Low-temperature electrochemical ammonia synthesis: measurement reliability and comparison to Haber-Bosch in terms of energy efficiency

09 February 2023, Version 3
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Recently several studies paved a way to nearly 100% selectivity of the electrochemical ammonia synthesis (EAS), which had been identified earlier as a main challenge. These results motivated us to benchmark the energy efficiency (EE) of EAS against the Haber-Bosch process. We present a method to calculate EE of EAS, which can be used by a broader audience. EAS studies historically suffered from reliability issues, and to avoid benchmarking of false-positive results, we established a method to calculate a reliability indicator to assess the measurement reliability of a published work. We used the indicator to evaluate the studies published in 2020, 2021 and 2022. We calculated the EE of EAS for works that were assessed as reliable with our indicator. We identified and discussed several promising systems and strategies enabling higher selectivity and EE. The EE of some aqueous EAS reports are up to 55%, and non-aqueous are below 15%.

Keywords

ammonia
haber-bosch
electrochemical ammonia synthesis
energy efficiency

Supplementary materials

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Title
SI to Low-temperature electrochemical ammonia synthesis: measurement reliability and comparison to Haber-Bosch in terms of energy efficiency
Description
1. Review of ENRR experimental protocols 2 2. Water oxidation potential 4 3. Reliability indicator of all ENRR works assessed in our work 5 4. Energy consumption for producing proton and electron sources in non-aqueous ENRR works 26 4.1 Hydrogen as proton and electron sources 26 4.2 Ethanol as proton and electron sources 26 5. Energy Efficiency of ENRR works 27 6. Practically maximum attainable energy efficiency of non-aqueous ENRR works using Li as a catalyst 31 7. References 32
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