scholarly journals Atom-by-atom analysis of sintering dynamics and stability of Pt nanoparticle catalysts in chemical reactions

2020 ◽  
Vol 378 (2186) ◽  
pp. 20190597 ◽  
Author(s):  
Thomas E. Martin ◽  
Robert W. Mitchell ◽  
Edward D. Boyes ◽  
Pratibha L. Gai
Keyword(s):  
Critical Role ◽  
Pt Nanoparticles ◽  
Carbon Support ◽  
Active Species ◽  
Chemical Processes ◽  
Single Atom ◽  
Complex Nature ◽  
Original Research ◽  
Single Atoms

Supported Pt nanoparticles are used extensively in chemical processes, including for fuel cells, fuels, pollution control and hydrogenation reactions. Atomic-level deactivation mechanisms play a critical role in the loss of performance. In this original research paper, we introduce real-time in-situ visualization and quantitative analysis of dynamic atom-by-atom sintering and stability of model Pt nanoparticles on a carbon support, under controlled chemical reaction conditions of temperature and continuously flowing gas. We use a novel environmental scanning transmission electron microscope with single-atom resolution, to understand the mechanisms. Our results track the areal density of dynamic single atoms on the support between nanoparticles and attached to them; both as migrating species in performance degradation and as potential new independent active species. We demonstrate that the decay of smaller nanoparticles is initiated by a local lack of single atoms; while a post decay increase in single-atom density suggests anchoring sites on the substrate before aggregation to larger particles. The analyses reveal a relationship between the density and mobility of single atoms, particle sizes and their nature in the immediate neighbourhood. The results are combined with practical catalysts important in technological processes. The findings illustrate the complex nature of sintering and deactivation. They are used to generate new fundamental insights into nanoparticle sintering dynamics at the single-atom level, important in the development of efficient supported nanoparticle systems for improved chemical processes and novel single-atom catalysis. This article is part of a discussion meeting issue ‘Dynamic in situ microscopy relating structure and function’.

Nanostructured PEFC Electrode Catalysts Prepared via In-situ Colloidal Impregnation

2004 ◽  
Vol 835 ◽  
Author(s):  
Kazunari Sasaki ◽  
Kenji Shinya ◽  
Shuhei Tanaka ◽  
Yuudai Kawazoe ◽  
Takashi Kuroki ◽  
...  
Keyword(s):  
Carbon Nanofibers ◽  
Pt Nanoparticles ◽  
Rotating Disk ◽  
Carbon Support ◽  
Crystallographic Structure ◽  
Pt Electrode ◽  
Support Materials ◽  
Catalyst Layers ◽  
Preparation Conditions

ABSTRACTNanostructured Platinum-based electrode catalysts were prepared via in-situ colloidal impregnation for polymer electrolyte fuel cells. Crystallite size, grain size, and distribution of Pt nanoparticles on carbon support materials were characterized by XRD, TEM, high-resolution FESEM, and STEM. Effective surface area and kinetically-controlled current density of Pt electrode catalysts were analyzed by cyclic and hydrodynamic voltammetry using rotating disk electrodes. PEFCs with these electrode catalysts were also prepared and their I-V characteristics were examined at 80°C.We have succeeded to develop Pt electrode catalysts with a diameter of a few nm, supported on carbon nanofibers with different structures (including herringbone-type fibers, platelet-type fibers, and highly-conductive vapor-grown fibers), carbon nanotubes, as well as carbon black. The dependencies of nanostructure and electrochemical properties on crystallographic structure of carbon support materials and preparation conditions of electrode catalysts are analyzed and discussed. Nanostructural design of PEFC electrode catalyst layers using carbon nanofibers as catalyst supports and electrode fillers is also discussed.

scholarly journals Ligand-coordinated Ir single-atom catalysts stabilized on oxide supports for ethylene hydrogenation and their evolution under a reductive atmosphere

2021 ◽  
Author(s):  
Linxiao Chen ◽  
Iyad S. Ali ◽  
George E. Sterbinsky ◽  
Xuemei Zhou ◽  
Eman Wasim ◽  
...  
Keyword(s):  
Structural Evolution ◽  
Single Atom ◽  
Ethylene Hydrogenation ◽  
Oxide Supports ◽  
Single Atoms ◽  
Reducing Atmosphere ◽  
Reductive Atmosphere

Effective, stable, durable, and tunable Ir-ligand single-atom catalysts for ethylene hydrogenation, studied in situ for structural evolution of Ir single-atoms under a reducing atmosphere.

