Direct visualisation of the surface atomic active sites of carbon-supported Co3O4 nanocrystals via high-resolution phase restoration

The atomic arrangement of the terminating facets on spinel Co3O4 nanocrystals is strongly linked to their catalytic performance. However, the spinel crystal structure offers multiple possible surface terminations depending on the synthesis. Thus, understanding the terminating surface atomic structure is essential in developing high-performance Co3O4 nanocrystals. In this work, we present direct atomic-scale observation of the surface terminations of Co3O4 nanoparticles supported on hollow carbon spheres (HCSs) using exit wavefunction reconstruction from aberration-corrected transmission electron microscopy focal-series. The restored high-resolution phases show distinct resolved oxygen and cobalt atomic columns. The data show that the structure of {100}, {110}, and {111} facets of spinel Co3O4 exhibit characteristic active sites for carbon monoxide (CO) adsorption, in agreement with density functional theory calculations. Of these facets, the {100} and {110} surface terminations are better suited for CO adsorption than the {111}. However, the presence of oxygen on the {111} surface termination indicates this facet also plays an essential role in CO adsorption. Our results demonstrate direct evidence of the surface termination atomic structure beyond the assumed stoichiometry of the surface

Cryogenic electron ptychographic single particle analysis with wide bandwidth information transfer

Advances in cryogenic transmission electron microscopy have revolutionised the determination of many macromolecular structures at atomic or near-atomic resolution. This method is based on conventional defocused phase contrast imaging. However, it has limitations of weaker contrast for small biological molecules embedded in vitreous ice, in comparison with cryo-ptychography, which shows increased contrast. Here we report a single-particle analysis based on the use of ptychographic reconstruction data, demonstrating that three dimensional reconstructions with a wide information transfer bandwidth can be recovered by Fourier domain synthesis. Our work suggests future applications in otherwise challenging single particle analyses, including small macromolecules and heterogeneous or flexible particles. In addition structure determination in situ within cells without the requirement for protein purification and expression may be possible

2020 roadmap on solid-state batteries

Li-ion batteries have revolutionized the portable electronics industry and empowered the electric vehicle (EV) revolution. Unfortunately, traditional Li-ion chemistry is approaching its physicochemical limit. The demand for higher density (longer range), high power (fast charging), and safer EVs has recently created a resurgence of interest in solid state batteries (SSB). Historically, research has focused on improving the ionic conductivity of solid electrolytes, yet ceramic solids now deliver sufficient ionic conductivity. The barriers lie within the interfaces between the electrolyte and the two electrodes, in the mechanical properties throughout the device, and in processing scalability. In 2017 the Faraday Institution, the UK's independent institute for electrochemical energy storage research, launched the SOLBAT (solid-state lithium metal anode battery) project, aimed at understanding the fundamental science underpinning the problems of SSBs, and recognising that the paucity of such understanding is the major barrier to progress. The purpose of this Roadmap is to present an overview of the fundamental challenges impeding the development of SSBs, the advances in science and technology necessary to understand the underlying science, and the multidisciplinary approach being taken by SOLBAT researchers in facing these challenges. It is our hope that this Roadmap will guide academia, industry, and funding agencies towards the further development of these batteries in the future

Transmission electron microscopy of titanium dioxide nanoplatelets and nanorods

As the size of the bulk crystal reduces to the nanometre scale, anatase titania exhibits enhanced photocatalytic properties. Nanostructuring of TiO2 involves engineering the crystal facets in a way that speci c types of surfaces dominate the 3D shape. The atomic structure of the surfaces and 3D morphology of the crystal determine the electronic properties of the material, and should be characterized with atomic precision. Due to its high spatial resolution (0.1 nm), aberration-corrected transmission electron microscopy was used to obtain morphological and structural information on anatase nanoplatelets and nanorods. TEM morphological analysis showed that the main 3D shape of the platelets is that of a truncated tetragonal bipyramid, where f001g facets dominate. This 3D shape is accessible via 2D projections of the crystal structure. In the nanorod specimens, the types of edge morphology found link to intermediate or nal stages of growth, occurred via oriented attachment of primary nanocrystals and classical monomer addition. The structural characterization of the nanocrystals was carried out by examining the exit plane wave of the specimen, which was reconstructed from a serial acquisition of aberration-corrected TEM images of di erent defocus. The phase of the reconstructed wave reproduces the atomic potential of the specimen, and provides information with the maximum resolution of the microscope. The optical properties of the platelets and rods were also analysed using a combination of STEM imaging and EELS. Due to the high surface to volume ratio of the platelets, the EELS spectrum is dominated by strong surface features that arise from the polarization of the surface electrons induced by the electron beam. The in uence of the surface excitations on the EELS spectrum is strongly determined by the thickness of the platelets: by modifying the crystal thickness below 20 nm, the frequency of the surface excitations changes, enabling the optical properties of titania to be tuned in the visible and UV range. Finally, preliminary EELS investigations on the nanorods suggest that, unlike metallic nanoparticles, the surface excitations are not in uenced by the morphology of the crystal, but strongly depend on its thickness.Open Acces

Role of the Deep Eutectic Solvent Reline in the Synthesis of Gold Nanoparticles.

This work presents a mechanistic understanding of the synthesis of small (<3 nm) gold nanoparticles in a nontoxic, eco-friendly, and biodegradable eutectic mixture of choline chloride and urea (reline) without the addition of external reducing or stabilization agents. Reline acts as a reducing agent by releasing ammonia (via urea hydrolysis), forming gold nanoparticles even at trace ammonia concentration levels. Reline also affects the speciation of the gold precursor forming gold chloro-complexes, stabilizing Au+ species, leading to an easier reduction and avoiding the otherwise fast disproportionation reaction. Such a capability is however lost in the presence of large amounts of water, where water replaces the chloride ligands in the precursor speciation. In addition, reline acts as a weak stabilizing agent, leading to small particles (<3 nm) and narrow distributions although agglomerates quickly form. Such properties are maintained in the presence of water, indicating that it is linked to the urea stabilization rather than the hydrogen-bonding network. This work has important implications in the field of green synthesis of nanoparticles with small sizes, especially for biomedical and health care applications, due to the nontoxic nature of the components of deep eutectic solvents in contrast to the conventional routes