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Hydrogen assisted synthesis of branched nickel nanostructures: a combined theoretical and experimental study

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Abstract

The selective adsorption of small molecules over specific facets plays an important role in morphology controlled synthesis of metal nanocrystals. In the present work, hydrogen is found to be a good capping agent for direct synthesis of branched nickel nanocrystals, i.e., secondary branching (Ni-SB) nanoparticles and multipods (Ni-MP). Using ab initio thermodynamics and the Wulff construction principle, it has been found that: (i) in the presence of hydrogen (PH2 = 6 bar), the facet structure stability follows the order of Ni(100) > Ni(111) > Ni(110), resulting in competitive over-growth along the 〈111〉 and 〈110〉 directions; (ii) with increasing hydrogen pressure, the Ni deposition rate over the crystal surface increases as a result of more Ni2+ reduction; the competition between deposition and surface diffusion, therefore, becomes the vital factor for the nanocrystal growth process; (iii) the diffusion energy barrier of a surface Ni atom on Ni(111) is lower than that on Ni(110), especially on hydrogen covered surfaces, indicating that the kinetic over-growth only along the 〈111〉 direction producing Ni-MP will be dominant under PH2 = 14 bar; (iv) the ab initio based Wulff construction principle predicts the shapes and morphologies at different hydrogen pressures which is further confirmed with HRTEM results. Finally, compared with nickel nanoparticles (Ni-NP) synthesized in the absence of hydrogen, the hydrogen assisted branched Ni nanomaterials, especially the Ni-MP, show higher catalytic activities for hydrogenation reactions of acetophenone and nitrobenzene.

Graphical abstract: Hydrogen assisted synthesis of branched nickel nanostructures: a combined theoretical and experimental study

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Publication details

The article was received on 11 Jul 2017, accepted on 07 Sep 2017 and first published on 08 Sep 2017


Article type: Paper
DOI: 10.1039/C7CP04673A
Citation: Phys. Chem. Chem. Phys., 2017, Advance Article
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    Hydrogen assisted synthesis of branched nickel nanostructures: a combined theoretical and experimental study

    X. Liang, N. Liu, H. Qiu, C. Zhang, D. Mei and B. Chen, Phys. Chem. Chem. Phys., 2017, Advance Article , DOI: 10.1039/C7CP04673A

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