Preparation of Nafion Membranes for Reproducible Ammonia Quantification in Nitrogen Reduction Reaction Experiments

Abstract

This study highlights the importance of following a strict protocol for Nafion membrane pretreatment for electrochemical nitrogen reduction reaction experiments. Atmospheric ammonia pollution can be introduced to the experimental setup through membranes and interpreted falsely as catalysis product from N2. The sources of ammonia contamination vary drastically between locations worldwide and even within the same location between days depending on temperature, wind direction, fertilizer use, and manure accumulation in its vicinity. The study shows that significant amounts of ammonium is accumulated in the membranes after commonly practiced pretreatment methods, where the amount depends on the ammonia concentration in the surrounding of the experiment. Therefore, we introduce a new pretreatment method which removes all the ammonium in the membrane. The membranes can be stored for several days but a short final step in the method needs to be carried out right before NRR experiments.

Electrochemical Synthesis of Nitric Acid from Nitrogen Oxidation

“…In addition, because the typical setup used in NOR is a double‐chamber cell separated by an ion‐exchange membrane (e.g., Nafion membrane), possible ammonium contamination may exist and accumulate in this membrane, according to previous reports [35] . Thus, a thorough and modified pretreatment of the Nafion membrane is suggested instead of the conventional method [36] . Additionally, there are various types of Nafion membranes, such as Nafion 211, Nafion 115, and Nafion 117, which are different in thickness.…”

Are There Any Overlooked Catalysts for Electrochemical NH3 Synthesis—New Insights from Analysis of Thermochemical Data

“…Here on the cathode, hydrogen in the form of H + and e À reduces N 2 stepwise to NH 3 (Skú lason et al, 2012). The research field is plagued with a number of false-positive measurements, which is the reason why rigorous experimental protocols have been published recently (Andersen et al, 2019;Greenlee et al, 2018;Hanifpour et al, 2020;Tang and Qiao, 2019;Suryanto et al, 2019). Earlier works or reports that do not follow the protocols and produce large amounts of NH 3 , and yet claim high efficiencies, should be taken with a great level of a precaution.…”

Demonstration of no catalytical activity of Fe‐N‐C and Nb‐N‐C electrocatalysts toward nitrogen reduction using in‐line quantification

“…The compartments of the working and counter electrodes (WE and CE) were separated by a Nafion™ 211 membrane. The Nafion™ was pretreated to prevent contamination of ammonia from the atmosphere as previously described 31 . Both electrode chambers were filled with 25 ml of 0.1 M KOH.…”

“…This minimizes external sources of contamination in samples providing a reproducible and reliable method to study NRR. The method only requires 200 μl volume of sample and has a detection limit as low as 1 ppb for ammonia, which allows for thorough and high‐throughput screening of potential NRR electrocatalysts 31 …”