Structurally distorted perovskite La0.8Sr0.2Mn0.5Co0.5O3-δ by graphene nanoplatelet and their composite for supercapacitors with enhanced stability.

Supercapacitors are promising energy storage devices with high charging/discharging speeds and power densities. To improve their poor stability, we fabricated electrodes by integrating perovskite materials (La0.8Sr0.2Mn0.5Co0.5O3-δ, LSMCO) possessing redox reaction ability with graphene nanoplatelets exhibiting good electronic properties. One of the resultant composites (L25G70) demonstrated high capacitance and excellent capacitance retention (95% after 5000 cycles). These results are superior to other electrodes (L50G45 and L75G20) containing a larger ratio of LSMCO, even L75G20 did not exhibit supercapacitor behavior after 3000 cycles. GN can induce structural distortion in LSMCO, thereby the high amount of adsorbed oxygen per lattice oxygen can explain the best electrochemical performance of L25G70, while structural collapse rationalized the failure of L75G20. The findings of this study demonstrated that the use of LSMCO can improve the cycling stability of supercapacitors.

Fabrication of Aluminum-Based Thermal Radiation Plate for Thermoelectric Module Using Aluminum Anodic Oxidization and Copper Electroplating.

In this study, electrolytic etching, anodic oxidation, and copper electroplating were applied to aluminum to produce a plate on which a copper circuit for a thermoelectric module was formed. An oxide film insulating layer was formed on the aluminum through anodic oxidation, and platinum was coated by sputtering to produce conductivity. Finally, copper electroplating was performed directly on the substrate. In this structure, the copper plating layer on the insulating layer served as a conductive layer in the circuit. The adhesion of the copper plating layer was improved by electrolytic etching. As a result, the thermoelectric module fabricated in this study showed excellent adhesion and good insulation characteristics. It is expected that our findings can contribute to the manufacture of plates applicable to thermoelectric modules with high dissipation performance.

A Novel Fabrication Method of Bi2Te3-Based Thermoelectric Modules by Indium Electroplating and Thermocompression Bonding.

In this study, we devised a method to bond thermoelectric elements directly to copper electrodes by plating indium with a relatively low melting point. A coating of indium, ~30 µm in thickness, was fabricated by electroplating the surface of a Bi2Te3-based thermoelectric element with a nickel diffusion barrier layer. They were then subjected to direct thermocompression bonding at 453 K on a hotplate for 10 min at a pressure of 1.1 kPa. Scanning electron microscopy images confirmed that a uniform bond was formed at the copper electrode/thermoelectric element interface, and the melted/solidified indium layer was defect free. Thus, the proposed novel method of fabricating a thermoelectric module by electroplating indium on the surface of the thermoelectric element and directly bonding with the copper electrode can be used to obtain a uniformly bonded interface even at a relatively low temperature without the use of solder pastes.

Exsolution trends and co-segregation aspects of self-grown catalyst nanoparticles in perovskites.

In perovskites, exsolution of transition metals has been proposed as a smart catalyst design for energy applications. Although there exist transition metals with superior catalytic activity, they are limited by their ability to exsolve under a reducing environment. When a doping element is present in the perovskite, it is often observed that the surface segregation of the doping element is changed by oxygen vacancies. However, the mechanism of co-segregation of doping element with oxygen vacancies is still an open question. Here we report trends in the exsolution of transition metal (Mn, Co, Ni and Fe) on the PrBaMn2O5+δ layered perovskite oxide related to the co-segregation energy. Transmission electron microscopic observations show that easily reducible cations (Mn, Co and Ni) are exsolved from the perovskite depending on the transition metal-perovskite reducibility. In addition, using density functional calculations we reveal that co-segregation of B-site dopant and oxygen vacancies plays a central role in the exsolution.

Fe@N-Graphene Nanoplatelet-Embedded Carbon Nanofibers as Efficient Electrocatalysts for Oxygen Reduction Reaction.

An activated carbon nanofiber (CNF) is prepared with incorporated Fe-N-doped graphene nanoplatelets (Fe@NGnPs), via a novel and simple synthesis approach. The activated CNF-Fe@NGnP catalysts exhibit substantially improved activity for the oxygen reduction reaction compared to those of commercial carbon blacks and Pt/carbon catalysts.

Solid oxide electrolysis: Concluding remarks.

Renewable energy resources such as solar energy, wind energy, hydropower or geothermal energy have attracted significant attention in recent years. Renewable energy sources have to match supply with demand, therefore it is essential that energy storage devices (e.g., secondary batteries) are developed. However, secondary batteries are accompanied with critical problems such as high cost for the limited energy storage capacity and loss of charge over time. Energy storage in the form of chemical species, such as H2 or CO2, have no constraints on energy storage capacity and will also be essential. When plentiful renewable energy exists, for example, it could be used to convert H2O into hydrogen via water electrolysis. Also, renewable energy resources could be used to reduce CO2 into CO and recycle CO2 and H2O into sustainable hydrocarbon fuels in solid oxide electrolysis (SOE).

