• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.143.2-143.2
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• 2016

The influence of electric field on CO adsorbed on Pt(111) was investigated with reflection-absorption infrared spectroscopy (RAIRS) in ultrahigh vacuum system. The ice film capacitor method was used to apply electric field to the amorphous ice film with CO on Pt(111). Two systems were compared by measuring the change of the CO stretching vibrational mode under applied electric field; one is CO on Pt(111), and the other is CO buried inside an ice film on Pt(111). By comparing them, we were able to calculate the additional effect of adsorption of CO on Pt(111) on peak shift. The CO adsorbed on Pt(111) has shown larger peak shift than CO adsorbed with H2O when we applied stronger electric field. Additionally, the differences were observable when the applied electric field exceeds $1{\times}10V/m^8$.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2012년도 자성 및 자성재료 국제학술대회
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• pp.172-172
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• 2012

A Pt-skin $Pt_3Ni$(111) surface was reported to show high catalytic activity. In this study, we investigated the magnetic properties and electronic structures of the various oriented surfaces of bulk-terminated and Pt-segregated $Pt_3Ni$ by using a first-principles calculation method. The magnetic moments of Pt and Ni are appreciably enhanced at the bulk-terminated surfaces compared to the corresponding bulk values, whereas the magnetic moment of Pt on the Pt-segregated $Pt_3Ni$(111) surface is just slightly enhanced because of the reduced number of Ni neighboring atoms. Spin-decomposed density of states shows that the dz2 orbital plays a dominant role in determining the magnetic moments of Pt atoms in the different orientations. The lowering of the d-band center energy (-2.22 eV to -2.46 eV to -2.51 eV to -2.65 eV) in the sequence of bulk-terminated (100), (110), (111), and Pt-segregated (111) may explain the observed dependence of catalytic activity on surface orientation. Our d-band center calculation suggests that an observed enhanced catalytic activity of a $Pt_3Ni$(111) surface originates from the Pt-segregation.

• Bulletin of the Korean Chemical Society
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• 제21권8호
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• pp.779-784
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• 2000

Comparing the adsorption properties and dissociation on a Pt(111) iththat ona Fe(111) surface, we have con-sidered seven coordination modes of the adsorbed binding site: $di-${\sigma}$${\Delta}$\mu\pi/\mu$, 1-fbld,2-fold, and 3-fbld sites. On the Pt(111) surface, t he adsorbed binding site of carbon dioxide was strongestat the1-fold site and weakest at the $\pi/\mu-site.$ The adsorbed binding site on the Fe(111) surface was strongest at the di-бsite and weakest at the 3-fold site. We have found that the binding energy at each site that excepted 3-fold on the Fe(111) surface was stronger than the binding energy on the Pt(111) surface and that chemisorbed $CO_2bends$ because of metal mixing with $2\piu${\rightarrow}$6a_1CO_2orbital.$, The dissociation reaction occured in two steps, with an intermediate com-plex composed of atomic oxygen and ${\pi}bonding$ CO forming. The OCO angles of reaction intermediate com-plex structure for the dissociation reaction $were115^{\circ}Con$ the Pt(111), and $117^{\circ}C$ on the Fe(111) surface. We have found that the $CO_2dissociation$ rea11) surface proceeds easily,with an activationenergy about 0.2 eV lower than that on the Pt(111) surface.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2011년도 자성 및 자성재료 국제학술대회
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• pp.14-14
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• 2011

Limited understanding of the surface properties of $Pt_3Ni$ for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cell (PEMFC) has motivated the study of magnetic properties and electronic structures of Pt segregated $Pt_3Ni$ (111) surface during adsorption of oxygen molecule on it. The first principle method based on density functional theory (DFT) is carried out. Nonmagnetic Pt has induced magnetic moment due to strong hybridization between Ni 3d and Pt 5d. It is found that an oxygen molecule prefers bridge site with Pt rich subsurface environment for adsorption on the surface of Pt segregated $Pt_3Ni$ (111). It is seen that there is very small charge transfer from $O_2$ to Pt. The curve of energy versus magnetic moment of the oxygen explains the magnetic moments in transition states. We found the dissociation barrier of 1.07eV significantly higher than dissociation barrier 0.77eV on Pt (111) suggesting that the dissociation is more difficult on Pt segregated $Pt_3Ni$ (111) surface. The spin polarized densities of states are presented in order to understand electronic structures of Pt and $O_2$ during the adsorption in detail.

