• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.235-242
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• 2011

This perspective describes recent advances made in the development of various electrochemical technologies to treat waste water containing organic pollutants, reducible/oxidizable and non-reducible/non-oxidizable anions and cations using redox reactions on the solid surface as well as at the interface between solid electrode and liquid electrolyte. Some of representative multiplexing and hybrid electrochemical treatment technologies are discussed, which have great advantages of high efficiency, stability and cost-effective instrumentation without the need of considering non-specific conditions such as high-temperature and high-pressure; however, choices and usages of electrode materials are absolutely critical issues.

• Clean Technology
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• v.27 no.3
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• pp.223-231
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• 2021

In order to address many issues associated with large volume changes of silicon, which has very low electrical conductivity but offers about 10 times higher theoretical capacity than graphite (Gr), a silicon nanoparticles/hollow carbon (SiNP/HC) composite having bimodal-mesopores was prepared using silica nanoparticles as a template. A control SiNP/C composite without a hollow structure was also prepared for comparison. The physico-chemical and electrochemical properties of SiNP/HC were analyzed by X-ray diffractometry, X-ray photoelectron spectroscopy, nitrogen adsorption/desorption measurements for surface area and pore size distribution, scanning electron microscopy, transmission electron microscopy, galvanostatic cycling, and cyclic voltammetry tests to compare them with those of the SiNP/C composite. The SiNP/HC composite showed significantly better cycle life and efficiency than the SiNP/C, with minimal increase in electrode thickness after long cycles. A hybrid composite, SiNP/HC@Gr, prepared by physical mixing of the SiNP/HC and Gr at a 50:50 weight ratio, exhibited even better cycle life and efficiency than the SiNP/HC at low capacity. Thus, silicon/carbon composites designed to have hollow spaces capable of accommodating volume expansion were found to be highly effective for long cycle life of silicon-based composites. However, further study is required to improve the low initial coulombic efficiency of SiNP/HC and SiNP/HC@Gr, which is possibly because of their high surface area causing excessive electrolyte decomposition for the formation of solid-electrolyte-interface layers.

• Clean Technology
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• v.20 no.4
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• pp.433-438
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• 2014

There is an increasing interest in the development of rechargeable batteries suitable for use in both hybrid electric vehicles and energy storage systems that require higher charge & discharge rates, bigger battery sizes and increased safety of the batteries. Spinel-type lithium titanium oxide ($Li_4Ti_5O_{12}$) as a potential anode for lithium ion batteries has many advantages. It is a zero-strain materials and it experiences no structural change during the charge/discharge precess. Thus, it has long cycle life due to its structural integrity. It also offers a stable operation voltage of approximately 1.55 V versus $Li^+/Li$, above the reduction potential of most organic electrolyte. In this study, Ru added $Li_4Ti_5O_{12}$ composites were synthesized by solid state process. The characteristics of active material were investigated with TGA-DTA, XRD, SEM and charge/discharge test. The capacity was reduced when Ru was added, however, the polarization decreased. The capacity rate of $Li_4Ti_5O_{12}$ with Ru (3%, 4%) addition was reduced during the charge/discharge precess with 10 C-rate as a high current density.