scholarly journals Precise fabrication of single-atom alloy co-catalyst with optimal charge state for enhanced photocatalysis

2020 ◽  
Author(s):  
Yating Pan ◽  
Yunyang Qian ◽  
Xusheng Zheng ◽  
Sheng-Qi Chu ◽  
Yijun Yang ◽  
...  
Keyword(s):  
Surface Charge ◽  
Charge State ◽  
Metal Organic Framework ◽  
Critical Role ◽  
Pt Nanoparticles ◽  
Single Atom ◽  
Co Catalyst ◽  
Coordination Environment ◽  
Charge Regulation ◽  
Single Atom Alloy

Abstract While surface charge state of co-catalysts plays a critical role for boosting photocatalysis, the study on surface charge regulation via their precise structure control, remains extremely rare. Herein, a metal-organic framework (MOF)-stabilized bimetallic Pd@Pt nanoparticles (NPs), which feature adjustable Pt coordination environment and the controlled structure from core-shell to single-atom alloy (SAA), have been fabricated. Significantly, apart from the formation of Mott-Schottky junction in a conventional way, we elucidate that Pt surface charge regulation can be alternatively achieved by changing its coordination environment and the structure of Pd@Pt co-catalyst, where the charge between Pd and Pt is redistributed. As a result, the optimized Pd10@Pt1/MOF composite, which involves unprecedented SAA co-catalyst, exhibits an exceptionally high photocatalytic hydrogen production activity, far surpassing its corresponding counterparts.

Tunable Carbon Surface from Mono- to Multi-Metallic Single Atoms

2020 ◽  
Author(s):  
Weihong Lai ◽  
Heng Wang ◽  
Quan jiang ◽  
Zichao Yan ◽  
Hanwen Liu ◽  
...  
Keyword(s):  
Synergistic Effects ◽  
Structural Evolution ◽  
Charge Compensation ◽  
Catalytic Reactions ◽  
Single Atom ◽  
Carbon Surface ◽  
Hydrogen Electrode ◽  
Single Atoms ◽  
Mass Activity ◽  
Co Doped

<p>Herein, we develop a non-selective charge compensation strategy to prepare multi-single-atom doped carbon (MSAC) in which a sodium p-toluenesulfonate (PTS-Na) doped polypyrrole (S-PPy) polymer is designed to anchor discretionary mixtures of multiple metal cations, including iron (Fe<sup>3+</sup>), cobalt (Co<sup>3+</sup>), ruthenium (Ru<sup>3+</sup>), palladium (Pd<sup>2+</sup>), indium (In<sup>3+</sup>), iridium (Ir<sup>2+</sup>), and platinum (Pt<sup>2+</sup>) . As illustrated in Figure 1, the carbon surface can be tuned with different level of compositional complexities, including unary Pt<sub>1</sub>@NC, binary (MSAC-2, (PtFe)<sub>1</sub>@NC), ternary (MSAC-3, (PtFeIr)<sub>1</sub>@NC), quaternary (MSAC-4, (PtFeIrRu)<sub>1</sub>@NC), quinary (MSAC-5, (PtFeIrRuCo)<sub>1</sub>@NC), senary (MSAC-6, (PtFeIrRuCoPd)<sub>1</sub>@NC), and septenary (MSAC-7, (PtFeIrRuCoPdIn)<sub>1</sub>@NC) samples. The structural evolution of carbon surface dictates the activities of both ORR and HER. The senary MSAC-6 achieves the ORR mass activity of 18.1 A·mg<sub>metal</sub><sup>-1</sup> at 0.9 V (Vs reversible hydrogen electrode (RHE)) over 30K cycles, which is 164 times higher than that of commercial Pt/C. The quaternary MSAC-4 presented a comparable HER catalytic capability with that of Pt/C. These results indicate that the highly complexed carbon surface can enhance its ability over general electrochemical catalytic reactions. The mechanisms regarding of the ORR and HER activities of the alternated carbon surface are also theoretically and experimentally investigated in this work, showing that the synergistic effects amongst the co-doped atoms can activate or inactivate certain single-atom sites.</p>

scholarly journals The influence of chemical parameters on the in-situ metal carbonyl complex formation studied with the fast on-line reaction apparatus (FORA)

