Phase Separation of CuPd Alloy Nanocatalysts in CO Oxidation.

Alloy nanocatalysts exhibit enhanced activity, selectivity, and stability mainly due to their versatile phases and atomic structures. However, nanocatalysts' "real" functional structures may vary from their as-synthesized status due to the structural and chemical changes during the activation and reaction conditions. Herein, we studied the activated CuPd/CeO nanocatalysts under the CO oxidation reaction featuring an atomic-scale phase separation process, resulting in a notable "hysteresis" in catalyst performance.

Deciphering the Metal-Support Interaction of Au/ZnO Catalyst Induced by H and O Pretreatment.

Metal-support interaction (MSI) provides great possibilities to tune the activity, selectivity, and stability of heterogeneous catalysts. Herein, the Au/ZnO catalyst is prepared by commercial ZnO and chloroauric acid, and the structure evolution of the catalyst pretreated by H and O gas at varied temperature is investigated to provide mechanistic insights of MSI. It is found that the H treatment at 300 °C and above can induce the formation of both the ZnO overlayer and bulk Au-Zn alloy.

In Situ Structural Dynamics of Atomic Defects in Tungsten Oxide.

Atomic defects are critical to tuning the physical and chemical properties of functional materials such as catalysts, semiconductors, and 2D materials. However, direct structural characterization of atomic defects, especially their formation and annihilation under practical conditions, is challenging yet crucial to understanding the underlying mechanisms driving defect dynamics, which remain mostly elusive. Here, through atomic imaging by an aberration-corrected environmental transmission electron microscope (AC-ETEM), we directly visualize the formation and annihilation mechanism of planar defects in monoclinic WO on the atomic scale in real time.

Revealing synergetic structural activation of a CuAu surface during water-gas shift reaction.

Bimetallic alloy catalysts show strong structural and compositional dependence on their activity, selectivity, and stability. Often referred to as the “synergetic effect” of two metal elements in the alloys, their detailed dynamic information, structurally and chemically, of catalyst surface under reaction conditions remains largely elusive. Here, using aberration-corrected environmental transmission electron microscopy, we visualize the atomic-scale synergetic surface activation of CuAu under a water–gas shift reaction condition.

Structural Evolution of Cu/ZnO Catalysts during Water-Gas Shift Reaction: An Transmission Electron Microscopy Study.

Supported metal catalysts experience significant structural evolution during the activation process and reaction conditions, which is critical to achieve a desired active surface and interface enabling efficient catalytic processes. However, such dynamic structural information and related mechanistic understandings remain largely elusive owing to the limitation of real-time capturing dynamic information under reaction conditions. Here, using environment transmission electron microscopy, we demonstrate the atomic-scale structural evolution of the model Cu/ZnO catalyst under relevant water-gas shift reaction (WGSR) conditions.

Atomic-Scale Interfacial Phase Transformation Governed Cu Oxidation in Water Vapor.

Metal oxidation initiates from surface adsorption to subsurface and bulk reaction through continuous interfacial phase transformation from metals to oxides. How the initial interfacial process affects the whole process of metal oxidation remains largely elusive because of the lack of direct observation of the evolving interface. Here, through atomic-scale environmental TEM observations of Cu surface reaction in water vapor, we demonstrate that the interfacial strain between the substrate and growing oxide is coupled into the continuing chemical reaction that determines the reaction kinetics.

Atomic Scale Mechanisms of Multimode Oxide Growth on Nickel-Chromium Alloy: Direct Observation of the Initial Oxide Nucleation and Growth.

The initial growth mode of oxide on alloy plays a decisive role in the development of protective oxide scales on metals and alloys, which is critical for their functionality for high temperature applications. However, the atomistic mechanisms dictating that the oxide growth remain elusive due to the lack of direct observation of the initial oxide nucleation and growth at atomic-scale. Herein, we employed environmental transmission electron microscopy and the first-principles calculations to elucidate the initial atomic process of nickel-chromium (Ni-Cr) alloy oxidation.

Direct Visualization of Atomic-Scale Graphene Growth on Cu through Environmental Transmission Electron Microscopy.

The functionalities of two-dimensional (2D) materials are solely determined by their perfect single-layer lattice or precisely stacking of multiple lattice planes, which is predominately determined during their growth process. Although the growth of graphene has been successfully achieved on different substrates with a large area up to millimeters, direct visualization of atomic-scale graphene growth in real time still lacks, which is vital to decipher atomistic mechanisms of graphene growth. Here, we employ aberration-corrected environmental transmission electron microscopy (AC-ETEM) to visualize the nucleation and growth of graphene at the atomic scale in real time.

Atomic-Scale Dynamic Interaction of H_{2}O Molecules with Cu Surface.

Atomic-scale interaction of water vapor with metal surfaces beyond surface adsorption under technologically relevant conditions remains mostly unexplored. Using aberration-corrected environmental transmission electron microscopy, we reveal the dynamic surface activation of Cu by H_{2}O at elevated temperature and pressure. We find a structural transition from flat to corrugated surface for the Cu(011) under low water-vapor pressure.

Dynamic Atom Clusters on AuCu Nanoparticle Surface during CO Oxidation.

Supported alloy nanoparticles are prevailing alternative low-cost catalysts for both heterogeneous and electrochemical catalytic processes. Gas molecules selectively interacting with one metal element induces a dynamic structural change of alloy nanoparticles under reaction conditions and largely controls their catalytic properties. However, such a multicomponent dynamic-interaction-controlled evolution, both structural and chemical, remains far from clear.

Real-Time Atomic-Scale Visualization of Reversible Copper Surface Activation during the CO Oxidation Reaction.

By using in situ aberration-corrected environmental transmission electron microscopy, for the first time at atomic level, the dynamic evolution of the Cu surface is captured during CO oxidation. Under reaction conditions, the Cu surface is activated, typically involving 2-3 atomic layers with the formation of a reversible metastable phase that only exists during catalytic reactions. The distinctive role of CO and O in the surface activation is revealed, which features CO exposure to lead to surface roughening and consequently formation of low-coordinated Cu atoms, while O exposure induces a quasi-crystalline CuOx phase.

Extracellular Biocoordinated Zinc Nanofibers Inhibit Malignant Characteristics of Cancer Cell.

Inhibition of the heat shock proteins (HSPs) has been considered to be one of the promising strategies for cancer treatment. However, developing highly effective HSP inhibitors remains a challenge. Recent studies on the evolutionarily distinct functions between intracellular and extracellular HSPs (eHSPs) trigger a new direction with eHSPs as chemotherapeutic targets.