Evaluation of Carbon Anodes during Saltwater Electrolysis
Bibliographic record
Abstract
Hydrogen is a promising alternative energy carrier to mitigate emissions arising from fossil fuel use. However, the most common methods of commercial hydrogen production, e.g., steam-methane reforming, are known to contribute significantly to greenhouse gas emissions. Therefore, there is significant interest in green hydrogen production through water electrolysis. At the same time, freshwater sources are limited and thus efforts are increasingly turning to saltwater electrolysis using renewable energy 1 . Key challenges encountered at the anode during saltwater electrolysis include the sluggish kinetics of the oxygen evolution reaction (OER) combined with low Faradaic efficiency due to competition from the chlorine evolution reaction (CER) 1 , as well as poor durability. The CER becomes a particular problem as electrolysis progresses because the local pH becomes more acidic as a result of the OER, causing the thermodynamic potentials of the OER and CER to become more similar 1,2 . However, Cl 2 is toxic and OCl - is corrosive to industrial equipment and thus we need to minimize chloride oxidation during saltwater electrolysis 1,2 . Current anode catalyst materials, such as metals and metal oxides, are known to be highly unstable at high potentials in chloride-containing solutions, while also being costly and lacking the desired selectivity towards the OER 3 . In addition, OCl - is known to make metallic anodes and other electrolyzer components susceptible to significant corrosion 3 . Thus, alternative anode materials that are low cost, catalytically active, and stable are needed. Carbon-based electrocatalysts are low in cost, readily available, relatively stable in neutral conditions, and can be easily functionalized to further enhance their activity and selectivity in various electrochemical systems 4 . However, few studies have investigated these systems, with little known yet about electrode stability or the impact of surface functionalization or heteroatom doping on carbon activity and selectivity in aqueous media and especially in saltwater. In the present work, we have evaluated the selectivity, activity and durability of a range of carbon materials, including graphite, graphene, carbon black, and colloid imprinted carbon powders, as anodes in salt solutions using cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. Multiple conditions have been varied to obtain a full picture of the electrochemistry underway, including doping the best performing carbons with nitrogen, altering the solution flow rate and varying the cell design. We are also tracking the solution concentration of all oxidized chloride species that are formed, while also monitoring the solution pH, and the composition of the gas evolved at the anode to determine the amount of oxygen vs chlorine gas produced. A detailed discussion and analysis of the electrochemistry, combined with chemical and physical characterization of the electrode materials and computational efforts, will be presented. Acknowledgements: This research is supported by the Natural Science and Engineering Research Council of Canada, the Canada First Research Excellence Fund, Alberta Innovates, Evolve Hydrogen Inc., Qualicase Ltd., and Fidelity Manufacturing Group. References: (1) Dresp, S.; Dionigi, F.; Klingenhof, M.; Strasser, P. ACS Energy Letters . 2019, pp 933–942. https://doi.org/10.1021/acsenergylett.9b00220. (2) Tang, X.; Arif, I.; Diao, P. Journal of Electroanalytical Chemistry 2023 , 942 , 1–7. https://doi.org/10.1016/j.jelechem.2023.117569. (3) Tiwari, J. N.; Sultan, S.; Myung, C. W.; Yoon, T.; Li, N.; Ha, M.; Harzandi, A. M.; Park, H. J.; Kim, D. Y.; Chandrasekaran, S. S.; Lee, W. G.; Vij, V.; Kang, H.; Shin, T. J.; Shin, H. S.; Lee, G.; Lee, Z.; Kim, K. S. Nat Energy 2018 , 3 (9), 773–782. https://doi.org/10.1038/s41560-018-0209-x. (4) Younis, M. A.; Lyu, S.; Zhao, Q.; Lei, C.; Zhang, P.; Yang, B.; Li, Z.; Lei, L.; Hou, Y.; Feng, X. BMC Mater 2019 , 1 (1). https://doi.org/10.1186/s42833-019-0006-2.
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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 | 0.000 |
| 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) | 0.000 | 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".