TY  - JOUR
AU  - Johnston, Christina Marie
AU  - Štrbac, Svetlana
AU  - Lewera, Adam
AU  - Sibert, Eric
AU  - Wiȩckowski, Andrzej
PY  - 2006
UR  - https://cer.ihtm.bg.ac.rs/handle/123456789/4348
AB  - Catalytic activity of the Pt(111)/Os surface toward methanol electrooxidation was optimized by exploring a wide range of Os coverage. Various methods of surface analyses were used, including electroanalytical, STM, and XPS methods. The Pt(111) surface was decorated with nanosized Os islands by spontaneous deposition, and the Os coverage was controlled by changing the exposure time to the Os-containing electrolyte. The structure of Os deposits on Pt(111) was characterized and quantified by in situ STM and stripping voltammetry. We found that the optimal Os surface coverage of Pt(111) for methanol electrooxidation was 0.7 ± 0.1 ML, close to 1.0 ± 0.1 Os packing density. Apparently, the high osmium coverage Pt(111)/Os surface provides more of the necessary oxygen-containing species (e.g., Os-OH) for effective methanol electrooxidation than the Pt(111)/Os surfaces with lower Os coverage (vs e.g., Ru-OH). Supporting evidence for this conjecture comes from the CO electrooxidation data, which show that the onset potential for CO stripping is lowered from 0.53 to 0.45 V when the Os coverage is increased from 0.2 to 0.7 ML. However, the activity of Pt(111)/Os for methanol electrooxidation decreases when the Os coverage is higher than 0.7 ± 0.1 ML, indicating that Pt sites uncovered by Os are necessary for sustaining significant methanol oxidation rates. Furthermore, osmium is inactive for methanol electrooxidation when the platinum substrate is absent: Os deposits on Au(111), a bulk Os ingot, and thick films of electrodeposited Os on Pt(111), all compare poorly to Pt(111)/Os. We conclude that a bifunctional mechanism applies to the methanol electrooxidation similarly to Pt(111)/Ru, although with fewer available Pt sites. Finally, the potential window for methanol electrooxidation on Pt(111)/Os was observed to shift positively versus Pt(111)/Ru. Because of the difference in the Os and Ru oxophilicity under electrochemical conditions, the Os deposit provides fewer oxygen-containing species, at least below 0.5 V vs RHE. Both higher coverage of Os than Ru and the higher potentials are required to provide a sufficient number of active oxygen-containing species for the effective removal of the site-blocking CO from the catalyst surface when the methanol electrooxidation process occurs.
PB  - American Chemical Society (ACS)
T2  - Langmuir
T1  - Characterization and methanol electrooxidation studies of Pt(111)/Os surfaces prepared by spontaneous deposition
VL  - 22
IS  - 19
SP  - 8229
EP  - 8240
DO  - 10.1021/la060164e
ER  - 

@article{
author = "Johnston, Christina Marie and Štrbac, Svetlana and Lewera, Adam and Sibert, Eric and Wiȩckowski, Andrzej",
year = "2006",
abstract = "Catalytic activity of the Pt(111)/Os surface toward methanol electrooxidation was optimized by exploring a wide range of Os coverage. Various methods of surface analyses were used, including electroanalytical, STM, and XPS methods. The Pt(111) surface was decorated with nanosized Os islands by spontaneous deposition, and the Os coverage was controlled by changing the exposure time to the Os-containing electrolyte. The structure of Os deposits on Pt(111) was characterized and quantified by in situ STM and stripping voltammetry. We found that the optimal Os surface coverage of Pt(111) for methanol electrooxidation was 0.7 ± 0.1 ML, close to 1.0 ± 0.1 Os packing density. Apparently, the high osmium coverage Pt(111)/Os surface provides more of the necessary oxygen-containing species (e.g., Os-OH) for effective methanol electrooxidation than the Pt(111)/Os surfaces with lower Os coverage (vs e.g., Ru-OH). Supporting evidence for this conjecture comes from the CO electrooxidation data, which show that the onset potential for CO stripping is lowered from 0.53 to 0.45 V when the Os coverage is increased from 0.2 to 0.7 ML. However, the activity of Pt(111)/Os for methanol electrooxidation decreases when the Os coverage is higher than 0.7 ± 0.1 ML, indicating that Pt sites uncovered by Os are necessary for sustaining significant methanol oxidation rates. Furthermore, osmium is inactive for methanol electrooxidation when the platinum substrate is absent: Os deposits on Au(111), a bulk Os ingot, and thick films of electrodeposited Os on Pt(111), all compare poorly to Pt(111)/Os. We conclude that a bifunctional mechanism applies to the methanol electrooxidation similarly to Pt(111)/Ru, although with fewer available Pt sites. Finally, the potential window for methanol electrooxidation on Pt(111)/Os was observed to shift positively versus Pt(111)/Ru. Because of the difference in the Os and Ru oxophilicity under electrochemical conditions, the Os deposit provides fewer oxygen-containing species, at least below 0.5 V vs RHE. Both higher coverage of Os than Ru and the higher potentials are required to provide a sufficient number of active oxygen-containing species for the effective removal of the site-blocking CO from the catalyst surface when the methanol electrooxidation process occurs.",
publisher = "American Chemical Society (ACS)",
journal = "Langmuir",
title = "Characterization and methanol electrooxidation studies of Pt(111)/Os surfaces prepared by spontaneous deposition",
volume = "22",
number = "19",
pages = "8229-8240",
doi = "10.1021/la060164e"
}

Johnston, C. M., Štrbac, S., Lewera, A., Sibert, E.,& Wiȩckowski, A.. (2006). Characterization and methanol electrooxidation studies of Pt(111)/Os surfaces prepared by spontaneous deposition. in Langmuir
American Chemical Society (ACS)., 22(19), 8229-8240.
https://doi.org/10.1021/la060164e

Johnston CM, Štrbac S, Lewera A, Sibert E, Wiȩckowski A. Characterization and methanol electrooxidation studies of Pt(111)/Os surfaces prepared by spontaneous deposition. in Langmuir. 2006;22(19):8229-8240.
doi:10.1021/la060164e .

Johnston, Christina Marie, Štrbac, Svetlana, Lewera, Adam, Sibert, Eric, Wiȩckowski, Andrzej, "Characterization and methanol electrooxidation studies of Pt(111)/Os surfaces prepared by spontaneous deposition" in Langmuir, 22, no. 19 (2006):8229-8240,
https://doi.org/10.1021/la060164e . .