Mohammad Choucair

University of Sydney, Sydney, New South Wales, Australia

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Publications (28)132.04 Total impact

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    ABSTRACT: Graphitic carbon material encasing chromium oxide nanoribbons [Cr2O3-C composite] is obtained by carbonizing a mixture of furfuryl alcohol and Cr–BDC MOF [BDC: benzene dicarboxylic acid; Cr3F(H2O)2O[(O2C)C6H4–(CO2)]3.nH2O] at 900 °C under inert atmosphere. The Ni–Pd nanoparticles synthesized by NaBH4 reduction method are loaded on the Cr2O3-C support via sonication. Morphological, structural, and chemical analysis of the designed chromia based carbon support and synthesized nanoparticles is carried out with PXRD, EDX, SEM, HR-TEM and BET surface area. The gas adsorption analyses reveal that BET surface area of Cr2O3-C support decreases from 438 m2 g−1 to 171 m2 g−1 by the incorporation Ni–Pd nanoparticles. The electro-oxidation reaction of methanol is carried out over the designed electrocatalysts in acidic media. The Ni–Pd nanoparticles supported on Cr2O3-C have presented a significant increase in catalytic activity for methanol oxidation and tolerance in comparison to the nanoparticles supported on activated carbon and glassy carbon electrode.
    No preview · Article · Jan 2016 · Materials Research Bulletin
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    ABSTRACT: Cobalt oxide embedded nitrogen-doped carbon nanotubes (CoO/N-CNT) are synthesized by the direct carbonization of a cobalt–benzimidazole framework (ZIF-12) at 950 °C under an inert atmosphere. X-ray photoelectron spectroscopy indicates the conducting graphitic networks of the CNT contain edge and aromatic substituted pyridinic-nitrogen. Microscopy reveals the extensive formation of multi-walled CNT encasing CoO nanoparticles. This trapping of CoO nanoparticles within the nitrogen doped CNT network is discussed as the key basis of improving the material's contact resistance and conductivity to achieve high power outputs, together with the high specific surface area (365 m2 g−1) and structural robustness of the novel composite material. The material shows an excellent lithium charge/discharge and storage, retaining ∼95% capacity after 50 cycles and a reversible capacity of ∼1100 mA h g−1 at a current density of 0.1 A g−1, which far exceeds the performance of conventional lithium ion battery anode materials under similar conditions.
    No preview · Article · Dec 2015 · RSC Advances
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    ABSTRACT: We report the first example of an ionic graphene salt containing boron. An anionic charge is introduced to the graphene surface by means of 7,8-nido-[C2B9H11](-) carborane clusters covalently and electronically bound to the graphene lattice, and this new material was isolated as its Cs(+) salt.
    No preview · Article · Dec 2015 · Chemical Communications
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    ABSTRACT: Microporous carbon materials are obtained by carbonizing a mixture of Zn-BTC MOF [Zn2 (BTC)3 {BTC; 1, 3, 5-benzenetricarboxylic acid}] and polyfurfuryl alcohol (Zn-BTC MOF/PFA) at different carbonization temperatures. The obtained samples are characterized by PXRD, XPS, SEM, TEM, gas sorption and Raman spectroscopic analysis. The maximum BET surface area of 1455 m2 g-1 is recorded for the porous carbon obtained at 950 °C. The incorporation of furfuryl alcohol in the 3D channels of Zn-BTC MOF results in creation of three distinct pore-regions; ultra-micropores (0.45-0.9 nm), micropores (0.9-2 nm) and mesopores (2-3.7 nm) exist with total pore volume of 2.03 cm3 g-1. The MPC-950 exhibits an enhanced specific capacitance of 471 F g-1 at 2 mV s-1 and 375 F g-1 at 0.75 A g-1 and retains ca. 96% of its initial capacitance over 3000 cycles.
    No preview · Article · Sep 2015 · International Journal of Hydrogen Energy
  • Mohammad Choucair · Philippe Mauron
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    ABSTRACT: We report the facile and versatile preparation of graphene-based nanocomposites of magnetite, silver, titania, nickel, and silicon by solid state mechanical mixing. The composites were directly employed for nitrogen and hydrogen gas adsorption studies at 77 K and equilibrium pressure of 1 atm. Under the experimental conditions the chemically synthesised graphene support had a solid state BET surface area of 499 m2/g and a total reversible hydrogen uptake of 0.5 wt.%. Among our prepared nanocomposite samples, the silver nanoparticles promoted the most significant increase in hydrogen uptake per metre squared of material by 30% when compared to the parent graphene sample. However, the total hydrogen uptake by weight percentage in the studied graphenic materials remains low. The hydrogen storage capacity observed for the graphene nanocomposites can be qualitatively accounted for by considering the contributions of the catalyst particles on the hydrogen storage, the contact between catalyst and graphene, and the structural nature of the graphene surface.
