Systematic Assessment of Electrode Wettability for Vanadium Redox Flow Batteries
Bibliographic record
Abstract
Vanadium redox flow batteries (VRFBs) are a promising energy storage technology due to their advantages such as long-life cycle and scalability. In these systems, porous electrodes such as carbon paper and carbon felts have been used because of their desirable properties such as good acid resistance and low cost. However, these materials may have poor reversibility and wettability, which can negatively affect the system performance. Recently, different activation methods have been proposed to enhance physico-chemical properties and overcome these limitations. Among different methods, surface treatments have been commonly used in the literature [1-5] since they can introduce desirable functional groups (e.g., oxygen, nitrogen) and enhance electrochemically active surface area (ECSA), which is believed to be the main mechanisms for electrode performance improvement. Although it is suggested that higher electrode performance can be achieved by enhancing wetted or active surface area [6], there is still a disparity in how to assess relevant wetting properties, since wettability assessment is often neglected and performance assessment is usually done based on VRFB cycling test results, which is costly and time consuming. Static contact angle (CA) is commonly used to characterize electrode wettability and evaluate the effect of different treatments on the electrode surface. However, this technique offers a limited understanding and superficial analysis, since samples are either classified as hydrophobic or hydrophilic, showing no correlation to electrochemical performance. Moreover, CA measurements are not adequate for porous electrodes, since porosity and surface roughness can impact on contact angle results. In the present work, we propose to use the method of standard porosimetry (MSP) and cyclic voltammetry (CV) to evaluate the impact of surface treatments on electrode wettability from a complete physical (pore size distribution), chemical (functional group density), and electrochemical (electrochemically active surface area) perspective. These tools offer richer information than basic CA measurements and only take a few hours to be performed, thus reducing the assessment time and cost compared to VRFB assembly and cycling tests. Preliminary results show that both MSP and CV techniques can provide useful information regarding physical and chemical properties that can correlate electrode wettability to electrochemical performance. While MSP results can provide electrode morphology (pore size distribution, porosity, specific and wetted surface area), CV measurements can provide surface chemistry information (functional groups density) and electrochemically active surface area (capacitance). Thus, both tools can be used synergistically to investigate how different treatments impact both physical and chemical properties and how wetting properties impact electrode performance. Achieving high performance is essential to increase system energy density and decrease both capital and operational cost, making VRFBs more competitive and suitable for grid-scale storage of renewable energy, having positive environmental impacts and facilitating sustainable transition. Acknowledgements This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation (CFI), British Columbia Knowledge Development Fund (BCKDF), Western Economic Diversification Canada (WD), Canada Research Chairs (CRC), and the National Research Council of Canada (NRC). Technical support from Elizabeth Fisher and Jonas Stoll is also acknowledged. References [1] B. Sun and M. Skyllas-Kazacos, “Modification of graphite electrode materials for vanadium redox flow battery application—I. Thermal Treatment,” Electrochimica Acta , vol. 37, no. 7, pp. 1253–1260, 1992. [2] B. Sun and M. Skyllas-Kazacos, “Chemical modification of graphite electrode materials for vanadium redox flow battery application—part II. acid treatments,” Electrochimica Acta , vol. 37, no. 13, pp. 2459–2465, 1992. [3] H. R. Jiang, W. Shyy, L. Zeng, R. H. Zhang, and T. S. Zhao, “Highly efficient and ultra-stable boron-doped graphite felt electrodes for vanadium redox flow batteries,” Journal of Materials Chemistry A , vol. 6, no. 27, pp. 13244–13253, 2018. [4] S. J. Yoon, S. Kim, D. K. Kim, S. So, Y. T. Hong, and R. Hempelmann, “Ionic liquid derived nitrogen-doped graphite felt electrodes for vanadium redox flow batteries,” Carbon , vol. 166, pp. 131–137, 2020. [5] Y.-H. Wang, I.-M. Hung, and C.-Y. Wu, “The characteristics and electrochemical performance of Graphite Felts with thermal and Fenton's reagent treatment for vanadium redox flow battery,” Ceramics International , vol. 44, 2018. [6] M.-A. Goulet, M. Skyllas-Kazacos, and E. Kjeang, “The importance of wetting in carbon paper electrodes for vanadium redox reactions,” Carbon , vol. 101, pp. 390–398, 2016.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| 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) | 0.000 | 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 teacher head, 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".