Manipulation of Pt-Ni Tetrahexahedral Nanoframes Using a Gaseous Etching Method
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MRS Advances © 2017 Materials Research Society DOI: 10.1557/adv.2017.633
Manipulation of Pt-Ni Tetrahexahedral Nanoframes Using a Gaseous Etching Method Yiliang Luan,1 Lihua Zhang,2 Chenyu Wang,1 Jingyue Liu,3 and Jiye Fang1 1
Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902, USA; 2Center for Functional Nanomaterials, Brookhaven National Libratory, Upton, New York 11973, USA; 3Department of Physics, Arizona State University, Tempe, Arizona 85287, USA
ABSTRACT
Nanosized Platinum (Pt) nanocrystals (NCs) have been extensively investigated in catalytic fields because of their high reactivity due to the unique electron structure. However, the rarity and the high cost of Pt limit its applications in industry. To reduce the usage of Pt in catalytic industry, research interests have been extended to Pt-based nanoalloys. Among various nanostructures, nanoframes (NFs) showed promising catalytic performance even with a lower metallic loading dose. Herein, we report a facile and robust method to transfer the Pt-Ni tetrahexahedral (THH) NCs into THH NFs in which carbon monoxide (CO) plays a role of the "etching reagent". The driving force of the etching is a formation of gaseous metallic complex, Ni(CO)4, known as Mond Process, preferentially dealloying nickel atoms along directions of the Pt-Ni THH NCs. It is determined that the resultant Pt-Ni THH NFs possess an open, stable and high-index preserved nanostructure, in which the outside atomic layers are composed of only Pt atoms with surface strains. Compared to a solution-based etching process, this approach requires less etching time and generates a well-defined structure. The associated thermal annealing operation also releases extra internal stress, making the NFs more stable with fewer surface defects. Such Pt-Ni THH NFs show interesting potentials in the improvement of stability and activity as advanced catalysts.
INTRODUCTION Pt is widely used in many catalytic fields including hydrogenation/dehydrogenation [1-4], catalytic reforming of alkene[5], CO/NO oxidation [6, 7] and electrocatalysis [8-10] due to its unique electron structure that leads to a high activity in breaking and forming of the related chemical bonds [11]. As a precious metal, however, the extremely low abundance of Pt in the earth's crust limits its applications. To reduce the usage of Pt, many 3d-transition metals such as Ni, Fe, Co, and Cu are incorporated into Pt lattice to form Pt-based bimetallic catalysts in replacing pure Pt. With size- and shape-controlled syntheses, Pt-based bimetallic NCs have attracted increased attention in catalytic applications because of their improved performance [12] and tunable capability in adsorbing the reaction intermediate due to the possibility of altering the Pt d-band center through alloying, strain and ligand effect [13]. It was reported that Pt-bimetallic NFs possess the additional features of the large specific surface area with surface strains [14], low catalyst loading amount required and
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