ESTEM imaging of single atoms under controlled temperature and gas environment conditions in catalyst reaction studies

Boyes, Edward; Ward, Michael R.; Lari, Leonardo; Gai, Pratibha L.

doi:10.1002/andp.201300068

Cited by 70 publications

(173 citation statements)

References 28 publications

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“…Figure 2 18 shows single atoms and clusters of Pt on a carbon support with a corresponding HAADF AC ESTEM image intensity profile of a single atom recorded at 25°C. The very thin (1-2 atoms high), raft-like clusters are made up primarily of partially ordered {111} spacings with a general (110) texture.…”

Section: Ac Estem Of Pt and Au Na Nocata Lystsmentioning

confidence: 99%

“…19 With the ESTEM, the complete population of single atoms has been identified and migratory single atoms on the support between the more substantial clusters have been imaged for the first time by the authors under controlled gas and temperature environments. 18 This observation of reacting single atoms is important in understanding the mechanisms of catalytic reactions and deactivation processes.…”

Section: Ac Estem Of Pt and Au Na Nocata Lystsmentioning

confidence: 99%

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Visualizing reacting single atoms in chemical reactions: Advancing the frontiers of materials research

Boyes

Gai

2015

MRS Bull.

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Heterogeneous gas-solid catalyst reactions occur at the atomic level, and understanding and controlling complex catalytic reactions at this level is crucial for the development of improved processes and materials. There are postulations that single atoms and very small clusters can act as primary active sites in chemical reactions. Early applications of our novel aberrationcorrected (AC) environmental (scanning) transmission electron microscope (E(S)TEM) with single-atom resolution are described. This instrument combines, for the frst time, controlled operating temperatures and a continuous gas environment around the sample with full AC STEM capabilities for real-time in situ analysis and visualization of single atoms and clusters in nanoparticle catalysis. ESTEM imaging and analysis in controlled gas and temperature environments can provide unique insights into catalytic reaction pathways that may involve metastable intermediate states. Benefts include new knowledge and more environmentally friendly technological processes for health care and renewable energy as well as improved or replacement mainstream technologies in the chemical and energy industries.

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Section: Ac Estem Of Pt and Au Na Nocata Lystsmentioning

confidence: 99%

Section: Ac Estem Of Pt and Au Na Nocata Lystsmentioning

confidence: 99%

Visualizing reacting single atoms in chemical reactions: Advancing the frontiers of materials research

Boyes

Gai

2015

MRS Bull.

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“…This insight has been aided by advances in analytical methodologies, notably the development of in situ or operando (under working conditions) spectroscopic [52][53][54] /microscopic [55][56][57][58] tools able to provide quantitative, spatio-temporal information on structurefunction relations of solid catalysts in the liquid and vapour phase. Parallel improvements in inorganic synthetic protocols offer finer control over preparative methods to direct the nanostructure (composition, morphology, size, valence and support architecture) of palladium catalysts [59][60][61] and thereby enhance activity, selectivity and lifetime in an informed manner.…”

Section: Introductionmentioning

confidence: 99%

Catalysing sustainable fuel and chemical synthesis

Lee

2014

Appl Petrochem Res

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Concerns over the economics of proven fossil fuel reserves, in concert with government and public acceptance of the anthropogenic origin of rising CO 2 emissions and associated climate change from such combustible carbon, are driving academic and commercial research into new sustainable routes to fuel and chemicals. The quest for such sustainable resources to meet the demands of a rapidly rising global population represents one of this century's grand challenges. Here, we discuss catalytic solutions to the clean synthesis of biodiesel, the most readily implemented and low cost, alternative source of transportation fuels, and oxygenated organic molecules for the manufacture of fine and speciality chemicals to meet future societal demands.

