• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.282-291
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• 2018

The pristine fluorine-doped $SnO_2$ (abbreviated as FTO) inverse opal (IO) was developed using a 410 nm polystyrene bead template. The nanolayered copper tungsten oxide ($CuWO_4$) was decorated on the FTO IO film using a facile electrochemical deposition, subsequently followed by annealing at $500^{\circ}C$ for 90 min. The morphologies, crystalline structure, optical properties and photoelectrochemical characteristics of the FTO and $CuWO_4$-decorated FTO (briefly denoted as $FTO/CuWO_4$) IO film were investigated by field emission scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and electrochemical impedance spectroscopy, showing FTO IO in the hexagonally closed-pack arrangement with a pore diameter and wall thickness of about 300 nm and 20 nm, respectively. Above this film, the $CuWO_4$ was electrodeposited by controlling the cycling number in cyclic voltammetry, suggesting that the $CuWO_4$ formed during 4 cycles (abbreviated as $CuWO_4$(4 cycles)) on FTO IO film exhibited partial distribution of $CuWO_4$ nanoparticles. Additional distribution of $CuWO_4$ nanoparticles was observed in the case of $FTO/CuWO_4$(8 cycles) IO film. The $CuWO_4$ layer exhibits triclinic structure with an indirect band gap of approximately 2.5 eV and shows the enhanced visible light absorption. The photoelectrochemical (PEC) behavior was evaluated in the 0.5 M $Na_2SO_4$ solution under solar illumination, suggesting that the $FTO/CuWO_4$(4 cycles) IO films exhibit a photocurrent density ($J_{sc}$) of $0.42mA/cm^2$ at 1.23 V vs. reversible hydrogen electrode (RHE, denoted as $V_{RHE}$), while the FTO IO and $FTO/CuWO_4$(8 cycles) IO films exhibited a $J_{sc}$ of 0.14 and $0.24mA/cm^2$ at $1.23V_{RHE}$, respectively. This difference can be explained by the increased visible light absorption by the $CuWO_4$ layer and the favorable charge separation/transfer event in the cascading band alignment between FTO and $CuWO_4$ layer, enhancing the overall PEC performance.

• 전기화학회지
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• 제14권1호
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• pp.33-37
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• 2011

$Li_4Ti_5O_{12}$는 우수한 안정성으로 고출력 배터리의 음극 물질로 주 목 받고 있다. 그러나 절연체로서 전도도의 개선이 필요한 상황으로 다양한 방법이 시도되고 있다. 본 연구에서는 Cr 도핑을 통해서 $Li_4Ti_5O_{12}$의 전도도 향상을 목표로 하였으며, X-선 흡수 실험 및 FEFF 8.4 코드를 이용한 제일원리 계산을 통해서 도핑에 의한 미세 구조 및 전자 구조의 변화를 분석하였다. Cr 도핑은 페르미 레벨을 Cr d 밴드의 중심에 위치시켜 전도성을향상시켰으며, Ti d 밴드의 전자밀도를 높여 XANES pre-edge및 White line의 변화를 야기했다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.251-251
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• 2016

