Electro-Oxidation of Borohydride in a Molten Alkali Hydroxide Eutectic Mixture and a Novel Borohydride/Periodate Molten Electrolyte Battery
Bibliographic record
Abstract
The NaBH4 electro-oxidation kinetics in a molten NaOH-KOH eutectic mixture (0.585:0.415 mole fractions) is investigated on Ni, electrochemically oxidized Ni and Pt electrodes in conjunction with the performance of a novel NaBH4/KIO4 battery [1, 2]. The oxidized Ni shows excellent electrocatalytic activity towards BH4 - oxidation at 458 K, with apparent exchange current density, Tafel slope and electron transfer coefficient of 22.54 mA cm-2, 127 mV dec-1 and 0.7 respectively. The activation energy of the BH4 - oxidation reaction is 16.3 kJ mol-1. The BH4 - diffusion coefficient was determined using a chronoamperometric technique. X-ray photoelectron spectroscopy (XPS) analysis of the anodically oxidized Ni reveals the formation of NiO, which is responsible for the increased catalytic activity towards BH4 - oxidation compared to the untreated Ni electrode. A compact molten NaOH-KOH eutectic electrolyte battery with dissolved NaBH4 at the anode, immobilized KIO4 at the cathode and sintered Ni separator, was assembled and investigated for the first time. An oxidized Ni gauze served as the anode, whereas the cathode was Pt mesh containing the immobilized KIO4. Figure 1 a and b, show the NaBH4/KIO4 battery polarization curves as a function of NaBH4 molal concentration and the discharge cell voltage profile over time at 160 mA cm-2, respectively. Fig. 1: a) Polarization curves of the NaBH4/KIO4 battery at 458 K in the NaOH-KOH eutectic mixture, b) Constant current discharge at 160 mA cm-2 with 500 milimolal NaBH4. Oxidized Ni gauze anode; Pt gauze cathode with 2.5 g cm-2 loading of KIO4; electrolyte: NaOH-KOH eutectic mixture with mole fractions 0.515:0.485. Factorial design of experiments revealed the main and interaction effects influencing the power output of the NaBH4/KIO4 battery. Temperature and cathodic KIO4 loading have the most significant main effects on the power density, whereas the NaBH4 concentration in the molal concentration range of 50 to 500 milimolal, has a comparatively smaller effect. A maximum power density of 210 mW cm-2 is achieved at 458 K. With further research and development it is proposed that the NaBH4 – KIO4 battery could be used together with solar – thermal energy storage systems. References: A.Wang and E.L. Gyenge J.Power Sources 282 (2015) 169-173. A. Wang and E.L. Gyenge, manuscript in preparation (2016). Figure 1
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 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 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".