• Bulletin of the Korean Chemical Society
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• 제23권3호
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• pp.395-399
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• 2002

The voltammetric behavior of spontaneously adsorbing Mo layers on Pt(111) and Pt(100) electrodes has been studied to estimate the number of electrons involved in the electrochemical processes of spontaneously adsorbed Mo and the number of the bloc ked Pt sites for hydrogen adsorption. On Pt(111) and Pt(100) surfaces, the spontaneously adsorbed Mo layers showed redox peaks at 0.10 V and 0.15 V, respectively, and continuous current-potential waves in the conventional hydrogen region. Since the potential range of the Mo redox processes on both surfaces overlapped partially with the potential range of hydrogen adsorption, the variation in the ratio of the total charge of Mo and H ($Q_H$ +$Q_{MO}$) to the hydrogen charge of clean Pt electrode ($Q_H^0$) was analyzed. From the analysis, six electrons were estimated to be involved in the electrochemical processes of the spontaneously adsorbed Mo, and four Pt sites for hydrogen adsorption were calculated to be blocked by one adsorbed Mo atom. Based on these figures and the pH dependence of the Mo redox processes, we have proposed an electrochemical equation for the spontaneously adsorbed Mo. This electrochemical equation led us to conclude that the saturation coverage of the spontaneously adsorbed Mo is 0.25. The coverage of Mo less than 0.25, however, could not be determined voltammetrically due to the convolution of the charges of Mo and H.

• 한국자기학회지
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• 제4권3호
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• pp.263-271
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• 1994

$Co_{1-x}Pt_{x}(X\;=\;0.53,\;0.75)$ 합금박막을 직류 마그네트론 스퍼터링 방법으로 증착하여 Ar 압력 및 증착온도 등의 증착조건에 따른 자기적 성질과 미세구조를 관찰하였다. 스퍼터링법으로 증착한 Co-Pt 합금박막은 모두 강한(111) 우선방위를 나타내었으며, 증착온도가 증가하거나 Ar 압력이 감소할수록 (111) 우선 방위는 커지는 것으로 나타났다. As-deposited 시편의 경우 수평자화를 나타내었고 (111) 우선방위와의 연관성은 나타나지 않았다. 증착한 합금박막을 열처리하여 미세구조 및 자기적 성질을 관찰한 결과 X = 0.53 조성의 시편은 열처리온도가 증가함에 따라 보자력과 각형비가 크게 증가함을 관찰하였고 X = 0.75 조성의 시편에서는 별다른 변화를 관찰하 지 못하였다. 미세구조를 XRD와 TEM을 이용하여 관찰한 결과 X = 0.53 조성의 시편에서는 CoPt 규칙상, X = 0.75 조성의 시편은 $CoPt_{3}$ 규칙상이 형성됨을 알 수 있었고 <001> 방향으로 Co 원자층과 Pt 원자층이 교대적층 되어 있는 CoPt 규칙상이 형성되었을 때 자기적 성질이 크게 변화하였다.

