Oxidation and Corrosion of Platinum–Nickel and Platinum–Cobalt Nanoparticles in an Aqueous Acidic Medium
Bibliographic record
Abstract
We report on the synthesis, characterization, and corrosion behavior of randomly oriented platinum–nickel and platinum–cobalt nanoparticles (PtNi-NPs, PtCo-NPs). Unsupported and carbon-supported nanocatalysts were synthesized using the “water-in-oil” microemulsion method. X-ray diffraction (XRD) was used to examine their average crystallite size, which was 2.3 nm in both cases. The shape, size, and size distribution of the nanoparticles were evaluated using transmission electron microscopy (TEM); they were determined to be spherelike with an average size of 3.3 and 3.2 nm for PtNi-NPs and PtCo-NPs, respectively, and a narrow size distribution. Comparison of the XRD and TEM data indicated that the nanocatalysts were polycrystalline in nature. Thermogravimetric analysis (TGA) measurements were carried out to evaluate the metal loadings of the carbon-supported nanocatalysts, which were 38.1 wt % for PtNi-NPs and 40.8 wt % for PtCo-NPs. Static Density Functional Theory (DFT) calculations were performed to analyze the structures and energetics of the PtNi and PtCo systems; it was found that the presence of Ni and Co introduced ca. 8% of volume reduction, as compared to the volume of pure, bulk Pt. Cyclic voltammetry (CV) measurements at potential scan rates of 5.0 and 50.0 mV s–1 in 0.50 M aqueous H2SO4 indicated that the specific surface areas (As) of the PtNi-NPs and PtCo-NPs were 74.5 m2 gPt–1 and 33.1 m2 gPt–1, respectively. In situ confocal Raman spectroscopy was successfully used to monitor the formation and reduction of surface oxide layers in the submonolayer and monolayer ranges. Corrosion of the nanocatalysts was studied using anodic and cathodic potentiodynamic polarization (PDP) measurements at a very low potential scan rate of s = 0.10 mV s–1 in 0.50 M aqueous H2SO4 saturated with different gases (N2(g), O2(g), or H2(g)). The nature of the dissolved gas had a profound impact on the corrosion characteristics of the nanoparticles. The nanocatalysts were stable in the electrolyte saturated with H2(g) and underwent slight corrosion in the electrolyte saturated with N2(g) and significant corrosion in the electrolyte saturated with O2(g). The carbon support was also observed to undergo corrosion and porosity changes. The degradation of the nanocatalysts was more pronounced in the case of the anodic PDP measurements than the cathodic ones. Cyclic voltammetry was employed to analyze the loss of As of the nanocatalysts as a result of PDP measurements, and the results were found to corroborate the corrosion data. Evolution of the value of As of the nanocatalysts in 0.50 M aqueous H2SO4 outgassed using N2(g) was examined by recording 500 CV transients in the 0.05 V ≤ E ≤ 1.45 V range at s = 50.0 mV s–1. It was found that in both cases this treatment resulted in a 50% reduction in As.
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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".