Rise of atomically dispersed metal catalysts: Are they a new class of catalysts?

김재형,주상훈 대한화학회 2024 Bulletin of the Korean Chemical Society Vol.45 No.4

Atomically dispersed metal catalysts or single‐atom catalysts have made great strides during the past decade in the catalysis field. While an initial vision of atomically dispersed metal catalysts was to combine the advantages of homogeneous and heterogeneous catalysts, their unexpected potentials continue to be discovered. In this account, we introduce historical backgrounds underpinning the emergence of atomically dispersed metal catalysts. Next, we illustrate some recent examples demonstrating the unusual reactivities of atomically dispersed metal catalysts, which are hard to realize by homogeneous or heterogeneous catalysts. We conclude the account by suggesting the remaining challenges in this exciting field. Atomically dispersed metal catalysts or single-atom catalysts have made great strides during the past decade in the catalysis field. While an initial vision of atomically dispersed metal catalysts was to combine the advantages of homogeneous and heterogeneous catalysts, their unexpected potentials continue to be discovered. In this account, we introduce historical backgrounds underpinning the emergence of atomically dispersed metal catalysts. Next, we illustrate some recent examples demonstrating the unusual reactivities of atomically dispersed metal catalysts, which are hard to realize by homogeneous or heterogeneous catalysts. We conclude the account by suggesting the remaining challenges in this exciting field.

Design of active bifunctional electrocatalysts using single atom doped transition metal dichalcogenides

Hwang, Jeemin,Noh, Seung Hyo,Han, Byungchan Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.471 No.-

<P><B>Abstract</B></P> <P>Single atom catalyst is designed to achieve high catalytic activity while extremely minimizing precious metal loadings for electrochemical energy conversion and storage applications. Using first-principles density functional theory calculations, we screen 48 combinations of single atom catalysts anchored at defective monolayer transition metal dichalcogenides (A<SUB>1</SUB>/TMD; A = Ni, Cu, Pd, Ag, Pt and Au; TM = Mo, W, Nb and Ta; D = S and Se). With established methodologies, we identify five best catalysts for each of oxygen reduction/evolution and hydrogen evolution reactions among the stable candidates. A scaling relation between the Gibb’s free energy for intermediates is figured out to understand the governing mechanism of single atom catalysts with varying transition metal dichalcogenides supports and to introduce key descriptor. Pt<SUB>1</SUB>/MoS<SUB>2</SUB> is proposed as the best bifunctional catalyst for oxygen reduction/evolution reaction. In addition, Pt<SUB>1</SUB>/NbSe<SUB>2</SUB> and Pt<SUB>1</SUB>/TaS<SUB>2</SUB> are promising candidates for oxygen and hydrogen evolution reactions. Treating the support itself as an active site for hydrogen evolution reaction, Pd<SUB>1</SUB>/NbS<SUB>2</SUB> and Pt<SUB>1</SUB>/NbS<SUB>2</SUB> are proposed as potential bifunctional catalysts toward oxygen reduction and evolution reaction, respectively. Conceptual design principle via high-throughput screening of single atom catalyst is demonstrated as a great approach to determine active and durable bifunctional single atom catalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single atom catalysts with transition metal dichalcogenides supports were screened. </LI> <LI> Five best catalysts were selected for redox reactions of oxygen and hydrogen. </LI> <LI> Pt<SUB>1</SUB>/MoS<SUB>2</SUB> was identified as a great bifunctional single atom catalyst. </LI> <LI> Scaling law was proposed as the key to understand catalytic mechanism. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Tuning atomic-level catalytic interaction on heterogeneous single atom catalyst

이병훈,현택환 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Enzymes control the specific interaction between the metal cofactor, mediating ligand and the reactants to maximize the catalytic performance. Likewise, homogeneous catalysts have been designed based on this reversible and cooperative activation process for a variety of important reactions. This interaction is not well defined in heterogeneous catalyst system and complicates the precise material design for various catalytic reactions. Here, we show how single atom catalysts can mitigate this issue. We show single atoms and the interaction with the surrounding support can control the catalytic characteristics and enables atomic-level tuning of catalytic performance as a consequence. Finally, we highlight how the cooperative interplay of atomic catalysts and adjacent environments can significantly modulate overall catalytic performance. This demonstration of atomic-level tuning represents a significant step for realizing reversible structure modulation in heterogeneous catalysts.

