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Glycerol selective oxidation to dihydroxyacetone was investigated systematically in a semibatch reactor over Pt−Bi/C catalyst. Catalysts with different metal loadings, supports, and preparation methods were synthesized, characterized, and tested. The sequential impregnation of Pt and then Bi, followed by NaBH4reduction, was the optimum synthesis method for high glycerol oxidation rate and maximum DHA yield. The optimum catalyst composition was determined to be 3 wt % Pt, 0.6 wt % Bi, supported on Norit Darco 20-40 mesh activated carbon (BET surface area 600 m2/g, average pore size 4 nm, average pore volume 0.53 cm3/g). In addition to the catalyst, the reaction conditions were also optimized by conducting experiments in the range of temperature 30−90 °C, oxygen pressure 0−180 psig, and initial pH 2−12. The optimum reaction conditions were identified as 80 °C, 30 psig, and initial pH = 2. Under these conditions, a maximum DHA yield of 48% was obtained at 80% glycerol conversion. The catalysts were characterized by using BET, ICP-OES, TEM, XRD, and XPS techniques. [ABSTRACT FROM AUTHOR]

The ever-increasing demand for flexible and portable electronics has stimulated research and development in building advanced electrochemical energy devices which are lightweight, ultrathin, small in size, bendable, foldable, knittable, wearable, and/or stretchable. In such flexible and portable devices, semi-solid/solid electrolytes besides anodes and cathodes are the necessary components determining the energy/power performances. By serving as the ion transport channels, such semi-solid/solid electrolytes may be beneficial to resolving the issues of leakage, electrode corrosion, and metal electrode dendrite growth. In this paper, the fundamentals of semi-solid/solid electrolytes (e.g., chemical composition, ionic conductivity, electrochemical window, mechanical strength, thermal stability, and other attractive features), the electrode–electrolyte interfacial properties, and their relationships with the performance of various energy devices (e.g., supercapacitors, secondary ion batteries, metal–sulfur batteries, and metal–air batteries) are comprehensively reviewed in terms of materials synthesis and/or characterization, functional mechanisms, and device assembling for performance validation. The most recent advancements in improving the performance of electrochemical energy devices are summarized with focuses on analyzing the existing technical challenges (e.g., solid electrolyte interphase formation, metal electrode dendrite growth, polysulfide shuttle issue, electrolyte instability in half-open battery structure) and the strategies for overcoming these challenges through modification of semi-solid/solid electrolyte materials. Several possible directions for future research and development are proposed for going beyond existing technological bottlenecks and achieving desirable flexible and portable electrochemical energy devices to fulfill their practical applications. It is expected that this review may provide the readers with a comprehensive cross-technology understanding of the semi-solid/solid electrolytes for facilitating their current and future researches on the flexible and portable electrochemical energy devices. [ABSTRACT FROM AUTHOR]

A unique synthesis was developedto immobilize Pd nanoparticleson pristine graphene (PG) sheets via a facile supercritical carbondioxide route. Pristine graphene was obtained by sonication-assistedexfoliation of graphite in an organic solvent. Finely dispersed worm-likePd nanoparticles are homogeneously deposited on the hydrophobic graphenesurfaces. The combination of pristine graphene sheets and well-dispersedPd nanoparticles provided large electrochemically active surface areas (ECSA) for bothdirect formic acid fuel cell (DFAFC) and methanol fuel cell (DMFC).The ECSA values are more than twice as large as those of reduced grapheneoxide and carbon nanotube based counterparts or six times those ofconventional XC-72 carbon black. Significant enhancements were alsoobserved in the electrocatalytic activity and stability measurements.The excellent electrochemical property of Pd/PG is attributable tothe well-preserved graphene structure that ensures electrical conductivityand stability of the composite. Its large surface area also allowsfor the deposition of small size and high dispersion of the Pd nanoparticles.This straightforward synthesis offers a new pathway for developinghighly active electrocatalysts based on pristine graphene with fullyoptimized properties. [ABSTRACT FROM AUTHOR]

Thispaper reports a convenient and facile preparation of single-crystallinepalladium with controllable shape based on the reduction of kineticcontrol via hydrochloric acid oxidative etching. The concentrationof HCl added to the reaction solution was found to be crucial forthe shape evolution of palladium nanocrystals from nanocubes boundedby {100} facets to octahedrons by {111} facets. Palladium nanocubescan be readily obtained at a fast reduction rate without the involvementof additional HCl. With the introduction of a certain amount of HClto the precursor solution, truncated nanocubes with {111} facets wereformed, and the increase of HCl led to the slower reduction rate andthe formation of palladium cuboctahedrons enclosed by six {100} facetsand eight {111} facets at the expense of gradual shrinkage of {100}facets. The probable mechanism of morphological transformation wasproposed upon a batch of experiments. The shape-dependent catalyticperformances of as-obtained palladium nanocrystals were investigatedby the structure-sensitive reaction of formic acid oxidation. It wasfound that catalytic activities of palladium nanocrystals displayeda strong dependence on the facets exposed on the surface, and cubicpalladium exhibited the best catalytic performance compared with cubooctahedraland octahedral palladium nanocrystals. [ABSTRACT FROM AUTHOR]