Ionomer-free Pt Microenvironment in Bimodal Carbon Scaffolds Generates Exceptional Oxygen Reduction Mass Activity in PEM Fuel Cells
Bibliographic record
Abstract
Pt nanoparticles (NPs) on carbon are widely used as catalysts in polymer exchange membrane (PEM) fuel cell cathodes. However, the Nafion ionomer/binder can poison Pt and reduce its electrocatalytic activity. To solve this dilemma, a bimodal ball-and-stick carbon scaffold (BCS) was developed, consisting of spheres containing 3-D-interconnected primary mesopores (12 nm) housing Pt NPs, with Nafion found only on the sphere surfaces, creating an ionomer-free micro-environment that protects Pt from Nafion poisoning. These catalysts exhibit exceptionally high mass activities for oxygen reduction (ORR) that are retained after accelerated durability testing in a membrane-electrode-assembly, even demonstrating performance improvement. The transport of protons to Pt NPs occurs via water on the hydrophilic mesopore surfaces, verified by the pronounced effect of RH on ORR kinetics and excellent ORR activity even without any Nafion added. These findings establish a clear link between ionomer poisoning of Pt and ORR activity and highlight the effectiveness of combining specific carbon morphologies and oxygen-rich surfaces to produce ultra-high performance.
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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 | 0.000 |
| 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) | 0.001 | 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".