Effect of Fe content on nonprecious cathodic catalysts derived from a metal–organic framework for direct ammonia fuel cells

Han‑Wool Jang,Seon Yeong Lee,Jong Yoon Lee,Han‑Ik Joh 한국탄소학회 2023 Carbon Letters Vol.33 No.1

Ammonia is considered a promising hydrogen carrier due to its high hydrogen density and liquefaction temperature. Considering that the energy efficiency generally decreases as chemical conversion is repeated, it is more efficient to directly use ammonia as a fuel for fuel cells. However, catalysts in direct ammonia fuel cells have the critical issues of sluggish ammonia oxidation reaction (AOR) rate and poisoning of reaction intermediates. In particular, the use of precious metal as cathodic catalysts has been limited due to ammonia crossover and poisoning. In this study, we introduce Fe-based single-atom catalysts with selective activity for the oxygen reduction reaction (ORR) even in the presence of ammonia. As the Fe content increased, the single-atom structure of the catalysts changed into Fe nanoparticles or carbides. Among our Fe–N–C catalysts, FeNC-50 with a Fe loading amount of 0.34 wt% showed the highest ORR performance regardless of the ammonia concentration. In particular, the difference in activity between the catalysts increased as the concentration increased. The FeNC-50 catalyst showed remarkable stability after 1000 cycles. Therefore, we believe that single-atom dispersion is an important factor in the development of stable non-precious catalysts with high activity and inactivity for the ORR and AOR, respectively.

Aging effect on the structure formation of active sites in single-atomic catalysts and their electrochemical properties for oxygen reduction reaction

이선영,이종윤,Han-Wool Jang,U Hyeok Son,Sungho Lee,조한익 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.117 No.-

FeANAC catalysts have attracted attention because of their superior oxygen reduction reaction (ORR)performance in alkaline media. However, there is a conflict between the active sites of FeANAC catalysts,namely single-atomic Fe–Nx sites and dual active sites consisting of atomic sites/iron carbide nanoparticles. Herein, we synthesized catalysts with different types of active sites by controlling the facile agingprocess. The main active sites varied from single active sites to dual active sites when the aging timeand Fe content was decreased and increased. A catalyst with 0.6 wt% Fe that is aged for 24 h(FeNC-24–0.6) has dual active sites, whereas a catalyst with 0.9 wt% Fe that is aged for 48 h(FeNC-48–0.9) consists mainly of single active sites. The catalysts showed outstanding ORR activity,exceeding the half-wave potential of the commercial 20 wt% Pt/C catalysts by 11 mV. Interestingly,the FeNC-48–0.9 catalyst exhibited a rare negative shift compared to the FeNC-24–0.6 catalyst in thedurability tests. Therefore, it is believed that increasing the number of single-atomic Fe–Nx sites is aneffective approach to enhance the ORR performance of FeANAC catalyst in alkaline media.

제일원리 전산 기반 에너지와 환경 소재 디자인

한병찬 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Single atom catalyst is designed to achieve high catalytic activity while extremely minimizing precious metal loadings for electrochemical energy conversion and storage applications. Using first-principles density functional theory calculations, we screen 48 combinations of single atom catalysts anchored at defective monolayer transition metal dichalcogenides. We identify five best catalysts for each of oxygen redox and hydrogen evolution reactions among the stable candidates. A scaling relation between the Gibb’s free energy for intermediates is figured out to understand the governing mechanism of single atom catalysts with varying transition metal dichalcogenides supports and to introduce key descriptor. Conceptual design principle via high-throughput screening of single atom catalyst is demonstrated as a great approach to determine active and durable bifunctional single atom catalysts.

