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Understanding the structure and behavior of intermediates in chemical reactions is the key to developing greater control over the reaction outcome. This principle is particularly important in the synthesis of metal nanocrystals (NCs), where the reduction, nucleation, and growth of the reaction intermediates will determine the final size and shape of the product. The shape of metal NCs plays a major role in determining their catalytic, photochemical, and electronic properties and, thus, the potential applications of the material. In this work, we demonstrate that layered coordination polymers, called lamellae, are reaction intermediates in Cu NC synthesis. Importantly, we discover that the lamella structure can be fine-tuned using organic ligands of different lengths and that these structural changes control the shape of the final NC. Specifically, we show that short-chain phosphonate ligands generate lamellae that are stable enough at the reaction temperature to facilitate the growth of Cu nuclei into anisotropic Cu NCs, being primarily triangular plates. In contrast, lamellae formed from long-chain ligands lose their structure and form spherical Cu NCs. The synthetic approach presented here provides a versatile tool for the future development of metal NCs, including other anisotropic structures.

All the indications are that the cultural sphere and the 'creative industries' altogether will be facing lean times in the coming years, especially as concerns funding. It is therefore high [...]

Among the perovskites used to catalyze the oxygen evolution reaction (OER), Ba0.5Sr0.5Co0.8Fe0.2O3−δ(BSCF) exhibits excellent activity which is thought to be related to dynamic reconstruction at the flexible perovskite surface due to accommodation of large amount of oxygen vacancies. By studying the local structure and chemistry of BSCF surfaces, in detail, via a range of transmission electron microscopy (TEM) methods, we show that the surfaces of the as-synthesized BSCF particles are Co/Fe rich, and remarkably, adopt a spinel-like structure with a reduced valence of Co ions. Post-mortem and identical location TEM analyses reveal that the Co/Fe spinel-like surface retains a stable chemical environment of the Co/Fe ions, although its structure weakens after electrochemical processing. Further, it is verified that prior to the onset of OER, the Co/Fe spinel-like surface promotes the formation of the highly active Co(Fe)OOH phase, which enhances the OER electrocatalytic properties of the underlying conductive BSCF perovskite. This study provides a detailed understanding of the fundamental transformations that oxide catalysts undergo during electrochemical processes and can aid in the development of novel oxide catalysts with enhanced activity.

Liquid-phase transmission electron microscopy (LPTEM) is an essential tool for studying the dynamics of materials interactions at the nanoscale, in and/or with their operational environment. Microfabricated SiNxmembrane cells further allow the integration of thin-film electrodes that opens the technique to studies of heterogeneous electrocatalysts under relevant electrochemical conditions. However, experiments remain challenging and the characteristics of the dedicated electrochemical cells and of the interactions of the electron beam with the liquid electrolyte demand careful interpretation of the results. Herein, we discuss important aspects that concern the implementation of electrochemical LPTEM (ec-LPTEM). We first consider the range of information that can be accessible with the technique for electrocatalytic applications and we detail the influence of the thickness and flow of liquid electrolytes using membrane-based microcells. Further, we provide guidelines pertinent to the electrochemical configuration of the substrate working, reference, and counter electrodes. We validate these considerations by experimentally demonstrating the application of ec-LPTEM for the CO2reduction reaction (CO2RR), the oxygen reduction reaction (ORR), and the oxygen evolution reaction (OER). The probed effects in metallic and oxide catalysts are directly related to the applied electrochemical stimuli and corroborate the representativity of the processes under investigation following the considerations described herein.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.