香港城市大学张华研究小组成功在非常规2H-Pd纳米颗粒上实现了异相纳米结构的相选择性外延生长。 相关论文发表在2020年10月21日出版的《美国化学会志》上。

研究人员先通过对无定形态钯（Pd）纳米颗粒进行可控相转变，制备了一种具有非常规密排六方晶格的钯纳米颗粒，即2H-Pd纳米颗粒。令人印象深刻的是，通过将2H-Pd纳米粒子作为种子，可以将具有不同晶相的金（Au）纳米材料外延生长在2H-Pd的特定暴露晶面上，例如，面心立方结构的金（fcc-Au）生长在2H-Pd的(002)_h面上，而2H-Au则生长在其他暴露晶面上，这样一来就获得了一种结构明确的fcc-2H-fcc异相Pd@Au核-壳纳米棒。

此外，通过这种独特的晶面诱导的晶相选择性外延生长，还可以制备一系列其他的非常规fcc-2H-fcc异相核壳纳米结构，包括Pd@Ag、Pd@Pt、Pd@PtNi和Pd@PtCo等。令人印象深刻的是，fcc-2H-fcc异相Pd@Au纳米棒在电催化二氧化碳还原（CO₂RR）为一氧化碳的反应中表现出优异的性能，在从-0.9 V到-0.4 V（相对于可逆氢电极）的超宽外加电势窗口下法拉第效率超过90%，可与现有报道的H型电解池中最好的CO₂RR催化剂相媲美。

据介绍，异质异相的贵金属纳米材料由于其在不同领域的广阔应用前景吸引了许多研究人员的兴趣。但是，形貌可控的贵金属异相纳米结构的理性合成仍面临着巨大的挑战。

附：英文原文

Title: Phase-Selective Epitaxial Growth of Heterophase Nanostructures on Unconventional 2H-Pd Nanoparticles

Author: Yiyao Ge, Zhiqi Huang, Chongyi Ling, Bo Chen, Guigao Liu, Ming Zhou, Jiawei Liu, Xiao Zhang, Hongfei Cheng, Guanghua Liu, Yonghua Du, Cheng-Jun Sun, Chaoliang Tan, Jingtao Huang, Pengfei Yin, Zhanxi Fan, Ye Chen, Nailiang Yang, Hua Zhang

Issue&Volume: October 21, 2020

Abstract: Heterostructured, including heterophase, noble-metal nanomaterials have attracted much interest due to their promising applications in diverse fields. However, great challenges still remain in the rational synthesis of well-defined noble-metal heterophase nanostructures. Herein, we report the preparation of Pd nanoparticles with an unconventional hexagonal close-packed (2H type) phase, referred to as 2H-Pd nanoparticles, via a controlled phase transformation of amorphous Pd nanoparticles. Impressively, by using the 2H-Pd nanoparticles as seeds, Au nanomaterials with different crystal phases epitaxially grow on the specific exposed facets of the 2H-Pd, i.e., face-centered cubic (fcc) Au (fcc-Au) on the (002)h facets of 2H-Pd while 2H-Au on the other exposed facets, to achieve well-defined fcc-2H-fcc heterophase Pd@Au core–shell nanorods. Moreover, through such unique facet-directed crystal-phase-selective epitaxial growth, a series of unconventional fcc-2H-fcc heterophase core–shell nanostructures, including Pd@Ag, Pd@Pt, Pd@PtNi, and Pd@PtCo, have also been prepared. Impressively, the fcc-2H-fcc heterophase Pd@Au nanorods show excellent performance toward the electrochemical carbon dioxide reduction reaction (CO2RR) for production of carbon monoxide with Faradaic efficiencies of over 90% in an exceptionally wide applied potential window from 0.9 to 0.4 V (versus the reversible hydrogen electrode), which is among the best reported CO2RR catalysts in H-type electrochemical cells.

DOI: 10.1021/jacs.0c09461

Source: https://pubs.acs.org/doi/10.1021/jacs.0c09461