• New & Renewable Energy
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• v.18 no.2
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• pp.40-49
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• 2022

In this study, the phase and electrochemical properties of Co and Ti substituted layered perovskites SmBaCo_2-xTi_xO_5+d (x=0.5, 0.7, 1.0, 1.1, 1.3, and 1.5) were analyzed, and their application as electrodes in solid oxide fuel cells (SOFCs) were evaluated. After calcination at 1300℃ for 6 h, a single phase was observed for two compositions of the SmBaCo_2-xTi_xO_5+d oxide system, SmBaCoTiO_5+d (x=1.0) and SmBaCo_0.9Ti_1.1O_5+d (x=1.1). However, the phases of SmBaCoTiO_5+d (SBCTO) and SmTiO₃ coexisted for compositions with x≥1.3 (Ti content). In contrast, for compositions of x≤0.7, the SmBaCo₂O_5+d phase was observed instead of the SmTiO₃ phase. To evaluate the applicability of these materials as SOFC electrodes, the electrical conductivities were measured under various atmospheres (air, N₂, and H₂). SBCTO exhibited stable semi-conductor electrical conductivity behavior in an air and N₂ atmosphere. However, SBCTO showed insulator behavior at temperatures above 600℃ in a H₂ atmosphere. Therefore, SBCTO may only be used as cathode materials. Moreover, SBCTO had an area specific resistance (ASR) value of 0.140 Ω·cm² at 750℃.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.50-54
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• 2012

In this study, PANI and PANI/$TiO_2$ composites were prepared as electrode materials for a supercapacitor application. Cyclic voltammetry (CV) was performed to investigate the supercapacity properties of these electrodes in an electrolyte solution of 6 M KOH. The PANI/$TiO_2$ composites were polymerized by amount of various ratios through a simple in-situ method. The morphological properties of composites were analyzed by SEM and TEM method. The crystallinity of the composite and $TiO_2$ particle size were identified using X-ray diffraction (XRD). In the electrochemical test, The electrode containing 10 wt% $TiO_2$ content against aniline units showed the highest specific capacitance (626 $Fg^{-1}$) and delivered a capacitance of 286 $Fg^{-1}$ reversibly at a 100 $mVs^{-1}$ rate. According to the surface morphology, the increased capacitance was related to the fact that nano-sized $TiO_2$ particles (~6.5 nm) were uniformly connected for easy charge transfer and an enhanced surface area for capacitance reaction of $TiO_2$ itself.

• Applied Chemistry for Engineering
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• v.24 no.2
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• pp.201-207
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• 2013

In this study, the surface of a phenol based activated carbon (AC) used as an electrode in an electric double layer capacitor was modified via boric acid treatment for the capacitance investigation. The effect of boric acid treatment on electrochemical performance was also investigated. The AC surface functional groups ratio of quinone-like (O=C) which is electrochemical active functional groups was increased after the boric acid treatment. And, boric acid treated AC showed an increase in the specific surface area, total pore volume, and micropore volume. In case of optimum boric acid treated AC, its specific capacitance increased by 20% in comparison to that of untreated AC. These results demonstrate that a boric acid treated carbon surface-based electric double layer capacitor electrode effectively enhances specific capacitance.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.11-17
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• 2010

Modifying surface of activated carbon for the electrode of EDLC with an organic electrolyte was investigated to improve the electrochemical performance of EDLC by the microwave radiation. Three kinds of activated carbons, prepared activated carbon from petroleum cokes and pitch cokes and commercial activated carbon BP-25, were used for this study. For all investigated activated carbons, hydrophilic functional groups-containing oxygen disappeared from the surface of activated carbon as microwave radiation. And as microwave radiation time was increased, the specific surface area and total pore volume of activated carbons were reduced and average pore diameter were increased. From theses effects, interfacial resistance of EDLC with the modified activated carbon electrode was drastically decreased, and discharge capacitance was increased although the specific surface area of activated carbon was reduced by this microwave radiation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.619-624
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• 2012

In this study, we demonstrated the operation of an electroosmotic pump with cylindrical porous glass frits and evaluated its long-term operation. The performance of this electroosmotic pump was characterized in terms of maximum flow rate, current, and pressure using deionized water and 1 mM borate buffer. The maximum flow rate, current, and pressure linearly increase with voltage. The maximum flow rate is normalized by the pumping area and voltage for comparison of the performance between the electroosmotic pumps with cylindrical and planar frits. The normalized maximum flow rate of the cylindrical-type pump is higher than that of the planar-type pump because of their different geometries. The cylindrical-type electroosmotic pump has five times better performance than the planartype electroosmotic pump for a given pump package volume. It can operate stably for over 3 hours.

• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.543-553
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• 1996

Oxygen reduction in an alkaline fuel cell was studied by using perovskite type oxides as an oxygen electrode catalyst. The high surface area catalysts were prepared by malic acid method and had a formula of $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$(x=0.00, 0.01, 0.10, 0.20, 0.35 and 0.50). From the result of XRD pattern and specific surface area due to the amount of Fe substitution and the consumption of ammonia-water, the complex formation of Fe ion with $NH_3$ was the main factor for both the phase stability of perovskite and the increase of specific surface area. Multi-step calcination was necessary to give a single phase of perovskite in catalyst precursor. The crystal structure of the catalysts was simple cubic perovskite, which was verified from the XRD patterns of the catalysts. The activity of oxygen reduction was monitored by the techniques of cyclic voltammetry, static voltage-current method, and current interruption method. The activity(current density) of oxygen reduction showed its minimum at x=0.01 and its maximum between 0.20 and 0.35 of x-value in $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$. This tendency was independent of the change of surface area.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.402-402
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• 2011

본 연구에서는 결정질 태양전지 제작에 있어 재료비 절감과 기존의 Screen Printing 공정 기술에서의 단점을 보완하기 위한 방안으로 후면 passivation 구조와 레이저를 이용한 국부적 후면 전극 형성(Laser Fired Contact) 방법에 대한 실험을 진행하였다. 후면 passivation 층으로 SiO2/ SiNx/SiO2 삼중막 구조와 SiNx 단일막 구조를 형성시킨 후 anneal 온도에 따른 소수캐리어의 lifetime 변화를 비교하였다. LFC 형성은 2 ${\mu}m$ 두께의 Al이 증착된 기판 후면에 1,064 nm 파장의 레이저를 통해 diameter와 dot pitch 등의 파라미터를 가변 하여 실시하였다. 실험 결과 800$^{\circ}C$의 고온 열처리 후 ONO 삼중막에서의 lifetime 향상이 우세하여 SiNx 단일 막 보다 열적 안정성이 우수함을 확인하였다. LFC 결과 diameter가 40, 50, 60 ${\mu}m$로 가변된 조건에서는 40 ${\mu}m$ 일 경우와 dot pitch가 200, 500, 1,000 ${\mu}m$로 가변된 조건에서는 1,000 ${\mu}m$일 경우 610 mV의 Voc 값을 보였다. 이는 레이저를 통해 국부적으로 Al-Si 간 alloy를 형성시킴으로써 접촉 면적이 최소화됨에 따라 후면에서의 캐리어의 재결합속도를 감소시키고, passivation 효과를 극대화시키기 때문이다.

• Journal of the Korean Wood Science and Technology
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• v.49 no.4
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• pp.299-314
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• 2021

In this study, we investigated the effect of temperature on specific surface area and electrochemical properties when lignin-based porous carbon (LBPC) with potassium hydroxide (KOH) is activated. After preparing LBPCs using lignin-polyacrylonitrile (PAN) copolymer, which was synthesized by graft polymerizing lignin and acrylonitrile as a precursor, activated LBPCs (KA-LBPC-6, 7, 8, 9) were manufactured by activating LBPC with KOH at 600℃, 700℃, 800℃ and 900℃. To identify the surface characteristics of KA-LBPC, observations were made with a scanning electron microscopy (SEM), and the pore characteristics were identified via specific surface area analysis. The electrochemical properties were analyzed using a three-electrode system. The experiment has shown that micropores formed by activation can be observed in SEM images. KA-LBPC-7 had the best pore characteristics among KA-LBPCs, with a specific surface area of 2480.1 m²/g, a micropore volume of 0.64 cm³/g, and a mesopore volume of 0.76 cm³/g. KA-LBPC-7 showed the best electrochemical properties with a specific capacitance of 151.3 F/g at the scan rate of 2 mV/s.

• Journal of the Korean Ceramic Society
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• v.42 no.4
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• pp.269-275
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• 2005

We analyzed the unit cell performance against the cathode porosity, which is supposed to be closely related with active sites for the cathode reaction. In order to fabricate the unit cells with different porosity in the cathode layer we changed the mixing ratio of fine and coarse LSCF cathode powders. The final porosity of each cathode layer was 14, 23, 27, $39\%$ respectively. According to the electrochemical analysis of unit cell performance via DC current interruption and AC impedance method, the electrodic polarization resistance was diminished as the cathode porosity increased. The decrease of polarization resistance was attributed due to the increase of active reaction sites and the enhancement of overall unit cell performance could be explained in the same line.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.305-309
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• 2016

Recently, there are many efforts focused on development of more economical non-fluorinated membranes for PEMFCs (Proton Exchange Membrane Fuel Cells). In this study, to test the durability of sPEEK MEA (Membrane and Electrode Assembly), ADT (Accelerated Degradation Test) of MEA degradation was done at the condition that membrane and electrode were degraded simultaneously. Before and after degradation, I-V polarization curve, hydrogen crossover, electrochemical surface area, membrane resistance and charge transfer resistance were measured. Although the permeability of hydrogen through sPEEK membrane was low, sPEEK membrane was weaker to radical evolved at low humidity and OCV condition than fluorinated membrane such as Nafion. Performance after MEA degradation for 144 hours and 271 hours were reduced by 15% and 65%, respectively. It was showed that the main cause of rapid decrease of performance after 144 hours was shorting due to Pt/C particles in the pinholes.