Electrochemical Production of Ammonia and Urea from Coreduction of Nitrite and Carbon Dioxide at Iron Phthalocyanine Electrodes and Comparison of Analytical Methods
Bibliographic record
Abstract
There is rapidly growing interest in the electrochemical reduction of both nitrite and carbon dioxide to mitigate environmental concerns and sustainably produce fuels, chemicals, and fertilizers. Ammonia and urea are key targets in this area, and have been produced simultaneously by coreduction of NO 2 ⁻ and CO 2 at a variety of electrocatalysts. The salicylate spectrophotometric method is commonly employed to quantify both products, with urea determined by difference following decomposition with urease. However, this method can be influenced by numerous interferences and matrix effects. Here the electrochemical coreduction of NO 2 ⁻ and CO 2 at iron phthalocyanine electrodes has been investigated in order to accurately determine the ammonia and urea production. Urea concentrations were determined by salicylate, diacetyl monoxime and liquid-chromatography-mass spectrometry methods, while the salicylate method and nuclear magnetic resonance spectroscopy were used to determine ammonia. Urea was produced at low overpotentials, with a maximum faradaic yield of 5.8% at −0.047 V vs RHE, while a maximum 85% yield of ammonia occurred at −0.347 V. It is shown that the salicylate method can provide accurate ammonia and urea analyses when a standard addition method is employed, reaction conditions are carefully controlled and the accuracy of calibration slopes are verified.
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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) | 0.001 | 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 | 0.001 |
| 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".