Understanding the Growth of Electrodeposited PtNi Nanoparticle Films Using Correlated Liquid Cell Transmission Electron Microscopy and Synchrotron Radiation.

Electrodeposition is a versatile method for synthesizing nanostructured films, but controlling the morphology of films containing two or more elements requires a detailed understanding of the deposition process. We used liquid cell transmission electron microscopy to follow the electrodeposition of PtNi nanoparticle films on a carbon electrode during cyclic voltammetry. These observations show that the film thickness increases with each cycle, and by the fourth cycle, branched and porous structures could be deposited.

Electrocatalytic Nitrate and Nitrite Reduction toward Ammonia Using CuO Nanocubes: Active Species and Reaction Mechanisms.

The electrochemical reduction of nitrate (NO) and nitrite (NO) enables sustainable, carbon-neutral, and decentralized routes to produce ammonia (NH). Copper-based materials are promising electrocatalysts for NO conversion to NH. However, the underlying reaction mechanisms and the role of different Cu species during the catalytic process are still poorly understood.

Enhanced Methanol Synthesis from CO Hydrogenation Achieved by Tuning the Cu-ZnO Interaction in ZnO/CuO Nanocube Catalysts Supported on ZrO and SiO.

The nature of the Cu-Zn interaction and especially the role of Zn in Cu/ZnO catalysts used for methanol synthesis from CO hydrogenation are still debated. Migration of Zn onto the Cu surface during reaction results in a Cu-ZnO interface, which is crucial for the catalytic activity. However, whether a Cu-Zn alloy or a Cu-ZnO structure is formed and the transformation of this interface under working conditions demand further investigation.

insights into correlating CO coverage and Cu-Au alloying with the selectivity of Au NP-decorated CuO nanocubes during the electrocatalytic CO reduction.

Electrochemical reduction of CO (CORR) is an attractive technology to reintegrate the anthropogenic CO back into the carbon cycle driven by a suitable catalyst. This study employs highly efficient multi-carbon (C) producing CuO nanocubes (NCs) decorated with CO-selective Au nanoparticles (NPs) to investigate the correlation between a high CO surface concentration microenvironment and the catalytic performance. Structure, morphology and near-surface composition are studied X-ray absorption spectroscopy and surface-enhanced Raman spectroscopy, high-energy X-ray diffraction as well as quasi X-ray photoelectron spectroscopy.

Reversible Structural Evolution of Metal-Nitrogen-Doped Carbon Catalysts During CO Electroreduction: An Operando X-ray Absorption Spectroscopy Study.

Electrochemical CO reduction (CO RR) is a rising technology, aiming to reduce the energy sector dependence on fossil fuels and to produce carbon-neutral raw materials. Metal-nitrogen-doped carbons (M-N-C) are emerging, cost-effective catalysts for this reaction; however, their long-term stability is a major issue. To overcome this, understanding their structural evolution is crucial, requiring systematic in-depth operando studies.

Electron Microscopy of Catalysts: The Missing Cornerstone in Heterogeneous Catalysis Research?

Heterogeneous catalysis in thermal gas-phase and electrochemical liquid-phase chemical conversion plays an important role in our modern energy landscape. However, many of the structural features that drive efficient chemical energy conversion are still unknown. These features are, in general, highly distinct on the local scale and lack translational symmetry, and thus, they are difficult to capture without the required spatial and temporal resolution.

Spatially and Chemically Resolved Visualization of Fe Incorporation into NiO Octahedra during the Oxygen Evolution Reaction.

The activity of Ni (hydr)oxides for the electrochemical evolution of oxygen (OER), a key component of the overall water splitting reaction, is known to be greatly enhanced by the incorporation of Fe. However, a complete understanding of the role of cationic Fe species and the nature of the catalyst surface under reaction conditions remains unclear. Here, using a combination of electrochemical cell and conventional transmission electron microscopy, we show how the surface of NiO electrocatalysts, with initially well-defined surface facets, restructures under applied potential and forms an active NiFe layered double (oxy)hydroxide (NiFe-LDH) when Fe ions are present in the electrolyte.

