Pd Doped Co3O4 Loaded on Carbon Nanofibers as Highly Efficient Free-Standing Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions

Self-supporting electrodes usually show excellent electrocatalytic performance which does not require coating steps, additional polymer binders, and conductive additives. Rapid in situ growth of highly active ingredient on self-supporting electric conductors is identified as a straight forward path to prepare binder-free and integrated electrodes. Here, Pd-doped Co3O4 loaded on carbon nanofiber materials through electrospinning and heat treatment was efficiently synthesized, and used as a free-standing electrode. Benefiting from its abundant active sites, high surface area and effective ionic conduction capability from three-dimensional (3D) nanofiber framework, Pd-Co3O4@CNF works as bifunctional oxygen electrode and exhibits superior activity and stability superior to commercial catalysts.

Structure and Properties of Mixed Former Aluminum Borate Glasses Modified With Silver Oxide

The current study focuses on glass preparation and characterization in the xAl2O3 (35-x) Ag2O.65B2O3 system (0≤x≤35 mol%), where Ag2O is replaced with Al2O3. To examine a wide range of both structure and morphology of the produced glasses, nuclear magnetic resonance (NMR) of 27Al nuclei, X-ray diffraction (XRD) spectroscopy, and transmission electron microscopy (TEM) are used. Changing the Al2O3 and Ag2O molar ratios reveals a substantial change in material structure. In Al2O3-rich glass, the well-formed AlO6, AlO5, and AlO4 structured groups are the well-formed units. In samples of (20 and 30 mol % Al2O3), tetrahedral AlO4 and traces from AlO6 units may be detected. At lower concentrations of Al2O3 (10 mol%), the dominant unit is only AlO4 groups containing non-bridging oxygen bonds (NBO). The XRD and EDP spectra confirm the amorphous nature of the glasses of Al2O3 ˂ 20 mol%. Glasses of higher Al2O3 concentrations contain crystalline Ag2Al2B2O7 which are formed due to the higher oxygen packaging of the mixed AlO5 and AlO4 compared with that of glasses containing only AlO4 species. The amount of higher coordinated Al species AlO5 and AlO6 are gradually increased in response to an increase in the ratios of Al2O3/Ag2O. The morphology of crystalline units is confirmed from TEM to differ from that of an amorphous composition. The conductivity decreases and the activation energy for ionic conduction increase with increasing Al2O3. The hardness number of the studied glasses is highly increased with increasing Al2O3 content. The increase of activation energy and the hardness number of the glasses led to an increase in the durability of the investigated glasses.

Diffusion in Metallic Glasses and in Oxide Glasses - An Overview

We remind the reader to some common features of metallic and oxide glasses. We then introduce the radiotracer method for diffusion studies, which can be applied for both types of glasses. We provide an overview on diffusion in metallic glasses in which we consider both types of metallic glasses – conventional and bulk metallic glasses. In the last part we discuss diffusion and ionic conduction in oxide glasses. For ionic glasses, conductivity measurements are an important complement to tracer diffusion studies. We remind the reader to the method of impedance spectroscopy. We discuss results for soda-lime silicate glasses, single alkali borate glasses and mixed alkali borate glasses and present evidence for collective jump processes in glasses.

Boron Hydrogen Compounds: Hydrogen Storage and Battery Applications

About 25 years ago, Bogdanovic and Schwickardi (B. Bogdanovic, M. Schwickardi: J. Alloys Compd. 1–9, 253 (1997) discovered the catalyzed release of hydrogen from NaAlH4. This discovery stimulated a vast research effort on light hydrides as hydrogen storage materials, in particular boron hydrogen compounds. Mg(BH4)2, with a hydrogen content of 14.9 wt %, has been extensively studied, and recent results shed new light on intermediate species formed during dehydrogenation. The chemistry of B3H8−, which is an important intermediate between BH4− and B12H122−, is presented in detail. The discovery of high ionic conductivity in the high-temperature phases of LiBH4 and Na2B12H12 opened a new research direction. The high chemical and electrochemical stability of closo-hydroborates has stimulated new research for their applications in batteries. Very recently, an all-solid-state 4 V Na battery prototype using a Na4(CB11H12)2(B12H12) solid electrolyte has been demonstrated. In this review, we present the current knowledge of possible reaction pathways involved in the successive hydrogen release reactions from BH4− to B12H122−, and a discussion of relevant necessary properties for high-ionic-conduction materials.

Hydrothermal Synthesis of Nanocrystalline ZrO2-8Y2O3-xLn2O3 Powders (Ln = La, Gd, Nd, Sm): Crystalline Structure, Thermal and Dielectric Properties

Zirconium dioxide (ZrO2) is one of the ceramic materials with high potential in many areas of modern technologies. ZrO2 doped with 8 wt.% (~4.5 mol%) Y2O3 is a commercial powder used for obtaining stabilized zirconia materials (8 wt.% YSZ) with high temperature resistance and good ionic conductivity. During recent years it was reported the co-doping with multiple rare earth elements has a significant influence on the thermal, mechanical and ionic conductivity of zirconia, due complex grain size segregation and enhanced oxygen vacancies mobility. Different methods have been proposed to synthesize these materials. Here, we present the hydrothermal synthesis of 8 wt.% (~4.5 mol%) YSZ co-doped with 4, 6 and 8 wt.% La2O3, Nd2O3, Sm2O3 and Gd2O3 respectively. The crystalline phases formed during their thermal treatment in a large temperature range were analyzed by X-ray diffraction. The evolution of phase composition vs. thermal treatment temperatures shows as a major trend the formation at temperatures >1000 °C of a cubic solid solutions enriched in the rare earth oxide used for co-doping as major phase. The first results on the thermal conductivities and impedance measurements on sintered pellets obtained from powders co-doped with 8 wt.% Y and 6% Ln (Ln = La, Nd, Sm and Gd) and the corresponding activation energies are presented and discussed. The lowest thermal conductivity was obtained for La co-doped 8 wt.% YSZ while the lowest activation energy for ionic conduction for Gd co-doped 8 wt.% YSZ materials.