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Pt-based nanoparticles supported on high-surface-area carbon (HSAC) show very good properties as catalysts in polymer electrolyte membrane fuel cells (PEMFC). In many cases, however, the initial high activity of such catalysts rapidly drops as caused by various detrimental phenomena occurring in a typical electrochemical environment. In this work, a detailed study of a highly active system composed of PtCu3/HSAC nanoparticles with partially ordered structure and Pt skin with the addition of Au is performed. By using aberration-corrected scanning transmission electron microscopy, the effects of adding small amounts of gold compared to the nonmodified sample are followed through the different stages of an electrochemical cycling degradation protocol. Various morphological changes such as faceting, reshaping, and thickening of the Pt skin are investigated for both sets of samples on the atomic level. Interesting features such as well-defined shapes and surface defects are observed after degradation. However, the most important differences in terms of durability seem related to particle porosity. Finally, the experimental morphological observations are successfully reproduced by dealloying simulation with kinetic Monte Carlo modeling. [ABSTRACT FROM AUTHOR]

In this study the performance enhancement effect of structural ordering for the oxygen reduction reaction (ORR) is systematically studied. Two samples of PtCu3 nanoparticles embedded on a graphitic carbon support are carefully prepared with identical initial composition, particle dispersion and size distribution, yet with different degrees of structural ordering. Thus we can eliminate all coinciding effects and unambiguously relate the improved activity of the ORR and more importantly the enhanced stability to the ordered nanostructure. Interestingly, the electrochemically induced morphological changes are common to both ordered and disordered samples. The observed effect could have a groundbreaking impact on the future directions in the rational design of active and stable platinum alloyed ORR catalysts. [ABSTRACT FROM AUTHOR]

Time- and potential-resolved electrochemical Pt dissolution from commercial Pt and prepared PtCu alloy nanoparticulate catalysts have been studied under potentiodynamic conditions in 0.1 M HClO4 by using on-line inductively coupled plasma mass spectrometry (ICP-MS). For the first time the exact amount of dissolved Pt per cycle has been measured on real electrocatalysts. Results show clearly that Pt dissolution depends on the particle size: approximately seven times as much Pt is released into the solution from commercial 3 nm Pt particles as from a commercial 30 nm Pt sample. The stability of our prepared PtCu electrocatalyst is higher than that of a commercial 3 nm electrocatalyst, which is, however, still slightly lower than that of a commercial 30 nm Pt electrocatalyst. [ABSTRACT FROM AUTHOR]

Abstract: Novel ways to synthesize CaCO3 based matrices to increase the dissolution rate of naproxen are investigated. The composites were prepared using 3 methods, all starting from aqueous solutions of CaCl2·6H2O and NaHCO3, while the differences were in how the solutions were mixed and dried. The fast disintegration of the matrix from the composites was explained by swift dispersion of the matrix into tiny drug particles, thus allowing for their fast dissolution. Modifications in the preparation procedures resulted in formation of different portions of CaCO3 crystal forms. Despite the identical drug composition, dissolution of naproxen from the composites was considerably faster than the dissolution of pure naproxen. The dissolution was the fastest in the samples containing the highest amount of the less stable CaCO3 crystal form, vaterite. The proposed composite formulation could be interesting for per os applications where fast attainment of high blood concentration and its preservation is required. [Copyright &y& Elsevier]

Abstract: Platinum copper alloy nanoparticle catalysts supported on graphitized carbon with and without partial crystal ordering were synthesized and tested for oxygen reduction and methanol oxidation reaction for potential use in direct methanol fuel cells and proton exchange membrane fuel cells. The activity enhancement by at least a factor of 2 is possible when Pm-3m phase is present in the nanoparticle with respect to the pure Fm-3m phase. A significance of Pt-skin type catalysts concept is explained for lowering the platinum content. [Copyright &y& Elsevier]

A two-step procedure for preparation of LiMnPO4withsmall particle size (15–20 nm) and embedded in a carbon matrixis presented. The crucial point that prevents excessive particle growthis the avoidance of lithium in the first firing step, so that smallMn2P2O7particles embedded in carbonare obtained. Because of the carbon matrix, the Mn2P2O7particles also cannot grow in the second step,which involves lithiation and heating to 700 °C in argon. Theprepared LiMnPO4shows a high theoretical capacity (upto 95% of the theoretical value) and a stable cycling (>130 mAh/g,even after 100 cycles at 55 °C and a rate of C/20). At room temperatureand using the CC–CV mode, the performance is comparable tothe best result shown in the literature so far. Finally, the performanceof LiMnPO4is briefly compared with that of LiFePO4. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to attach a model drug (naproxen) onto superparamagnetic iron oxide nanoparticles (SPION). First, SPION were coated with thin layer of silica that contained micropores. We demonstrated that such surface functionalization could be optimized by the use of citric acid which prevented SPION agglomeration during the procedure. HRTEM investigation showed a uniform 1–2-nm-thick silica coating around SPION. This coating did not affect significantly the magnetic properties of the SPION. Into the coated SPION we successfully incorporated about 30wt% of naproxen. The latter was readily released after immersion into a testing solution. The composites could be interesting for potential use in diagnostics. [Copyright &y& Elsevier]

