Carbon-Supported Fe–N<sub><i>x</i></sub> Catalysts Synthesized by Pyrolysis of the Fe(II)–2,3,5,6-Tetra(2-pyridyl)pyrazine Complex: Structure, Electrochemical Properties, and Oxygen Reduction Reaction Activity
Bibliographic record
Abstract
Carbon-supported Fe–N x /C catalysts were synthesized at several pyrolysis temperatures such as 600, 700, 800, and 900 °C in the effort to investigate the temperature effect on the catalyst structures. The Fe contents in the synthesized catalysts were found to be about 1 wt % more than that in the Fe–TPPZ/C precursor complex (5 wt %), indicating that both the carbon support and complex ligand might be decomposed during the pyrolysis. X-ray diffraction (XRD) analysis revealed that the samples at 600–800 °C had no iron species segregation, while that formed at 900 °C showed the formation of Fe 3 C and Fe 3 O 4, confirmed by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and energy dispersive X-ray analysis (EDX) measurements. TEM images clearly showed that the large sizes of Fe 3 C and Fe 3 O 4 species with a diameter of about 500 nm were wrapped up by a thin carbon layer. For Fe states, X-ray photoelectron spectroscopy (XPS) data revealed that Fe 3+ was the dominant Fe species in the Fe–N x /C sample. Several nitrogen-containing species such as pyridinic N, the Fe–N(pyr) bond, quaternary N, N -oxides, as well as graphitic nitrogen were identified by XPS in the catalyst samples. Electrochemical characterization revealed a reversible Fe(III)–N x /Fe(II)–N x redox wave at 0.63 V vs RHE, which is believed to be the active sites for the oxygen reduction reaction (ORR). The density of this active site was found to be dependent on the pyrolysis temperature, and high densities were obtained in the temperature range of 700–800 °C. In addition, the morphology of the catalyst samples was also analyzed using the change of double-layer charge with the potential scan rate. Furthermore, the Fe–N x /C catalysts were found to have strong catalytic activity toward oxygen reduction reaction with an overall electron transfer number of 3.6.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".