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Bifunctional oxygen electrocatalysts have great potentials for energy storage and conversion applications. Here we report a facile strategy toward bifunctional electrocatalysts by supporting mixed platinum and cobalt oxide nanoparticles on carbon black. The composite electrocatalyst (denoted as Pt+CoOx/C) is found to exhibit higher oxygen evolution reaction (OER) activity than CoOx/C, but slightly lower oxygen reduction reaction (ORR) activity than Pt/C in alkaline electrolytes. The bifunctional catalytic performance is ascribed to the in situ formation of heterogenous platinum-cobalt (hydro)oxide (Pt-CoOxHy) interfaces under the electrochemical reaction conditions. Calculated electrochemical phase (Pourbaix) diagrams suggest that the migration of Co species was driven by the relative stability of Pt-CoOxHy interfaces versus bulk (hydroxy)oxides or aqueous ions of cobalt. [ABSTRACT FROM AUTHOR]

All-solid-state Li-ion batteries (ASSLiB) attracted lots of attention mainly due to their higher safety compared with commercial Li-ion batteries. The research of solid electrolyte is critical for the development of ASSLiB, and among all the candidates of solid electrolytematerials, amorphous Lithium Lanthanum Titanate Oxide (LLTO) is promising because of its outstanding electrochemical stability up to 12V. However, the fundamental relationship among the ionic conductivity, microstructure, and mechanism of Li ion transport is still unrevealed. In this study, both amorphous LLTO thin film and LLTO powder were successfully prepared by sol-gel process. In order to determine the relationship between microstructure and ionic conductivity, various annealing time at 500°C were applied. This work shows that the ionic conductivity increases from 2.32 × 10-8 S/cm to 9.01 × 10-6 S/cm with the annealing time before LLTO starts to crystallize and decreases back to ~1.6 × 10-9 S/cm after the formation of crystal phase. The absolute value of difference is close to 3 orders of magnitude. Furthermore, the morphology of the thin film changes accordingly, solvent evaporation, surface refinement and crystallization phases would occur sequentially, and this indicates that there is an optimal synthesis condition for the LLTO film. However, the changes of structure, morphology and ionic conductivity does not affect activation energy. This will help researchers to find optimized synthesis condition of amorphous LLTO and potentially search for and design other solid electrolyte materials. [ABSTRACT FROM AUTHOR]

Carbon supports are vital for a wide range of electrochemical reactions, yet the production of useful carbon supports largely relies on costly precursors and fabrication methods. Here, we present a new economical process to fabricate carbon-based supports for electrocatalysts using recycled tire rubber as the main feedstock. Using the oxygen reduction reaction (ORR) as an example, we deposited Pt nanocubes on tire-derived carbon with different textural properties and surface chemistries. Our results show that Pt nanocubes are most effective toward the ORR when loaded onto tire-derived carbon with an increased electrochemically active surface area, a decreased average pore diameter, low sulfur content, and good crystallinity. These properties collectively allow for high dispersion of Pt nanocubes onto the tire-derived carbon support, and hence, increase the activity toward oxygen reduction. When benchmarked against a commercial carbon black support (Ketjen-300), the tire-derived carbon support achieved similar performance. Our results highlight an effective approach to converting waste tires into carbon supports for electrocatalysis. [ABSTRACT FROM AUTHOR]

The article takes a look at functional electron microscopy for electrochemistry research from the atomic to the micro level. Topics covered include the advances in various in situ techniques and platforms that allow the observation of dynamic processes under various external stimuli inside an electron microscope, and electron microscopy studies revealing unexpected structural and chemical evolutions at atomic-scale.

Delafossite CuCrO2 and spinel CuCr2O4 with mesoporous structures have been successfully synthesized using nanocasting methods based on a KIT-6 template. The functional activity of the mesoporous materials was evaluated in applications as heterogeneous catalysts. The activity for photocatalytic hydrogen production of the delafossite structures with different morphologies was characterized and the oxidation state changes associated with photocorrosion of Cu+ investigated using electron energy loss spectroscopy (EELS). Mg2+ doping was found to facilitate the casting of ordered structures for CuCrO2 and improves the photocorrosion resistance of delafossite structures. The mesoporous spinel CuCr2O4 nanostructures were found to be active for low temperature CO oxidation. [ABSTRACT FROM AUTHOR]

High voltage Li-ion cathodes push the limits of stability for both cathode and electrolyte. Here sub-nanometer coatings of an amorphous thin-film electrolyte (Lipon) improved the room temperature and 60°C cycling stability of a LiMn1.5Ni0.5O4 spinel cathode when charged to 4.9 V with a standard LiPF6 carbonate electrolyte. The cathodes delivered superior C-rate performances up to a 5C discharge, when compared to the uncoated cathodes. Enhanced performance extended for at least 100 cycles. Electrochemical impedance spectroscopy indicates that Lipon slows the increase of interface resistance. Thicker 1-3 nm Lipon coatings are sufficiently insulating as to block electronic transport to the cathode particles. Thick coatings also slow Mn dissolution. Results suggest that Lipon may act to scavenge impurities or block active sites that promote electrolyte decomposition. While greatly improved by the Lipon coating, cycling is not yet sufficiently stable for applications requiring thousands of cycles or prolonged operation at higher temperatures. Further work is needed to assess what surface properties of coatings will ultimately stabilize the high voltage cathodes in carbonate liquid electrolyte cells. Comments include insight from other studies of Lipon-coated cathodes and the focus for future research. [ABSTRACT FROM AUTHOR]

Relations between synthesis conditions, detailed crystal structures, and electrochemical properties of the Li-excess layered oxides Li[NixLi1/3-2x/3Mn2/3-x/3]O2(O < x < ½) are studied by X-ray diffraction, scanning electron microscopy (EELS), X-ray photo- electron spectroscopy (XPS), transmission electron microscopy (TEM), and electron energy-loss spectrometry, combined with electrochemical property measurements including potentiostatic intermittent titration technique (PITT). Optimal synthesis conditions are obtained for stoichiometric samples sintered at 1000°C in air followed by furnace cooling. The materials exhibit capacities of ~ 250, 230, and 200 mAh/g within a voltage range of 2-4.8 V on discharge for x = 1/5, ¼ and 1/3, respectively. Diffraction data of electrochemically cycled electrode materials show an expanded c/a lattice ratio and changing Li/Ni interlayer mixing indicating peculiar cation migration in the structures. High resolution TEM images and XPS spectra show obvious differences in the surface characteristics of the samples synthesized with stoichiometric and excess amount of LiOH, suggesting that surface characteristics is one of the contributing factors to the difference in electrochemicat properties. Our results suggest that the first cycle irreversible capacity is affected by both the bulk and surface characteristics of pristine materials, which is strongly influenced by precursor chemistry. The PITT results suggest that cation rearrangement during the charge/discharge has a significant impact on the lithium chemical diffusivity. [ABSTRACT FROM AUTHOR]