• Journal of Microbiology and Biotechnology
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• 제23권12호
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• pp.1765-1773
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• 2013

The cathode reaction is one of the most seriously limiting factors in a microbial fuel cell (MFC). The critical dissolved oxygen (DO) concentration of a platinum-loaded graphite electrode was reported as 2.2 mg/l, about 10-fold higher than an aerobic bacterium. A series of MFCs were run with the cathode compartment inoculated with activated sludge (biotic) or not (abiotic) on platinum-loaded or bare graphite electrodes. At the beginning of the operation, the current values from MFCs with a biocathode and abiotic cathode were $2.3{\pm}0.1$ and $2.6{\pm}0.2mA$, respectively, at the air-saturated water supply in the cathode. The current from MFCs with an abiotic cathode did not change, but that of MFCs with a biotic cathode increased to 3.0 mA after 8 weeks. The coulomb efficiency was 59.6% in the MFCs with a biotic cathode, much higher than the value of 15.6% of the abiotic cathode. When the DO supply was reduced, the current from MFCs with an abiotic cathode decreased more sharply than in those with a biotic cathode. When the respiratory inhibitor azide was added to the catholyte, the current decreased in MFCs with a biotic cathode but did not change in MFCs with an abiotic cathode. The power density was higher in MFCs with a biotic cathode ($430W/m^3$ cathode compartment) than the abiotic cathode MFC ($257W/m^3$ cathode compartment). Electron microscopic observation revealed nanowire structures in biofilms that developed on both the anode and on the biocathode. These results show that an electron-consuming bacterial consortium can be used as a cathode catalyst to improve the cathode reaction.

• 한국세라믹학회지
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• 제51권4호
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• pp.278-282
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• 2014

Due to high ionic conductivity and favorable oxygen electrocatalysis, doped $Bi_2O_3$ systems are promising candidates as solid oxide fuel cell cathode materials. Recently, several researchers reported reasonably low cathode polarization resistance by adding electronically conducting materials such as (La,Sr)$MnO_3$ (LSM) or Ag to doped $Bi_2O_3$ compositions. Despite extensive research efforts toward maximizing cathode performance, however, the inherent catalytic activity and electrochemical reaction pathways of these promising materials remain largely unknown. Here, we prepare a symmetrical structure with identically sized $Y_{0.5}Bi_{1.5}O_3$/LSM composite electrodes on both sides of a YSZ electrolyte substrate. AC impedance spectroscopy (ACIS) measurements of electrochemical cells with varied cathode compositions reveal the important role of bismuth oxide phase for oxygen electrocatalysis. These observations aid in directing future research into the reaction pathways and the site-specific electrocatalytic activity as well as giving improved guidance for optimizing SOFC cathode structures with doped $Bi_2O_3$ compositions.

• 한국수소및신에너지학회논문집
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• 제24권2호
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• pp.186-192
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• 2013

In order to reduce the costs and to improve the durability of solid oxide fuel cell (SOFC), the operating temperature should be decreased while the power density is maintained as much as possible. However, lowering the operating temperature increases the cathode interfacial polarization resistances dramatically, limiting the performance of low-temperature SOFC at especially purely electronic conducting cathode. To improve cathode performance at low temperature, the number of reaction sites for the oxygen reduction should be increased by using a mixed ionic and electronic conducting (MIEC) material. In this study, anode-supported fuel cells with two different thicknesses of the MIEC cathode were fabricated and tested at various operating temperatures. The anode supported cell with $32.5{\mu}m$-thick BSCFZn-LSCF cathode layer showed much lower polarization resistance than that with $3.2{\mu}m$ thick cahtode and higher power density especially at low temperature. The effects of cathode layer thickness on the electrochemical performance are discussed with analysis of impedance spectra.

