Seeded Synthesis of Unconventional 2H-Phase Pd Alloy Nanomaterials for Highly Efficient Oxygen Reduction

Abstract

Crystal phase engineering of noble-metal-based alloy nanomaterials paves a new way to the rational synthesis of high-performance catalysts for various applications. However, the controlled preparation of noble-metal-based alloy nanomaterials with unconventional crystal phases still remains a great challenge due to their thermodynamically unstable nature. Herein, we develop a robust and general seeded method to synthesize PdCu alloy nanomaterials with unconventional hexagonal close-packed (hcp, 2H type) phase and also tunable Cu contents. Moreover, galvanic replacement of Cu by Pt can be further conducted to prepare unconventional trimetallic 2H-PdCuPt nanomaterials. Impressively, 2H-Pd67Cu33 nanoparticles possess a high mass activity of 0.87 A mg–1 Pd at 0.9 V (vs reversible hydrogen electrode (RHE)) in electrochemical oxygen reduction reaction (ORR) under alkaline condition, which is 2.5 times that of the conventional face-centered cubic (fcc) Pd69Cu31 counterpart, revealing the important role of crystal phase on determining the ORR performance. After the incorporation of Pt, the obtained 2H-Pd71Cu22Pt7 catalyst shows a significantly enhanced mass activity of 1.92 A mg–1 Pd+Pt at 0.9 V (vs RHE), which is 19.2 and 8.7 times those of commercial Pt/C and Pd/C, placing it among the best reported Pd-based ORR electrocatalysts under alkaline conditions.

Dimensional‐Transformation of Ternary‐Alloy through the Manipulation of Reduction Kinetics

“…To control the variable of the difference between PtCuPb nanocrystals and other nanoparticles lies in the Pt composition, the loading amounts of Pt were all kept at 12.5 µg cm −2 in ORR tests. [10,37] , respectively (Figure 3b). The CV curve of PtCuPb-NW/C shows the biggest reduction peak of PtOx at 0.80 V (vs RHE).…”

“…[5][6][7] To further improve the ORR performance of Pt-based electrocatalysts, tremendous efforts have been dedicated to catalyst morphology engineering. Some of these practices include shaping Pt [8] or Pt-based alloys, [9] crystal phase engineering, [10] forming a Pt skin on the catalyst surface, [11,12] synthesis of multidimensional nanostructures, [13] strain-engineering electrocatalysis, [4,6,14] etc. In addition, reduction factors (thermodynamic and kinetic) were used to control the morphology of the Pt-based alloy NCs for enhanced ORR.…”

Preparation of Au@Pd Core–Shell Nanorods with fcc-2H-fcc Heterophase for Highly Efficient Electrocatalytic Alcohol Oxidation

“…Bimetallic nanomaterials have received increasing research interest due to their excellent performance in various catalytic reactions arising from the synergistic effect between different components. − Taking core–shell bimetallic nanostructures as a typical example, the lattice and electronic structure of the metallic shell can be effectively modulated by the core composed of another metal with different lattice parameters and electronic configuration. , In particular, in the core–shell bimetallic nanostructures obtained by epitaxial growth, the lattice variation, including lattice expansion and compression, of the shell can be realized based on the lattice difference between the core and shell. Consequently, the lattice variation of the shell can effectively modulate its electronic configuration and thus change the adsorption interaction with the reaction intermediate species, leading to the regulation of catalytic activities. − For instance, due to the simultaneously compressed and expanded lattices of the Pt shell along different axes, PtPb@Pt core–shell nanoplates exhibited outstanding electrocatalytic oxygen reduction mass activity, which is 4.1 and 33.9 times those of the PtPb nanoparticles and commercial Pt/C, respectively .…”

Oxidative Stability Matters: A Case Study of Palladium Hydride Nanosheets for Alkaline Fuel Cells

“…Previous studies have shown that the ORR activity of Pd is comparable to that of Pt among noble metal-based single crystals in alkaline media, indicating that Pd can be a promising alkaline ORR electrocatalyst. Recently, there have been reports of improved ORR performance with Pd-based electrocatalysts in alkaline media, which even outperformed Pt-based electrocatalys. − Among those high-performance Pd-based electrocatalysts, Pd-based nanosheets exhibited some of the highest ORR activities, as their two-dimensional (2D) structure provided a high specific surface area, strain effects with atomic thickness, as well as high density of unsaturated atoms exposed on the surface. , Moreover, Pd hydride (PdH x ) has been demonstrated to play an important role in enhancing ORR activity. , …”