For several decades, industrial processes consume a huge amount of raw water for various objects that consequently results in the generation of large amounts of wastewater. Wastewaters are consisting of complex mixture of different inorganic and organic compounds and some of them can be toxic, hazardous and hard to degrade. These effluents are mainly treated by conventional technologies such are aerobic and anaerobic treatment and chemical coagulation. But, these processes are not suitable for eliminating all hazardous chemical compounds form wastewater and generate a large amount of toxic sludge. Therefore, other processes have been studied and applied together with these techniques to enhance purification results. These include photocatalysis, absorption, advanced oxidation processes, and ozonation, but also have their own drawbacks. In recent years, electrochemical techniques have received attention as wastewater treatment process that could be show higher purification results. Among them, boron doped diamond (BDD) attract attention as electrochemical electrode due to good chemical and electrochemical stability, long lifetime and wide potential window that necessary properties for anode electrode. So, there are many researches about high quality BDD on Nb, Ta, W and Si substrates, but, their application in effluents treatment is not suitable due to high cost of metal and low conductivity of Si. To solve these problems, Ti has been candidate as substrate in consideration of cost and property. But there are adhesion issues that must be overcome to apply Ti as BDD substrate. Al, Cu, Ti and Nb thin films were deposited on Ti substrate to improve adhesion between substrate and BDD thin film. In this paper, BDD films were deposited by hot filament chemical vapor deposition (HF-CVD) method. Prior to deposition, cleaning processes were conducted in acetone, ethanol, and isopropyl alcohol (IPA) using sonification machine for 7 min, respectively. And metal layer with the thickness of 200 nm were deposited by DC magnetron sputtering (DCMS). To analyze microstructure X-ray diffraction (XRD, Bruker gads) and field emission scanning electron microscopy (FE-SEM, Hitachi) were used. It is confirmed that metal layer was effective to adhesion property and improved electrode property. Electrochemical measurements were carried out in a three electrode electrochemical cell containing a 0.5 % H2SO4 in deionized water. As a result, it is confirmed that metal inter layer heavily effect on BDD property by improving adhesion property due to suppressing formation of titanium carbide.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.81-86
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• 2014

The process parameter in optimized KOH alkali activation of soft carbon series coke material in high purity was set with DOE experiments design. The activated carbon was produced by performing the activation process based on the set process parameters. The specific surface area was measured and pore size was analyzed by $N_2$ absorption method for the produced activated carbon. The surface functional group was analyzed by Boehm method and metal impurities were analyzed by XRF method. The specific surface area was increased over 2,000 $m^2/g$ as the mixing ratio of activation agent increased. The micro pores in $5{\sim}15{\AA}$ and surface functional group under 0.4 meq/g were obtained. The contents of the metal impurity in activated carbon which is the factor for reducing the electrochemical characteristics was reduced less than 100 ppm through the cleansing process optimization. The electrochemical characteristics of activated carbon in 38.5 F/g and 26.6 F/cc were checked through the impedance measuring with cyclic voltammetry scan rate in 50~300 mV/s and frequency in 10 mHz ~100 kHz. The activated carbon was made in the optimized activation process conditions of activation time in 40 minutes, mixing ratio of activation agent in 4.5 : 1.0 and heat treatment temperature over $650^{\circ}C$.

• 태양에너지
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• 제10권1호
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• pp.92-97
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• 1990

태양에너지 이용시스템 개발에 있어서 태양열을 효율적으로 이용하기 위한 태양광의 선택흡수막의 제조시 가장 중요한 것이 선택흡수막의 파장별 광학적 특성이다. 이러한 광학적 특성은 전기도금액의 조성에 따라 달라지고 전기도금 방법의 선택 및 도금조건에 따라 영향을 받게 된다. 본 연구에서는 미국에서 개발되고 가장 널리 사용되는 ChromOnyx 도금액을 근거로 새로이 Chromic acid-Propionic acid 흑크름 도금액을 제조하였으며 액을 구성하고 있는 성분별 전기화학적 역할을 고찰하였다. 실제 전기도금법에 의해 제작된 흑크름 선택 흡수막의 광학적특성에 관한 연구는 다시 상세히 다루어 발표할 예정이다.

• Bulletin of the Korean Chemical Society
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• 제28권7호
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• pp.1175-1182
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• 2007

A series of new organic semiconductors hexyl end-capped thiophene-anthracene oligomers containing the anthracene moiety in the center of the oligomers are synthesized. The target oligomers have been obtained by Stille coupling reactions as key step reactions. The synthesized thiophene-anthracene oligomers were characterized by 1H-NMR, 13C-NMR and high-resolution mass spectroscopy, respectively. All of the oligomers are soluble in chlorinated solvents. Their optical, thermal and electrochemical properties were measured. The hexyl end-capped oligomers and their unsubstituted oligomers exhibit the same absorption behavior in dilute toluene solution. Hexyl end-capped bis-terthienylanthracene oligomer is observed to show liquid crystalline mesophase at 166 oC in heating process. The thermal analyses as well as the electrochemical measurement data indicate that the designed materials show better thermal and oxidation stability than the corresponding oligothiophenes without anthracene core. Fluorescence lifetimes and fluorescence quantum yields of the thiophene-anthracene oligomers are measured to be 10-14 ps and 3.4-9.9 × 10?3 which are much shorter and lower than those of oligothiophenes respectively.