• 한국전기전자재료학회논문지
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• 제21권5호
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• pp.447-452
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• 2008

We synthesized nano-sized $La_{1-x}Sr_xCoO_3$ ($x=0.1{\sim}0.4$) cathode catalyst for the zinc air secondary batteries by citrate method, And we measured the cathode's electrochemical characteristics according to content of strontium compose the cathode catalyst. We controlled the pH of precursor solution by 10 in the process of manufacturing the precursor, We heat treated the prepared precursor at various calcination temperature ($500{\sim}900^{\circ}C$), and examined the optimum calcinations temperature by XRD analysis and electrochemical evaluation. We examined the ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) performance of the prepared $La_{1-x}Sr_xCoO_3$ catalyst powder. When we consider ORR and OER performance simultaneously, $La_{0.7}Sr_{0.3}CoO_3$ catalyst has shown the best performance because of its lowest voltage deference between charge and discharge.

• 한국세라믹학회지
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• 제36권9호
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• pp.982-990
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• 1999

YSZ/LSM composite cathode was fabricated by dip-coating of YSZ sol on the internal pore surface of a LSM cathode followed by sintering at low temperature (800-100$0^{\circ}C$) The YSZ coating significantly increased the TPB(Triple Phase Boundary) where the gas the electrode and the electrolyte were in contact with each other. Sinter the formation of resistive materials such as La2Zr2O7 or SrZrO3 was prevented due to the low processing temperature and TPB was increased due to the YSZ film coating the electrode resistance (Rel) was reduced about 100 times compared to non-modified cathode. From the analysis of a.c impedance it was shown that microstructural change of the cathode caused by YSZ film coating affected the oxygen reduction reaction. In the case of non-modified cathode the RDS (rate determining step) was electrode reactions rather than mass transfer or the oxygen gas diffusion in the experimental conditions employed in this study ($600^{\circ}C$-100$0^{\circ}C$ and 0,01-1 atm of Po2) for the YSZ film coated cathode however the RDS involved the oxygen diffusion through micropores of YSZ film at high temperature of 950-100$0^{\circ}C$ and low oxygen partial pressure of 0.01-0.03 atm.

• 한국환경과학회지
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• 제23권6호
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• pp.1175-1182
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• 2014

In this study, we examined the effect of cathode from electrolysis reactor for treating ballast water. We are going to select a suitable cathode for seawater electrolysis after considering the effect on the generation of the oxidant of cathode and the electrode deposition materials adhering to the surface of cathode. Anode is Ru-Ti-Pd electrode and cathode are Ti, Pt, JP520 (Ni-Pt-Ce) electrodes. Using the cathode of the three types, experiments were conducted to examine the effects of TRO (total residual oxidants) generation concentration and RNO (N, N-Dimethyl-4-nitrosoaniline, indicator of the generation of OH radical) degradation concentration (in 1, 35 psu), ohmic drop, FESEM(field emission scanning electron microscope) observation of cathode surface and EDX (energy dispersive X-ray spectroscopy) measurements of attached fouling material. The results showed that TRO generation concentration and RNO degradation concentration in according to each type of cathode are not different. The attached fouling materials were observed on the surface of Ti and the JP520 electrode by the observation of SEM after electrolysis for two hours, but it was not observed on the surface of Pt electrode. When considering the surface ohmic drop of cathode and the attached fouling materials, Pt electrode was judged as the excellent cathode.

• 한국수소및신에너지학회논문집
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• 제3권2호
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• pp.55-62
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• 1992

본 연구에서는 용융탄산염 연료전지의 각 구성요소에서 발생하는 분극현상을 조사하였다. 기준 전극을 부착한 단위전지를 제작하고 전류단락법을 이용하여 전지의 내부저항에 의한 전압손실 및 그이외의 과전압을 측정하였다. $150mA/cm^2$의 전류밀도에서 anode의 과전압은 60mV이하였으나 cathode의 과전압은 130mV 정도로 크게 나타났으며, 전지의 내부저항에 의한 과전압도 170mV정도로커서 cathode의 성능 개선 빛 내부저항의 감소가 필요함을 알았다. 박막 모델을 사용하여 전극의 과전압을 실험치와 근접하게 예측할 수 있었으며, 전극 전해질 계면의 면적 및 전해질 박막의 두께를 조절하여 과전압이 최소가 되도록 전극의 구조를 조절하는 것이 매우 중요함을 알 수 있었다.

