Zeitschriftenaufsätze

Nanostructured transition metal nitrides (TMNs) have been considered as a promising substitute for precious metal catalysts toward ORR due to their multi-electron orbitals, metallic properties, and low cost. To design TMN catalysts with high catalytic activity toward ORR, the intrinsic features of the influencing factor on the catalytic activity toward ORR of nanostructured TMNs need to be investigated. In this paper, titanium nitride (TiN), zirconium nitride (ZrN), and hafnium nitride (HfN) nanoparticles (NPs) are highly efficient and synthesized in one step by the direct current arc plasma. TiN, ZrN, and HfN NPs with an oxidation layer are applied as the catalysts of hybrid sodium-air batteries (HSABs). The effect of the composition and structural attributes of TMNs on ORR catalysis is defined as follows: (i) composition effect. With the increase in the oxygen content, the catalytic ORR capability of TMNs decreases progressively due to the reduction in oxygen adsorption capacity; (ii) structure effect. The redistribution of the density of states (DOS) of ZrN indicates higher ORR activity than TiN and HfN. HSABs with ZrN exhibit an excellent cyclic stability up to 137 cycles (about 140 h), an outstanding rate performance, and a specific capacity of 2817 mAh&hahog;g−1 at 1.0 mA&hahog;cm−2.

Scanning tunneling microscopy and spectroscopy experiments on surface-localized electron states confined to nanometer-scaled resonators are reviewed from the first observations to the recently discovered novel reflection mechanism of electron de Broglie waves. The focus of the presented work is on lateral confinement and on processes leading to finite decay rates of the confined states.

With the development of the energy system transformation the quality and efficiency of the rechargeable batteries, particularly the Li ion technology, gain major importance. In spite of the enormous advances, along with many other technological challenges corrosion of the metallic battery parts is often a difficult obstacle for producers and researchers. Li-metal batteries and especially the “anode-free” battery concept could significantly increase the energy density. However, contact corrosion of the Li anode, can occur in this cell configuration since there is a high probability of a three-phase contact between Li-metal, current collector and electrolyte, a condition triggering an intensive Li corrosion. In this work, a new in-situ analytical methodology based on combining electrochemical (ZRA) and microgravimetric (QCM) techniques is proposed for studying the galvanic corrosion. The applicability of this approach is explored in three different electrolyte compositions. Beside the analysis of the conventional electrochemical parameters an in-situ gravimetric detection of the deposited electrolyte decomposition products on the cathode surface is demonstrated. Adsorbed polymer layer on the Cu surface is applied for cathodic inhibition of the galvanic corrosion process, which is studied by means of the novel ZRA-QCM approach.

Designing core-shell heterostructures with multicomponents, more electroactive sites, hierarchical structures, and stable geometrical configurations is an effective approach to enhance the electrochemical properties of supercapacitors. Herein, we report the fabrication of a hierarchical candied-haws-like NiCo2O4NiCo-hydrocarbonate heterostructure on Ni foam (NiCo2O4@NiCo-HCs), which consists of NiCo2O4 nanowires acting as “rebars” that are tightly strung with NiCo-HC nanoparticles. The strong interfacial reaction between the NiCo2O4 “core” and the NiCo-HC “shell” accelerates the charge transfer within the heterostructure, while the hierarchical structure containing quantities of paths and pores provides fast ion diffusion throughout the whole electrode, hence remarkably boosting the electrochemical performance of a NiCo2O4@NiCo-HC electrode. As expected, the NiCo2O4@NiCo-HC electrode shows a high specific capacitance of 3216.4 F g-1 at a current density of 1 A g-1 and 2259.9 F g-1 even at 20 A g-1 (1.6-fold that of the NiCo2O4 electrode and 5.5-fold that of NiCo-HCs). In addition, an assembled asymmetric supercapacitor NiCo2O4@NiCo-HCs//AC delivers a high energy density of 47.46 Wh kg-1 at a power density of 708.94 W kg-1, together with 96.2% capacitance retention after 6000 cycles, surpassing most of the reported analogues. These results suggest that our hierarchical candied-haws-like heterostructure design is potential for the performance enhancement of supercapacitors.

The drying of highly concentrated aqueous salt solutions in sand and soil has been investigated by one-dimensional spatially resolved low-field relaxation measurements of 1H nuclei in water as well as high-field MRI of 1H and 23Na nuclei of water and sodium ions. Water evaporates until the solutions in the solid matrix reach saturation conditions, when salt begins to crystallize. Depending on salt type and conditions, such as actual soil water content and air humidity, this crystallization can occur above (efflorescent) or below (subflorescent) the soil surface. Both effects occur in nature and affect the evaporation behavior of water. The formation of salt precipitate domains is demonstrated by MRI, where the precipitate domains remain penetrable to water. Complete drying is achieved in the top 2 mm of soil with the exception of strongly hygroscopic perchlorates which maintain a constant amount of liquid water under ambient laboratory conditions and dry air. This situation is considered similar to the co-existence of perchlorates and water in strongly eutectic mixtures on Mars.