Bottom-up assembly of bimetallic nanocluster catalysts from oxide-supported single-atom precursors

Sarma, Bidyut Bikash; Agostini, Giovanni; Farpón, Marcos G.; Marini, Carlo; Pfänder, Norbert; Prieto, Gonzalo

doi:10.1039/d1ta00421b

Cited by 13 publications

(7 citation statements)

References 66 publications

(71 reference statements)

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“…In fact, SACs are especially suitable to be studied by bulk averaging techniques such as XAS. Beyond the ex situ characterization, more important is to understand the dynamic behavior of SACs with XAS under operating conditions, as pointed out by various research groups. − As X-rays can penetrate easily through solid materials in either crystalline or amorphous phase, XAS can account for reversible or irreversible transformation in catalysts sintering/agglomeration from atom to nanoparticle under oxidizing or reducing atmosphere as shown in Figure .…”

Section: Introductionmentioning

confidence: 99%

Design of Single-Atom Catalysts and Tracking Their Fate Using Operando and Advanced X-ray Spectroscopic Tools

et al. 2022

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The potential of operando X-ray techniques for following the structure, fate, and active site of single-atom catalysts (SACs) is highlighted with emphasis on a synergetic approach of both topics. X-ray absorption spectroscopy (XAS) and related X-ray techniques have become fascinating tools to characterize solids and they can be applied to almost all the transition metals deriving information about the symmetry, oxidation state, local coordination, and many more structural and electronic properties. SACs, a newly coined concept, recently gained much attention in the field of heterogeneous catalysis. In this way, one can achieve a minimum use of the metal, theoretically highest efficiency, and the design of only one active site-so-called single site catalysts. While single sites are not easy to characterize especially under operating conditions, XAS as local probe together with complementary methods (infrared spectroscopy, electron microscopy) is ideal in this research area to prove the structure of these sites and the dynamic changes during reaction. In this review, starting from their fundamentals, various techniques related to conventional XAS and X-ray photon in/out techniques applied to single sites are discussed with detailed mechanistic and in situ/operando studies. We systematically summarize the design strategies of SACs and outline their exploration with XAS supported by density functional theory (DFT) calculations and recent machine learning tools.

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Section: Introductionmentioning

confidence: 99%

Design of Single-Atom Catalysts and Tracking Their Fate Using Operando and Advanced X-ray Spectroscopic Tools

et al. 2022

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“…4,5 Despite these high energy requirements, this process has attracted significant attention because it converts both methane and carbon dioxide, two major greenhouse gases, into the valuable chemical feedstocks, CO and H 2 . 6−8 One significant deactivation mechanism for DRM catalysts is the sintering of the active metal sites, a high-temperature process by which the catalytically active metal atoms migrate (Ostwald ripening) 9,10 and/or metal particles coalesce and form less and/or fewer active sites for the reaction (sintering). 11,12 Our research groups have previously reported that the initial deactivation of Ni/Al 2 O 3 catalysts under DRM conditions is caused by the sintering of the Ni particles with an apparent activation energy of 161 kJ mol −1 .…”

Section: Introductionmentioning

confidence: 99%

“…Many heterogeneous catalysts suffer from deactivation over time due to coking and sintering during the catalytic reaction. − Harsh operating reaction conditions, for example, high temperatures or high chemical potentials, are likely to cause severe deactivation because such conditions can increase the rates of coke formation, agglomeration of active metal sites, and/or other deactivating processes. Dry reforming of methane (DRM), in which methane is used to reduce CO 2 , is a classic example of an endothermic (Δ H 298K = + 247 kJ mol –1 ) catalytic reaction requiring harsh conditions (operating temperature > 600–700 °C), resulting in severe catalyst deactivation. , Despite these high energy requirements, this process has attracted significant attention because it converts both methane and carbon dioxide, two major greenhouse gases, into the valuable chemical feedstocks, CO and H 2 . − One significant deactivation mechanism for DRM catalysts is the sintering of the active metal sites, a high-temperature process by which the catalytically active metal atoms migrate (Ostwald ripening) , and/or metal particles coalesce and form less and/or fewer active sites for the reaction (sintering). , Our research groups have previously reported that the initial deactivation of Ni/Al 2 O 3 catalysts under DRM conditions is caused by the sintering of the Ni particles with an apparent activation energy of 161 kJ mol –1 …”

