Electrochemical nitrogen reduction: an intriguing but challenging quest

Operando isotope selective ammonia quantification in nitrogen reduction studies via gas chromatography-mass spectrometry

“…Purication is necessary to remove any 14/15 NH 3 or 14/15 NO x from the feed gasses. The 15 NH 3 produced from 15 N 2 , when reported over time and in quantitative agreement with the ammonia obtained with 14 N 2 , represents the ultimate validation to conrm dinitrogen reduction to ammonia. Therefore, reliable and rapid detection methods, capable of quantitative discrimination of NH 3 isotopologues, are paramount for high throughput catalyst testing and the advancement of this research eld.…”

“…In recent years, the field of electrochemical nitrogen reduction reaction (NRR) to ammonia has witnessed an increasing number of published scientific reports that have been later proven to be false positives, causing misspending of time and resources in pursuing misleading results. 7,8 As such, due to the limited amount of ammonia produced in typical electrocatalytic experiments, rigorous protocols must be followed to categorically exclude false positive results that might arise from extraneous NH 3 contaminations or from labile nitrogen-containing compounds [9][10][11][12][13][14] (e.g. NO x ).…”

“…32 The proposed GC-MS method can quantify 15 NH 3 / 14 NH 3 , down to 1 ppm in the gas phase, and simultaneously detect other gaseous species, giving a complete set of relevant information to better asses reaction selectivity and the presence of contaminants. We further compare the results obtained from GC-MS with those from 1 H NMR measurements for the same mixed 15 N and 14 N ammonia solution, conrming the consistent quan-tication of mixed ammonia isotope samples with the two methods.…”

“…With the proposed system, aliquots of the gaseous analyte are directly collected from the reactor headspace by owing a carrier gas, i.e. Ar, 14 N 2 or 15 N 2 , avoiding any external sample manipulations. The ammonia concentration in equilibrium in the gas phase is strongly correlated with the ammonia present in the electrolyte, allowing a complete quantication of the produced NH 3 in both liquid and gas phases.…”

Overcoming Nitrogen Reduction to Ammonia Detection Challenges: The Case for Leapfrogging to Gas Diffusion Electrode Platforms

“… 23 Therefore, higher mass transport limited current densities for NRR can be reached in GDE cells. 40 , 41 Both the anolyte and catholyte are recycled between the cell and a reservoir. During electrolysis insoluble reaction products will enter the gas compartment and leave the cell with the feed gas.…”