Atomic Layer-by-Layer Deposition of Platinum on Palladium Octahedra for Enhanced Catalysts toward the Oxygen Reduction Reaction

Abstract

We systematically evaluated two different approaches to the syntheses of Pd@PtnL (n = 2-5) core-shell octahedra. We initially prepared the core-shell octahedra using a polyol-based route by titrating a Pt(IV) precursor into the growth solution containing Pd octahedral seeds at 200 °C through the use of a syringe pump. The number of Pt atomic layers could be precisely controlled from two to five by increasing the volume of the precursor solution while fixing the amount of seeds. We then demonstrated the synthesis of Pd@PtnL octahedra using a water-based route at 95 °C through the one-shot injection of a Pt(II) precursor. Due to the large difference in reaction temperature, the Pd@PtnL octahedra obtained via the water-based route showed sharper corners than their counterparts obtained through the polyol-based route. When compared to a commercial Pt/C catalyst based upon 3.2 nm Pt particles, the Pd@PtnL octahedra prepared using both methods showed similar remarkable enhancement in terms of activity (both specific and mass) and durability toward the oxygen reduction reaction. Calculations based upon periodic, self-consistent density functional theory suggested that the enhancement in specific activity for the Pd@PtnL octahedra could be attributed to the destabilization of OH on their PtnL*/Pd(111) surface relative to the {111} and {100} facets exposed on the surface of Pt/C. The destabilization of OH facilitates its hydrogenation, which was found to be the rate-limiting step of the oxygen reduction reaction on all these surfaces.

The growth and degradation of binary and ternary octahedral Pt–Ni-based fuel cell catalyst nanoparticles studied using advanced transmission electron microscopy

“…However, a major obstacle that currently limits their performance is the sluggish oxygen reduction reaction (ORR) at fuel cell cathodes. Although Pt-based catalysts show very high activity and stability in PEM fuel cells [1,2], it is important to reduce the proportion of rare and expensive Pt that they contain without compromising their activity for the ORR, for example by alloying them with abundant low-cost transition metals [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Such alloying strategies can be used to introduce lattice compression effects [20,21] and/or modified electronic properties [22,23].…”

Synthesis of surfactant-free Cu–Pt dendritic heterostructures with highly electrocatalytic performance for methanol oxidation reaction

“…Very recently, metallic nano-heterostructures with distinctive architecture and size have been motivated to tailor catalytic performance and thermal stability for achieving more potential applications such as oxygen reduction, [1][2][3] methanol oxidation [4,5] and formic acid oxidation. [6] Considerable attention has been focused on platinum (Pt)-based nanostructures with various morphologies, which could be applied for electrocatalytic methanol oxidation reaction (MOR) because of its slow kinetics and the demand for fuel-cell cathodes.…”

Aberration-Corrected STEM Study of Shape Controlled Metallic Core-Shell Nanoparticles for Catalytic Applications

“…The corresponding line profile of EDS scanning (Figure 1c) confirms the structure of Pt shell/Pd core. The Pd-Pt core shell octahedra exhibited at least 4-fold enhancement in specific activity toward the oxygen reduction reaction (ORR) when compared to a commercial Pt/C based upon 3.2 nm Pt particles [3]. Figure 2 shows the HAADF-STEM image of a Pt-Ni alloy octahedral nanocrystal and (d) EDS line scan showing Pt and Ni distributions along the arrow marked in (c).…”