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Pt?Au?Cu 三元核殼結構納米線的制備與結構表征

Synthesis and structural characterization of Pt?Au?Cu ternary core-shell nanowires

  • 摘要: 通過水溶液還原法在80 ℃合成Cu納米線,再利用液相還原法在低溫水溶液中將Au負載于其表面,最后通過暴露的Cu納米線與Pt前驅體鹽發生Galvanic置換反應,將Pt負載在Au?Cu納米線表面,構成Pt?Au?Cu三元核殼結構納米線。根據對樣品形貌、結構的表征和分析,探討了Pt?Au?Cu納米線的合成機理。結果表明:合成納米線物相組成為單質Cu,平均直徑約為83 nm;負載Au后的Au?Cu納米線平均直徑約為90 nm,表面附著的小顆粒為單質Au顆粒,構成了核殼結構;負載Pt后得到Pt?Au?Cu三元核殼結構納米線,平均直徑約為120 nm。Cu納米線表面Au顆粒的形成依賴于異相形核與長大機制,并遵循先層狀后島狀生長的混合生長模式。負載Pt過程中存在Pt、Cu互擴散,使得最終納米線表面多為Pt顆粒而整體則形成CuPt 合金相。

     

    Abstract: Platinum-based catalysts have been widely used in fuel cells due to their excellent activity in oxygen reduction reactions. At the same time, using Pt in large quantities is costly. To solve the high cost of fuel cell catalysts, research into low-Pt-content and highly efficient catalysts with special structures has attracted considerable attention. However, conditions required for synthesis of these catalysts are highly restrictive and the synthetic methods are energy-intensive and harmful to the environment. In this study, Cu nanowires (NWs) were synthesized hydrothermally at 80 ℃. Growth of the Au shell on the Cu NWs, achieved through a liquid phase reduction method, was carried out in aqueous solution at low temperature. Finally, Pt layers were deposited on the surface of the Au?Cu NWs by Galvanic displacement between the uncovered copper NWs and chloroplatinic acid. Subsequently, Pt?Au?Cu ternary core-shell catalysts were constructed. The as-synthesized catalysts were characterized in depth using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM). The growth mechanism of the Pt?Au?Cu NWs was also explored. Results show that the phase composition of the synthetic NWs is monolithic Cu with an average diameter of about 83 nm; average diameter of the Au?Cu NWs is about 90 nm, and the small particles attached to the surface are Au. After Pt loading, the Pt?Au?Cu ternary core shell structure of the NWs is obtained with an average diameter of 120 nm. It is confirmed that the formation of the surface Au nanoparticles on the Cu NWs depends on the heterogeneous nucleation and growth mechanism, and that the growth mode conforms to the Stranski-Krastanow (S-K) mode. Pt and Cu interdiffusion exists during Pt loading, so that the surface of the NW is mostly Pt particles and the whole is a CuPt alloy phase. This study demonstrates a new strategy in synthesis of ternary core-shell NWs.

     

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