Corrosion of TiHfZrNbx high-entropy alloys in a simulated condition of proton exchange membrane water electrolyser
Bibliographic record
Abstract
• TiHfZrNb x HEAs resist corrosion 600 x than Ti in 0.5 m H 2 SO 4 + 5 ppm F – solution at 70 °C. • Hf, Zr, Nb synergistically form a dense passive film consisted of HfO 2 , ZrO 2 , TiO 2 , Nb 2 O 5 . • The passive film is an n-type semiconductor with low electron-donor concentration. • The lower the Nb content in the HEAs the lower the corrosion current density. • Nb has a small role toward passivation in the aggressive acidic solution. In the present work, the corrosion behavior and passive film properties of TiHfZrNb x ( x = 0.2, 0.3 and 0.4) high-entropy alloys (HEAs) were evaluated under a simulated condition of a proton exchange membrane water electrolyser (PEMWE) in view of their application as bipolar plates. Results from electrochemical-impedance spectroscopy, cyclic- and static-polarizations evaluation revealed that in a 0.5 M H 2 SO 4 + 5 ppm F – solution at 70 °C the HEAs exhibited about 600 times higher polarization resistance than that of CP-Ti, with the highest achieved at 79.57 kΩ.cm 2 for TiHfZrNb 0.2 , leading to a sharp contrast in the corrosion-current density, 805.11 µA.cm -2 for the CP-Ti vs. 0.92 µA.cm -2 for the TiHfZrNb 0.2 , reflecting a far superior corrosion resistance of the HEAs. X-ray photoelectron spectroscopy analysis confirmed the formation of a multi-oxide passive film, predominantly by HfO 2 > ZrO 2 > TiO 2 , with a presence of Nb 2 O 5 only in TiHfZrNb 0.4 , all possess an n-type semiconducting characteristic and a much lower electron-donor concentration in the HEAs than in the CP-Ti. The complementary analyses of scanning electron microscopy, atomic force microscopy and solution chemistry highlighted the synergistic effects of Hf, Zr, and Nb in enhancing protectiveness of the passive film, but the absence of Nb 2 O 5 on the top surface of TiHfZrNb 0.2 and TiHfZrNb 0.3 indicated a small role of Nb toward passivation.
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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".