Discharge performance of solid-state oxygen shuttle metal-air battery using Ca-stabilized ZrO2 electrolyte.

The effects of metal choice on the electrochemical performance of oxygen-shuttle metal-air batteries with Ca-stabilized ZrO2 (CSZ) as the electrolyte and various metals as the anodes were studied at 1073 K. The equilibrium oxygen partial pressure (P O 2) in the anode chamber was governed by the metal used in the anode chamber. A lower-P O 2 environment in the anode decreased the polarization resistance of the anode. The oxidation of oxide ions to oxygen in the anode is drastically enhanced by the n-type conduction generated in the CSZ electrolyte when it is exposed to a reducing atmosphere. A high discharge potential and high capacity can be achieved in an oxygen-shuttle battery with a Li or Mg anode because of the fast anode reaction compared to that of cells with a Zn, Fe, or Sn anode. However, only the mildly reducing metals (Zn, Si, Fe, and Sn) can potentially be used in rechargeable metal-air batteries because the transport number of the CSZ electrolyte must be unity during charge and discharge. Oxygen shuttle rechargeable batteries with Fe, and Sn electrodes are demonstrated.

Layered oxygen-deficient double perovskite as an efficient and stable anode for direct hydrocarbon solid oxide fuel cells.

Different layered perovskite-related oxides are known to exhibit important electronic, magnetic and electrochemical properties. Owing to their excellent mixed-ionic and electronic conductivity and fast oxygen kinetics, cation layered double perovskite oxides such as PrBaCo2O5 in particular have exhibited excellent properties as solid oxide fuel cell oxygen electrodes. Here, we show for the first time that related layered materials can be used as high-performance fuel electrodes. Good redox stability with tolerance to coking and sulphur contamination from hydrocarbon fuels is demonstrated for the layered perovskite anode PrBaMn2O5+δ (PBMO). The PBMO anode is fabricated by in situ annealing of Pr0.5Ba0.5MnO3-δ in fuel conditions and actual fuel cell operation is demonstrated. At 800 °C, layered PBMO shows high electrical conductivity of 8.16 S cm(-1) in 5% H2 and demonstrates peak power densities of 1.7 and 1.3 W cm(-2) at 850 °C using humidified hydrogen and propane fuels, respectively.

Development of double-perovskite compounds as cathode materials for low-temperature solid oxide fuel cells.

A class of double-perovskite compounds display fast oxygen ion diffusion and high catalytic activity toward oxygen reduction while maintaining excellent compatibility with the electrolyte. The astoundingly extended stability of NdBa(1-x)Ca(x)Co2O(5+δ) (NBCaCO) under both air and CO2-containing atmosphere is reported along with excellent electrochemical performance by only Ca doping into the A site of NdBaCo2O(5+δ) (NBCO). The enhanced stability can be ascribed to both the increased electron affinity of mobile oxygen species with Ca, determined through density functional theory calculations and the increased redox stability from the coulometric titration.

Mg-air oxygen shuttle batteries using a ZrO2-based oxide ion-conducting electrolyte.

A new concept of an "oxygen shuttle" type battery for Mg-air solid oxide batteries using a Ca-stabilized ZrO2 electrolyte was proposed and studied. The observed open circuit potential and discharge capacity were 1.81 V and 1154 mA h gMg(-1) (52% of the theoretical capacity), respectively.

Adsorption of toluene on carbon nanofibers prepared by electrospinning.

This paper reports the novel results of activated carbon nanofibers (ACNF) used to improve the toluene adsorption capacity. The ACNF was prepared by stabilization, carbonization and activation after electrospinning the polymer solution of polyacrylonitrile (PAN) in N, N-dimethylformamide. The average diameter of the ACNF was approximately 300 nm, ranging from 200 to 500 nm. The toluene adsorption capacity of ACNF10 activated at 1000 degrees C increased to 65 g-toluene/100 g-ACNF. This was attributed to the high specific surface area (1403 m(2)/g), large micropore volume (0.505 cm(3)/g), and narrow average pore diameter (6.0 A). The oxygen to carbon ratio (O/C ratio) in ACNF10 was 1.8%. This O/C ratio appears to induce a higher toluene adsorption capacity, which originates from a non-polar interaction between the ACNF surface and toluene. In conclusion, the electrospun ACNF prepared in this study promotes the adsorption of toluene through the high specific surface area, large pore volume, narrow pore diameter and low O/C ratio.