Pt-Au-Cu三元核壳结构纳米线的制备与结构表征

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

通过水溶液还原法在80℃合成Cu纳米线,再利用液相还原法在低温水溶液中将Au负载于其表面,最后通过暴露的Cu纳米线与Pt前驱体盐发生Galvanic置换反应,将Pt负载在Au−Cu纳米线表面,构成Pt−Au−Cu三元核壳结构纳米线.根据对样品形貌、结构的表征和分析,探讨了Pt−Au−Cu纳米线的合成机理.结果表明:合成纳米线物相组成为单质Cu,平均直径约为83 nm;负载Au后的Au−Cu纳米线平均直径约为90 nm,表面附着的小颗粒为单质Au颗粒,构成了核壳结构;负载Pt后得到Pt−Au−Cu三元核壳结构纳米线,平均直径约为120 nm.Cu纳米线表面Au颗粒的形成依赖于异相形核与长大机制,并遵循先层状后岛状生长的混合生长模式.负载Pt过程中存在Pt、Cu互扩散,使得最终纳米线表面多为Pt颗粒而整体则形成CuPt合金相.

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.