Understanding the structure and reactivity of NiCu nanoparticles: an atomistic model

Quaino, Paola; Belletti, Gustavo Daniel; Shermukhamedov, Shokirbek A.; Glukhov, Dmitrii V.; Santos, Elizabeth; Schmickler, Wolfgang; Nazmutdinov, Renat R.

doi:10.1039/c7cp04641c

Cited by 14 publications

(7 citation statements)

References 47 publications

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“…The simulations were performed at room temperature ( T = 298 K). Other pertinent details can be found in ref . In this work, we also performed a supplementary analysis of our previous MC simulations of a Ni 95 Cu 5 nanoparticle of the same size (162133 atoms) and shape …”

Section: Methodsmentioning

confidence: 99%

Bimetallic NiM/C (M = Cu and Mo) Catalysts for the Hydrogen Oxidation Reaction: Deciphering the Role of Unintentional Surface Oxides in the Activity Enhancement

et al. 2022

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Emerging interest in the platinum group metal (PGM)-free electrocatalysts calls for a fundamental understanding of the key factors determining their activity, the latter being critical for the development of efficient catalysts. Ni-based materials show high promises as PGM-free anodes of anion exchange membrane fuel cells (AEMFCs). However, their hydrogen oxidation reaction (HOR) activity can differ by several orders of magnitude, and the factors responsible for this are still being debated. In this work, the effect of unintentional surface oxides in Ni/C and NiM/C (M = Cu and Mo) is revealed by benchmarking either the catalysts conventionally stored under ambient conditions or purposely reduced “oxide-free” materials. The analysis of electrocatalytic data complemented by detailed material characterization, Monte Carlo simulations, and density functional calculations, underlines the key importance of surface oxides in the HOR catalysis on Ni, NiCu, and NiMo electrodes. These findings underscore the need to measure the HOR activity of Ni-based catalysts in the absence of surface oxides in order to unambiguously interpret the influence of other factors (such as the electronic effect of the second element) on activity enhancement.

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Section: Methodsmentioning

confidence: 99%

Bimetallic NiM/C (M = Cu and Mo) Catalysts for the Hydrogen Oxidation Reaction: Deciphering the Role of Unintentional Surface Oxides in the Activity Enhancement

et al. 2022

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“…Defining the surface structure of the catalyst was required to describe H ad transfer on the surface. NiCu bimetal in the model was assumed as a phase-separated composite with the heterostructure. , The H ad atoms could diffuse at the surface of Ni and Cu particles and spill over at the boundary (Figure a). In the previous reports, the H ad atom diffusion and hydrogen spillover were separately described by Fick’s law (eq ) and the continuum approach .…”

Section: Theoretical Modelingmentioning

confidence: 99%

Simulation Study Reveals the Role of Hydrogen Spillover in pH- and Potential-Dependent Hydrogen Evolution over the NiCu Bimetal Catalyst

et al. 2022

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Accelerating electrocatalytic water splitting via hydrogen spillover has received increasing attention. However, the underlying mechanism of hydrogen spillover on hydrogen evolution is still ambiguous. Herein, a simulation study was carried out to determine the role of hydrogen spillover in pH- and potential-dependent hydrogen evolution over the NiCu bimetal catalyst. It was found that the current density was most prominently improved by hydrogen spillover in the neutral condition at −0.35 to −0.2 V vs reversible hydrogen electrode. By the parameter study, it was indicated that the potential and pH could improve the effect of hydrogen spillover on the current density by altering the surface reaction rates which include the hydrogen adsorption and desorption rates on the Ni and Cu particles. The pH would also affect the current density enhancement from the hydrogen spillover by the mass transfer limitation. To effectively utilize the hydrogen spillover for improved electrocatalytic hydrogen production, managing the surface reaction rate was important. Typically, the key principle was increasing the hydrogen adsorption rate of hydrogen donors and hydrogen desorption rate of hydrogen acceptors in the presence of hydrogen spillover. This fundamental understanding of hydrogen spillover contributes to the development of advanced electrocatalytic systems for hydrogen production.

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“…Alloying the metallic NPs with a dis-similar element is one of the common approaches to tailor such properties. The resulting bimetallic NPs, such as Au–Ag, Pt–Pd, Au–Pt, , Ag–Ni, Au–Cu, and Ni–Cu clusters − and Al coated Ni NP, , often offer tunable catalytic activity/selectivity and enhanced stability, attracting much attention in catalysis research. The Ni–Cu system is perhaps among the most widely examined bimetallic catalysts for a wide variety of processes including oxidation, hydrogenation, and reforming reactions. − The small lattice-size disparity between the Cu and the Ni (3.62 and 3.54 Å, respectively) enables complete solid-state miscibility in the alloy. , Particularly in the methane dry reforming reaction (DRM), which involves the interaction of methane and carbon dioxide to yield synthesis gas, the Ni–Cu catalyst has been extensive investigated thanks to its excellent resistance to coking and high catalytic activity. , …”

Section: Introductionmentioning

confidence: 99%

Cooperative Atom Motion in Ni–Cu Nanoparticles during the Structural Evolution and the Implication in the High-Temperature Catalyst Design

Yang¹,

Lin

Yan

et al. 2019

ACS Appl. Energy Mater.

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Bimetallic nanoparticles (NPs) are widely used in catalysis for a wide range of applications. Like other catalysts, their catalytic performance may also degrade during reactions. The structural evolution and the interfacial segregation of one constituting element are among the many degradation mechanisms. Understanding the atomic motions during this dynamics process promises to serve as a reference in designing a better catalyst. In this work, we used molecular dynamics simulation to examine the interfacial dynamics during the surface enrichment of Cu in an ∼4 nm Ni–Cu bimetallic NP. The Ni/Cu ratio on the surface after segregation was quantified and plotted as a function of the nominal composition in the bulk. Interestingly, the “outward” migration of Cu atoms and the “inward” migration of Ni were not all independent; rather, it showed the simultaneous motion by consecutive atoms along a string. Such collective motion comprised of two elements facilitated the surface segregation, intensified the shape reconstruction, and was rarely observed in previous studies. The simulation results also enabled us to rationally take advantage of the Cu segregation phenomena and design a high-performance yet robust 94Ni6Cu/Al2O3 catalyst for methane dry reforming (DRM) reactions at 850 °C. The proportion of Cu on the surface was more than 50% higher than that in the bulk, offering complementary performances of coking resistance and high activity. The combined computational–experimental study provided one of the possible reasons explaining the large inconsistency in the literature regarding the optimal Ni/Cu ratio of the Ni–Cu DRM catalyst and might shed light on the de novo design of high-temperature bimetallic catalysts.

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Understanding the structure and reactivity of NiCu nanoparticles: an atomistic model

Cited by 14 publications

References 47 publications

Bimetallic NiM/C (M = Cu and Mo) Catalysts for the Hydrogen Oxidation Reaction: Deciphering the Role of Unintentional Surface Oxides in the Activity Enhancement

Bimetallic NiM/C (M = Cu and Mo) Catalysts for the Hydrogen Oxidation Reaction: Deciphering the Role of Unintentional Surface Oxides in the Activity Enhancement

Simulation Study Reveals the Role of Hydrogen Spillover in pH- and Potential-Dependent Hydrogen Evolution over the NiCu Bimetal Catalyst

Cooperative Atom Motion in Ni–Cu Nanoparticles during the Structural Evolution and the Implication in the High-Temperature Catalyst Design

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