2021 ◽  
Vol 109 (4) ◽  
pp. 243-260 ◽  
Author(s):  
Yves Wittwer ◽  
Robert Eichler ◽  
Dominik Herrmann ◽  
Andreas Türler
Keyword(s):  
Metal Carbonyl ◽  
Ambient Air ◽  
Single Atom ◽  
Carbonyl Complex ◽  
Carbonyl Complexes ◽  
On Line ◽  
Carrier Gases ◽  
And Performance ◽  
Atom Chemistry

Abstract A new setup named Fast On-line Reaction Apparatus (FORA) is presented which allows for the efficient investigation and optimization of metal carbonyl complex (MCC) formation reactions under various reaction conditions. The setup contains a 252Cf-source producing short-lived Mo, Tc, Ru and Rh isotopes at a rate of a few atoms per second by its 3% spontaneous fission decay branch. Those atoms are transformed within FORA in-situ into volatile metal carbonyl complexes (MCCs) by using CO-containing carrier gases. Here, the design, operation and performance of FORA is discussed, revealing it as a suitable setup for performing single-atom chemistry studies. The influence of various gas-additives, such as CO2, CH4, H2, Ar, O2, H2O and ambient air, on the formation and transport of MCCs was investigated. O2, H2O and air were found to harm the formation and transport of MCCs in FORA, with H2O being the most severe. An exception is Tc, for which about 130 ppmv of H2O caused an increased production and transport of volatile compounds. The other gas-additives were not influencing the formation and transport efficiency of MCCs. Using an older setup called Miss Piggy based on a similar working principle as FORA, it was additionally investigated if gas-additives are mostly affecting the formation or only the transport stability of MCCs. It was found that mostly formation is impacted, as MCCs appear to be much less sensitive to reacting with gas-additives in comparison to the bare Mo, Tc, Ru and Rh atoms.

Cobalt Single Atom Site Isolated Pt Nanoparticles for Efficient ORR and HER in Acid Media

Nano Energy ◽  
2021 ◽  
pp. 106221
Author(s):  
Lvhan Liang ◽  
Huihui Jin ◽  
Huang Zhou ◽  
Bingshuai Liu ◽  
Chenxi Hu ◽  
...  
Keyword(s):  
Pt Nanoparticles ◽  
Single Atom ◽  
Acid Media

Improving peroxymonosulfate activation by copper ion-saturated adsorbent-based single atom catalysts for the degradation of organic contaminants: electron-transfer mechanism and the key role of Cu single atoms

2021 ◽  
Author(s):  
Jingwen Pan ◽  
Baoyu Gao ◽  
Pijun Duan ◽  
Kangying Guo ◽  
Muhammad Akram ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Organic Contaminants ◽  
High Salinity ◽  
Copper Ion ◽  
Single Atom ◽  
Electron Transfer Mechanism ◽  
Persulfate Oxidation ◽  
Single Atoms ◽  
Oxidation Technology

Nonradical pathway-based persulfate oxidation technology is considered to be a promising method for high-salinity organic wastewater treatment.

scholarly journals Selective hydroboration of unsaturated bonds by an easily accessible heterotopic cobalt catalyst

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Chuhan Li ◽  
Shuo Song ◽  
Yuling Li ◽  
Chang Xu ◽  
Qiquan Luo ◽  
...  
Keyword(s):  
Base Metal ◽  
Large Scale ◽  
Metal Cluster ◽  
Active Species ◽  
Cobalt Catalysts ◽  
Metal Salts ◽  
One Pot ◽  
Practical Utilization ◽  
Earth Abundant

AbstractHomogeneous earth-abundant metal catalysis based on well-defined molecular complexes has achieved great advance in synthetic methodologies. However, sophisticated ligand, hazardous activator and multistep synthesis starting from base metal salts are generally required for the generation of active molecular catalysts, which may hinder their broad application in large scale organic synthesis. Therefore, the development of metal cluster catalysts formed in situ from simple earth-abundant metal salts is of importance for the practical utilization of base metal resource, yet it is still in its infancy. Herein, a mixture of catalytic amounts of cobalt (II) iodide and potassium tert-butoxide is discovered to be highly active for selective hydroboration of vinylarenes and dihydroboration of nitriles, affording a good yield of diversified hydroboration products that without isolation can readily undergo further one pot transformations. It should be highlighted that the alkoxide-pinacolborane combination acts as an efficient activation strategy to activate cobalt (II) iodide for the generation of metastable heterotopic cobalt catalysts in situ, which is proposed to be catalytically active species.

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