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The current energy transition presents many technological challenges, such as the development of highly stable catalysts. Herein, we report a novel "top‐down" synthesis approach for preparation of a single‐site Mo‐containing nanosized ZSM‐5 zeolite which has atomically dispersed framework‐molybdenum homogenously distributed through the zeolite crystals. The introduction of Mo heals most of the native point defects in the zeolite structure resulting in an extremely stable material. The important features of this single‐site Mo‐containing ZSM‐5 zeolite are provided by an in‐depth spectroscopic and microscopic analysis. The material demonstrates superior thermal (up to 1000 °C), hydrothermal (steaming), and catalytic (converting methane to hydrogen and higher hydrocarbons) stability, maintaining the atomically disperse Mo, structural integrity of the zeolite, and preventing the formation of silanols. [ABSTRACT FROM AUTHOR]

• The genesis of Pd nanocatalysts on Al 2 O 3 can be adequately followed by in situ ETEM. • Fast tomography in ETEM unravels the 3D evolution of NPs during calcination. • Oxidation and reduction of Pd NPs is followed down to the atomic scale in ETEM. • In situ tracking of Pd NPs in ETEM evidences that they grow by Ostwald Ripening. The quality of metallic nanoparticles (NPs) used in heterogeneous catalysis relies through many aspects on their small size, on the homogeneity of their spatial distribution on their supports and on their ability to resist to sintering or coalescence. It is thus very important to quantify these parameters and understand the mechanisms controlling the growth of NPs during the genesis process of the catalyst. Whereas conventional Transmission Electron Microscopy (TEM) is currently used for these purposes, it most frequently remains a 'static' method where results are obtained in high vacuum and post mortem, i.e. after the typical drying, calcination and reduction steps without the possibility to follow directly the evolution of both NPs and supports during those treatments. Environmental TEM (ETEM) unlocks this blocking and allows elementary mechanisms, such as Ostwald Ripening and coalescence to be unravelled through direct in situ observations. We report here an ETEM study of the preparation of Pd-based narrow NPs, less than 5 nm in size, deposited on a δ-alumina support. We focused on 3 main objectives: (i) quantifying the sizes of NPs at each preparation step performed in situ under environmental (i.e. respectively oxygen or air and hydrogen atmospheres at working temperatures) and comparing them to post mortem measurements; (ii) identify the oxidation state of the NPs through an in situ High Resolution imaging study of their crystallographic structure; (iii) explore the possibilities of environmental tri-dimensional (3D) studies by tilt series based Electron Tomography. This last item represents a challenging breakthrough in the characterization of nanocatalysts; it will be demonstrated that the use of modern instruments (microscope and accessories) allows tomographic acquisitions to be performed very fast, within a few minutes and even seconds, which opens the way to the 3D tracking of microstructures almost in real time during their evolution under gas and at high temperature. [ABSTRACT FROM AUTHOR]

Electron Tomography (ET) is of greatest interest in studying nano- and biological materials since it gives access to 3D morphological, chemical and physical features. Even though ET techniques have been continuously improved in the last decades, they are still limited: lengthy time scales (tens of minutes) are generally needed for the tilt series acquisition prior to the volume reconstruction step. Such long exposures to a relatively intense electron beam lead to large electron doses received by the sample. This may promote extensive irradiation damage in the case of soft materials like polymers and bio-materials when they are not protected through dedicated sample preparation methods, and any tomographic reconstruction will then be meaningless. More importantly, the time constraints drastically limit 3D investigations during dynamic in-situ experiments where the sample rapidly evolves during the acquisition. We present here developments for acquiring tilt series of projections in very short time scales, readily down to a few seconds. After an outlook of possible ways to speed up the data acquisition in the bright field imaging mode (BF-TEM), strategies for the fastest methods in 'step-by-step' and 'continuous tilt' ET will be described. Applications of these procedures are presented on various systems, including metallic Pd nanoparticles deposited on alumina, and soft materials like polymer nanocomposites and biological matter. A special reference is made to fast operando nano-tomography performed on nanomaterials during their dynamic evolution. The feasibility of fast ET is exemplified by a calcination study of Pd catalysts supported by SiO 2 at 400 °C and 500 °C under 4 mbar H 2 in a dedicated Environmental Transmission Electron Microscope (ETEM). Unlabelled Image • Fast image acquisition for Electron Tomography (ET) can take only a few seconds. • A continuous rotation of the sample allows relevant and fast acquisition for ET. • Fast ET is possible under gas and temperature conditions in-situ in a ETEM. • Repeated acquisitions on the same object allow to follow its evolution in operando. • The resistance to sintering of Pd@SiO 2 nanocatalyst is quantified in situ in 3D. [ABSTRACT FROM AUTHOR]

