• Journal of Electrochemical Science and Technology
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• v.5 no.1
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• pp.1-18
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• 2014

Li-air cell is an exotic type of energy storage and conversion device considered to be half battery and half fuel cell. Its successful commercialization highly depends on the timely development of key components. Among these key components, the catalyst (i.e., the core portion of the air electrode) is of critical importance and of the upmost priority. Indeed, it is expected that these catalysts will have a direct and dramatic impact on the Li-air cell's performance by reducing overpotentials, as well as by enhancing the overall capacity and cycle life of Li-air cells. Unfortunately, the technological advancement related to catalysts is sluggish at present. Based on the insights gained from this review, this sluggishness is due to challenges in both the commercialization of the catalyst, and the fundamental studies pertaining to its development. Challenges in the commercialization of the catalyst can be summarized as 1) the identification of superior materials for Li-air cell catalysts, 2) the development of fundamental, material-based assessments for potential catalyst materials, 3) the achievement of a reduction in both cost and time concerning the design of the Li-air cell catalysts. As for the challenges concerning the fundamental studies of Li-air cell catalysts, they are 1) the development of experimental techniques for determining both the nano and micro structure of catalysts, 2) the attainment of both repeatable and verifiable experimental characteristics of catalyst degradation, 3) the development of the predictive capability pertaining to the performance of the catalyst using fundamental material properties. Therefore, under the current circumstances, it is going to be an extremely daunting task to develop appropriate catalysts for the commercialization of Li-air batteries; at least within the foreseeable future. Regardless, nano materials are expected to play a crucial role in this field.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1150-1154
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• 2003

The voltage profile during discharge of the zinc air battery has very flat pattern until reach to end of discharge voltage. But, when zinc air battery is discharged by high current, the discharge voltage and energy becomes low. Therefore, we focused on effects of catalyst size to solve this problems by increasing active sites of oxygen reduction reaction. The size of catalyst was reduced from 27 to l${\mu}{\textrm}{m}$ and we examined average discharge voltage, capacity, energy, resistance and characteristics during GSM pulse discharge of zinc air battery with change of current density. And we also measured porosity of the cathode according to the ASTM. So we have got improvement of average discharge voltage and energy when catalyst was minimized and we have got optimum size of catalyst at 5${\mu}{\textrm}{m}$.

• Progress in Superconductivity and Cryogenics
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• v.21 no.2
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• pp.15-21
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• 2019

In the mine exploration sites, sustainable treatment system of mine water with energy saving and minimized chemical additives is required. Since most of the mine water contains highly-concentrated ferrous ion, it is necessary to study on the removal method of iron ions. We propose the system consisting of two processes; precipitation process by air oxidation using solid catalyst-modified magnetite and separation process combining gravitational sedimentation and magnetic separation using a permanent magnet. Firstly, in the precipitation process (a former process of the system), we succeeded to prepare solid catalyst-modified magnetite. Air oxidation using solid catalyst-modified magnetite using $Fe_2(SO_4)_3$ as a starting material showed high iron removal capability. Secondly, in the separation process (latter process of the system), solid catalyst-modified magnetite using $Fe_2(SO_4)_3$ as a starting material can be separated by a superconducting bulk magnet and a permanent magnet.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.115-124
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• 2002

The optimum design of auto-catalyst needs a good compromise between the pressure drop and flow distribution in the monolith. One of the effective methods to achieve this goal is to use the concept of radially variable cell density. However, there has been no study of evaluating the usefulness of this method on light-off catalyst. We have computationally investigated the effectiveness of variable cell density technique applied to the light-off catalyst using a three-dimensional integrated CFD model. in which transient chemical reacting calculations are involved. Computed results show that variable cell density technique can reduce the accumulated emissions of CO and HC during the early 100sec of FTP cycle by 86.78 and 80.87%, respectively, The effect of air-gap between the monoliths has been also examined. It is found that air-gap has a beneficial effect on reducing pressure drop and cold-start emissions.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.1
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• pp.46-53
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• 1981

This paper describes emission control of hydrocarbon and carbon-monoxide due to oxidizing catalyst. The experiment was performed on a precious metal pelleted catalyst(Pt). The factors of the efficiency for purification due to oxidizing catalyst are space velocity, temperature, composition of exhaust gas and supplementary air. The experiment was carried out to control the factors of efficiency for purification. The results of experimental study show that temperature of catalytic converter, supplementary air and space velocity affected the efficiency for purification of hydrocarbon and carbon monoxide.

