Dressing of Cu Atom over Nickel Cluster Stimulating the Poisoning-Free CO Oxidation: An Ab Initio Study

Abstract

In this work using first-principles calculations based on spin-polarized density functional theory (DFT), the role of the Cu atom in degrading the poisoning of carbon monoxide (CO) over Ni n Cu clusters is unveiled. The search has been initiated with the examination of structural, magnetic, and electronic properties of Ni n+1 and Ni n Cu clusters (1 ≤ n ≤ 12). X-ray absorption near-edge structure (XANES) spectra of Ni K-edge are computed to extract the information on the oxidation states and coordination environment of metal sites of the clusters. This study is operated with the two forms of dispersion corrections, i.e., D2 and D3, with standard DFT (with LDA and GGA functionals) for the consideration of van der Waals interactions during CO adsorption. The PBE and PBE-D3 approaches are found to be capable of yielding the experimentally observed preferential site for CO adsorption. The effect of spin-polarization on the reactivity of transition metals (TMs) toward CO adsorption is crucially assessed by the electronic reactivity descriptors such as d-band center, d-band width, and fractional filling of d-band using a spin-polarized d-band center model. The effective charge transfer from Cu to Ni atoms makes Ni atoms more efficient of charge and is attributed to the degrading adsorption of CO over Ni n Cu clusters. The Ni12Cu cluster stands out with good CO oxidation activity for the Langmuir–Hinshelwood (L–H) reaction pathway.

Downshift of the Ni d band center over Ni nanoparticles in situ confined within an amorphous silicon nitride matrix

“…As a result, there is an appropriate binding strength to maximize the catalytic activity. [6][7][8][9] As a general trend, the d band center of TM shifts down from left to right, and from 3d to 5d TMs in the periodic table. 10 Thus, downshifting the d band center of 3d TMs such as nickel is one of the reasonable strategies to approach the catalytic performance of noble metals.…”

“…In general, the binding strength between hydrogen and TMs highly influences the subsequent catalytic performance, and the d band theory well represents the relationship between the binding strength and catalytic activity of TMs. [6][7][8][9] Based on this theory, the d band center relative to the Fermi energy (ε d -E F ), which is related to the density of states for d electrons of TMs, is found to show a correlation with the binding strength between TMs and adsorbates. [6][7][8][9] The down (up) shift of the d band center relative to the Fermi energy means that the less (higher) availability of empty antibonding states between the TM and adsorbate results in weaker (stronger) interactions between them.…”

“…[6][7][8][9] Based on this theory, the d band center relative to the Fermi energy (ε d -E F ), which is related to the density of states for d electrons of TMs, is found to show a correlation with the binding strength between TMs and adsorbates. [6][7][8][9] The down (up) shift of the d band center relative to the Fermi energy means that the less (higher) availability of empty antibonding states between the TM and adsorbate results in weaker (stronger) interactions between them. 8 On the one hand, the weak binding strength between TMs and adsorbates makes the dissociative chemisorption of adsorbates difficult, and on the other hand, the strong binding strength makes the desorption of adsorbates difficult during the catalytic reaction.…”

“…[6][7][8][9] The down (up) shift of the d band center relative to the Fermi energy means that the less (higher) availability of empty antibonding states between the TM and adsorbate results in weaker (stronger) interactions between them. 8 On the one hand, the weak binding strength between TMs and adsorbates makes the dissociative chemisorption of adsorbates difficult, and on the other hand, the strong binding strength makes the desorption of adsorbates difficult during the catalytic reaction. As a result, there is an appropriate binding strength to maximize the catalytic activity.…”