Section: Introductionmentioning

confidence: 99%

Stabilizing Supported Ni Catalysts for Dry Reforming of Methane by Combined La Doping and Al Overcoating Using Atomic Layer Deposition

et al. 2022

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Deposition of La 2 O 3 and Al 2 O 3 on Al 2 O 3 -supported Ni catalysts was performed to study their effects on heterogeneous catalysts for the dry reforming of methane (DRM) reaction. An alumina-supported Ni catalyst (Ni/Al 2 O 3 , 2 wt % of Ni), synthesized via incipient wetness impregnation, loses ∼87% of its initial activity within 45 h under DRM conditions. While overcoating of Al 2 O 3 on this catalyst via atomic layer deposition (ALD) helps stabilize the catalytic activity in long time-on-stream (TOS) tests, this overcoated catalyst is ca. 40 times less active than the uncoated catalyst at peak activity. This Al 2 O 3 -overcoated Ni/Al 2 O 3 catalyst also exhibits a long induction period (∼20 h) due to the slow reduction of Ni 2+ within the catalytically inactive nickel aluminate (NiAl 2 O 4 ) phase, formed by the interaction of metallic Ni with the Al 2 O 3 overcoat during pre-DRM treatment at the 700 °C reaction temperature. Here, we report that, while doping small amounts of La (∼0.03 wt %) into the Ni/Al 2 O 3 catalyst does not significantly affect the catalytic activity or stability by itself, the addition of ALD-Al 2 O 3 on top of the La 2 O 3 -promoted Ni catalysts significantly suppresses the long TOS deactivation, helps recover the peak activity of uncoated Ni/ Al 2 O 3 , and eliminates the DRM induction period. This strategy obtains the stabilization benefits of Al 2 O 3 overcoating on Ni/Al 2 O 3 while, at the same time, avoiding the formation of undesirable NiAl 2 O 4 species.

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“…The atomically dispersed nature of SACs allows the utilization of almost 100% of its activity, which bodes well for newer opportunities in several applications. Apart from carbon as a support material, several other porous metal oxides including 2D nanomaterials have been successfully utilized for the preparation of SACs. ,− …”

Section: Synthesis Of Fe-sacsmentioning

confidence: 99%

Single-Atom (Iron-Based) Catalysts: Synthesis and Applications

et al. 2021

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Supported single-metal atom catalysts (SACs) are constituted of isolated active metal centers, which are heterogenized on inert supports such as graphene, porous carbon, and metal oxides. Their thermal stability, electronic properties, and catalytic activities can be controlled via interactions between the single-metal atom center and neighboring heteroatoms such as nitrogen, oxygen, and sulfur. Due to the atomic dispersion of the active catalytic centers, the amount of metal required for catalysis can be decreased, thus offering new possibilities to control the selectivity of a given transformation as well as to improve catalyst turnover frequencies and turnover numbers. This review aims to comprehensively summarize the synthesis of Fe-SACs with a focus on anchoring single atoms (SA) on carbon/graphene supports. The characterization of these advanced materials using various spectroscopic techniques and their applications in diverse research areas are described. When applicable, mechanistic investigations conducted to understand the specific behavior of Fe-SACs-based catalysts are highlighted, including the use of theoretical models. CONTENTS 1. Introduction 13620 2. Scope of This Review 13623 3. Synthesis of Fe-SACs 13623 3.1. N-Doped Graphene-Based Fe-SACs 13623 3.2. Nitrogen-Doped Porous Carbon-Based Fe-SACs 13626 3.3. C 3 N 4 -Based Fe-SACs 13634 4.

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Bottom-up assembly of bimetallic nanocluster catalysts from oxide-supported single-atom precursors

Abstract: The precise synthesis and stabilization of oxide-supported bimetallic nanoclusters in the low-to-sub nanometer size regime is highly relevant in various fields, from optics and sensing to electrochemistry and catalysis. In...

Cited by 13 publications

References 66 publications

Design of Single-Atom Catalysts and Tracking Their Fate Using Operando and Advanced X-ray Spectroscopic Tools

Design of Single-Atom Catalysts and Tracking Their Fate Using Operando and Advanced X-ray Spectroscopic Tools

Stabilizing Supported Ni Catalysts for Dry Reforming of Methane by Combined La Doping and Al Overcoating Using Atomic Layer Deposition

Single-Atom (Iron-Based) Catalysts: Synthesis and Applications

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