| 1. |
- Deng, Yunfeng, et al.
(författare)
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A comparative theoretical study on core-hole excitation spectra of azafullerene and its derivatives
- 2014
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 140:12, s. 124304-
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Tidskriftsartikel (refereegranskat)abstract
- The core-hole excitation spectra-near-edge x-ray absorption spectroscopy (NEXAFS), x-ray emission spectroscopy (XES), and x-ray photoelectron spectroscopy (XPS) shake-up satellites have been simulated at the level of density functional theory for the azafullerene C59N and its derivatives (C59N)(+), C59HN, (C59N)(2), and C59N-C-60, in which the XPS shake-up satellites were simulated using our developed equivalent core hole Kohn-Sham(ECH-KS) density functional theory approach [B. Gao, Z. Wu, and Y. Luo, J. Chem. Phys. 128, 234704 (2008)] which aims for the study of XPS shake-up satellites of large-scale molecules. Our calculated spectra are generally in good agreement with available experimental results that validates the use of the ECH-KS method in the present work. The nitrogen K-edge NEXAFS, XES, and XPS shake-up satellites spectra in general can be used as fingerprints to distinguish the azafullerene C59N and its different derivatives. Meanwhile, different carbon K-edge spectra could also provide detailed information of (local) electronic structures of different molecules. In particular, a peak (at around 284.5 eV) in the carbon K-edge NEXAFS spectrum of the heterodimer C59N-C-60 is confirmed to be related to the electron transfer from the C59N part to the C-60 part in this charge-transfer complex.
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| 2. |
- Li, Fushao, et al.
(författare)
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SOFC cathode material of La1.2Sr0.8CoO4±δ with a fibrous morphology : Preparation and electrochemical performance
- 2023
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Ingår i: International journal of hydrogen energy. - : Elsevier BV. - 0360-3199 .- 1879-3487. ; 48:8, s. 3204-3215
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Tidskriftsartikel (refereegranskat)abstract
- Using soluble salts as metal-ion sources and polyacrylonitrile (PAN) as a polymer matrix, La1.2Sr0.8CoO4±δ cathode material with a fibrous morphology is prepared by electrostatic spinning, and microstructural characteristic of this material is investigated by field-emission scanning microscopy and X-ray diffraction. Electrochemical performance of the material in solid-oxide fuel cells is then tested. The results demonstrate that phase-pure La1.2Sr0.8CoO4±δ fibrils with tetragonal structure can be prepared from fresh silky precursors using electrospinning after annealing at high temperature. Compared to the conventional cathode material that possesses a plain granular structure, La1.2Sr0.8CoO4±δ fibrils exhibit superior electrochemical performance. At a temperature of 800 °C, the area specific resistance with this fibrous cathode is as low as 0.043 Ω cm2, and maximum power density with the corresponding single-cell is 716 mW cm−2, demonstrating the fast electrode kinetics in the O2 reduction reaction. Comparatively, the area specific resistance with the plain cathode is 0.062 Ω cm2, and the maximum power density with the corresponding single-cell is only 642 mW cm−2. Under a constant voltage load of 0.6 V at a fixed temperature of 750 °C, the power output from a single-cell with the fiber-structured cathode maintains between 615 mW cm−2 and 585 mW cm−2 even after 15 h of running time, showing a slower fading rate and a more stable electrochemical performance than the plain cathode.
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| 3. |
- Li, Xiao-Fei, et al.
(författare)
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Unraveling the formation mechanism of graphitic nitrogen-doping in thermally treated graphene with ammonia
- 2016
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen-doped graphene (N-graphene) has attractive properties that has been widely studied over the years. However, its possible formation process still remains unclear. Here, we propose a highly feasible formation mechanism of the graphitic-N doing in thermally treated graphene with ammonia by performing ab initio molecular dynamic simulations at experimental conditions. Results show that among the commonly native point defects in graphene, only the single vacancy 5-9 and divacancy 555-777 have the desirable electronic structures to trap N-containing groups and to mediate the subsequent dehydrogenation processes. The local structure of the defective graphene in combining with the thermodynamic and kinetic effect plays a crucial role in dominating the complex atomic rearrangement to form graphitic-N which heals the corresponding defect perfectly. The importance of the symmetry, the localized force field, the interaction of multiple trapped N-containing groups, as well as the catalytic effect of the temporarily formed bridge-N are emphasized, and the predicted doping configuration agrees well with the experimental observation. Hence, the revealed mechanism will be helpful for realizing the targeted synthesis of N-graphene with reduced defects and desired properties.
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| 4. |
- Liu, Lingling, et al.
(författare)
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Uniform and perfectly linear current-voltage characteristics of nitrogen-doped armchair graphene nanoribbons for nanowires
- 2017
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 19:1, s. 44-48
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Tidskriftsartikel (refereegranskat)abstract
- Metallic nanowires with desired properties for molecular integrated circuits (MICs) are especially significant in molectronics, but preparing such wires at a molecular level still remains challenging. Here, we propose, from first principles calculations, experimentally realizable edge-nitrogen-doped graphene nanoribbons (N-GNRs) as promising candidates for nanowires. Our results show that edge N-doping has distinct effects on the electronic structures and transport properties of the armchair GNRs and zigzag GNRs (AGNRs, ZGNRs), due to the formation of pyridazine and pyrazole rings at the edges. The pyridazine rings raise the Fermi level and introduce delocalized energy bands near the Fermi level, resulting in a highly enhanced conductance in N-AGNRs at the stable nonmagnetic ground state. Especially for the family of AGNRs with widths of n = 3p + 2, their semiconducting characteristics are transformed to metallic characteristics via N-doping, and they exhibit perfectly linear current-voltage (I-V) behaviors. Such uniform and excellent features indicate bright application prospects of the N-AGNRs as nanowires and electrodes in molectronics.
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