Irreversible contraction of inclusion bodies was found to have a huge impact on sedimentation velocity, solubility and extractability of target protein from non-classical inclusion bodies. The downstream process during protein isolation from non-classical IBs is also affected. Based on extractability studies accompanied by electron microscopy, a hypothetical model of IBs formation mechanism is presented, which is supported by usually observed single IB per E. coli cell. [ABSTRACT FROM AUTHOR]

• Electrochemical stability of Rh/C was studied by accelerated degradation protocols. • IL-SEM and ex-situ TEM were used to study local nanoscale degradation mechanisms. • EFC-ICP-MS was used to track Rh dissolution during degradation tests. • Severe degradation of Rh/C occurs during cycling between 0.05 V RHE and 1.4 V RHE. • Degradation of Rh/C occurs via dissolution followed by re-deposition. Electrochemical stability of a commercial Rh/C catalyst has been studied in an acidic electrolyte by accelerated degradation protocols (ADP) which involved 5000 rapid voltammetric scans (1 V/s) in two potential regions: ADP1 was performed between 0.4 V RHE and 1.4 V RHE , while ADP2 was performed between 0.05 V RHE and 1.4 V RHE. Degradation of Rh/C was monitored by the changes in Rh electrochemical surface area (ECSA) and electrocatalytic activity for hydrogen evolution (HER) and oxygen reduction (ORR). Rh/C catalyst was particularly stable during ADP1 showing only a minor loss of ECSA, while its electrocatalytic activity for HER and ORR was practically unaffected, which was further corroborated with identical location SEM (IL-SEM) imaging. In the case of ADP2, severe degradation of Rh/C occurred followed by substantial decay in its electrocatalytic activity. Coupling of the electrochemical flow cell (EFC) with ICP-MS revealed much higher Rh dissolution in ADP2 than in ADP1. IL-SEM in combination with ex-situ TEM imaging showed that degradation of the Rh/C sample is not homogeneous during ADP2, as dissolution prevails on certain locations, while dissolution followed by re-deposition occurs on others. According to the results obtained in this work, Rh/C catalysts are exceptionally sensitive to the sudden potential jumps between particularly low and high values. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal annealing processes for supported Pt-based nanoparticles are usually developed based on iterative empirical findings resulting from ex-situ characterization of pre- and post-annealed samples. Such an approach, however, offers limited insight into processes occurring during the heating step. In this work, we first exemplify typical findings that are accessible by ex-situ investigation using typical conventional techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), and thin film – rotating disc electrode (TF-RDE). As a model system we select a well-researched Pt-Cu alloy which, as demonstrated, offers exciting new insights into the dynamics occurring during heat treatment on the nano-to-atomic scale. This dynamics can be viewed by upgrading the ex-situ findings with a high resolution TEM imaging in combination with carefully designed in-situ heating protocol. This way one can directly observe the particle growth mechanisms during heat treatment. Such direct observations, in turn, provide new understanding of morphology-performance correlations in alloys. For example, it is shown that the enhanced activity of the present PtCu 3 /C electrocatalyst is due to Cu enrichment during heat treatment. This enrichment, however, is only possible due to the presence of relatively large excess CuO needle-like particles left over from the previous double passivation galvanic displacement step. Very importantly, we further show that the mechanism of Cu enrichment at elevated temperatures involves migration of Cu single atoms via the carbon support. At moderate temperatures (up to 500 °C), other effects have also been observed such as reshaping into a sphere-like shape as well as ordering of the crystal lattice which could not occur without enrichment of the initial Pt-Cu nanoparticles with Cu. In that region, Cu enrichment is also responsible for the initial growth of PtCu nanoparticles. By contrast, upon heating till 800 °C, the growth is mainly due to coalescence. Ostwald ripening, on the other hand, does not seem to play a significant role in the increase in the nanoparticle size. The new general insights can be readily extended to various other similar alloy systems. Image 1 • In-situ heating TEM provides detailed insight into the process of alloy formation during the heating step. • The present Pt-Cu system was found to be a good model system for the study of dynamics on the nano-to-atomic scale. • Nanoparticle growth mechanisms were studied both in-situ and at identical location. • Evaporation of the less noble metal was observed upon in-situ heating to 800 °C or higher under TEM conditions. [ABSTRACT FROM AUTHOR]