Let’s not forget isotope effect when replacing H2O with D2O for operando neutron studies – Kinetics and transport considerations in PEM water electrolyzer
Bibliographic record
Abstract
Operando neutron imaging techniques are at the forefront of advanced characterization strategies to investigate core phenomena in electrochemical energy devices such as proton exchange membrane water electrolyzers (PEMWEs). The replacement of H 2 O with D 2 O is a practical approach to minimizing attenuation and incoherent scattering effects during neutron imaging, though its impact on the PEMWE performance has not been well-studied. Herein, we comprehensively analyzed PEMWE cells fed with five D 2 O/H 2 O mixtures using electrochemical methods and operando neutron imaging. While the PEMWE characterization highlighted an overpotential of around 190 mV at 1 A cm -2 in the case of using D 2 O instead of H 2 O, the kinetic and ion conductivity differences of these isotopes were confirmed by separate electrochemical studies. Moreover, the water profile inside the PEMWE cell was calculated for the studied D 2 O/H 2 O concentrations, further supporting the results obtained by the electrochemical tests. The neutron data showed a more than two times faster H 2 O permeation compared to D 2 O at 1500 mA cm -2 in PEMWE cells, which perfectly aligned with faster ionic conduction and higher OER performance of H 2 O-fed cells. Also, more stationary D 2 O molecules in the membrane area, even at higher currents, were detected, explaining the lower diffusion of D 2 O through the membrane and the higher electrochemical stability of the D 2 O-fed PEMWE cell. These results were translated to the higher kinetic energy demanded for D 2 O bond breakdown and reduced electro-osmotic drag for D 2 O due to its stronger bond to the membrane and higher viscosity. • The kinetic and transport properties of H 2 O and D 2 O in a PEM water electrolyzer were investigated using electrochemical and operando neutron radiography methods. • Fully-H 2 O operated PEMWE cells showed 190 mV less overpotential at 1 A cm -2 , and four times higher ionic conductivity in the membrane than their D 2 O counterpart. • Faster OER kinetics of the IrO x catalyst in the H 2 O-based electrolyte were measured, while more chemically stable OER activity was associated with the D 2 O-based electrolyte. • More water permeation through the membrane in H 2 O-fed PEMWE cells and more stagnant water inside the membrane in D 2 O-fed PEMWE cells were observed by neutron radiography. • Dynamic phenomenon studies in neutron radiography, e.g. replacing H 2 O with D 2 O, must take the isotope effect into account.
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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 | 0.001 | 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 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".