    No preview · Article · May 2015 · International Journal of Hydrogen Energy
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    ABSTRACT: A B S T R A C T Novel graphitic material containing chromium oxide (Cr 2 O 3) nanoribbons is obtained by carbonizing a mixture of polyfurfuryl alcohol and MIL–101(Cr) at 900 C. Morphological, structural, and chemical analysis of the product is carried out with HR–TEM, SEM, XPS, XRD, and BET surface area. The maximum BET surface area recorded for the nanocomposite is 438 m 2 g À1. The nanocomposite exhibits a specific capacitance as high as 300 F g À1 at 2 mV s À1 and 291 F g À1 at 0.25 A g À1 , and presents 95.5% long–term cycling stability over 3000 cycles. The pseudo-capacitive role of Cr 2 O 3 nanoribbons is found to be important towards total capacitance of nanocomposite material. ã
    Full-text · Article · May 2015 · Electrochimica Acta
  • Mohammad Choucair · Matthew R. Hill · John A. Stride
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    ABSTRACT: Carbon nanospheres are obtained by reacting metallic sodium at 100 °C with tetrachloromethane under a flow of N2 gas at ambient pressure. The product consisted of both hollowed and solid carbon spheres, ranging between 20 and 300 nm in size and comprised of concentrically oriented, disordered graphitic fragments. The maximum surface area recorded for this nanostructured carbon is 830 m2 g−1. Morphological, structural, and chemical analysis of the product is carried out with HR-TEM, BET surface area, XPS, XRD, and Raman spectroscopy. The formation of the spherical shape of the carbon nanoparticles is discussed based on direct observations of the reaction at the interfacial phase boundary.
    No preview · Article · Mar 2015 · Materials Chemistry and Physics
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    ABSTRACT: The electron spin lifetime in an assembly of chemically synthesized graphene sheets was found to be extremely sensitive to oxygen. Introducing small concentrations of physisorbed O2 onto the graphene surface reduced the exceptionally long 140 ns electron spin lifetime by an order of magnitude. This effect was completely reversible: Removing the O2 by using a dynamic vacuum restored the spin lifetime. The presence of covalently bound oxygen also decreased the electron spin lifetime in graphene, although to a far lesser extent compared to physisorbed O2 . The conduction electrons in graphene were found to play a significant role by counter-balancing the spin depolarization caused by oxygen molecules. Our results highlight the importance of chemical environment control and device packing in practical graphene-based spintronic applications.
    Full-text · Article · Jan 2015 · Chemistry - A European Journal
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    Bálint Náfrádi · László Forró · Mohammad Choucair
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    ABSTRACT: Graphene is theoretically expected to be a highly suitable material for spintronic and quantum computation applications. Current experimental reports assign surprisingly low spin lifetimes to graphene and related carbon structures. Recently, we showed a solvothermal synthesis method that can be employed to produce a high-purity sample, which approximates very well the assembly of graphene sheets. Using the contactless spectroscopic technique of electron spin resonance (ESR), we were able to identify in this graphene material the ESR of both conduction electrons and localized spins [Náfrádi et al., Carbon 74, 346–351 (2014)]. Here, we show the temperature dependent evolution of the ESR of these two spin species.
    Full-text · Article · Dec 2014 · physica status solidi (b)
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    Jan U Kahlert · Aditya Rawal · James M Hook · Louis M Rendina · Mohammad Choucair
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    ABSTRACT: The conjugated aromatic system of graphene was used to trap the reactive, boron-rich 1,2-carborane cluster. Functionalization of the graphene surface was confirmed by solid-state MAS (11)B NMR spectroscopy and quantified by X-ray photoelectron spectroscopy. This work represents the first confirmed example of direct functionalization of a graphene lattice with carboranes.
    Full-text · Article · Aug 2014 · Chemical Communications
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    Bálint Náfrádi · Mohammad Choucair · László Forró