• 대한기계학회논문집B
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• 제31권1호
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• pp.62-67
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• 2007

Optimization of cathode properties for intermediate temperature-operating SOFC (IT-SOFC) is carried out by using composite-type electrode structure in this study. Composite cathode may lower cathode overpotential by enhancing mixed ionic-electronic conductivity. In this study, particularly, LSM/YSZ, LSF/YSZ, LSCF/CGO, and PSC/CGO were selected as cathode materials. LSM/YSZ composite cathode showed the best performance of about 0.9${\Omega}cm^2$ at $700^{\circ}C$. It is inferred that the resistance is mainly affected by the reactivity between cathode and electrolyte which can cause the formation of resistive phases. Area specific resistance (ASR) characteristics were not changed significantly with decreasing sintering temperature of cathode, because reaction sites were increased even with worse adhesion of cathode on electrolytes.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.112-119
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• 2022

Molten carbonate fuel cells (MCFCs) are environmentally friendly, large-capacity power generation devices operated at approximately 650℃. If MCFCs are to be commercialized by improving their competitiveness, their cell life should be increased by operating them at lower temperatures. However, a decrease in the operating temperature causes a reduction in the cell performance because of the reduction in the electrochemical reaction rate. The cell performance can be improved by introducing a coating on the cathode of the cell. A coating with a high surface area expands the triple phase boundaries (TPBs) where the gas and electrolyte meet on the electrode surface. And the expansion of TPBs enhances the oxygen reduction reaction of the cathode. Therefore, the cell performance can be improved by increasing the reaction area, which can be achieved by coating nanosized LiCoO₂ particles on the cathode. However, although a coating improves the cell performance, a thick coating makes gas difficult to diffuse into the pore of the coating and thus reduces the cell performance. In addition, LiCoO₂-coated cathode cell exhibits stable cell performance because the coating layer maintains a uniform thickness under MCFC operating conditions. Therefore, the performance and stability of MCFCs can be improved by applying a LiCoO₂ coating with an appropriate thickness on the cathode.

• E2M - 전기 전자와 첨단 소재
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• 제10권2호
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• pp.141-149
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• 1997

L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders were prepared by both GNP(Glycine-Nitrate Process) and solid state reaction method in various of calcination temperature(800-1000.deg. C) and time in air. Also, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contacts on YSZ(Yttria-Stabilized Zirconia) substrate were prepared by screen printing and sintering method as a function of sintering temperature(1100-1450.deg. C) in air. Sintering behaviors have been investigated by SEM(Scanning Electron Microscope) and porosity measurement. Compositional and structural characterization were carried out by X-ray diffractometer and ICP AES(Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Electrical characterization was carried out by the electrical conductivity with linear 4 point probe method. As the calcination period increased in solid state reaction method, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ phase increased. Although L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ single phase was obtained only for 48hrs at 1000.deg. C, in GNP method it was easy to get single and ultra-fine L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders with submicron particle size at 650.deg. C for 30min. The particle size and thickness of L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contact by solid state reaction method did not change during the heat treatment, while those by GNP method showed good sintering characteristics because initial powder size fabricated from GNP method is smaller than that fabricated from solid state reaction method. Based on enthalpy change from thermodynamic data and ICP-AES analysis, it was suggested to make cathode contact in composition of (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$ Mn $O_{3}$ which have little second phase (L $a_{2}$Z $r_{2}$ $O_{7}$) for high efficient solid oxide fuel cells applications. As (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$Mn $O_{3}$ cathode contact on YSZ substrate was sintering at 1250.deg. C the temperature that liquid phase sintering did not occur. It was possible to obtain proper cathode contacts with electrical conductivity of 150(S/cm) and porosity content of 30-40%.m) and porosity content of 30-40%.