• 전기화학회지
• /
• 제8권2호
• /
• pp.106-114
• /
• 2005

This article covers the theoretical ac-impedance models for the analysis of oxygen reduction on the porous cathode electrode f3r solid oxide fuel cell (SOFC). Firstly, ac-impedance models were explained on the basis of the mechanism of oxygen reduction, which were classified into the rate-determining steps; (i) adsorption of oxygen atom on the electrode surface, (ii) diffusion of adsorbed oxygen atom along the electrode surface towards the three-phase (electrode/electrolyte/gas) boundaries, (iii) surface diffusion of adsorbed oxygen atom m ixed with the adsorption reaction of oxygen atom on the electrode surface and (iv) diffusion of oxygen vacancy through the electrode coupled with the charge transfer reaction at the electrode/gas interface. In each section for ac-impedance model, the representative impedance plots and the interpretation of important parameters attributed to the oxygen reduction reaction were explained. Finally, we discussed in detail the applications of the proposed theoretical ac-impedance models to the real electrode of SOFC system.

• Bulletin of the Korean Chemical Society
• /
• 제27권12호
• /
• pp.2037-2039
• /
• 2006

The adsorption and surface reactions of $SO_2$ on Ni(100), c($2{\times}2$)_O/Ni (100) and NiO(111)/Ni(100) surfaces have been investigated using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) technique. On Ni(100), chemisorbed $SO_2$ is formed at 160 K. When $SO_2$ is adsorbed on c($2{\times}2$)_O/Ni(100) at 160 K, $SO_2$ reacts with oxygen to form $SO_3$ and trace amount of $SO_4$ species. $SO_3$ is adsorbed on this surface with its $C_3$ axis perpendicular to the surface. On a NiO(111)/Ni(100) surface, both $SO_3$ and $SO_4$ species are formed at 160 K from adsorbed $SO_2$.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 추계학술발표회
• /
• pp.56-63
• /
• 2003

Fractional composition and mobility of sediments some heavy metals in Okdong stream are investigated. The fractional scheme for sediment heavy metal was made for five chemically defined heavy metal forms as adsorbed fraction, carbonate fraction, reducible fraction, organic fraction, and residual fraction (Tessier et at., 1979). The most abundant fraction of the sediment heavy metal is reducible and secondly abundant organic fraction. Adsorbed fraction is minor part of the total heavy metals. Mobilization of sediment heavy metals in stream Okdong is occur 19.8∼56.7% of total cadmium concentrate. The most abundant fraction of the sediment metal is organic fraction in Cu, Pb metals investigated. Labile fraction of sediment metals are 0.5%∼48.5% of total Zn, 2.6%∼48.1% of total Pb, 0.2∼36.9% of total Cu respectively, Most of labile fraction consists of reducible fraction for Cd, Zn, adsorbed fraction for Pb, reducible fraction for Cu, adsorbed fraction for Ni. The Mobilization of Zn and Cu is most likely to occur when oxygen depletes and that of Pb and Ni occurs when physical impact, oxygen depletion and pH reduction.

• Bulletin of the Korean Chemical Society
• /
• 제5권1호
• /
• pp.41-44
• /
• 1984

The oxidation of carbon monoxide has been investigated on Ni-doped ${\alpha}-Fe_2O_3$ catalyst at 300 to $450^{\circ}$. The oxidation rates have been correlated with 1.5-order kinetics; first with respect to CO and 1/2 with respect to $O_2$. Carbon monoxide is adsorbed on lattice oxygen of Ni-doped ${\alpha}-Fe_2O_3$, while oxygen appears to be adsorbed on oxygen vacancy formed by Ni-doping. The conductivities show that adsorption of CO on O-lattice produces conduction electron and adsorption of $O_2$ on O-vacancy withdraws the conduction electron from vacancy. The adsorption process of CO on O-lattice is rate-determining step and dominant defect of Ni-doped ${\alpha}-Fe_2O_3$ is suggested from the agreement between kinetic and conductivity data.