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    ABSTRACT: A chemically synthesized graphitic material where the structural coherence between the layers is missing approximates very well the assembly of graphene sheets. Our multi-frequency (9.4–420 GHz) electron spin resonance (ESR) study clearly identifies itinerant and localized electrons below 50 K. The metallic signal ascribed to the conduction electrons in graphene is characterized by a remarkably long spin lifetime of 65 ns. Above this temperature incoherent in-plane and inter-plane scattering give a motionally narrowed single line at g = 2.0044.
    Full-text · Article · Aug 2014 · Carbon
  • Mohammad Choucair · Bin Gong · John Arron Stride
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    ABSTRACT: The inability to readily upscale nanofabrication of carbon nanomaterials often restricts their application, despite outstanding performances reported in both the research laboratory and prototype stages. Here we report the direct chemical synthesis of graphene nanoribbons by a bottom-up approach based on the common laboratory reagents sodium and propanol; these are solvothermally reacted to give an intermediate precursor that is then rapidly pyrolized yielding single- and few-layer graphene nanoribbons. Our results show that confinement of the lateral dimensions of graphene can be achieved simply by varying the alcohol feedstock. The ability to produce bulk quantities of graphene nanoribbons by a low cost and scalable approach is anticipated to enable a wider range of affordable real-world graphene applications.
    No preview · Article · Mar 2014 · Materials Letters
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    ABSTRACT: Post-synthetic modification of H3[(Cu4Cl)3(BTTri)8] or CuBTTri, where H3BTTri = 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene, with piperazine (pip) has yielded the grafted framework H3[(Cu4Cl)3(BTTri)8(pip)12], pip-CuBTTri, which exhibits an improved CO2 uptake at pressures pertinent to postcombustion flue gas capture compared with the non-grafted material. In particular, the volumetric capacity of pip-CuBTTri was 2.5 times higher than that of CuBTTri at ca. 0.15 bar and 293 K. A chemisorption mechanism for CO2 adsorption was proposed on the basis of diffuse reflectance infrared spectra (DRIFTS) and the high initial isosteric heat of adsorption (−Qst, ≈96.5 kJ/mol). Application of the Ideal Adsorbed Solution Theory (IAST) to a simulated mixture of 0.15 bar CO2/0.75 bar N2 revealed a selectivity factor of 130. Both pressure and temperature swing processes were found to be suitable for facile regeneration of the material over multiple adsorption–desorption cycles.
    No preview · Article · Jul 2013 · Microporous and Mesoporous Materials
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    ABSTRACT: The hydrogen absorption of sodium intercalated fullerenes (NaxC60) was determined and compared to pure fullerenes (C60). Up to 3.5 mass% hydrogen can reversibly be absorbed in NaxC60 at 200 °C and a hydrogen pressure of 200 bar. The absorbed amount of hydrogen is significantly higher than for the case when only the sodium would be hydrogenated (1 mass% for x = 10). At 200 bar the onset of hydrogen absorption is observed at 150 °C. At a pressure of 1 bar hydrogen the major desorption starts at 250 °C and is completed at 300 °C (heating rate 1 °C min−1). This absorption and desorption temperatures are significantly reduced compared to pure C60, either due to a catalytic reaction of hydrogen on sodium or due to the negatively charged C60. The hydrogen ab/desorption is accompanied by a partial de/reintercalation of sodium. A minor part of the hydrogen is ionically bonded in NaH and the major part is covalently bonded in C60Hx. The sample can be fully dehydrogenated and no NaH is left after desorption. In contrast to C60, where the fullerene cages for high hydrogen loadings are destroyed during the sorption process, the NaxC60 sample stays intact. The samples were investigated by X-ray, in-situ neutron powder diffraction and infrared spectroscopy. NaxC60 was synthesized by reacting sodium azide (NaN3) with C60 (molar ratio of Na:C60 is 10:1).
    Full-text · Article · Oct 2012 · International Journal of Hydrogen Energy
  • Mohammad Choucair · Bin Gong · John A. Stride
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    ABSTRACT: Large multi-walled carbon nanotubes (MWCNTs) have been synthesized by the reaction of polytetrafluoroethylene and ethanol with metallic lithium under solvothermal conditions. Production of the MWCNTs depends on a series of coupled reactions that utilize the liberation of chemical energy in the thermodynamically closed system. Various characterization studies show tubes with diameters of 50–150 nm and micrometer lengths. The interwall spacing was found to be 0.39 ± 0.04 nm. X-ray photoelectron spectroscopy reveals the tubes are functionalized with up to 2.2 %/wt. fluorine and 6.0 %/wt. oxygen.
