Temperature-Dependence of the Electro-oxidation of the Irreversibly Chemisorbed As on Pt(111)
Bibliographic record
Abstract
An overlayer of chemisorbed arsenic, As chem, on Pt(111) having a surface coverage of θ As is prepared, and the impact of T variation on the surface-oxidation behavior in 0.5 M aqueous H 2 SO 4 is examined. Temperature variation in the 273−313 K range does not affect the As chem surface coverage, but the cyclic-voltammetry (CV) profiles undergo qualitative changes. The anodic and cathodic peaks shift toward more-positive potentials, and a charge-density redistribution between two anodic and cathodic features is observed, the latter effect being more pronounced in the anodic scans. At T = 313 K, the CV transients are symmetrical with respect to the potential axis. In the case of As chem overlayers having θ As well below 0.33, the CV profiles representative of the As chem oxidation reveal only one peak. An analysis of the possible reaction pathways indicates that the surface oxidation proceeds in one step involving transfer of three electrons and addition of three OH groups, thus in formation of As(OH) 3chem . An analysis of the As 3+ and OH - radii indicates that the As(OH) 3chem layer is densely packed. The existence of two anodic and two cathodic peaks in CV transients is explained in terms of formation two energetically slightly different structures of As(OH) 3chem, their origin being two different ways of coordinating As(OH) 3chem to Pt(111). The standard enthalpy of the surface process is determined from the slope of the E / T versus 1/ T plots, and the standard enthalpy of formation of As(OH) 3chem, (As(OH) 3chem ), is found to be −678 kJ mol - 1 . The value of (As(OH) 3chem ) is characteristic of As being in the 3+ oxidation state and being attached to three OH groups. The conclusion that As(OH) 3chem is the species formed agrees with the CV, IR spectroscopy, and ex-situ scanning tunneling microscopy data which point to an oxygenated As 3+ surface compound formed in the course of As chem electro-oxidation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".