A highly active and durable lanthanum strontium cobalt ferrite cathode for Intermediate-Temperature solid Oxide fuel cel

Solid oxide fuel cells (SOFCs) are promising techniques for high energy efficiency, fuel flexibility, and low pollutant emissions. For commercialization of SOFCs, it is required to decrease the operating temperature. At this intermediate temperature region, the cathodic polarization resistance significant due to the thermally activated oxygen reduction reaction (ORR). To compensate this, highly active cathode materials have been considered and lanthanum strontium cobalt ferrite (LSCF6428, La0.6Sr0.4Co0.2Fe0.8O3-δ) has been attracted as a cathode material for SOFCs because of its high mixed electronic and ionic conducting (MIEC) nature. However, one of the major concerns of LSCF6428 is the degradation during the long-term operation. Currently, Sr segregation has been reported as one of the major reasons for the LSCF degradation. In this study, we investigated LSCF2882 (La0.2Sr0.8Co0.8Fe0.2O3-δ) and compared with LSCF6428 as a SOFC cathode. X-ray diffraction (XRD) and Rietveld refinement were applied to analyze phase structures. By electrical conductivity relaxation (ECR) technique, Oxygen surface exchange coefficients (kchem) and chemical diffusion coefficients (Dchem) of LSCF2882 were evaluated and we observed enhancements compare to LSCF6428. For interpretation of enhanced oxygen transport kinetics, we tried to visualize the interstitial oxygen conduction pathways and the bond valence sum (BVS) mapping method was utilized by Valence program. BVS mapping results show clearly demonstrating the 3D network of the interstitial pathways at 600oC in LSCF2882. Electrochemical performances were investigated by EIS (Electrochemical Impedance Spectroscopy) and single cell performance was also evaluated. In addition, long-term stability test was performed for over 500 hours. LSCF2882 showed better performances and it exhibited no degradation during the stability test. Please click Additional Files below to see the full abstract

Analysis of Environmental Carrying Capacity with Emergy Perspective of Jeju Island

Jeju Island experienced an approximately 42% increase in energy consumption from 2006 to 2015 and the demand for energy consumption is expected to continue to increase. Thus, Jeju Island is planning a project entitled “Carbon Free Island by 2030” to promote sustainable development and is required to estimate the environmental carrying capacity for future energy demand changes. The purpose of this study was to calculate the emergy inherent in Jeju Island’s energy, materials, and information in 2015 using the emergy analysis method and local characteristics. In addition, this study aimed to estimate the emergy indices to evaluate the environmental carrying capacity for sustainable development in 2005, 2015, and 2030 considering the future energy demand. This study’s outputs provide the environmental carrying capacity with emergy indices, such as the percent renewable (%Renew), emergy yield ratio (EYR), environmental loading ratio (ELR), sustainability index (SI), and carrying capacity of the population (CCP) for social and economic activities on Jeju Island, which are expected to be saturated. These findings show regions with heavy tourism require development strategies, including the concept of environmental carrying capacity

Evaluating the effectiveness of HOCl application on odor reduction and earthworm population growth during vermicomposting of food waste employing Eisenia fetida.

Vermicomposting has been recommended as an eco-friendly method to transform organic waste into nutrient resources with minimum energy input. However, odor and pest issues associated with this method limit the use of vermicomposting, especially in indoor conditions. This study evaluated the effectiveness of applying hypochlorous acid (HOCl) to deodorize the vermicomposting process and improve the breeding environment for earthworms (Eisenia fetida). The deodorization performance of HOCl was compared by measuring the amount of ammonia (NH3) and amine (R-NH2) released from the decaying process of two types of food waste: HOCl-treated (HTW) waste and non-treated waste (NTW). The total and individual weights of earthworms in the waste treated with HOCl was measured to evaluate the impact on earthworm reproduction after applying HOCl. The results showed that HOCl application could reduce NH3 by 40% and R-NH2 by 80%, and increase the earthworm population size and total weight by up to 29% and 92%, respectively, compared to the control group. These results suggest that HOCl application is potentially an efficient method to control the odor and to boost earthworm reproduction and thus facilitate vermicomposting for improved food waste treatment and environmental quality

