Atomic-Structural Synergy for Catalytic CO Oxidation over Palladium–Nickel Nanoalloys

Abstract

Alloying palladium (Pd) with other transition metals at the nanoscale has become an important pathway for preparation of low-cost, highly active and stable catalysts. However, the lack of understanding of how the alloying phase state, chemical composition and atomic-scale structure of the alloys at the nanoscale influence their catalytic activity impedes the rational design of Pd-nanoalloy catalysts. This work addresses this challenge by a novel approach to investigating the catalytic oxidation of carbon monoxide (CO) over palladium-nickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable maximal catalytic activity at Pd:Ni ratio of ~50:50. Key to understanding the structural-catalytic synergy is the use of high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis to probe the atomic structure of PdNi nanoalloys under controlled thermochemical treatments and CO reaction conditions. Three-dimensional (3D) models of the atomic structure of the nanoalloy particles were generated by reverse Monte Carlo simulations (RMC) guided by the experimental HE-XRD/PDF data. Structural details of the PdNi nanoalloys were extracted from the respective 3D models and compared with the measured catalytic properties. The comparison revealed a strong correlation between the phase state, chemical composition and atomic-scale structure of PdNi nanoalloys and their catalytic activity for CO oxidation. This correlation is further substantiated by analyzing the first atomic neighbor distances and coordination numbers inside the nanoalloy particles and at their surfaces. These findings have provided new insights into the structural synergy of nanoalloy catalysts by controlling the phase state, composition and atomic structure, complementing findings of traditional density functional theory studies.

Heterogeneous PdAg alloy catalyst for selective methylation of aromatic amines with formic acid under an additive-free and solvothermal one-pot condition

“…It is well documented that a bimetallic alloy system would induce primary changes in not only the bond length due to the strain, 33 but also the bonding interactions of the surface heterometallic (Pd-M). [34][35][36][37][38] To confirm the alloying effect, Ag cores and Pd shells were synthesized and dispersed in Vulcan carbon, as previously reported.…”

Configurational Thermodynamics of Alloyed Nanoparticles with Adsorbates

“…But in general, the GS at such high O-coverage is a mixture of all four types of adsorption sites. For Pd 15 Rh 40 O 40 , all 40 Rh now stay in the shell and the core is purely Pd. Indeed, a total core−shell reversal can be induced by increasing O-coverage.…”

A promising single atom catalyst for CO oxidation: Ag on boron vacancies of h-BN sheets

“…2 Typical catalysts for CO oxidation consist of noble metals, such as Pt, [3][4][5][6][7][8] Pd, 5,6,[9][10][11][12] Ru 13 and Au, [14][15][16][17] and they have been widely investigated for decades. To further increase the catalytic performance and reduce the cost, recent research attention has turned to ''single atom catalysts'' (SACs) 18,19 by downsizing the catalyst to the atomic scale, which provides a platform for the establishment of new fundamental science as well as the design of excellent catalysts.…”