• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.1019-1024
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• 1993

The coadsorption of carbon monoxide and oxygen on polycrystalline nickel surface has been studied using XPS at the room temperaure. The adsorption of CO on the nickel surface precovered partially with oxygen is found to take place by the following steps: The CO molecules react with the preadsorbed oxygen atoms to liberate $CO_2$ gas at the initial stage of low CO exposures, and they are coadsorbed gradually with the increasing CO exposures. The extent of coadsorption at the higher CO exposures is found to decrease with the increasing degree of oxygen preadsorption. This finding is explained in terms of the reduced adsorption site for CO as a consequence of oxygen preadsorption. The CO molecules preadsorbed on the nickel surface inhibited the adsorption of $O_2$ molecules. The increase of oxygen exposure led to the dissociation of preadsorbed CO, and the NiO layers were formed concurrently. The dissociation was rendered to arise from an oxygen-to-CO energy transfer.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.153-153
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• 2000

Si 산화는 반도체 공정상 필요한 과정으로 산업적으로나 학문적으로 중요하고 많이 연구되었다. 이중에서 Si(1110-7x7표면에서 초기 흡착된 산소는 준안정적 상태로 존재하며 표면온도, 산소의 노출량 그리고 진공도에 따라 그 수명이 제한된다. 이러한 준안정적 상태의 산소의 화학적 성질은 여러 표면분석장비가 동원되어 연구되었으나 아직까지 논쟁이 되고 있다. 이 경우 산소가 어떤 상태로 존재하는가는 표면화학종을 검출함으로서 해결될 수 있다. 저에너지 Cs+ 이온 반응성 산란은 이러한 요구를 충족시킬수 있는 가장 적합한 실험 방법중의 하나이다. 저에너지 Cs+ 이온 산란의 특징 중의 하나는 입사된 Cs+ 이온이 표면에 흡착된 화학종과 충돌후 탈착되면서 반응을 하여 송이 이온을 형성한다는 것이다. 이 송이 이온을 관측함으로서 표면에 존재하는 화학종을 알아 낼 수 있다. 이에 산소가 흡착된 Si(111)-7x7 표면에서의 산소의 준안정적 상태가 저에너지 Cs+ 이온 산란 실험을 통하여 연구되었다. 실험은 0.2-2L(1Langmuir = 10-6 Torr x 1 sec) 산소 노출량과 -15$0^{\circ}C$ - $25^{\circ}C$의 표면온도 그리고 5eV - 20eV의 Cs+ 이온 충돌에너지에서 CsSiO+ 이온이 유일한 생산물로서 검출되었다. CsSiO+ 이온은 입사된 Cs+ 이온과 표면에 존재하는 SiO 분자가 충돌 후 반응하여 탈착된 것으로 생각된다. 이것은 낮은 산소 노출량 즉, 초기 산화 단계에서 SiO가 표면에 존재한다는 것을 의미한다. 즉, 산소 분자는 산화단계의 초기에 해리되어 표면에 흡착되고 선구물질인 SiO를 형성함을 제시한다. 최근의 이론적 계산인 density functional calculation에서도 산소분자가 Si(111)-7$\times$7 표면의 준안정적 산화상태의 선구물질일 가능성을 배제한다. 이는 본 저에너지 Cs+ 이온 반응성 산란실험을 뒷받침하는 계산 결과이다. 높은 Cs+ 이온 충돌에너지에서 CsSi+, Si+, SiO+, Si2+, Si2O+ 등이 추가로 검출되었다. 이는 CsSi 이온을 제외하고 수 keV의 충돌에너지를 사용하는 이차 이온 질량 분석법과 비슷한 결과이다.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.183-188
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• 2008

We have studied the chemisorption of oxygen at room temperature on Fe layers deposited on Pt(111) substrates by using core-level X-ray photoelectron spectroscopy. It was found that the oxygen atoms are chemisorbed when the thickness of the Fe layers is not larger than 6 monolayers. Upon post-annealing, it was found that part of the chemisorbed atoms are desorbed at a temperature range 600 - 700 K, after which the intermixing between Fe and Pt atoms occurs. The overall trend of this intermixing was very similar to the Fe/Pt(111) surface without oxygen exposure. The remaining oxygen adatoms, the amount of which is about a half of the total, were found to be eventually desorbed from the surface upon post-annealing at 1000 K. The binding energy of this phase was higher than that of the oxygen atoms desorbed at lower temperatures by 1.3 eV.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.189-198
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• 1994

The adsorptive behaviors of carbon monoxide and methanol over $V_2O_5$catalyst were studied by means of thermal desorptlon spectroscopy (TDS) under ultrahigh vacuum conditions. Carbon monoxide adsorbed on oxygen-deficient V sites as well as on V=O groups of the $V_2O_5$ surface. CO adsorbed on the V sites desorbed at 380 K while CO adsorbed on the V=O groups formed carbonate species with surface oxygen of $V_2O_5$ and desorbed as $CO_2$ resulting in the reduction of the surface of she $V_2O_5$catalyst. The amount of CO adsorbed in the form of carbonate species increased by both the pre- and post-adsorbed oxygen. The adsorptive behavior of methanol over the catalyst was studied by thermal desorption experiments of $CH_3OH$, HCHO, CO, and $H_2$ upon methanol adsorption at 298 K. The results showed that methanol was adsorbed dissociatively on the $V_2O_5$catalyst as methoxy and hydroxyl groups at 298K.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.38-43
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• 2022

