Nanostructure Optimization of Platinum-Based Nanomaterials for Catalytic Applications

Abstract

Platinum-based nanomaterials have attracted much interest for their promising potentials in fields of energy-related and environmental catalysis. Designing and controlling the surface/interface structure of platinum-based nanomaterials at the atomic scale and understanding the structure-property relationship have great significance for optimizing the performances in practical catalytic applications. In this review, the strategies to obtain platinum-based catalysts with fantastic activity and great stability by composition regulation, shape control, three-dimension structure construction, and anchoring onto supports, are presented in detail. Moreover, the structure-property relationship of platinum-based nanomaterials are also exhibited, and a brief outlook are given on the challenges and possible solutions in future development of platinum-based nanomaterials towards catalytic reactions.

Keywords: catalytic; nanostructure control; platinum; structure-property relationship.

Figure 1

Schematic illustration of four ways of structural regulation of Pt-based NMs.

Figure 2

Transition metal doped octahedral Pt₃Ni/C catalysts: (a,b) Typical high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) images of the (a) Pt₃Ni/C and (b) Mo-Pt₃Ni/C catalysts. High-resolution transmission electron microscopy (HRTEM) images of individual octahedral (c) Pt₃Ni/C and (d) Mo-Pt₃Ni/C catalysts. (e) Cyclic voltammograms of octahedral Mo-Pt₃Ni/C, octahedral Pt₃Ni/C, and commercial Pt/C catalysts recorded at room temperature in N₂-purged 0.1 M HClO₄ solution with a sweep rate of 100 mV/s. (f) ORR polarization curves recorded at room temperature in an O₂-saturated 0.1 M HClO₄ aqueous solution with a sweep rate of 10 mV/s and a rotation rate of 1600 rpm. (g) The electrochemically active surface area (top), area specific activity (middle), and mass specific activity (bottom) at 0.9 V versus RHE for these transition metal–doped M-Pt₃Ni/C catalysts. Adapted from [65], with permission from AAAS, 2015.

Figure 3

Pt-rich PtCo NPs with Pt-rich shells: (a) ADF-STEM image of a Pt₃Co@Pt NPs. (b–d) EELS mapping of Pt (red), Co (green), and the composite image of Pt vs. Co. (e) Line-profile analysis from the indicated area of (a,d), demonstrating about 0.5 nm Pt skin thickness. Reproduced from [49], with permission from American Chemical Society, 2016.

Figure 4

Sequentially seeded growth of M–Pt–Fe₃O₄ heterogenous nanostructure (M = Ag, Au, Ni, Pd). (a) Schematic illustration of the chemoselective growth of M–Pt–Fe₃O₄ heterotrimers, along with the most possible products and their observed frequencies. Representative TEM images of (b) Pt NP seeds, (c) Pt–Fe₃O₄ heterodimers, (d) Au–Pt–Fe₃O₄, (e) Ag–Pt–Fe₃O₄, (f) Ni–Pt–Fe₃O₄, and (g) Pd–Pt–Fe₃O₄ heterotrimers (scale bar: 25 nm). (h) Photographs of a vial containing Au–Pt–Fe₃O₄ heterotrimers in hexane (left), which responds to an external Nd–Fe–B magnet, the same vial with Au–Pt–Fe₃O₄ heterotrimers in a larger volume of hexanes (middle) and the same vial after precipitation of the heterotrimers with ethanol (right). Reproduced from [28], with permission from Nature Publishing Group, 2011.

Figure 5

Pt NPs with different shapes: (a,b,i) cubes, (c,d,j) octahedrons, (e,f,k,l) icosahedrons, (g) cuboctahedrons, (h,n) spheres, (m) truncated cube, (o) tetrapod, (p) star-like octapod, (q) multipod, (r) 5-fold twinned decahedron. Scale bars: (a,e,g,h) 20 nm, (b,d,f) 50 nm, (c,o,p,q) 10 nm, 100 nm, (i,j) 2 nm, (k,l,m,n,r) 5 nm. Reproduced from [79], with permission from American Chemical Society, 2013.

Figure 6

Scheme illustration of Pt-based nanocages with subnanometer-thick walls: (a) Pt atoms deposited on the Pd surface may diffuse (“hop”) across the surface or substitute into the surface, leading to a mixed outer-layer composition. (b) Schematic of the major steps involved in the continuous dissolution of Pd atoms from a Pd@Pt_4L cube to generate a Pt cubic nanocage. (c–f) TEM images of Pd@Pt_4L cubes after Pd etching for (c) 0, (d) 10, (e) 30, and (f) 180 min. Adapted from [96], with permission from AAAS, 2015.

Figure 7

Hollow Pt based NMs with the combination of sacrificial template method and galvanic replacement reaction: (a) Schematic illustration for the formation of NiPt hollow spheres, adapted from [105], with the permission from the Royal Society of Chemistry, 2015. TEM images of (b) NiPt hollow sphere, adapted from [103], with the permission from the Royal Society of Chemistry, 2011, (c) NiPt double-layered nanobowls, adapted from [106], with the permission from Tsinghua University Press and Springer-Verlag BerlinHeidelberg, 2016, (d) NiPt single-layered nanobowls, adapted from [106], with the permission from Tsinghua University Press and Springer-Verlag BerlinHeidelberg, 2016, (e) CoPt hollow nanochains, adapted from [104], with the permission from American Chemical Society, 2012, and (f) FePt oriented hollow nanochains, adapted from [107], with the permission from the Royal Society of Chemistry, 2016.

Figure 8

Schematic illustration of the evolution process from polyhedrons to nanoframes: (a) initial solid PtNi₃ polyhedrons, (b) PtNi intermediates, (c) final hollow Pt₃Ni nanoframes, and (d) annealed Pt₃Ni nanoframes with Pt(111)-skin–like surfaces dispersed on high–surface area carbon. Reproduced from [115], with permission from AAAS, 2014.

Figure 9

Schematic illustrations of the synthesis procedures of Pt/C, Pt-Au/C and Au/C structures. Reproduced from [121], with permission from Elsevier, 2018.

Figure 10

Pt₁/Fe₂O₃ supported single atom catalyst. (b) and (c) are the enlarged HAADF-STEM images of two parts in image (a) for Pt₁/Fe₂O₃ SAC. The red circles indicate the isolated Pt atoms occupied Fe-top positions, and the yellow squares indicate that the isolated Pt atoms possess O-top positions. Reproduced from [133], with permission from IOP Publishing, 2018.