The removal of inevitable NOx species in catalysts and the selection of appropriate membrane for measuring electrocatalytic ammonia synthesis accurately

Ammonia synthesis by electrocatalytic nitrogen reduction reaction (NRR) is considered as a promising alternative to the Haber−Bosch process. However, due to the extremely low ammonia yield and easily accessible extraneous contamination in the laboratory, NRR study always suffers from fluctuation and variability. Finding and eliminating all kinds of possible extraneous contamination is crucial to evaluate the performance of electrocatalytic ammonia synthesis accurately. In this work, we systematically explored two factors that affect NRR results but are easy to be ignored: the selection of membrane for NRR and the unconscious N-source in NRR catalysts. After series of experiments, we proposed a low-cost and almost pollution-free Celgard 3501 membrane as the separator for NRR to avoid the adsorption and release of ammonia by the membrane. In addition, we proposed a pre-reduction strategy to remove residual or adsorbed NO x contaminants in catalysts. These two solutions will help the community to evaluate the NRR activity more accurately.