Operando Identification of Temperature-Dependent Pore-Scale Gas Saturations in PEM Water Electrolyzers
Bibliographic record
Abstract
Polymer electrolyte membrane (PEM) water electrolysis is a promising solution for the chemical storage of intermittent renewable energy in the form of clean hydrogen (1). For the widespread adoption of this technology, the efficiency of PEM electrolyzers must be improved through informed material design and tailored operating conditions to compete with incumbent carbon-emitting technologies (2). A main source of inefficiency is related to mass transport losses, where oxygen gas, a by-product of the anode reaction, accumulates in the anode porous transport layer (PTL) and hinders reactant liquid water delivery to reaction sites (3). Although extensive studies have explored this two-phase flow phenomenon, the consideration of operating temperature on gas accumulation in the PTL adds further complexity. A duality in temperature effects has been reported in the literature where increasing the operating temperature may encourage gas coverage which obstructs liquid water transport, but it may also enhance liquid water delivery due to favorable fluid property changes in viscosity and surface tension (4). Efforts have been made previously to reconcile these competing observations using 2D visualization methods (5), however a closer investigation using 3D visualization techniques will provide valuable pore-scale insights in the comprehensive understanding of the impact of operating temperature on gas transport in the PTL, and subsequently mass transport losses in the PEM electrolyzer. In this work, we employed operando X-ray computed tomography (CT) to visualize three-dimensional (3D) pore-scale gas saturations in the PTL at various industrially relevant operating conditions. Specifically, a custom in-house electrolyzer was imaged with synchrotron CT at five different temperatures (40°C, 50°C, 60°C, 70°C, 80°C) and current densities ranging from 0.5 A/cm² to 4.0 A/cm² with 0.5 A/cm² incremental steps. Electrochemical impedance spectroscopy and Tafel measurements were also acquired to characterize the relationship between gas distributions and corresponding mass transport overpotentials. Considering X-ray transparency, a model PTL made of carbon fibers was used to achieve sufficient contrast to quantify water and gas in the obtained images. Using precise volume registration and subtraction methods, pore-scale gas distributions in the PTL were quantified to reveal changes in bubble accumulation and coverage area at different operating temperatures and over operation time. The novel insights from this work will aid in our understanding of the complex relationship between operating temperature and multiphase flow phenomena in the PTL, which is vital for tailoring operating conditions of PEM electrolyzers to curtail the costs of green hydrogen production.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".