Atomic-scaled surface engineering Ni-Pt nanoalloys towards enhanced catalytic efficiency for methanol oxidation reaction
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Atomic-scaled surface engineering Ni-Pt nanoalloys towards enhanced catalytic efficiency for methanol oxidation reaction Aixian Shan1,2, Shuoyuan Huang1, Haofei Zhao1, Wengui Jiang1, Xueai Teng1, Yingchun Huang3, Chinping Chen2 (), Rongming Wang1 (), and Woon-Ming Lau1,3 () 1
Beijing Advanced Innovation Center for Materials Genome Engineering, Center for Green Innovation, Beijing Key Laboratory for MagnetoPhotoelectrical Composite and Interface Science, School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China 2 Department of Physics, Peking University, Beijing 100871, China 3 Shunde Graduate School of University of Science and Technology Beijing, Foshan 528300, China © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 26 May 2020 / Revised: 8 July 2020 / Accepted: 9 July 2020
ABSTRACT Surface engineering is known as an effective strategy to enhance the catalytic properties of Pt-based nanomaterials. Herein, we report on surface engineering Ni-Pt nanoalloys with a facile method by varying the Ni doping concentration and oleylamine/oleicacid surfactant-mix. The alloy-composition, exposed facet condition, and surface lattice strain are, thereby manipulated to optimize the catalytic efficiency of such nanoalloys for methanol oxidation reaction (MOR). Exemplary nanoalloys including Ni0.69Pt0.31 truncated octahedrons, Ni0.45Pt0.55 nanomultipods and Ni0.20Pt0.80 nanoflowers are thoroughly characterized, with a commercial Pt/C catalyst as a common benchmark. Their variations in MOR catalytic efficiency are significant: 2.2 A/mgPt for Ni0.20Pt0.80 nanoflowers, 1.2 A/mgPt for Ni0.45Pt0.55 nanomultipods, 0.7 A/mgPt for Ni0.69Pt0.31 truncated octahedrons, and 0.6 A/mgPt for the commercial Pt/C catalysts. Assisted by density functional theory calculations, we correlate these observed catalysis-variations particularly to the intriguing presence of surface interplanar-strains, such as {111} facets with an interplanar-tensile-strain of 2.6% and {200} facets with an interplanar-tensile-strain of 3.5%, on the Ni0.20Pt0.80 nanoflowers.
KEYWORDS surface-strain, high-index facets, Ni-Pt alloy, controllable synthesis, electrocatalysis
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Introduction
Bimetallic nanoparticles (NPs), composed of two distinct metal elements, have certain chemistry sequences, mixing structures and geometry architectures [1]. They are functional materials often with high catalytic activities, and sometimes with novel magnetic/optical properties. They are typically superior to their single-element counterparts due mainly to their structural diversities and the synergistic effects of mixing two atomic constituents [2–9]. At nanoscale, the physical and chemical properties of bimetallic NPs are significantly dependent on their compositions, morphologies, sizes, and crystallinities with/without lattice-strains. This has triggered considerable efforts on the development of controllable synthesis of bimetallic nanomaterials [10]. The ultimate goal is to rationally
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