The effect of introducing oxygen functional groups by oxygen plasma treatment of activated carbon on adsorption properties of cesium ions was investigated. During the oxygen plasma treatment, the frequency, power, and oxygen gas flow rates were fixed at 100 kHz, 80 W, and 60 sccm, respectively, while the reaction time was varied. Under the experimental conditions, the amount of cesium ion adsorption increased as the content of oxygen groups on C-O-C and O=C-O bonds increased when the reaction time with oxygen gas was 10 minutes. However, when the reaction time increased to 15 minutes, the oxygen functional group content decreased resulting in the decrease of the adsorbed cesium ion amount. On the other hand, unlike the oxygen content of the surface-treated activated carbon, the specific surface area and pore properties were hardly affected by the oxygen plasma reaction time. As a result, the oxygen plasma-treated activated carbon improved the cesium ion removal rate by up to 97.3% compared to that of the untreated activated carbon. This is considered to be due to the content of oxygen groups on C-O-C and O=C-O bonds introduced on the surface of the activated carbon through oxygen plasma treatment.

• Clean Technology
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• v.24 no.4
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• pp.348-356
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• 2018

The adsorption equilibria of oxygen, nitrogen and argon on carbonaceous adsorbent with slit-shaped and randomly etched graphite (REG) pores were calculated by molecular simulation method. Reliable models of adsorbents and adsorbates for adsorption equilibria are important for the correct design of industrial adsorptive separation processes. At the smallest physical pore of $5.6{\AA}$, only oxygen molecules were accommodated at the center of the slit-shaped pore, and from $5.9{\AA}$ nitrogen and argon molecules could be accommodated in the pores. Slit pores showed higher adsorption capacity compared with REG pores with same averaged reenterance pore size due to dead volume and inaccessible volume in defected pores. And it was shown the adsorption capacities of oxygen and argon was same in larger pore size. From calculated adsorption isotherms at 298 K it showed that the adsorption capacity ratio of oxygen to nitrogen is increased as pressure is increased.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.160-166
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• 2019

In this study, oxygen functional groups were introduced on activated carbon fibers (ACFs) by oxygen plasma treatment to improve the adsorption performance on an acetic acid which is a sick house syndrome induced gas. The active species was generated more as the flow rate of the oxygen gas increased during the plasma treatment. For this reason, the specific surface area (SSA) of the ACFs decreased with much more physical and chemical etching. In particular, the SSA of the sample (A-O60) injected with an oxygen gas flow rate of 60 sccm was reduced to about $1.198m^2/g$, which was about 6.95% lower than that of the untreated samples. On the other hand, the oxygen content introduced into the surface of ACFs increased up to 35.87%. Also, the adsorption performance on the acetic acid gas of the oxygen plasma-treated ACFs was improved by up to 43% compared to that of using the untreated ACFs. It is attributed to the formation of the hydrogen bonding due to the dipole moments between acetic acid molecules and oxygen functional groups such as O=C-O introduced by the oxygen plasma treatment.

• Journal of the Mineralogical Society of Korea
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• v.18 no.1
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• pp.1-9
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• 2005

The electrocatalytic reduction of O₂ was investigated with methyl viologen and methylene blue incorporated clay-modified electrodes. Clay suspensions were prepared with Na-montmorillonite, Ca-montmorillonite, and kaolinite. The methyl viologen-clay modified electrodes were made by coating clay suspensions adsorbing methyl viologen on a glassy carbon electrode. Cyclic voltammetry were performed in aqueous media to investigate the electrocatalytic property of the modified electrode in reducing O₂. A Na-montmorillonite modified electrode showed the greatest adsorption capacity for methyl viologen. The modified electrode made of Na-montmorillonite suspension of 0.87 g/10 mL and a 2.5 mM of methyl viologen solution showed the most effective electrocatalytic property, where the catalytic reduction potential was shifted by 242.6 mV toward the positive potential. The electrocatalytic ability was more significant in acidic (pH=3.7) and alkaline (pH=12.7) media than the neutral pH range (6.3∼8.3). The methyl viologen-Na-montmorillonite modified electrode had the good reproducibility and maintain the electrocatalytic property over 20 times reuse.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.609-615
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• 1994

Partial oxidation of ethylene over 10wt% $Ag/{\alpha}-Al_2O_3$ catalyst was studied with a pulse reactor which was connected directly to a G. C. When ethylene was injected after oxygen injection at the temperature where molecular adsorption of oxygen is difficult ethylene oxide was evolved. From the results, it is suggested that adsorbed atomic oxygen is related with the evolution of ethylene oxide. The selectivity to ethylene oxide decreased with the decrease of the amounts of adsorbed oxygen and bulk oxygen. Ethylene oxide was either decomposed to ethylene and adsorbed oxygen or isomerized to acetaldehyde. However, the isomerization of ethylene oxide to acetaldehyde was strongly suppressed by the preadsorbed oxygen.

• Journal of the Korean Chemical Society
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• v.24 no.3
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• pp.218-224
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• 1980

The surface reactions of CO and $C_2H_4$ with adsorbed oxygen on ZnO were studied by means of EPR spectroscopy. The EPR spectra of $O_2$ adsorbed ZnO at various temperatures were compared, and the signal at g = 2.014 was characterized as trapped $O^-$ at oxygen vacancy. CO and $C_2H_4$ react with $O^-$ at $25^{\circ}C$ and desorbed as $CO_2$ and $H_2O$ above $200^{\circ}C$. $O_2^-$ species interact with $C_2H_4$ about $100^{\circ}C$, but desorption of partial oxidation products also was not observed until the temperature was raised to $200^{\circ}C$.