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“…A combined ESTEM and ETEM system with both probe and image correctors has been built in-house at York on a JEOL 2200 FS platform, with full performance of the core retained uncompromised and in parts enhanced. Full HAADF STEM Z-contrast imaging with single atom resolution and sensitivity is enabled, as is high quality EDX analysis (now enhanced rather than diminished by additional column apertures), and introduces key new mapping functionalities [6]. Even with our early (2006) platform system at York, we have sub-Angstrom (<0.1nm) imaging in both ETEM and ESTEM modes.…”

mentioning

confidence: 99%

“…Even with our early (2006) platform system at York, we have sub-Angstrom (<0.1nm) imaging in both ETEM and ESTEM modes. Furnace holder electronics must be improved for ESTEM resolution [6] but the introduction of high stability MEMS hot stages (here by DENS Solutions) have greatly improved diverse applications. Short mark (exposure) to long space (beam blanked) ratios can now be used to analyse and limit e-beam effects which could otherwise lead to chemical artefact sampling.…”

mentioning

confidence: 99%

Whys and Wherefores of Open Aperture ESTEM for in-situ Catalyst Reaction Studies

Boyes

Gai

2018

Microsc Microanal

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Heterogeneous solid-state catalysts for gas reaction chemistry, often with nanoparticle or single atom active phases highly dispersed on ceramic supports, are widely used in chemical industry manufacturing and for environmental controls. Catalysis contributes to >25% of GDP as well as to societal well-being. The goal of ESTEM is single atom resolution in-situ studies of continuous dynamic chemical reaction processes under realistic conditions of controlled gas atmosphere and specimen temperature. It accesses key intermediate reaction states which may only exist in dynamic in-situ experiments with continuous gas flow, because they may be metastable with respect to reaction conditions of temperature or gas environment. They cannot therefore be studied reliably ex-situ. Many reactive species have to be restored or activated in the reactor after transfer through air, as is common practice industrially, and we need to do something similar to achieve real world relevant results. Catalyst surfaces deactivate chemically and by single atom and small particle migration, leading to the growth of larger entities with a lower fraction of surface atoms accessible for active reaction (the bang-for-buck criterion); and even fewer in favoured low co-ordination selective sites. The mechanisms and dynamics of the underlying deactivation processes, atom-by-atom, determine reaction outcomes and thereby the feasibility and costs of commercial reactor processes. ESTEM analyses of single atoms attached to nanoparticle surfaces and existing independently guide better operational practices in existing processes and new developments.There is a long history of environmental facilities on older TEMs, reviewed by Butler and Hale [1], which took off scientifically at modest (nms) resolution with the HVEMs of the 1970s (Swann [2], Gai [3], and in contemporaneous TEM projects. HR ETEM came in with the purpose-built E-conversion of a then state-of-the-art Phillips CM30 HRTEM in the early 1990s (at DuPont Co, USA, Boyes and Gai [4]). The approach was based on the then innovative and now standard multiple differentially pumped ECELL apertures up and down the microscope column; starting inside the tip of each objective lens polepiece, rather than in the gap; and adding new gas tolerant TMP pumping systems while retaining resolution. In this way the highest pressure gas region is restricted to a few mm of beam path length and with sub-mbar or low mbar gas pressures does not affect resolution. This design is very successful for TEM, producing 100s of publications from ~20 sites globally using commercial instruments based on the DuPont design. More recent versions benefit from TEM image aberration correction. This is especially important for dynamic in-situ experiments where image interpretation often needs to be based on single images (at optimum, near zero, defocus) of ever changing scenes, restricting use of the usual through focal series, and to enable high contrast TEM imaging with small amounts of negative Cs [5].A revised approach is needed to ...

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ESTEM imaging of single atoms under controlled temperature and gas environment conditions in catalyst reaction studies

Cited by 70 publications

References 28 publications

Visualizing reacting single atoms in chemical reactions: Advancing the frontiers of materials research

Visualizing reacting single atoms in chemical reactions: Advancing the frontiers of materials research

Catalysing sustainable fuel and chemical synthesis

Whys and Wherefores of Open Aperture ESTEM for in-situ Catalyst Reaction Studies

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