Activation of carbon dioxide on potassium-modified silver(111) single crystals

Abstract

of indole is a reversible reaction, and the number of related electrons is 2. Structure analysis of anodic precipitates suggests that the polymerization of indole is based on the formation of radical cations as intermediates.When the thermogravimetric analysis for the (PI)BF4 powder was conducted, the reaction rates for thermal decomposition were calculated by a computer connected to a thermal analyzer. A comparison between thermal characteristics of the (PI)BF4 and other polyindole-and polyaniline-based polymers, such as PIP, PIPF6, PAP, PAPF6, and (PA)BF4, revealed that the polyindole-based polymers were thermally decomposed at higher temperatures than the polyaniline-based ones. The maximum values of the reaction rate (R,) in the polyindole-based systems were not seriously affected by the kind of dopants. However, the values of the polyaniline-based polymers were affected by the kind of electron acceptors.Electrical conductivity for the pressed pellet of (PI)BF4 was measured in the temperature range from -150 to 25 OC. The value of log C T at 25 O C was -2.43 S/cm, and the activation energy calculated from an Arrhenius plot was 0.4057 eV. The conductivity result suggests that a possible conduction mechanism for (PI)BF4 is hopping conduction and that the charge carriers are polarons. We suggest that the conductivity for (PI)BF4 is induced from doping with BF4-anions as electron acceptors. A single ESR peak for (PI)BF4 powder at 25 OC was obtained. The values of AHpp, g, and spectral ratio were also calculated. Acknowledgment.We are grateful to Doctor H. W. Rhee, Korea Institute of Science and Technology, for cyclic voltammetry measurements.429-07-2; TEAP, 2567-83-1; indole (homopolymer), 120-72-9.The adsorption of carbon dioxide on potassium-dosed Ag(ll1) has been investigated with temperature-programmed desorption (TPD), work function measurements, and Auger electron (AES), X-ray photoelectron (XPS), and high-resolution electron energy loss (HREELS) spectroscopies. Unlike the behavior observed for other K-modified single-crystal metal surfaces, the TPD spectra of near-saturation coverages of C 0 2 on K/Ag( 11 1) for K coverages in the range 0.13 C C 0.47, where the close-packed monolayer corresponds to OK = ]I3, exhibit a sharply defined m/e = 44 peak at 796 f 6 K with no evidence for the desorption of CO at any temperature. Similar TPD experiments involving mixtures of natural and 180-labeled C02 indicate that the oxygen atoms undergo partial scrambling, suggesting that the overall process cannot be represented in terms of a simple adsorption/desorption of C02. The HREELS spectra of C02-saturated K/Ag( 11 1) show, in addition to very minor features, a sharp peak at -1480 cm-l, and XPS spectra of the same interface display a C(1s) peak with a binding energy characteristic of an electron-rich carbon species. This information is consistent with the presence of a carbon-bound CO species on the surface. Evidence against the complete dissociation of C02 was obtained from TPD, which failed to reveal features associa...

Chlorine-Modified Properties of Ag(111) Probed by C2H4, C3H6, C3H5Cl, and CO

“…RAIRS exhibits no detectable CO stretching mode between 2000 and 2300 cm -1 . These results are consistent with literature; CO does not adsorb at 77 K on Ag(111). −

1 RAIRS (left panel) and TPD (right panel) following a standard dose (see text) of CO on Ag(111) and Cl-modified, <θ Cl = 0.12>, Ag(111) at 77 K. The expanded portion of the RAIRS spectra details the shoulder on the high energy side of the 2163 cm -1 peak. The TPD curve from clean Ag is superimposed (dashed curve) on the TPD from Cl-modified Ag(111).

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Photolysis of the CO2 + K/Au(111) System

“…The probability of the dissociative chemisorption of CO 2 on Rh(111) at room temperature and at low pressure was calculated to be of the order of 10 −11 −10 −15 . , However, potassium due to its electron-donation character can reduce the work function of the metals and induce the activation of CO 2 . This was first demonstrated on a K-dosed Pd(100) surface, , followed by extensive studies on Rh(111), − Pt(111), , Pd(111), , Ru(0001), − Ag(111), Co(1010), Mo 2 C/Mo(100), Cu(110), and Cu(115). , Further enhancement of the electron transfer to CO 2 can be achieved by the illumination of adsorbed CO 2 , as was first demonstrated on the Rh(111) surface . In the present paper, an account is given on the photolysis of the CO 2 + K/Au(111) system.…”

“…11,12 However, potassium due to its electron-donation character can reduce the work function of the metals and induce the activation of CO 2 . This was first demonstrated on a K-dosed Pd(100) surface, 13,14 followed by extensive studies on Rh(111), [15][16][17] Pt(111), 18,19 Pd(111), 20,21 Ru(0001), [22][23][24] Ag(111), 25 Co(1010), 26 Mo 2 C/Mo(100), 27 Cu(110), and Cu(115). 28,29 Further enhancement of the electron transfer to CO 2 can be achieved by the illumination of adsorbed CO 2 , as was first demonstrated on the Rh(111) surface.…”

Reactivity of lithium toward nonaqueous solvents of relevance to energy storage applications as studied by surface analytical techniques

“…On the basis of these results it has been concluded that condensed TDF reacts with Li to yield at about room temperature LiD as the main reaction product. A det~iled analysis of all other mass fragments strongly suggest a mixture of cyclopropane, formaldehyde and CO as the most likely thermally desc·rbed 14 products of the adsorbed, activated species generated at lower temperatures.…”