• 공업화학
• /
• 제3권2호
• /
• pp.256-265
• /
• 1992

NaCl(30wt%)/ZnO(60wt%)/${\alpha}-Al_2O_3$ 촉매상에서 메탄의 oxidative coupling 반응의 속도식을 연구하여 활성 산소종에 관하여 고찰하였다. 반응온도 $650^{\circ}C$에서 $750^{\circ}C$까지 메탄의 전화율 10%미만의 범위에서 메탄과 산소의 분압을 변화시켜 가면서 메탄의 전환속도를 측정하여 속도식을 검증하였다. 제안된 메틸라디칼의 생성반응은 Langmuir-Hinshelwood형 반응기구를 따른다. 촉매표면의 서로 다른 활성점에 흡착된 메탄분자와 산소분자가 반응하여 메틸라디칼이 생성되는 반응이 속도결정단계이며, 이때 활성화 에너지는 약 39kcal/mol이었다. 메탄의 C-H 결합의 해리에 관여하는 산소종은 표면상의 이원자 산소인 $O{_2}{^{2-}}$나 $O_2{^-}$로 제시할 수 있었다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2009년도 제37회 하계학술대회 초록집
• /
• pp.321-321
• /
• 2009

• Bulletin of the Korean Chemical Society
• /
• 제27권4호
• /
• pp.545-548
• /
• 2006

We investigated the Surface-enhanced Raman Spectroscopy (SERS) spectrum of ethephone (2-chloroethylphosphonic acid). We observed significant signals in the ordinary Raman spectrum for solid-state ethephone as well as when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids that were prepared by the $\gamma$-irradiation method. The influence of pH and the influence of anion $(Cl^-,\;Br^-,\;I^-)$ on the adsorption orientation were investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions. The chlorine atom or the chlorine and two oxygen atoms were adsorbed on the colloidal silver surface. Among halide ions, $Br^-$ and $I^-$ were more strongly adsorbed on the colloidal silver surfaces. As a result, the adsorption of ethephone was less effective due to their steric hinderance.

• Bulletin of the Korean Chemical Society
• /
• 제8권4호
• /
• pp.291-296
• /
• 1987

Vibrational spectroscopy has been applied to the benzenethiol molecule adsorbed on the silver surface. The results of infrared and Raman spectral studies have led to the conclusion that benzenethiol is chemisorbed dissociatively on the silver surface by rupture of S-H bond and the benzenethiolate formed upon adsorption is bound to silver via its sulfur atom. It seemed more likely that benzenethiol is adsorbed as being inclined to the silver surface. On contact with oxygen, the geometry of the adsorbed species appeared to bear a resemblance to that of silver benzenethiolate salt. The infrared bands of adsorbed species remained with little decrease of intensity even after the prolonged evacuation at 673 K, indicating that benzenethiol is very strongly chemisorbred to the silver surface.

• 공업화학
• /
• 제7권4호
• /
• pp.653-660
• /
• 1996

산소 PSA 장치 구성을 위하여, 여러 가지 흡착제에 대한 산소 및 질소의 평형흡착량을 측정하여 유효흡착량을 비교함으로써 산소 PSA에 적절한 흡착제를 선정하였고 Langmuir isotherm parameter를 구하였다. PSA 공정의 단계는 흡착, 탈착, 축압, 세정 및 균압 등으로 구성하고 흡착압력은 2atm을 기준으로 운전하였고 탈착압력은 120~400torr이며 cycle time은 2탑 80, 3탑 180초로 운전하였다. 2탑식과 3탑식 산소 PSA 장치의 운전특성과 경제성을 비교 분석하기 위하여, 운전조건에 따른 2탑식 및 3탑식 공정의 제품 생산성, 산소농도, 회수율을 비교하였고, 세정 및 축압단계의 영향을 분석하였으며, 대형화 하였을 경우의 투자비와 전력비를 추산하여 2탑식과 3탑식 산소 PSA의 경제성을 비교하여 $700Nm^3/hr$ 이하 규모에서는 2탑식이 유리함을 확인하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.128.2-128.2
• /
• 2013

Crucially, effective catalysts must be capable of efficiently catalyzing the protonation of adsorbed CO to adsorbed CHO or COH. One of the strategies is alloying with metals with higher oxygen affinity and Au-Zn alloy is one of the best candidates. At first, we made Au-Zn alloy using vacuum evaporating method. Zn was deposited on the Au(211) surface and the amount was estimated by X-ray photoelectron spectroscopy (XPS) using the relative sensitivity of Au 4f and Zn 3d. We investigated CO adsorption on a clean Au(211) and Au-Zn alloy using temperature-programmed desorption (TPD) and XPS. From the TPD results, we can conclude that the presence of the particular step sites at the Au(211) surface imparts stronger CO bonding and Zn atoms are sitting on the step sites at the Au(211) when Zn is deposited. The XPS results show the oxygen atoms of CO bond Zn atoms on Au-Zn surface. It should be an evidence that alloying Zn atoms that has high oxygen affinity into an electrocatalyst may allow CHO* to bind to the surface through both the carbon and oxygen atoms.