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Start Over Author "Qu, Xuanhui" Journal journal of alloys and compounds
47 results on '"Qu, Xuanhui"'

39. Improved hydrogen storage performances of MgH2–NaAlH4 system catalyzed by TiO2 nanoparticles

Author

Zahid Asghar, G. H. Zahid, Qu Xuanhui, Rafi-ud-din, E. Ahmad, Muhammad Shahzad, and M. Iqbal

Subjects
Materials science, Hydrogen, Mechanical Engineering, Kinetics, Inorganic chemistry, Metals and Alloys, Nanoparticle, chemistry.chemical_element, Catalysis, Hydrogen storage, chemistry, Mechanics of Materials, Desorption, Materials Chemistry, Dehydrogenation, Titanium
Abstract

The effects of addition of TiO 2 nanoparticles on the hydrogen sorption properties and reaction mechanism of MgH 2 –NaAlH 4 (mole ratios 1:2, 1:1 and 2:1) composites were investigated. The results indicated that TiO 2 nanoparticles were active in improving the dehydriding/rehydriding kinetics and reducing the dehydrogenation temperature of MgH 2 –NaAlH 4 composite. Isothermal volumetric measurements revealed that the kinetics of TiO 2 doped samples were 1.5 and 6 times that of undoped binary and MgH 2 samples. The doped sample displayed substantially reduced activation energies for NaAlH 4 , Na 3 AlH 6 , MgH 2 , and NaH relevant decompositions. TiO 2 doping had also markedly enhanced the reversible capacity of binary composites, persisting well during three dehydrogenation/rehydrogenation cycles. XRD, XPS, and FESEM–EDS analyses had demonstrated that finely dispersed oxygen-deficient titanium species, formed during the first desorption, were migrated to the bulk of composite during cycling. It was suggested that these finely dispersed oxygen-deficient titanium species might contribute to kinetic improvement by serving as active sites to facilitate the hydrogen diffusion during dehydrogenation/rehydrogenation processes.

Published
2014
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41. Catalytic effects of nano-sized TiC additions on the hydrogen storage properties of LiAlH4

Author

Li Ping, Qu Xuanhui, Rafi-ud-din, and Lin Zhang

Subjects
Dopant, Hydrogen, Chemistry, Mechanical Engineering, Metals and Alloys, Analytical chemistry, chemistry.chemical_element, Catalysis, Thermogravimetry, Hydrogen storage, Differential scanning calorimetry, Mechanics of Materials, Desorption, Materials Chemistry, Dehydrogenation
Abstract

The catalytic effect of TiC nanopowder addition in varying proportions on the hydrogen storage properties of LiAlH4 has been investigated by pressure-composition-temperature (PCT) experiments, thermogravimetry (TG), and differential scanning calorimetry (DSC). The results indicate that doped samples are able to dehydrogenate at much lower temperatures; for example, the onset of dehydrogenation is 85 °C for LiAlH4–2 mol% TiC, and the majority of hydrogen (∼6.9 wt.%) can be released by 188 °C. About 5 out of 6.9 wt.% of H2 can be released in the range of 85–138 °C (heating rate 4 °C min−1). Isothermal desorption results at 115 °C reveal that doped alanate exhibits dehydriding rate 7–8 times faster than that of pure LiAlH4. DSC measurements indicate that enthalpies of decomposition in LiAlH4 decrease significantly with doping. From Kissinger analysis, the apparent activation energies are estimated to be 59 kJ/mol, 70 kJ/mol and 99 kJ/mol for the decompositions of LiAlH4, Li3AlH6 and LiH, respectively. The results of first rehydrogenation indicate that 5 mol% dopant exhibits the maximum absorption of about 1.9 wt.%. XRD, FESEM, EDS, FTIR, and XPS analyses are utilized to put forward a possible catalytic mechanism of nano-sized TiC in ameliorating the dehydriding/rehydriding characteristics of doped LiAlH4.

Published
2010
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