High-Indexed Pt₃Ni Alloy Tetrahexahedral Nanoframes Evolved through Preferential CO Etching

Abstract

Chemically controlling crystal structures in nanoscale is challenging, yet provides an effective way to improve catalytic performances. Pt-based nanoframes are a new class of nanomaterials that have great potential as high-performance catalysts. To date, these nanoframes are formed through acid etching in aqueous solutions, which demands long reaction time and often yields ill-defined surface structures. Herein we demonstrate a robust and unprecedented protocol for facile development of high-performance nanoframe catalysts using size and crystallographic facet-controlled PtNi tetrahexahedral nanocrystals prepared through a colloidal synthesis approach as precursors. This new protocol employs the Mond process to preferentially dealloy nickel component in the ⟨100⟩ direction through carbon monoxide etching of carbon-supported PtNi tetrahexahedral nanocrystals at an elevated temperature. The resultant PtNi alloy tetrahexahedral nanoframes possess an open, stable, and high-indexed microstructure, containing a segregated Pt thin layer strained to the Pt-Ni alloy surfaces and featuring a down-shift d-band center as revealed by the density functional theory calculations. These nanoframes exhibit much improved catalytic performance, such as high stability under prolonged electrochemical potential cycles, promoting direct electro-oxidation of formic acid to carbon dioxide and enhancing oxygen reduction reaction activities. Because carbon monoxide can be generated from the carbon support through thermal annealing in air, a common process for pretreating supported catalysts, the developed approach can be easily adopted for preparing industrial scale catalysts that are made of Pt-Ni and other alloy nanoframes.

Stability of High‐Performance Pt‐Based Catalysts for Oxygen Reduction Reactions

“…Fang and co‐workers prepared a unique Pt 3 Ni nanoframe, the surface of which was covered with a thin and discrete Pt thin layer. It revealed a declining d‐band center due to density functional theory (DFT) calculations, which led to elevated catalytic properties . Lee and co‐workers prepared a Pt@Ni core–shell octahedron nanoframe to explore the combination of the core–shell structure and nanoframe structure.…”

Advanced Catalysts Derived from Composition‐Segregated Platinum–Nickel Nanostructures: New Opportunities and Challenges

“…Copyright 2016, American Chemical Society. d–j) Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…Therefore, such phenomena have been actively pursued to prepare enhanced catalysts. There were various composition‐segregated Pt–Ni nanostructures reported, such as Pt–Ni octahedra, Pt–Ni rhombic dodecahedra (RDHs), Pt–Ni tetrahexahedra (THHs), Pt–Ni nanowires (NWs), as well as Pt–Cu RDHs, PtNiCu RDHs, and so on.…”

“…Owing to intrinsic differences in the chemical reactivity of the metallic components, these composition‐segregated nanostructures are exploited to develop unusual nanostructures with desirable functionalities. From the structural and chemical perspectives, one obvious advantage of the highly composition‐segregated Pt–Ni NCs is that they can be readily sacrificed to construct concave, frame, and porous structures with fascinating geometrical beauty and interesting chemical and physical properties, a kind of promising yet new class of nanostructures with 3D large accessible surface area and interconnected edges. The directional movements of the constituting atoms may be accomplished even within the matrix of facet‐controlled alloy nanoparticles (NPs) using the well‐differentiated morphology‐dependent NPs surface energies.…”

Design of Ultrathin Pt‐Based Multimetallic Nanostructures for Efficient Oxygen Reduction Electrocatalysis

“…The octopod nanoframes still exhibit high mass activity of 2.95 A mg Pt −1 after 10 000 cycles potential cycling (Figure c). The high‐indexed Pt 3 Ni alloy tetrahexahedral nanoframes were also prepared by employing the thermal annealing process under CO atmosphere to preferentially dealloy nickel component in the ⟨100⟩ direction through carbon monoxide etching of PtNi 4 tetrahexahedral nanocrystals at an elevated temperature . The Pt 3 Ni tetrahexahedral nanoframes exhibit significantly improved ORR mass activity.…”