With its unique redox properties, ceria is an oxide with a range of applications, including automotive catalytic converters, which consist of platinum-group metal nanoparticles on ceria-containing supports. In this work, the 3 D architecture of a ceria-based material synthesized by the widely employed glycine-nitrate solution combustion method is revealed for the first time. Together with N2 adsorption volumetry, scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM), STEM tomography provides a comprehensive picture of the multimodal porous network of a pre-reduced Pt-CeO2 catalyst, from the nanometer to the micrometer scale. This material consists of ceria nanocrystallites forming 3 D aggregates and puzzle-like 2 D walls separating large roundish mesopores and macropores. The small voids between imperfectly assembled crystallites give rise to some microporosity. In addition, it is demonstrated that a significant proportion of platinum nanoparticles (3-4 nm) are not located at the ceria surface following the one-step synthesis process, about half of them are buried within ceria. This result is valid for another metal (Rh) and another fuel (oxalyl dihydrazide), and has important implications for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Bulk nanoporous silicon prepared by top-down method form Li-ion batteries was investigated combining different conventional technique such as nitrogen physisorption and high resolution electron microscopy with electron tomography. It was found that the Si nanorods are forming porous aggregates with a half of the volume of the particle occupied by pores. The nanorods are preferentially oriented along the main axis of the aggregate. The porosity and the lack of compaction between the aggregates provide space for the Si expansion during the lithiation process. It was found that the Si nanorods mainly expose the {111} family plane as an external faces. The size distributions of the porous and solid phases in a granule were found to be similar. The pores represent 50% of the total volume of an aggregate. The shape orientation of the particles was quantified and it was found to exhibit a narrow distribution. [ABSTRACT FROM AUTHOR]

Commercial zeolites with CHA, MFI, and LTL framework topology are subjected to acid treatment with chromic acid (H 2 CrO 4) solutions with concentrations ranging between 0.1 and 10 w /%. As chromic acid forms polymeric species as a function of concentration, specific effects are obtained with these three zeolites, differing by their framework topology, pore size, Si/Al ratios and crystal size. The etched zeolites are characterized by X-ray diffraction, SEM, TEM, N 2 physisorption, ICP-AES, 27Al and 29Si MAS NMR, 29Si{1H} cross-polarization spectra, EDX. Their acidic properties are probed with pyridine and d 3 -acetonitrile by in situ FTIR. Results indicate that the 8 MR (CHA) and 10 MR (MFI) zeolites are more resistant to acid treatment with chromic acid than the 12 MR (LTL) zeolite. This paves the way for rational control of zeolite dealumination since adjusting chromic acid concentration will generate anions appropriate for treating a particular zeolite. [Display omitted] • CHA, MFI, and LTL zeolites are subjected to treatment with chromic acid (H 2 CrO 4). • Chromic acid forms polymeric species as a function of concentration. • CHA and MFI zeolites resist more to the chromic acid treatment than the LTL zeolite. • Tuning the acid concentration yields anions apt for treating a particular zeolite. [ABSTRACT FROM AUTHOR]

Fast tomography in Environmental Transmission Electron Microscopy (ETEM) is of a great interest for in situ experiments where it allows to observe 3D real-time evolution of nanomaterials under operating conditions. In this context, we are working on speeding up the acquisition step to a few seconds mainly with applications on nanocatalysts. In order to accomplish such rapid acquisitions of the required tilt series of projections, a modern 4K high-speed camera is used, that can capture up to 100 images per second in a 2K binning mode. However, due to the fast rotation of the sample during the tilt procedure, noise and blur effects may occur in many projections which in turn would lead to poor quality reconstructions. Blurred projections make classical reconstruction algorithms inappropriate and require the use of prior information. In this work, a regularized algebraic reconstruction algorithm named SIRT-FISTA-TV is proposed. The performance of this algorithm using blurred data is studied by means of a numerical blur introduced into simulated images series to mimic possible mechanical instabilities/drifts during fast acquisitions. We also present reconstruction results from noisy data to show the robustness of the algorithm to noise. Finally, we show reconstructions with experimental datasets and we demonstrate the interest of fast tomography with an ultra-fast acquisition performed under environmental conditions, i.e. gas and temperature, in the ETEM. Compared to classically used SIRT and SART approaches, our proposed SIRT-FISTA-TV reconstruction algorithm provides higher quality tomograms allowing easier segmentation of the reconstructed volume for a better final processing and analysis. [ABSTRACT FROM AUTHOR]