| 1. |
- Ataman, Evren, et al.
(författare)
-
Adsorption of L-cysteine on rutile TiO2(110)
- 2011
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 605:1-2, s. 179-186
-
Tidskriftsartikel (refereegranskat)abstract
- We have used X-ray photoelectron spectroscopy to study the adsorption of L-cysteine on a rutile TiO2(110) surface at room temperature and -65 degrees C. For the molecules in direct contact with the surface our results suggest that the molecules bind dissociatively to the fivefold-coordinated Ti atoms of the surface through their deprotonated carboxylic groups. A second, dissociative interaction occurs between the molecular thiol groups and the surface. It is attributed to a dissociative bond to the bridging oxygen vacancies. Most likely, the thiol groups are deprotonated and a bond is formed between the thiolates and defects. In an alternative scenario, the C-S bond is cleaved and atomic sulfur binds to the defects. With regard to the molecular amino groups, they remain neutral at the lowest investigated coverages (0.3-0.5 ML), but already starting from around 0.7 ML nominal coverage protons are being transferred to them. The fraction of protonated amino groups increases with coverage and becomes dominating in multilayers prepared at room temperature and -65 degrees C. In these multilayers the carboxylic groups are deprotonated. (C) 2010 Elsevier B.V. All tights reserved.
|
|
| 2. |
- Blomberg, Sara, et al.
(författare)
-
A high pressure X-ray photoelectron spectroscopy study of oxidation and reduction of Rh(100) and Rh nanoparticles
- 2014
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 628, s. 153-158
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the oxidation and reduction of Rh(100) and SiO2 supported Rh particles using high pressure X-ray photoelectron spectroscopy. We show that the formation and reduction of Rh bulk oxide can be followed in situ in O-2 and CO pressures in the range of 0.1 Torr. In general, the oxidation/reduction processes are similar on Rh(100) and the nanoparticles, but there are significant differences in temperature dependence. Already at a sample temperature of 140 degrees C, the particles show clear signs of a thin bulk oxide, while an ultra-thin so-called surface oxide covers the single crystal at the same temperature. Both of these oxide films, however, hinder further oxidation, and a thick oxide is only found at a temperature of at least 300 degrees C, for both samples. The reduction, in contrast, starts at a higher temperature on the particles as compared to the single crystal, but once started the particles are completely reduced at lower temperatures. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Blomberg, Sara, et al.
(författare)
-
Generation and oxidation of aerosol deposited PdAg nanoparticles
- 2013
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 616, s. 186-191
-
Tidskriftsartikel (refereegranskat)abstract
- PdAg nanoparticles with a diameter of 10 nm have been generated by an aerosol particle method, and supported on a silica substrate. By using a combination of X-ray Energy Dispersive Spectroscopy and X-ray Photoelectron Spectroscopy it is shown that the size distribution of the particles is narrow and that the two metals form an alloy with a mixture of 75% Pd and 25% Ag. Under oxidizing conditions, Pd is found to segregate to the surface and a thin PdO like oxide is formed similar to the surface oxide previously reported on extended PdAg and pure Pd surfaces. (C) 2013 Elsevier B.V. All rights reserved.
|
|
| 4. |
- Blomberg, Sara, et al.
(författare)
-
Structure of the Rh2O3(0001) surface
- 2012
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 606:17-18, s. 1416-1421
-
Tidskriftsartikel (refereegranskat)abstract
- We have studied the (0001) surface termination of Rh2O3 on a Rh(111) single crystal using a combination of high resolution core level spectroscopy, low energy electron diffraction, scanning tunneling microscopy and density functional theory. By exposing the Rh(111) to atomic oxygen we are able to grow Rh2O3 layers exposing the (0001) surface. The experiments support the theoretical predictions stating that the surface is terminated with an O-Rh-O trilayer yielding a RhO2 termination instead of a bulk Rh2O3 termination. The structural details as found by the DFT calculations are presented and reasons for the previously observed strong differences in catalytic activity between the structurally similar RhO2 surface oxide, and the Rh2O3(0001) surface are discussed. (C) 2012 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Bolton, Kim, et al.
