Leteba Gerard M, Mitchell David R G, Levecque Pieter B J, Lang Candace I
Department of Chemical Engineering, Catalysis Institute, University of Cape Town, Cape Town 7700, South Africa.
School of Engineering, Macquarie University, Sydney NSW 2109, Australia.
Nanomaterials (Basel). 2018 Jun 26;8(7):462. doi: 10.3390/nano8070462.
Nanoalloys with anisotropic morphologies of branched and porous internal structures show great promise in many applications as high performance materials. Reported synthetic approaches for branched alloy nanostructures are, however, limited by the synthesis using a seed-growth process. Here, we demonstrate a conveniently fast and one-pot solution-phase thermal reduction strategy yielding nanoalloys of Pt with various solute feed ratios, exhibiting hyperbranched morphologies and good dispersity. When Pt was alloyed with transition metals (Ni, Co, Fe), we observed well-defined dendritic nanostructures in PtNi, PtCo and Pt(NiCo), but not in PtFe, Pt(FeNi) or Pt(FeCo) due to the steric hindrance of the trivalent Fe(acac)₃ precursor used during synthesis. In the case of Pt-based nanoalloys containing Ni and Co, the dendritic morphological evolution observed was insensitive to large variations in solute concentration. The functionality of these nanoalloys towards the oxygen reduction reaction (ORR); however, was observed to be dependent on the composition, increasing with increasing solute content. Pt₃(NiCo)₂ exhibited superior catalytic activity, affording about a five- and 10-fold enhancement in area-specific and mass-specific catalytic activities, respectively, compared to the standard Pt/C nanocatalyst. This solution-based synthetic route offers a new approach for constructing dendritic Pt-based nanostructures with excellent product yield, monodispersity and high crystallinity.
具有分支状和多孔内部结构的各向异性形态的纳米合金作为高性能材料在许多应用中显示出巨大潜力。然而，报道的用于分支合金纳米结构的合成方法受到种子生长过程合成的限制。在此，我们展示了一种简便快速的一锅溶液相热还原策略，可制备具有各种溶质进料比的铂纳米合金，呈现超支化形态且分散性良好。当铂与过渡金属（镍、钴、铁）合金化时，我们在PtNi、PtCo和Pt（NiCo）中观察到明确的树枝状纳米结构，但在PtFe、Pt（FeNi）或Pt（FeCo）中未观察到，这是由于合成过程中使用的三价Fe（acac）₃前驱体的空间位阻。在含镍和钴的铂基纳米合金的情况下，观察到的树枝状形态演变对溶质浓度的大幅变化不敏感。然而，观察到这些纳米合金对氧还原反应（ORR）的功能取决于组成，随溶质含量增加而增加。与标准Pt/C纳米催化剂相比，Pt₃（NiCo）₂表现出优异的催化活性，分别使比表面积催化活性和比质量催化活性提高了约5倍和10倍。这种基于溶液的合成路线为构建具有优异产率、单分散性和高结晶度的树枝状铂基纳米结构提供了一种新方法。
