The fate of FeNC catalysts: Influence of storage conditions on structure and performance evolution
Bibliographic record
Abstract
FeNC materials are considered as promising catalysts for fuel cell application and CO 2 reduction. However, a general obstacle is their instability when stored at ambient conditions, typically this resulted in structural changes and loss of ORR activity as observed in half-cell measurements. So far little work was done to systematically explore the root-cause of this phenomenon and to correlate it with FC performance data. In this work, we investigated the degradation of two distinct FeNC catalysts (one initially pure and one impure) under various storage conditions to identify the impact of gas and temperature and to see to what extent the degradation depends on the purity of the pristine material. The catalysts are characterized by 57 Fe Mössbauer spectroscopy, X-ray diffraction, scanning transmission electron microscopy and X-ray absorption spectroscopy to follow structural changes as well as by rotating ring disk electrode experiments and fuel cell tests to check for performance changes. Our findings reveal that degradation occurs across all tested environments, albeit with varying degrees of severity. While inert storage under argon gas leads to Fe 3 C formation, storage under air and 80 °C causes further inorganic side phases to appear and had the strongest impact on performance. We identified iron carbide and iron( III )oxide as the main degradation products and assessed their influence on the oxygen reduction reaction (ORR) activity and selectivity. In this context, it was shown that the degradation of specific FeN 4 sites leads to the inorganic phases mentioned above. Notably, our results indicate here that axial ligands play a critical role in influencing both site stability and ORR performance, highlighting their significance in the catalytic behavior of FeNC systems. • Study on the shelf-degradation of a pure and impure FeNC catalyst. • Comparison of structural changes induced with three storage conditions: inert_RT, air_RT, air_80C. • Correlation between performance (FC, RRDE) and changes in composition. • Identification of two degradation vs transformation pathways. • The stability of FeN 4 moieties depends severely on the ligand environments.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".