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As high rate charge and discharge characteristics of energy storage devices become more important with the market of electric vehicles intensively growing, the kinetics of lithiation or delithiation of electrode materials for lithium ion batteries require enhancement. Graphites, the most widely used anode materials, have a limited power density at high discharge rates, while their alternatives, such as silicon and transition metal oxides, show even inferior rate capability. This work was motivated from an idea of what if the edge opening of graphite was zipped more open to lithium ions in the electrolyte. By edge-selective functionalization, the peripheral d-spacing of graphite (d(0)) was locally controlled. Larger values of d(0) led to higher capacity especially at high discharge rates. Around 2-fold enhancement of capacity or energy density was achieved at 50C discharge rate from 110 to 190 mAh g(-1) by exfoliating graphite locally in its edge region. Also, the d(0) dependency of delithiation kinetics confirmed that the electrochemical step of Li(+) influx into or efflux out of the interlayer space of graphite is possibly the rate-determining step of lithiation or delithiation.

This paper presents experimental results of the impact of CO(2) co-feed on a gasification/pyrolysis process for various feedstocks (biomass, coal, and municipal solid waste (MSW)). Various feedstocks were thermo-gravimetrically characterized under various atmospheric conditions and heating rates. A substantial amount of char burn out was identified in the presence of CO(2) via a series of thermo-gravimetric analysis tests, which enabled high conversion of final mass (approximately 99%) to be achieved. The impact of CO(2) co-feed on the volatilization regime during the pyrolysis/gasification process was not apparent at a heating rate of 10-40 degrees C min(-1). However, the impact of CO(2) on the volatilization regime at a fast heating rate (950 degrees C min(-1)) was substantial. For example, significant enhancement in the generation of CO, by a factor of approximately 2, was observed in the presence of CO(2). The generation of major chemical species, such as CH(4) and C(2)H(4), were enhanced, but this was not as apparent as in the case with CO. In addition, introducing CO(2) to the pyrolysis/gasification process enabled the amount of condensable liquid hydrocarbons, such as tar (approximately 30-40%) to be significantly reduced in the presence of CO(2), in that injecting CO(2) into the pyrolysis/gasification process expedites cracking the volatilized chemical species. Experimental work confirmed that biomass and MSW could be feasible and desirable feedstocks for the pyrolysis/gasification process as these feedstocks can be easily treated compared to coal. To extend this understanding to a more practical level, various feedstocks were tested in a tubular reactor and drop tube reactor under various experimental conditions.

Abstractπ‐Conjugated polyelectrolytes (CPEs) have been studied as interlayers on top of a separate hole transport layer (HTL) to improve the wetting, interfacial defect passivation, and crystal growth of perovskites. However, very few CPE‐based HTLs have been reported without rational molecular design as ideal HTLs for perovskite solar cells (PeSCs). In this study, the authors synthesize a triphenylamine‐based anionic CPE (TPAFS‐TMA) as an HTL for p‐i‐n‐type PeSCs. TPAFS‐TMA has appropriate frontier molecular orbital (FMO) levels similar to those of the commonly used poly(bis(4‐phenyl)‐2,4,6‐trimethylphenylamine) (PTAA) HTL. The ionic and semiconducting TPAFS‐TMA shows high compatibility, high transmittance, appropriate FMO energy levels for hole extraction and electron blocking, as well as defect passivating properties, which are confirmed using various optical and electrical analyses. Thus, the PeSC with the TPAFS‐TMA HTL exhibits the best power conversion efficiency (PCE) of 20.86%, which is better than that of the PTAA‐based device (PCE of 19.97%). In addition, it exhibits negligible device‐to‐device variations in its photovoltaic performance, contrary to the device with PTAA. Finally, a large‐area PeSC (1 cm2) and mini‐module (3 cm2), showing PCEs of 19.46% and 18.41%, respectively, are successfully fabricated. The newly synthesized TPAFS‐TMA may suggest its great potential as an HTL for large‐area PeSCs.

Cogeneration plants, which simultaneously produce electricity and heat energy, have been introduced increasingly for commercial and domestic applications in Korea because of their energy efficiency. The optimal plant configuration of a specific commercial building can be determined by selecting the sizes and the number of cogeneration systems and the auxiliary equipment based on the annual demands of electricity, heating and cooling. In this study, a mixed-integer, linear programming, utilizing the branch and bound algorithm was used to obtain the optimal solution. Both the optimal configuration system equipment and the optimal operational mode were determined based on the annual cost method for the installation of a cogeneration system to a hospital and a group of apartments in Seoul, Korea. In addition, the economic evaluation for the optimal cogeneration system depending on the fuel tariff system was calculated. A short payback period and higher internal rate of return on the initial investment were found to be essential for the adoption of cogeneration plants to hospitals and apartments.

