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LiCoPO4cathode materials have been synthesized by a sol–gel route. X-ray diffraction analysis confirmed that LiCoPO4was well-crystallized in an orthorhombic structure in the Pmnaspace group. From the high-resolution transmission electron microscopy (HR-TEM) image, the lattice fringes of {001} and {100} are well-resolved. The HR-TEM image and selected area electron diffraction pattern reveal the highly crystalline nature of LiCoPO4having an ordered olivine structure. The atom-by-atom structure of LiCoPO4olivine has been observed, for the first time, using high-angle annular dark-field (HAADF) and annual bright-field scanning transmission electron microscopy. We observed the bright contrast in Li columns in the HAADF images and strong contrast in the ABF images, directly indicating the antisite exchange defects in which Co atoms partly occupy the Li sites. The LiCoPO4cathode materials delivered an initial discharge capacity of 117 mAh/g at a C/10 rate with moderate cyclic performance. The discharge profile of LiCoPO4shows a plateau at 4.75 V, revealing its importance as a potentially high-voltage cathode. The direct visualization of atom-by-atom structure in this work represents important information for the understanding of the structure of the active cathode materials for Li-ion batteries.

We develop a simple approach to fabricate graphene-loaded TiO2thin films on glass substrates by the spin-coating technique. Our graphene-loaded TiO2films were highly conductive and transparent and showed enhanced photocatalytic activities. More significantly, graphene/TiO2films displayed superhydrophilicity within a short time even under a white fluorescent light bulb, as compared to a pure TiO2film. The enhanced photocatalytic activity of graphene/TiO2films is attributed to its efficient charge separation, owing to electrons injection from the conduction band of TiO2to graphene. The electroconductivity of the graphene-loaded TiO2thin film also contributes to the self-cleaning function by its antifouling effect against particulate contaminants. The present study reveals the ability of graphene as a low cost cocatalyst instead of expensive noble metals (Pt, Pd), and further shows its capability for the application of self-cleaning coatings with transparency. The promising characteristics of (inexpensive, transparent, conductive, superhydrophilic, and highly photocatalytically active) graphene-loaded TiO2films may have the potential use in various indoor applications.

In this study, we achieve the direct conversion of metallic Cu–In films to compound semiconductor CuInSe2films, at quite low temperature around 300 °C using less hazardous metalorganic selenium source in supercritical fluid (SCF). We investigated the effects of temperature and fluid (ethanol) density, and found that supercritical ethanol plays a crucial role in this low-temperature selenization reaction. Such SCF-assisted direct conversion reactions can facilitate large-scale, low-temperature, and rapid synthesis of CuInSe2films, which can potentially lead to the low-cost production of solar cells.

A triaxial LiFePO4nanowire with a multi wall carbon nanotube (VGCF:Vapor-grown carbon fiber) core column and an outer shell of amorphous carbon was successfully synthesized through the electrospinning method. The carbon nanotube core oriented in the direction of the wire played an important role in the conduction of electrons during the charge−discharge process, whereas the outer amorphous carbon shell suppressed the oxidation of Fe2+. An electrode with uniformly dispersed carbon and active materials was easily fabricated via a single process by heating after the electrospinning method is applied. Mössbauer spectroscopy for the nanowire showed a broadening of the line width, indicating a disordered coordination environment of the Fe ion near the surface. The electrospinning method was proven to be suitable for the fabrication of a triaxial nanostructure.

The electroreduction of carbon dioxide is considered a key reaction for the valorization of CO2emitted in industrial processes or even present in the environment. Cobalt–nitrogen co-doped carbon materials featuring atomically dispersed Co–N sites have been shown to display superior activities and selectivities for the reduction of carbon dioxide to CO, which, in combination with H2(i.e., as syngas), is regarded as an added-value CO2-reduction product. Such catalysts can be synthesized using heat treatment steps that imply the carbonization of Co–N-containing precursors, but the detailed effects of the synthesis conditions and corresponding materials’ composition on their catalytic activities have not been rigorously studied. To this end, in the present work, we synthesized cobalt–nitrogen co-doped carbon materials with different heat treatment temperatures and studied the relation among their surface- and Co-speciation and their CO2-to-CO electroreduction activity. Our results reveal that atomically dispersed cobalt–nitrogen sites are responsible for CO generation while suggesting that this CO-selectivity improves when these atomic Co–N centers are hosted in the carbon layers that cover the Co nanoparticles featured in the catalysts synthesized at higher heat treatment temperatures.