Facts or artifacts: pitfalls in quantifying sub-ppm levels of ammonia produced from electrochemical nitrogen reduction Suchi Biswas 1 , Smita Biswas 1 , Arunava Saha 1 and Muthusamy Eswaramoorthy 1,2 1 JNCASR, India, 2 International Centre for Materials Science, India In the recent years, the concept of synthesizing ammonia through electrochemical nitrogen reduction (ENR) in aqueous medium, under ambient conditions has emerged as an attractive research area. 1 However, several reports claiming high ammonia production rate, were found to falsely analyze ammonia contamination present in the surrounding as their result. 2 Even ammonia obtained from reduction of nitrogen oxides-based contaminants were also claimed as ENR result. 3 In addition to it, we observed that in majority of the cases, the concentration of ammonia quantified in the electrolyte post ENR reaction lies in the sub-ppm level. Therefore, in our work we have highlighted the artifacts present in the commonly used indophenol method for determining ammonia concentration through elaborative control experiments. It is significant to choose appropriate indophenol protocol encompassing admissible level of oxidant and a complexing agent, citrate (to mitigate the effect of interfering metal ions). Additionally, the importance to set lowest limit of ammonia concentration that can be accurately quantified by indophenol method was also justified. Further, the experimental observations were summarized into a protocol which was followed to re-evaluate the performance of two well-claimed electrocatalysts for ENR reported recently in the literature. References 1. MacFarlane, D. R. et al. A roadmap to the ammonia economy. 4 , 1186-1205 (2020). 2. Chen, G. F. et al. Advances in electrocatalytic N2 reduction—strategies to tackle the selectivity challenge. 3 , 1800337 (2019). 3. Choi, J. et al. Reassessment of the catalytic activity of bismuth for aqueous nitrogen electroreduction. 5 , 382-384 (2022).
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