(författare)
-
DFT study of the adsorption and dissociation of water on Ni(111), Ni(110) and Ni(100) surfaces
- 2014
-
Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 627, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Water adsorption and dissociation on catalytic metal surfaces play a key role in a variety of industrial processes, and a detailed understanding of this process and how it is effected by the surface structure will assist in developing improved catalysts. Hence, a comparative study of the adsorption and dissociation of water on Ni(111), Ni(110) and Ni(100) surfaces, which is often used as catalyst, has been performed using density functional theory. The results show that the adsorption energies and dissociation rates depend on the surface structure. The adsorption energies for H2O and OH decrease in the order Ni(110) > Ni(100) > Ni(111), and for the O and H atoms the adsorption energies decrease in the order Ni(100) > Ni(111) > Ni(110). In addition, the splitting of water to OH and H has lower activation energies over less packed Ni(110) and Ni(100) surfaces compared to the highly packed Ni(111) surface. The subsequent splitting of the OH to O and H also has the lowest activation energy on the Ni(110) surface. At 463 K, which is typical for industrial processes that include the water gas shift reaction, the H2O splitting is approximately 6000 and 10 times faster on the Ni(110) surface compared to the Ni(111) and Ni(100) surfaces, respectively, and OH splitting is 200 and 3000 times faster, respectively. The complete water dissociation reaction rate decreases in the order Ni(110) > Ni(100) > Ni(111).
|
|
| 6. |
- Ericsson, Leif, 1964-, et al.
(författare)
-
Photoemission study of ZnO nanocrystals : Thermal annealing in UHV and induced band bending
- 2013
-
Ingår i: Surface Science. - Amsterdam : Elsevier. - 0039-6028 .- 1879-2758. ; 612, s. 10-15
-
Tidskriftsartikel (refereegranskat)abstract
- ZnO nanocrystals distributed by spin-coating on SiO2/Si surfaces were annealed in UHV and studied in situ by synchrotron radiation based X-ray Photoelectron Spectroscopy. Changes in chemical composition and electronic structure of ZnO nanocrystal surfaces were found with increasing annealing temperatures. Annealing at 650 °C reduces the surface contaminant levels without any observed de-composition of ZnO. After annealing at 700 °C an initial de-composition of ZnO together with further reduction of contaminants was observed. As a result, 650 °C is found to be the optimal annealing temperature for thermal cleaning of ZnO nanocrystals. Chemical changes and induced point defect formation cause changes in the band structure of the ZnO/SiO2/Si system. An upward band bending of 0.7 eV on the surfaces of the ZnO nanocrystals was found after annealing at 300 °C. The bands on the surfaces of ZnO nanocrystals gradually bend downwards with increasing annealing temperatures. A downward band bending of 1.4 eV is the result after annealing at 750 °C for 1 h. This large downward band bending is explained as due to the change in balance of oxygen vacancies and zinc vacancies on the surfaces of ZnO nanocrystals.
|
|
| 7. |
- Eriksson, Jan Christer, et al.
(författare)
-
Additional remarks related with the discussion inaugurated by the article "Incompatibility of the Shuttleworth equation with Hermann's mathematical structure of thermodynamics" by D. J. Bottomley et al. [Surf. Sci. 603 (2009) 97]
- 2010
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 604:11-12, s. 1062-1063
-
Tidskriftsartikel (refereegranskat)abstract
- Jan Christer Eriksson and Anatoly I. Rusanov critically analyze a paper titled 'Incompatibility of the Shuttleworth equation with Hermann's mathematical structure of thermodynamics' by D. J. Bottomley and co-researchers. According to him, the problem of double counting that Bottomley and co-researchers supposed to be due to involving pairs of terms of the kind xdy + ydx, is not a true research issue but rather a pedagogical one. Within the formal scheme adopted by Gibbs, this problem is properly dealt with by means of a Gibbs Duhem condition. The critics underline that the incompatibility with the mathematical structure of thermodynamics erroneously claimed by Bottomley and co-researchers would apply not just to solid but to liquid interfaces as well, thus invalidating even the firmly rooted Gibbs surface tension equation.
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Fernandes, V. R., et al.
(författare)
-
Reduction behavior of oxidized Pd(100) and Pd75Ag25(100) surfaces using CO
- 2014
-
Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 621, s. 31-39
-
Tidskriftsartikel (refereegranskat)abstract
- The reduction of the (A root 5x root 5)R27 degrees surface oxide on Pd(100) and Pd75Ag25(100) surfaces by CO has been investigated by high-resolution X-ray photoelectron spectroscopy in combination with kinetic analysis using the Avrami-Erofeev theory. For both surfaces we observed faster reduction with increasing temperature. Kinetic analysis indicates that the reduction process is phase boundary controlled for Pd(100) in the temperature range investigated, from 30 degrees C to 120 degrees C On Pd75Ag25(100) the surface oxide reduction is significantly slower compared to Pd(100). Also in this case, a phase boundary controlled reduction of the surface oxide is observed at temperatures of 120 C and above, while at T <= 70 degrees C the reduction is found to be diffusion limited. Density functional theory calculations show that the presence of silver in the outermost surface layer significantly increases the CO diffusion barriers on the reduced areas, supporting a diffusion limited reduction process for Pd75Ag25(100) at lower temperatures. (C) 2013 Elsevier B.V. All rights reserved.
|
|