A High-Capacity and Long-Cycle-Life LithiumIon Battery Anode Architecture: Silver Nanoparticle-Decorated SnO2/NiO Nanotube

The combination of high-capacity and long-term cyclability has always been regarded as the first priority for next generation anode materials in lithium-ion batteries (LIBs). To meet these requirements, the Ag nanoparticle decorated mesoporous SnO2/NiO nanotube (m-SNT) anodes were synthesized via an electrospinning process, followed by fast ramping rate calcination and subsequent chemical reduction in this work. The one-dimensional porous hollow structure effectively alleviates a large volume expansion during cycling as well as provides a short lithium-ion duffusion length. Furthermore, metallic nickel (Ni) nanoparticles converted from the NiO nanograins during the lithiation process reversibly decompose Li2O during delithiation process, which significantly improves the reversible capacity of the m-SNT anodes. In addition, Ag nanoparticles uniformly decorated on the m-SNT via a simple chemical reduction process significantly improve rate capability and also contribute to long-term cyclability. The m-SNT@Ag anodes exhibited excellent cycling stability without obvious capacity fading after 500 cycles with a high capacity of 826 mAh g(-1) at a high current density of 1000 mA g(-1). Furthermore, even at a very high current density of 5000 mA g(-1), the charge-specific capacity remained as high as 721 mAh g(-1), corresponding to 60% of its initial capacity at a current density of 100 mA g(-1).clos

Fast, Scalable Synthesis of Micronized Ge3N4 at C with a High Tap Density for Excellent Lithium Storage

Nanostructuring has significantly contributed to alleviating the huge volume expansion problem of the Ge anodes. However, the practical use of nanostructured Ge anodes has been hindered due to several problems including a low tap density, poor scalability, and severe side reactions. Therefore, micrometer-sized Ge is desirable for practical use of Ge-based anode materials. Here, micronized Ge3N4 with a high tap density of 1.1 mg cm-2 has been successfully developed via a scalable wet oxidation and a subsequent nitridation process of commercially available micrometer-sized Ge as the starting material. The micronized Ge3N4 shows much-suppressed volume expansion compared to micrometer-sized Ge. After the carbon coating process, a thin carbon layer (≈3 nm) is uniformly coated on the micronized Ge3N4, which significantly improves electrical conductivity. As a result, micronized Ge3N4 at C shows high reversible capacity of 924 mAh g-1 (2.1 mAh cm-2) with high mass loading of 3.5 mg cm-2 and retains 91% of initial capacity after 300 cycles at a rate of 0.5 C. Additionally, the effectiveness of Ge3N4 at C as practical anodes is comprehensively demonstrated for the full cell, showing stable cycle retention and especially excellent rate capability, retaining 47% of its initial capacity at 0.2 C for 12 min discharge/charge condition.clos

Multifunctional molecular design as an efficient polymeric binder for silicon anodes in lithium-ion batteries

This work demonstrates the design, synthesis, characterization, and study of the electrochemical performance of a novel binder for silicon (Si) anodes in lithium-ion batteries (LIBs). Polymeric binders with three different functional groups, namely, carboxylic acid (COOH), carboxylate (COO-), and hydroxyl (OH), in a single polymer backbone have been synthesized and characterized via 1H NMR and FTIR spectroscopies. A systematic study that involved varying the ratio of the functional groups indicated that a material with an acid-to-alcohol molar ratio of 60:40 showed promise as an efficient binder with an initial columbic efficiency of 89%. This exceptional performance is attributed to the strong adhesion of the binder to the silicon surface and to cross-linking between carboxyl and hydroxyl functional groups, which minimize the disintegration of the Si anode structure during the large volume expansion of the lithiated Si nanoparticle. Polymers with multiple functional groups can serve as practical alternative binders for the Si anodes of LIBs, resulting in higher capacities with less capacity fade.close0

Revisiting on the effect and role of TiO2 layer thickness on SnO2 for enhanced electrochemical performance for lithium-ion batteries

