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Abstract The electrochemical reduction of nitrates (NO3−) enables a pathway for the carbon neutral synthesis of ammonia (NH3), via the nitrate reduction reaction (NO3RR), which has been demonstrated at high selectivity. However, to make NH3synthesis cost‐competitive with current technologies, high NH3partial current densities (jNH3) must be achieved to reduce the levelized cost of NH3. Here, the high NO3RR activity of Fe‐based materials is leveraged to synthesize a novel active particle‐active support system with Fe2O3nanoparticles supported on atomically dispersed Fe–N–C. The optimized 3×Fe2O3/Fe–N–C catalyst demonstrates an ultrahigh NO3RR activity, reaching a maximum jNH3of 1.95 A cm−2at a Faradaic efficiency (FE) for NH3of 100% and an NH3yield rate over 9 mmol hr−1cm−2. Operando XANES and post‐mortem XPS reveal the importance of a pre‐reduction activation step, reducing the surface Fe2O3(Fe3+) to highly active Fe0sites, which are maintained during electrolysis. Durability studies demonstrate the robustness of both the Fe2O3particles and Fe–Nxsites at highly cathodic potentials, maintaining a current of −1.3 A cm−2over 24 hours. This work exhibits an effective and durable active particle‐active support system enhancing the performance of the NO3RR, enabling industrially relevant current densities and near 100% selectivity.
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Electrocatalytic Reduction of Nitrate to Ammonia at Oxidized Vanadium Surfaces with V(3 + ) and V(4 + ) Oxidation States
The electrochemical reduction of nitrate to ammonia is of interest as an energy/environmentally friendly source of ammonia for agriculture and energy applications and as a route toward groundwater purification. We report in situ photoemission data, electrochemical results, and density functional theory calculations that demonstrate vanadium oxide—prepared by ambient exposure of V metal, with a distribution of surface V3+and V4+oxidation states—specifically adsorbs and reduces nitrate to ammonia at pH 3.2 at cathodic potentials. Negligible cathodic activity in the absence of NO3−indicates high selectivity with respect to non-nitrate reduction processes. In situ photoemission data indicate that nitrate adsorption and reduction to adsorbed NO2is a key step in the reduction process. NO3RR activity is also observed at pH 7, albeit at a much slower rate. The results indicate that intermediate (non-d0) oxidation states are important for both molecular nitrogen and nitrate reduction to ammonia.
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- PAR ID:
- 10530411
- Publisher / Repository:
- ECS
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 171
- Issue:
- 7
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- 076504
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1149/1945-7111/ad60f8
