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      Shape controlled synthesis of porous tetrametallic PtAgBiCo nanoplates as highly active and methanol-tolerant electrocatalyst for oxygen reduction reaction†

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          Abstract

          We present a new two-step synthetic route combining the concepts of crystal symmetry, seed ratio and oxidative etching that yields tetrametallic PtAgBiCo nanoplates.

          Abstract

          Mechanistic control is a powerful means for manufacturing specific shapes of metal nanostructures and optimizing their performance in a variety of applications. Thus, we successfully synthesized multimetallic nanoplates (PtAgBiCo and PtAgBi) by combining the concepts of crystal symmetry, oxidative etching and seed ratio, and tuned their activity, stability and methanol tolerance, as well as Pt utilization, for the oxygen reduction reaction in direct methanol fuel cells. Systematic studies reveal that the formation of PtAgBiCo triangular nanoplates with a high morphological yield (>90%) can be achieved by crystallinity alteration, while electrochemical measurements indicate that the PtAgBiCo nanoplates have superior electrocatalytic activity towards the oxygen reduction reaction. The specific and mass activity of the PtAgBiCo nanoplates are 8 and 5 times greater than that of the commercial Pt/C catalyst, respectively. In addition, the tetrametallic PtAgBiCo nanoplates exhibit a more positive half-wave potential for the oxygen reduction reaction and possess an excellent methanol tolerance limit compared with the commercial Pt/C catalyst.

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          Most cited references36

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          Heterogeneous Spin States in Ultrathin Nanosheets Induce Subtle Lattice Distortion To Trigger Efficient Hydrogen Evolution.

          The exploration of efficient nonprecious metal eletrocatalysis of the hydrogen evolution reaction (HER) is an extraordinary challenge for future applications in sustainable energy conversion. The family of first-row-transition-metal dichalcogenides has received a small amount of research, including the active site and dynamics, relative to their extraordinary potential. In response, we developed a strategy to achieve synergistically active sites and dynamic regulation in first-row-transition-metal dichalcogenides by the heterogeneous spin states incorporated in this work. Specifically, taking the metallic Mn-doped pyrite CoSe2 as a self-adaptived, subtle atomic arrangement distortion to provide additional active edge sites for HER will occur in the CoSe2 atomic layers with Mn incorporated into the primitive lattice, which is visually verified by HRTEM. Synergistically, the density functional theory simulation results reveal that the Mn incorporation lowers the kinetic energy barrier by promoting H-H bond formation on two adjacently adsorbed H atoms, benefiting H2 gas evolution. As a result, the Mn-doped CoSe2 ultrathin nanosheets possess useful HER properties with a low overpotential of 174 mV, an unexpectedly small Tafel slope of 36 mV/dec, and a larger exchange current density of 68.3 μA cm(-2). Moreover, the original concept of coordinated regulation presented in this work can broaden horizons and provide new dimensions in the design of newly highly efficient catalysts for hydrogen evolution.
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            High-yield seedless synthesis of triangular gold nanoplates through oxidative etching.

            We demonstrate that monodispersed triangular gold nanoplates with high morphological yield (>90%) can be synthesized through a rapid one-pot seedless growth process. The edge length of triangular Au nanoplates can be readily tuned between 40 and 120 nm by varying the reaction parameters. Systematic studies reveal that distinct from previous hypothesis that the formation of nanoplates is mainly determined by the selective binding of iodide ions, our results show that iodide ions could have dual functions: it can selectively bind to the Au {111} facets and also selectively remove other less stable shape impurities through oxidative etching by forming tri-iodide ions (I(3)(-)), thus facilitating the formation of nuclei with dominant planar structure. This new synthetic route will not only help to better understand the growth mechanism of triangular gold nanoplates but also promote the research in anisotropic noble metal nanostructures.
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              Anisotropic phase segregation and migration of Pt in nanocrystals en route to nanoframe catalysts.

              Compositional heterogeneity in shaped, bimetallic nanocrystals offers additional variables to manoeuvre the functionality of the nanocrystal. However, understanding how to manipulate anisotropic elemental distributions in a nanocrystal is a great challenge in reaching higher tiers of nanocatalyst design. Here, we present the evolutionary trajectory of phase segregation in Pt-Ni rhombic dodecahedra. The anisotropic growth of a Pt-rich phase along the 〈111〉 and 〈200〉 directions at the initial growth stage results in Pt segregation to the 14 axes of a rhombic dodecahedron, forming a highly branched, Pt-rich tetradecapod structure embedded in a Ni-rich shell. With longer growth time, the Pt-rich phase selectively migrates outwards through the 14 axes to the 24 edges such that the rhombic dodecahedron becomes a Pt-rich frame enclosing a Ni-rich interior phase. The revealed anisotropic phase segregation and migration mechanism offers a radically different approach to fabrication of nanocatalysts with desired compositional distributions and performance.
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                Author and article information

                Journal
                Chem Sci
                Chem Sci
                Chemical Science
                Royal Society of Chemistry
                2041-6520
                2041-6539
                1 June 2017
                22 March 2017
                : 8
                : 6
                : 4292-4298
                Affiliations
                [a ] Key Lab of Organic Optoelectronics and Molecular Engineering , Department of Chemistry , Tsinghua University , Beijing , 100084 , China . Email: wangxun@ 123456mail.tsinghua.edu.cn
                Author information
                http://orcid.org/0000-0002-8066-4450
                Article
                c7sc00318h
                10.1039/c7sc00318h
                5468992
                32aa81b1-8d9f-457e-abeb-6f0fbc867b31
                This journal is © The Royal Society of Chemistry 2017

                This is an Open Access article distributed under the terms of the Creative Commons Attribution 3.0 Unported License ( http://creativecommons.org/licenses/by/3.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 22 January 2017
                : 21 March 2017
                Categories
                Chemistry

                Notes

                †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc00318h


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