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO2)) on metal oxide anodes (such as tin (IV) oxide (SnO2)) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO2 overlayer on SnO2 can have significant influence in the overall parameters of electro-chemistry. It is revealed that TiO2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g(-1) even at high current density (5000 mA g(-1)). Surprisingly, it was further discovered that TiO2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO2. The improvements in both ionic and electrical conductivity of TiO2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO2@SnO2, which demonstrates that TiO2 overlayer results in homogeneous and thinner interphase layer compared with SnO2 NTs. (c) 2017 Elsevier Ltd. All rights reserved1231sciescopu

Agarose-biofunctionalized, dual-electrospun heteronanofiber mats: toward metal-ion chelating battery separator membranes

A facile and efficient way to impart compelling chemical functionality is the utilization of bio-relatedmaterials that are easily accessible from natural products. Here, inspired by anomalous physicochemical features and natural abundance of agarose, we demonstrate a new class of agarose-biofunctionalized, dual-electrospun heteronanofiber mats as a chemically active separator membrane for high-performance lithium-ion batteries. The agarose-enabled metal ion chelation effect of the separator membrane, in combination with its highly porous structure and superior electrolyte wettability, provides unprecedented improvement in cell performance far beyond those accessible with conventional battery separator membranesclose0

Stress-Tolerant Nanoporous Germanium Nanofibers for Long Cycle Life Lithium Storage with High Structural Stability

Nanowires (NWs) synthesized via chemical vapor deposition (CVD) have demonstrated significant improvement in lithium storage performance along with their outstanding accommodation of large volume changes during the charge/discharge process. Nevertheless, NW electrodes have been confined to the research level due to the lack of scalability and severe side reactions by their high surface area. Here, we present nanoporous Ge nanofibers (NPGeNFs) having moderate nanoporosity via a combination of simple electrospinning and a low-energetic zincothermic reduction reaction. In contrast with the CVD-assisted NW growth, our method provides high tunability of macro/microscopic morphologies such as a porosity, length, and diameter of the nanoscale 1D structures. Significantly, the customized NPGeNFs showed a highly suppressed volume expansion of less than 15% (for electrodes) after full lithation and excellent durability with high lithium storage performance over 500 cycles. Our approach offers effective 1D nanostructuring with highly customized geometries and can be extended to other applications including optoelectronics, catalysis, and energy conversion

An efficient and robust lanthanum strontium cobalt ferrite catalyst as a bifunctional oxygen electrode for reversible solid oxide cells

Reversible solid oxide cells (SOCs) are unique devices that perform interconversion between chemical energy (particularly hydrogen) and electricity, providing efficient energy storage for site-specific and weather-dependent solar and wind resources. One of the key requirements for achieving high-performance reversible SOCs is the development of highly active bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we investigate a La0.2Sr0.8Co0.8Fe0.2O3−δ(LSCF2882) material as a novel oxygen electrode for reversible SOCs at intermediate temperatures. Unlike most widely used La0.6Sr0.4Co0.2Fe0.8O3−δ(LSCF6428) with a rhombohedrally distorted perovskite structure, LSCF2882 possesses a simple cubic perovskite structure with a symmetric BO6octahedral network. Furthermore, the 3D bond valence sum calculation of the LSCF2882 structure suggests a reduction in oxygen ion conduction barrier energy. Oxygen surface exchange (kchem) and diffusion (Dchem) coefficients of LSCF2882 determined by electrical conductivity relaxation are consistently remarkably higher by >2 and 20 times compared to those of LSCF6428 at 700 °C, respectively. This result is further supported by a 43% reduction in the oxygen vacancy formation energy of LSCF2882 determined from density functional theory calculations. The reversible SOCs with LSCF2882 oxygen electrodes greatly outperform LSCF6428 cells in both fuel cell (2.55 W cm−2) and electrolysis mode (2.09 A cm−2at 1.3 V) at 800 °C, with excellent reversible cycling stability. Our findings strongly suggest that LSCF2882 is a promising candidate as a bifunctional oxygen electrode for high performance reversible SOCs at reduced temperatures. © The Royal Society of Chemistry 2021.1