| 1. |
- Lu, Xinnan, et al.
(författare)
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Ni2P Nanoparticles Embedded in Mesoporous SiO2 for Catalytic Hydrogenation of SO2 to Elemental S
- 2021
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 4:6, s. 5665-5676
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Tidskriftsartikel (refereegranskat)abstract
- Highly active nickel phosphide (Ni2P) nanoclusters confined in a mesoporous SiO2 catalyst were synthesized by a two-step process targeting tight control over the Ni2P size and phase. The Ni precursor was incorporated into the MCM-41 matrix by one-pot synthesis, followed by the phosphorization step, which was accomplished in oleylamine with trioctylphosphine at 300 °C so to achieve the phase transformation from Ni to Ni2P. For benchmarking, Ni confined by the mesoporous SiO2 (absence of phosphorization) and 11 nm Ni2P nanoparticles (absence of SiO2) was also prepared. From the microstructural analysis, it was found that the growth of Ni2P nanoclusters was restricted by the mesoporous channels, thus forming ultrafine and highly dispersed Ni2P nanoclusters (<2 nm). The above approach led to promising catalytic performance following the order u-Ni2P@m-SiO2 > n-Ni2P > u-Ni@m-SiO2 > c-Ni2P in the selective hydrogenation of SO2 to S. In particular, u-Ni2P@m-SiO2 exhibited SO2 conversions of 94% at 220 °C and ∼99% at 240 °C, which are higher than the 11 nm stand-alone Ni2P particles (43% at 220 °C and 94% at 320 °C), highlighting the importance of the role played by SiO2 in stabilizing ultrafine nanoparticles of Ni2P. The reaction activation energy Ea over u-Ni2P@m-SiO2 is ∼33 kJ/mol, which is lower than those over n-Ni2P (∼36 kJ/mol) and c-Ni2P (∼66 kJ/mol), suggesting that the reaction becomes energetically favored over the ultrafine Ni2P nanoclusters.
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| 2. |
- Lu, Xinnan, et al.
(författare)
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Nickel Phosphide Nanoparticles for Selective Hydrogenation of SO2 to H2S
- 2021
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 4:7, s. 6568-6582
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Tidskriftsartikel (refereegranskat)abstract
- Highly mesoporous SiO2-encapsulated NixPy crystals, where (x, y) = (5, 4), (2, 1), and (12, 5), were successfully synthesized by adopting a thermolytic method using oleylamine (OAm), trioctylphosphine (TOP), and trioctylphosphine oxide (TOPO). The Ni5P4@SiO2 system shows the highest reported activity for the selective hydrogenation of SO2 toward H2S at 320 degrees C (96% conversion of SO2 and 99% selectivity to H2S), which was superior to the activity of the commercial CoMoS@Al2O3 catalyst (64% conversion of SO2 and 71% selectivity to H2S at 320 degrees C). The morphology of the Ni5P4 crystal was finely tuned via adjustment of the synthesis parameters receiving a wide spectrum of morphologies (hollow, macroporous-network, and SiO2-confined ultrafine clusters). Intrinsic characteristics of the materials were studied by Xray diffraction, high-resolution transmission electron microscopy/scanning transmission electron microscopy-high-angle annular dark-field imaging, energydispersive X-ray spectroscopy, the Brunauer-Emmett-Teller method, H-2 temperature-programmed reduction, X-ray photoelectron spectroscopy, and experimental and calculated P-31 magic-angle spinning solid-state nuclear magnetic resonance toward establishing the structure-performance correlation for the reaction of interest. Characterization of the catalysts after the SO2 hydrogenation reaction proved the preservation of the morphology, crystallinity, and Ni/P ratio for all the catalysts.
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| 3. |
- Papawassiliou, Wassilios, et al.
(författare)
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Crystal and electronic facet analysis of ultrafine Ni2P particles by solid-state NMR nanocrystallography
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Structural and morphological control of crystalline nanoparticles is crucial in the field of heterogeneous catalysis and the development of reaction specific catalysts. To achieve this, colloidal chemistry methods are combined with ab initio calculations in order to define the reaction parameters, which drive chemical reactions to the desired crystal nucleation and growth path. Key in this procedure is the experimental verification of the predicted crystal facets and their corresponding electronic structure, which in case of nanostructured materials becomes extremely difficult. Here, by employing P-31 solid-state nuclear magnetic resonance aided by advanced density functional theory calculations to obtain and assign the Knight shifts, we succeed in determining the crystal and electronic structure of the terminating surfaces of ultrafine Ni2P nanoparticles at atomic scale resolution. Our work highlights the potential of ssNMR nanocrystallography as a unique tool in the emerging field of facet-engineered nanocatalysts. Structural and morphological control of crystalline nanoparticles is crucial in heterogeneous catalysis. Applying DFT-assisted solid-state NMR spectroscopy, we determine the surface crystal and electronic structure of Ni2P nanoparticles, unveiling NMR nanocrystallography as an emerging tool in facet-engineered nanocatalysts.
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| 4. |
- Stamou, Christina, et al.
(författare)
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Indium(III) in the "Periodic Table" of Di(2-pyridyl) Ketone : An Unprecedented Transformation of the Ligand and Solid-State In-115 NMR Spectroscopy as a Valuable Structural Tool
- 2021
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 60:7, s. 4829-4840
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Tidskriftsartikel (refereegranskat)abstract
- Reactions of di(2-pyridyl) ketone, (py)(2)CO, with indium(III) halides in CH3NO2 have been studied, and a new transformation of the ligand has been revealed. In the presence of In-III, the C=O bond of (py)(2)CO is subjected to nucleophilic attack by the carbanion -:CH2NO2, yielding the dinuclear complexes [In2X4{(py)(2)C(CH2NO2)(O)}(2)] (X = Cl, 1; X = Br, 2; X = I, 3) in moderate to good yields. The alkoxo oxygens of the two eta(1):eta(2):eta(1)-(py)(2)C(CH2NO2)(O)- ligands doubly bridge the In-III centers and create a {In-2(mu(2)-OR)(2)}(4+) core. Two pyridyl nitrogens of different organic ligands and two terminal halogeno ions complete a distorted-octahedral stereochemistry around each In(III) ion. After maximum excitation at 360 or 380 nm, the solid chloro complex 1 emits blue light at 420 and 440 nm at room temperature, the emission being attributed to charge transfer within the coordinated organic ligand. Solid-state In-115 NMR spectra, in combination with DFT calculations, of 1-3 have been studied in detail at both 9.4 and 14.1 T magnetic fields. The nuclear quadrupolar and chemical shift parameters provide valuable findings concerning the electric field gradients and magnetic shielding at the nuclei of indium, respectively. The experimentally derived C-Q values are 40 +/- 3 MHz for 1, 46 +/- 5 MHz for 2, and 50 +/- 10 and 64 +/- 7 MHz for the two crystallographically independent InIII sites for 3, while the diso values fall in the range 130 +/- 30 to -290 +/- 60 ppm. The calculated C-Q and asymmetry parameter (eta(Q)) values are fully consistent with the experimental values for 1 and 2 and are in fairly good agreement for 3. The results have been analyzed and discussed in terms of the known (1, 3) and proposed (2) structural features of the complexes, demonstrating that In-115 NMR is an effective solid-state technique for the study of indium(III) complexes.
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