A review of synthesis strategies for MOF-derived single atom catalysts

황종국 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.6

Single atom catalysts (SACs) have attracted great attention as promising catalysts that integrate the benefits of both heterogeneous and homogeneous catalysts. SACs exhibit unique properties that are otherwise difficult to achieve, such as high atom utilization efficiency, unprecedentedly high catalytic activity and selectivity. However, it still remains a great challenge to prepare stable SACs without particle aggregation and sintering. Among the various fabrication methods for SACs, metal-organic framework (MOF)-derived synthesis routes have shown great potential by taking advantage of MOFs’ high structural/chemical tunability, large surface area and high porosity. In this review, the synthesis strategies for MOF-derived SACs are comprehensively summarized and classified into five classes, metal node modification, ligand modification, guest encapsulation, migration and trapping, and others. The current challenges and future opportunities of MOF-derived SACs are further discussed. This review will be useful for the rational design of MOF-derived SACs for various catalytic reactions.

Exploring Rational Design of Single-Atom Electrocatalysts for Efficient Electrochemical Reduction of CO2 to CO

마준희,조진혁,이강원,김수영 한국재료학회 2023 한국재료학회지 Vol.33 No.2

The electrochemical reduction of carbon dioxide (CO2) to value-added products is a remarkable approach for mitigating CO2 emissions caused by the excessive consumption of fossil fuels. However, achieving the electrocatalytic reduction of CO2 still faces some bottlenecks, including the large overpotential, undesirable selectivity, and slow electron transfer kinetics. Various electrocatalysts including metals, metals oxides, alloys, and single-atom catalysts have been widely researched to suppress HER performance, reduce overpotential and enhance the selectivity of CO2RR over the last few decades. Among them, single-atom catalysts (SACs) have attracted a great deal of interest because of their advantages over traditional electrocatalysts such as maximized atomic utilization, tunable coordination environments and unique electronic structures. Herein, we discuss the mechanisms involved in the electroreduction of CO2 to carbon monoxide (CO) and the fundamental concepts related to electrocatalysis. Then, we present an overview of recent advances in the design of high-performance noble and non-noble singleatom catalysts for the CO2 reduction reaction.

A Platform of Two Trades: Interface-Confined Pt Single-Atoms with Record-High Activity and Excellent Stability

강은지,유미,최혁,하현우,윤지은,최진석,( Richard Celestre ),( David A. Shapiro ),유영상,김천중,김현유 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Single-atom (SA) catalysts have been regarded as a next generation catalyst with exceptional catalytic efficiency. However, the general concern about thermodynamic instability of the SAs questions their practical values. Moreover, whether the SAs’ inherent catalytic activity is superior to the larger clusters or nanoparticles is still under debate. Here, we end above two controversies by achieving both high activity and stability of Pt-SAs in a single catalyst platform, Pt/CeO_x-TiO₂. Based on a hierarchical protocol of density functional theory calculation, time-resolved catalyst performance test, and operando synchrotron-based X-ray analysis, we present the record-high specific rate toward CO oxidation and excellent long-term stability under the harsh reaction conditions of Pt-SAs confined at the CeO_x-TiO₂ interfaces.

Platinum Single Atoms on Carbon Nanotubes as Efficient Catalyst for Hydroalkoxylation

우현제,이은경,윤수원,박신애,박강현,김용태 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.10

We report a facile synthesis of Pt single atoms on thiolated carbon nanotubes. To obtain Pt single atoms, it is crucial to treat thiol groups on carbon nanotubes. Pt single atoms on carbon nanotubes were used efficient catalyst for hydroalkoxylation of 3-buten-1-ol or 4-penten-1-ol. Hydroalkoxylation represents an atom-economic route to construct four or five- membered cyclic ethers through intramolecular addition of hydroxyl group. This catalyst exhibited higher catalytic activity than Pt complex and Pt nanoparticles on carbon nanotubes.