Shape-Dependent CO Hydrogenation to Methanol over CuO Nanocubes Supported on ZnO.

The hydrogenation of CO to methanol over Cu/ZnO-based catalysts is highly sensitive to the surface composition and catalyst structure. Thus, its optimization requires a deep understanding of the influence of the pre-catalyst structure on its evolution under realistic reaction conditions, including the formation and stabilization of the most active sites. Here, the role of the pre-catalyst shape (cubic vs spherical) in the activity and selectivity of ZnO-supported Cu nanoparticles was investigated during methanol synthesis.

Periodic structural changes in Pd nanoparticles during oscillatory CO oxidation reaction.

Nanoparticle (NP) catalysts are ubiquitous in energy systems, chemical production, and reducing the environmental impact of many industrial processes. Under reactive environments, the availability of catalytically active sites on the NP surface is determined by its dynamic structure. However, atomic-scale insights into how a NP surface reconstructs under reaction conditions and the impact of the reconstruction on catalytic activity are still lacking.

Iodide-mediated Cu catalyst restructuring during CO electroreduction.

Catalyst restructuring during electrochemical reactions is a critical but poorly understood process that determines the underlying structure-property relationships during catalysis. In the electrocatalytic reduction of CO (CORR), it is known that Cu, the most favorable catalyst for hydrocarbon generation, is highly susceptible to restructuring in the presence of halides. Iodide ions, in particular, greatly improved the catalyst performance of Cu foils, although a detailed understanding of the morphological evolution induced by iodide remains lacking.

Highly Stable and Reactive Platinum Single Atoms on Oxygen Plasma-Functionalized CeO Surfaces: Nanostructuring and Peroxo Effects.

Atomically dispersed precious metals on oxide supports have recently become increasingly interesting catalytic materials. Nonetheless, their non-trivial preparation and limited thermal and environmental stability constitutes an issue for their potential applications. Here we demonstrate that an oxygen plasma pre-treatment of the ceria (CeO ) surface serves to anchor Pt single atoms, making them active and resistant towards sintering in the CO oxidation reaction.

Dynamic transformation of cubic copper catalysts during CO electroreduction and its impact on catalytic selectivity.

To rationally design effective and stable catalysts for energy conversion applications, we need to understand how they transform under reaction conditions and reveal their underlying structure-property relationships. This is especially important for catalysts used in the electroreduction of carbon dioxide where product selectivity is sensitive to catalyst structure. Here, we present real-time electrochemical liquid cell transmission electron microscopy studies showing the restructuring of copper(I) oxide cubes during reaction.

Growth Dynamics of Vertical and Lateral Layered Double Hydroxide Nanosheets during Electrodeposition.

Layered double hydroxides (LDHs) are a class of lamellar materials with a wide range of potential catalytic applications. LDHs form from positively charged 2D atomic layers separated by charge-balancing anions and solvent molecules. Typically, nanoscale LDH sheets can grow vertical or parallel to a substrate, exposing their different active facets.

Selectivity Control of Cu Nanocrystals in a Gas-Fed Flow Cell through CO Pulsed Electroreduction.

In this study, we have taken advantage of a pulsed CO electroreduction reaction (CORR) approach to tune the product distribution at industrially relevant current densities in a gas-fed flow cell. We compared the CORR selectivity of Cu catalysts subjected to either potentiostatic conditions (fixed applied potential of -0.7 V) or pulsed electrolysis conditions (1 s pulses at oxidative potentials ranging from = 0.

andelectron microscopy in heterogeneous catalysis-insights into multi-scale chemical dynamics.

This review features state-of-the-artandelectron microscopy (EM) studies of heterogeneous catalysts in gas and liquid environments during reaction. Heterogeneous catalysts are important materials for the efficient production of chemicals/fuels on an industrial scale and for energy conversion applications. They also play a central role in various emerging technologies that are needed to ensure a sustainable future for our society.