• 대한화학회지
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• 제40권4호
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• pp.264-272
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• 1996

ASED-MO(Atom Superposition and Electoron Delocalization-Molecular Orbtal)이론을 이용하여 Pt(lll)과 ${\upsilon}-Al_2O_3$(III) 표면 모델에 대한 계면간 결합 세기에 관해 연구하였다. $Al^{3+}$의 환원 정도가는 알루미나 뭉치(cluster)에 대한 산소와 알루미늄의 비에 따라 달라진다. $Al^{3+}$의 환원 정도가 크면 클수록 Pt 원소들에 대해 강한 결합 에너지를 가진다. 산소로 덮인 ${\gamma}-Al_{20}_3$(III) 표면과 Pt 계면간 결합이 매우 약하지만 백금의 산화 조건에서의 결합은 매우 강하다. 백금 표면에서 부분적으로 빈 O-2p 띠(band)와 $Al^{3+}$ dangling surface orbital로 전하가 이동하는 전하이동(charge transfer) 메카니즘에 의해 백금과 알루미나 계면간 결합은 가능하다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.332-332
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• 2011

The adsorption and desoprtion properties on Pt(111) of chiral molecules, propylene oxide (PO) and 1,3-dimethyl butylamine (DMBA), have be characterized in utrahigh vacuum. Precision-doses of PO and DMBA onto a Pt(111) surface at 90 K have been achieved with a directed tubular molecular doser controlled by a micron-sized orifice and the reservoir gas pressure. Temperature-programmed desorption (TPD) mass spectra have been employed together with low-energy electron diffraction (LEED) analyses. In addition to the separate adsorption behaviors of PO and DMBA, the enantioselective adsorption of R- and S-PO on Pt(111) precovered with R- or S-DMBA have been investigated thoroughly, and the results will be presented.

• 한국진공학회지
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• 제7권4호
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• pp.300-305
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• 1998

rf magnetron sputtering 증착법으로 Al2O3(0001)기판위에 적층생장시킨 Pt박막의 결정성 및 이의 구조적 특성을 backscattering spectrometry(BS)/channeling, transmission electron microscopy(TEM)등을 이용해 분석하였다. $MeV^4$He ion channeling 결과, 증착시 기판의 온도가 $600^{\circ}C$, 증착된 Pt층의 두께가 3500$\AA$이었을 때 최소산란수율(channeling minimum yield)이 4%인 결정성이 우수한 Pt박막이 생장되었음을 확인하였으며, 동일한 증 착조건하에서 증착된 Pt층은 $Al_2O_3$(0001)기판위에 6중 대칭구조를 지닌(111)면방향으로 적층 생장되었으며, (111)면방향을 중심으로 대칭적인 원자배열 구조를 갖고 있는 쌍정구조를 형 성하고 있었다. 단면 TEM 분석결과에서도 격자부정합에 의한 strain을 감소시키기 위하여 형성된 쌍정을 관찰할 수 있었으며 strain이 집중되는 쌍정경계면에서 표면거칠기의 증가 또는 관찰되었다.

• 한국진공학회지
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• 제17권3호
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• pp.183-188
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• 2008

내각준위 X선 광전자 분광법을 이용하여 Pt(111) 표면 위에 증착된 Fe 초박막의 산소 흡착에 대한 연구를 수행하였다. 6개 단층 이하의 두께를 갖는 Fe 초박막을 상온에서 산소에 노출시켜 산소 원자가 화학흡착된 것을 확인하고, 후열처리 과정에 따른 탈착 및 Fe층의 변화를 살펴보았다. 흡착된 산소 원자는 $600{\sim}700K$에서 부분적으로 탈착되고, 700 K 이상에서 Fe 원자들이 Pt 기판 안으로 섞여 들어감을 내각준위 스펙트럼 세기들로부터 알 수 있었다. Fe 원자들과 Pt 원자들 간의 섞임은 산소가 흡착되지 않은 경우와 거의 동일한 경향을 보였으며, 섞임에 의한 Fe-Pt 합금의 형성은 Fe $2p_{3/2}$ 광전자 스펙트럼의 속박에너지의 변화로부터 확인할 수 있었다. 탈착되지 않고 남은 산소의 양은 전체의 1/2로서 속박에너지가 $600{\sim}700K$ 사이에서 탈착된 산소보다 약 1.3 eV 커서 Fe층 위에 흡착된 산소들과는 다른 상임을 알 수 있었다. 이들 산소 원자는 1000 K에서야 탈착되었다.