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This study is a contribution to development of material based on transition metal oxides with application in electrochemical devices. A pyrochlore-like solid solution with general chemical formula Bi1.2Ce0.3Sb1.5CuO7 was synthesised. The pyrochlore structure was determined by X-ray powder diffraction. The pressed pyrochlore powder sample was analysed by scanning electron microscopy to show effect of substitution fraction of cerium and to determine its grain size and morphology. Energy dispersive of X-rays was performed to confirm effective substitution of bismuth for cerium. The EDX analysis was supported by X-ray photoelectron spectroscopy which also gave information on respective oxidation states of cations. Several modes of vibration due to metal-oxygen bonds of pyrochlore-like material were studied by Fourier-transform infrared spectroscopy. The results suggested that this compound contained major component of pyrochlore and minor component of CeO2. The dielectric measurements carried out at frequency 1 MHz in temperature range –40°C–90°C proved that pyrochlore compound possessed dielectric constants ranging between 12 and 28. Furthermore, owing to its high electrical conductivity, synthesised material has been utilised as bioanode in a microbial fuel cell. This bio-electrochemical device converted organic wastes into electricity using microorganisms as biocatalysts. It displayed greater electron transfer from electroactive biofilm towards the bioanode by improving its electrical energy output. The presence of pyrochlore in electrode allowed a power density of 25 mW/m2. It was almost the same as that obtained with a graphite carbon modified by the conducting polymer polypyrrole. The MFC with pyrochlore solid oxide was advantageously more stable having longer lifetime and indicating its suitability to substitute the polypyrrole at the bioanode. Besides, the colour of the coffee mac leachate in the anolyte (anode compartment) became less dark, which means that the maximum chemical oxygen demand (COD) was removed and converted into electric energy. [ABSTRACT FROM AUTHOR]

A facile and original approach based on a one-pot non-aqueous sol–gel solvothermal process was developed to synthesize 2D Tungsten trioxide (WO3) nanoplatelets with an average size ranging from 30 to 50 nm, and a correspondingly high surface area. The structural, morphological, functional group, optical properties of the materials, and the properties of the adsorption surfaces were all investigated; the degree of surface hydroxyls (–OH groups) has been examined. Nuclear Magnetic Resonance Spectroscopy techniques indicated the formation of di-hexyl ether as a result of the solvothermal reaction. The optical absorption, measured using UV–Vis Diffuse Reflectance Spectroscopy, revealed a narrow bandgap (Eg = 2.18 and 2.48 eV for WO3-24 and WO3-48, respectively) compared to that of for bulk WO3 (2.7 eV), attributable to oxygen vacancies. The as-prepared WO3 nanoplatelets displayed excellent photocatalytic performance for degrading Rhodamine B under visible light-emitting diode light with up 99% degradation rate that was achieved in 120 min. Thus, the enhanced Rhodamine B photodegradation in the presence of WO3-24 along with H2O2 was assigned to the reactive oxygen species such as ·OH and RhB*+, involving in the strong synergistic effect between WO3 and H2O2, effectively separating of photocarriers and, as a consequence, boosting the photocatalytic efficiency. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C3N4 were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C3N4 and exfoliated g-C3N4 was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C3N4 synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH4 and CO resulting from the reduction of CO2 were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis and structural determination by the Rietveld method of a new compound with pyrochlore-like structure (Bi1.524Cu0.476)(Sb1.524Cu0.476)O7+δ . A new polycristalline compound with pyrochlore-like structure and chemical formula (Bi1,524Cu0,476)(Sb1,524Cu0,476)O7+δ has been synthesized using the classical solid-state reaction method. The Rietveld structure determination shows that the cubic cell parameter is a =10.430(1) Å and the space group Fd m with eight formula units per cell. The reliability factors are R p =7.1; R wp =9.28 and R exp =5.33. The electric resistivity measured by means of the four probe method at room temperature on sintered pellets is about 105 Ω cm. The magnetic susceptibility measurements achieved between 300 and 800 K show the existence of an effective moment μeff =2.27 μB. To cite this article: M. Sellami et al., C.R. Chimie 8 (2005) . [Copyright &y& Elsevier]

Graphitic carbon nitride (g-C3N4), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C3N4 were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C3N4 and exfoliated g-C3N4 was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C3N4 synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH4 and CO resulting from the reduction of CO2 were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]

Abstract: Synthesis and magnetic properties study of solids solutions (Bi1.524–x M x Cu0.476)[Sb1.524Cu0.476]O7+δ with M=Ca et Pb. The solid solutions with pyrochlore-like structure and general chemical formula (Bi1.524–x M x Cu0.476)[Sb1.524Cu0.476]O7+δ (M= Ca2+, Pb2+) have been synthesized by solid-state chemical reaction at high temperature. The two solutions crystallize in the cubic system, with Fd m space group. Domains of homogeneity are 0≤ x ≤0.30 and 0≤ x ≤0.26 for calcium and lead, respectively. A regular decreasing of the cell parameter has been observed in the calcium solid solution. The state oxidation +5 of antimony has been put in evidence by the Mössbauer spectrometry of 121Sb. Magnetic susceptibility measurements showed that the effective magnetic moment of copper in these compounds decreases when bismuth is substituted for calcium. To cite this article: M. Sellami et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]

Abstract: A new pyrochlore solid solution with formula Bi1.5Sb1.5Cu1−x Mn x O7 has been synthesized using ceramic method at 1000°C. The cell parameter decreases linearly with increasing manganese concentration. Rietveld refinements for (B1.5Mn0.5)(Sb1.5Mn0.5)O7 compound using X-ray powder diffraction data confirmed an overall A2B2O7 cubic pyrochlore structure with a =10.42749 (4)Å and Fd-3m symmetry. The reliability factors are R wp =3.48%; R p =2.37%; R exp =1.65% and R Bragg =1.58%. The magnetic susceptibility measurements achieved between 4 and 300K indicate a paramagnetic behaviour with an oxidation state “2+” of the manganese ion. The electric resistance measured using complex impedance spectroscopy method put in evidence a decrease of the electric resistance with the temperature, which reached 5×102 Ω at 675K. Dielectric properties depend on the variation of frequency and temperature, results indicate a conductive compound. [Copyright &y& Elsevier]