pt in 0.1 M S2- alkaline electrolyte, yields 2.13×10-2 ml mg-1 of H2 after 4 h of irradiation with the visible output of a 500 W halogen lamp...