Sum frequency generation spectroscopic study of CO/ethylene coadsorption on the Pt() surface and CO poisoning of catalytic ethylene hydrogenation

Structure, Mobility, and Composition of Transition Metal Catalyst Surfaces. High-Pressure Scanning Tunneling Microscopy and Ambient-Pressure X-ray Photoelectron Spectroscopy Studies

“…Two O 1s peaks, evidencing the CO chemisorption on Pt(100), grow after decreasing the C 2 H 4 pressure to 500 mTorr and subsequently dosing 10 mTorr of CO, as in Figure 6-11c. More than 90% of the ethylene-related adsorbates remain on the Pt(100) surface after CO incorporation, in agreement with results on other Pt surfaces, [50][51][52] since the area of C 1s peak at ~284 eV decreases by less than 10%. Ethylidyne and di-σ-bonded ethylene may convert to vinylidene, since the island structure on Pt(100) does not have three-fold sites.…”

“…Pt tends to segregate towards surface under H 2 because of its strong tendency to segregate towards surface while coexisting with Ni. [51][52][53] Similar reversible trend of surface composition is also observed on Pt 3 Ni frameworks at 393 K, as in Figure 8-13b. The Ni concentration at ~0.9 nm IMFP is ~32% initially under H 2 , and increases to ~38% under O 2 .…”

“…Figure 3-6a shows that 1.5 h after evacuating O 2 from 1 Torr to 10 -8 Torr, almost all the 2D surface Pt oxide clusters disappear with steps forming again on the Pt(557), although some of the steps are no longer as straight as they originally were on the clean Pt(557) surface in The disappearance of the 2D oxide clusters with O 2 evacuation is worth discussing. Given that Pt oxide decomposition and oxygen desorption both occur slowly on Pt at 298 K 51 and that a thin Pt oxide film is thermodynamically more stable than bulk Pt oxide, 52 it would be surprising that the 2D oxide has decomposed within 1.5 h of O 2 gas removal. The reactions between surface Pt oxide and background gases (CO and H 2 ) are likely responsible for removing the 2D oxide, because CO can quickly reduce surface Pt oxide even at 273 K. 30,32 Reactions of the 2D oxide with H 2 and CO on Pt(557) are further studied with HP-STM and AP-XPS, which reveals that the surface Pt oxide clusters are indeed removed by H 2 at a low H 2 :O 2 pressure ratio.…”

Molecular interactions between gold nanoparticles and model cell membranes

“…41,42,[46][47][48][49][50][51][52][53][54] SFG experiments involved two input laser beams, one frequency tunable IR beam and one frequency fixed visible beam, overlapping on the sample in time and in space, generating an output laser beam with a frequency at the sum of two input frequencies. 41,42,[46][47][48][49][50][51][52][53][54] SFG experiments involved two input laser beams, one frequency tunable IR beam and one frequency fixed visible beam, overlapping on the sample in time and in space, generating an output laser beam with a frequency at the sum of two input frequencies.…”

Sample mounting and transfer mechanism for in situ IR-visible sum frequency generation vibrational spectroscopy in high-pressure ultrahigh vacuum system

“…͓DOI: 10.1063/1.1606529͔ Sum frequency generation ͑SFG͒ vibrational spectroscopy, a nonlinear optical technique, has recently been utilized to monitor surface intermediates in situ during catalytic reactions on metal surfaces under ambient conditions. [1][2][3][4] In a SFG experiment, visible ( VIS ) and tunable infrared ( IR ) beams are spatially and temporally overlapped on a surface. As the infrared beam is scanned over the frequency range of interest, vibrational spectra of molecules present on the surface are obtained by sum frequency output ( SFG ϭ VIS ϩ IR ) via a second-order nonlinear optical process.…”