COVID-19 pandemic has brought tremendous environmental burden due to huge amount of medical wastes (about 54,000 t/d as of November 22, 2020), including face mask, gloves, clothes, goggles, and sanitizer/disinfectant containers. A proper waste management is urgently required to mitigate the spread of the disease, minimize the environmental impacts, and take their potential advantages for further utilization. This work provides a prospective review on the possible thermochemical treatments for those COVID-19 related medical wastes (CMW), as well as their possible conversion to fuels. The characteristics of each waste are initially analyzed and described, especially their potential as energy source. It is clear that most of CMWs are dominated by plastic polymers. Thermochemical processes, including incineration, torrefaction, pyrolysis, and gasification, are reviewed in terms of applicability for CMW. In addition, the mechanical treatment of CMW into sanitized refuse-derived fuel (SRDF) is also discussed as the preliminary stage before thermochemical conversion. In terms of material flexibility, incineration is practically applicable for all types of CMW, although it has the highest potential to emit the largest amount of CO2 and other harmful gasses. Furthermore, gasification and pyrolysis are considered promising in terms of energy conversion efficiency and environmental impacts. On the other hand, carbonization faces several technical problems following thermal degradation due to insufficient operating temperature.

Abstract Gas crossover is an unavoidable phenomenon in proton exchange membrane fuel cells. Gas crossover leads to heat and water generations without conducting any useful works, hence increasing fuel consumption. Particularly, Gas crossover can result in the degradation and formation of pinholes inside the membrane. Therefore, the gas crossover is a critical factor significantly affecting the durability of a fuel cell and quality of the membrane. Herein, we numerically investigate the effects of gas crossover across the membrane in a proton exchange membrane fuel cell. A two-dimensional, two-phase, steady state model of the gas crossover using the partial differential equation solver FreeFem++, was built to investigate the crossover characteristics of hydrogen and oxygen across the membrane versus changes in operating conditions and various geometric structure of components in the proton exchange membrane fuel cell. Results indicated that higher equivalent weight of Nafion® is required to significantly decrease gas crossover phenomenon while the cell performance was reduced negligibly. In addition, as the increase in the stoichiometric flow ratio and channel length, the gas crossover decreased and the cell performance improved.

A high efficiency 2 stage vapour compression cycle is developed for domestic refrigerator-freezer application. The 2 stage refrigeration system consists of two evaporators, two compressors, a condenser, two heat exchangers, expansion valves and a vapour-liquid separator. A new high efficiency cycle is selected depending on the arrangement of evaporators and compressors. The cycle simulation is carried with the refrigerant of R600a. It is found the 2 stage cycle with two serial evaporators and two parallel compressors gives the highest COP. COP of 2 stage cycle with two serial evaporators and two parallel compressors is more than 10.74% COP of 2 stage cycle with two parallel evaporators and two serial compressors.

The potential of deoiled Azolla pinnata biomass (DAB) as electrode and substrate was evaluated for microbial fuel cell (MFC) operation. The anode electrode was fabricated using biochar obtained by subjecting DAB to pyrolysis at 600 °C, while the reducing sugars after hydrolysis of DAB by acid pretreatment was used as substrate. The post pyrolyzed biochar (P-DAB) was characterized for structural and elemental functionalities using SEM, XRD and Raman spectroscopy, whereas the reducing sugar obtained from hydrolyzed DAB (H-DAB) was analyzed for its composition. Experimental results indicated that at a given 3 g COD/L resulted in a voltage of 382 mV with 65.6% of COD reduction in closed circuit (CC) mode of operation. Cyclic voltammetric analysis depicted maximum oxidative and reductive peak currents of 3.42 mA and -4.0 mA. Noticeable peaks were also identified in CC (-0.2 V to +0.2 V and -0.19 V to -0.3 V) and OC (+0.2 V to +0.4 V and -0.1 V to -0.3 V) corresponding to complex IV cytochrome c couples (cytochrome Cox (Cyt Cox)/cytochrome Crd (Cyt Crd)), signifying the participation of electron carriers during electron transfer. The microbiome diversity showed dominance of Proteobacteria, a phylum known for exo-electrogenic bacterial species. The DAB-derived products account to environmental sustainability and support circular bioeconomy in a biorefinery mode.

Thermoelectric (TE) material is a class of materials that can convert heat to electrical energy directly in a solid-state-device without any moving parts and that is environmentally friendly. The study and development of TE materials have grown quickly in the past decade. However, their development goes slowly by the lack of cheap TE materials with high Seebeck coefficient and good electrical conductivity. Carbon nanotubes (CNTs) are particularly attractive as TE materials because of at least three reasons: (1) CNTs possess various band gaps depending on their structure, (2) CNTs represent unique one-dimensional carbon materials which naturally satisfies the conditions of quantum confinement effect to enhance the TE efficiency and (3) CNTs provide us with a platform for developing lightweight and flexible TE devices due to their mechanical properties. The TE power factor is reported to reach 700–1000 μ W / m K 2 for both p-type and n-type CNTs when purified to contain only doped semiconducting CNT species. Therefore, CNTs are promising for a variety of TE applications in which the heat source is unlimited, such as waste heat or solar heat although their figure of merit Z T is still modest (0.05 at 300 K). In this paper, we review in detail from the basic concept of TE field to the fundamental TE properties of CNTs, as well as their applications. Furthermore, the strategies are discussed to improve the TE properties of CNTs. Finally, we give our perspectives on the tremendous potential of CNTs-based TE materials and composites.