• 한국수소및신에너지학회논문집
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• 제28권6호
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• pp.669-674
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• 2017

In this study, the novel electrochemical and colorimetric analysis methods are suggested to estimate the degree of phosphoric acid ion poisoning on Pt based catalyst surface and to confirm the possibility of replacing the expensive and long time consumed conventional methods. As the ways, the electrochemical half cell tests such as cyclic voltammetry (CV) and linear sweep voltammetry (LSV) are used and the change in chemical behavior by absorption of the phosphoric acid ion on Pt based catalyst surface and hydrogen peroxide decomposition reaction are successfully recognized by colorimetric measurements. Conclusively, it is proved that the new methods show superior sensitivity for identifying the degree of phosphoric acid poisoned on Pt based catalyst.

• 전기화학회지
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• 제13권3호
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• pp.175-180
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• 2010

전도성 폴리아닐린을 합성하여 용액 공정을 적용한 유기박막 투명전극을 제조, 그 특성을 조사하였다. 용액에 분산된 폴리아닐린을 스핀코팅하여 얻어진 박막 전극은 200 nm의 두께에서 $380{\Omega}/m^2$ 의 면저항을 보였고, 450 nm 이상의 파장에서 85% 이상의 균일한 광투과성을 나타내었다. 전극의 $130^{\circ}C$이상의 온도변화에서는 비교적 높은 저항변화율이 관찰되었다.

• 한국전기전자재료학회논문지
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• 제16권12S호
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• pp.1273-1277
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• 2003

The effects of molecular structure on the redox properties are explored by the cyclic voltammetry, constant current potentiometry and spectroscopy using the thin films of organic electroluminescence materials of Poly(N-vinylcarbazole); PVK and 2- (4'-tert-butylphenyl) -5-(4"-bisphenyl) -1,3,4-oxadiazole; PBD. The UV/visible absorption maxima and band gap (E$\_$g/) show at 310nm (4.00eV) and 368nm (3.37eV) for FBD, 344nm (3.60eV) and 356nm (3.48eV) for PVK, respectively. The measured electrochemical ionization potential (IP) and electron affinity (EA) of these materials we 5.87 and 2.82eV for PBD, 5.80 and 3.17eV for PVK, respectively. The electrical band gaps are 3.05eV for PBD and 2.78eV for PVK, respectively. The electrical hole gap and electron gap with respect to the first rising potentials and the inflection potentials are obtained to be 0.39V and 0.41V for PBD, 0.25V and 0.28V for FVK, respectively.

• Bulletin of the Korean Chemical Society
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• 제24권10호
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• pp.1465-1469
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• 2003

A neutral ligand is synthesized and studied for the binding properties with anions by electrochemical methods. The binding of 1,8-bis[(N'-phenylureido)ethyloxy]anthraquinone (BPUA) with $H_2PO_4^-$ makes cathodic shift of its electrochemical potentials and red shift of absorption band. This novel neutral anion receptor BPUA binds anions through hydrogen bonding and show high selectivity with $H_2PO_4^-$ over $CH_3CO_2^-,CI^-,{\;}and{\;}HSO_4^-$. The selecivity of H_2PO_4^-$ over $CH_3CO_2^-,CI^-,{\;}and{\;}HSO_4^-$ may be attributed to the stronger hydrogen bonding with urea moiety and also with anthraquinone moiety of BPUA receptor, and also the higher complementarity of the cavity of BPUA for tetrahedral H_2PO_4^-$.