    No preview · Article · Jun 2012 · Journal of Nanoparticle Research
  • Mohammad Choucair · John Arron Stride
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    ABSTRACT: The combustion of naphthalene has been found to yield gram-scale quantities of carbon onions that are free of impurities and furthermore without the use of catalysts. X-ray diffraction (XRD) indicates that the interlayer spacing between concentric shells of the carbon onions is not uniform across the particle; rather it decreases from a graphite-like 0.34nm and approaches a diamond-like 0.29nm interlayer spacing towards the inner layers. The dispersion in the interlayer spacing is believed to result from differing external pressures exerted on the individual nanometer-sized graphitic membranes during formation of the onions. Electron microscopy techniques such as high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy demonstrate the extensive formation of carbon onions. The HRTEM indicates that the onions consist of 50–54 shells, found to be in good agreement with the XRD data.
    No preview · Article · Mar 2012 · Carbon
  • Mohammad Choucair · Nicholas M.K. Tse · Matthew R. Hill · John A. Stride
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    ABSTRACT: Here we explore the exceptional structural characteristics of a set of graphene-related materials prepared by a wet chemical approach. We present a comprehensive study of the effects of morphology, sonication, temperature, probe species, and stacking behaviour on the measurement of graphene surface area. Nitrogen gas was used in the solid state gas adsorption measurements and methylene blue dye for adsorption measurements on aqueous dispersions of graphene. The surface area values obtained are among the highest reported for synthetic graphenes: 1700 m2 g− 1 in aqueous dispersions and 612 m2 g− 1 in the solid state. Microscopy revealed the graphene used in the study was present in large part as free sheets and electron diffraction confirmed the successful synthesis of high quality graphene with a regular C–C bond length of 1.41 ± 0.02 Å.Highlights► Surface area measurements of graphene in the solid state and as aqueous dispersions. ► Surface area of graphene is tuneable based on post-synthesis preparation. ► Nitrogen adsorption was affected by the consolidation of the graphene layers. ► Kinetic effects influenced the outcome of methylene blue dye adsorption.
    No preview · Article · Jan 2012 · Surface Science
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    ABSTRACT: Here, we present the first muon spectroscopy investigation of graphene, focused on chemically produced, gram-scale samples, appropriate to the large muon penetration depth. We have observed an evident muon spin precession, usually the fingerprint of magnetic order, but here demonstrated to originate from muon-hydrogen nuclear dipolar interactions. This is attributed to the formation of CHMu (analogous to CH(2)) groups, stable up to 1250 K where the signal still persists. The relatively large signal amplitude demonstrates an extraordinary hydrogen capture cross section of CH units. These results also rule out the formation of ferromagnetic or antiferromagnetic order in chemically synthesized graphene samples.
    Full-text · Article · Nov 2011 · Nano Letters
  • Jia-Zhao Wang · Lin Lu · Mohammad Choucair · John A. Stride · Xun Xu · Hua-Kun Liu
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    ABSTRACT: Sulfur-graphene (S-GNS) composites have been synthesized by heating a mixture of graphene nanosheets and elemental sulfur. According to field emission electron microscopy, scanning electron microscopy with energy dispersive X-ray mapping, Raman spectroscopy, and thermogravimetric analysis, sulfur particles were uniformly coated onto the surface of the graphene nanosheets. The electrochemical results show that the sulfur-graphene nanosheet composite significantly improved the electrical conductivity, the capacity, and the cycle stability in a lithium cell compared with the bare sulfur electrode.
    No preview · Article · Aug 2011 · Journal of Power Sources
  • M Choucair · J Stride

    No preview · Chapter · Jul 2011

Publication Stats

991 Citations
132.04 Total Impact Points

Institutions

  • 2013-2016
    • University of Sydney
      • School of Chemistry
      Sydney, New South Wales, Australia
  • 2012
    • Università degli studi di Parma
      Parma, Emilia-Romagna, Italy
  • 2008-2012
    • University of New South Wales
      • School of Chemistry
      Kensington, New South Wales, Australia