• Advances in Energy Research
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• v.2 no.2
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• pp.73-84
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• 2014

Fuel cells of proton exchange membrane type (PEMFC) working with hydrogen in the anode and ambient air in the cathode ('air breathing') have been prepared and characterized. The cells have been studied with variable thickness of the cathode catalyst layer ($L_{CL}$), maintaining constant the platinum and ionomer loads. Polarization curves and electrochemical active area measurements have been carried out. The polarization curves are analyzed in terms of a model for a flooded passive air breathing cathode. The analysis shows that $L_{CL}$ affects to electrochemical kinetics and mass transport processes inside the electrode, as reflected by two parameters of the polarization curves: the Tafel slope and the internal resistance. The observed decrease in Tafel slope with decreasing $L_{CL}$ shows improvements in the oxygen reduction kinetics which we attribute to changes in the catalyst layer structure. A decrease in the internal resistance with $L_{CL}$ is attributed to lower protonic resistance of thinner catalyst layers, although the observed decrease is lower than expected probably because the electronic conduction starts to be hindered by more hydrophilic character and thicker ionomer film.

• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.842-845
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• 2011

Wet air oxidation (WAO) of oily sludge was carried out using $Fe^{3+}$ as catalyst, placed in a 0.5 L batch autoclave in the temperature range of $250-330^{\circ}C$. Experiments were conducted to investigate the effects of temperature, the initial COD, reaction time, concentration of catalyst and $O_2$ excess (OE) on the oxidation of the oily sludge. The results showed that in the WAO 88.4% COD was achieved after 9 min reaction at temperature of $330^{\circ}C$, OE of 0.8 and the initial COD of 20000 mg/L. Temperature was found to have a significant impact on the oxidation of oily sludge. Adding a catalyst significantly improved the COD removal. Homogenous catalyst, $Fe^{3+}$, showed effective removal for pollutants. COD removal was 99.7% in the catalytic wet air oxidation (CWAO) over $Fe^{3+}$ catalyst. The results proved that the CWAO was an effective pretreatment method for the oily sludge.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.6
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• pp.822-829
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• 1997

A catalytic burner was studied which can be used as a heater operated in medium temperature. Noble metal catalysts (Pd/NiO) were used, which were supported on alumina wash coated honeycomb. The maximum heat-resisting temperature of the catalyst is about 900.deg. C. Combustion efficiency of the catalytic burner reached more than 99.5 % at the excess air ratio above 1.25.NOx emissions were lower than 1.0 ppm at all operation conditions. The operation condition for a stable catalytic combustion was obtained. It was dependent on the catalyst thickness. The 30 mm thick catalyst showed the widest stable catalytic combustion region. Stable catalytic combustion region of 30 mm thick catalyst was the operation condition of excess air ratio 1.25 - 1.75 and heat flux 7 - 14 kcal/h center dot cm$^{2}$.

• Journal of Power System Engineering
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• v.7 no.3
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• pp.12-17
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• 2003

The purpose of this study is to observe the purification characteristics of NOx, CO and HC in various catalysts and excess air ratio conditions. For this purpose, we installed various catalysts on the back stream of the coaxial diffusion burner with swirler. As the result, in the case of NOx, Pt-Rh catalyst shows very high value that is more than 90%-conversion efficiency without the relation with the excess air ratio. After excess air ratio of ${\alpha}=1.14$, it shows that the conversion efficiencies were more than 80% in the every Pt catalyst in the view of conversion of every exhaust with changing of the excess air ratio.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.425-431
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• 2019

As rechargeable metal-air batteries will be ideal energy storage devices in the future, an active cathode electrocatalyst is required with bi-functionality on both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharge and charge, respectively. Here, a class of perovskite cathode catalyst with a micro-tubular structure has been developed by controlling bi-functionality from different Ru and Ni dopant ratios. A micro-tubular structure is achieved by the activated carbon fiber (ACF) templating method, which provides uniform size and shape. At the perovskite formula of $LaCrO_3$, the dual dopant system is successfully synthesized with a perfect incorporation into the single perovskite structure. The chemical oxidation states for each Ni and Ru also confirm the partial substitution to B-site of Cr without any changes in the major perovskite structure. From the electrochemical measurements, the micro-tubular feature reveals much more efficient catalytic activity on ORR and OER, comparing to the grain catalyst with same perovskite composition. By changing the Ru and Ni ratio, the $LaCr_{0.8}Ru_{0.1}Ni_{0.1}O_3$ micro-tubular catalyst exhibits great bi-functionality, especially on ORR, with low metal loading, which is comparable to the commercial catalyst of Pt and Ir. This advanced catalytic property on the micro-tubular structure and Ru/Ni synergy effect at the perovskite material may provide a new direction for the next-generation cathode catalyst in metal-air battery system.