Operando high-pressure investigation of size-controlled CuZn catalysts for the methanol synthesis reaction.

Although Cu/ZnO-based catalysts have been long used for the hydrogenation of CO to methanol, open questions still remain regarding the role and the dynamic nature of the active sites formed at the metal-oxide interface. Here, we apply high-pressure operando spectroscopy methods to well-defined Cu and CuZn nanoparticles supported on ZnO/AlO, γ-AlO and SiO to correlate their structure, composition and catalytic performance. We obtain similar activity and methanol selectivity for Cu/ZnO/AlO and CuZn/SiO, but the methanol yield decreases with time on stream for the latter sample.

Three-step nucleation of metal-organic framework nanocrystals.

Metal-organic frameworks (MOFs) are crystalline nanoporous materials with great potential for a wide range of industrial applications. Understanding the nucleation and early growth stages of these materials from a solution is critical for their design and synthesis. Despite their importance, the pathways through which MOFs nucleate are largely unknown.

A data reduction and compression description for high throughput time-resolved electron microscopy.

Fast, direct electron detectors have significantly improved the spatio-temporal resolution of electron microscopy movies. Preserving both spatial and temporal resolution in extended observations, however, requires storing prohibitively large amounts of data. Here, we describe an efficient and flexible data reduction and compression scheme (ReCoDe) that retains both spatial and temporal resolution by preserving individual electron events.

Dynamic Imaging of Nanostructures in an Electrolyte with a Scanning Electron Microscope.

The development of microfabricated liquid cells has enabled dynamic studies of nanostructures within a liquid environment with electron microscopy. While such setups are most commonly found in transmission electron microscope (TEM) holders, their implementation in a scanning electron microscope (SEM) offers intriguing potential for multi-modal studies where the large chamber volume allows for the integration of multiple detectors. Here, we describe an electrochemical liquid cell SEM platform that employs the same cells enclosed by silicon nitride membrane windows found in liquid cell TEM holders and demonstrate the imaging of copper oxide nanoparticles in solution using both backscattered and transmitted electrons.

Enhanced Formic Acid Oxidation over SnO-decorated Pd Nanocubes.

The formic acid oxidation reaction (FAOR) is one of the key reactions that can be used at the anode of low-temperature liquid fuel cells. To allow the knowledge-driven development of improved catalysts, it is necessary to deeply understand the fundamental aspects of the FAOR, which can be ideally achieved by investigating highly active model catalysts. Here, we studied SnO-decorated Pd nanocubes (NCs) exhibiting excellent electrocatalytic performance for formic acid oxidation in acidic medium with a SnO promotion that boosts the catalytic activity by a factor of 5.

Growth Dynamics and Processes Governing the Stability of Electrodeposited Size-Controlled Cubic Cu Catalysts.

The renewable energy-powered conversion of industrially generated CO into useful chemicals and fuels is considered a promising technology for the sustainable development of our modern society. The electrochemical reduction of CO (CORR) is one of the possible conversion processes that can be employed to close the artificial carbon cycle, mimicking nature's photosynthesis. Nevertheless, to enable green catalytic processes, selectivity for the desired products must be achieved.

Two-dimensional adaptive membranes with programmable water and ionic channels.

Membranes are ubiquitous in nature with primary functions that include adaptive filtering and selective transport of chemical/molecular species. Being critical to cellular functions, they are also fundamental in many areas of science and technology. Of particular importance are the adaptive and programmable membranes that can change their permeability or selectivity depending on the environment.

Partitioning the interlayer space of covalent organic frameworks by embedding pseudorotaxanes in their backbones.

Mono- or few-layer sheets of covalent organic frameworks (COFs) represent an attractive platform of two-dimensional materials that hold promise for tailor-made functionality and pores, through judicious design of the COF building blocks. But although a wide variety of layered COFs have been synthesized, cleaving their interlayer stacking to obtain COF sheets of uniform thickness has remained challenging. Here, we have partitioned the interlayer space in COFs by incorporating pseudorotaxane units into their backbones.