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

Abstract

Rapid advances in electrocatalytic ammonia synthesis are impeded by laborious detection methods commonly used in the field and by constant risk of external contaminations, which generates misleading false positives. We...

In Situ Study of Hydrogen Permeable Electrodes for Electrolytic Ammonia Synthesis Using Near Ambient Pressure XPS

“…Ammonia quantification is carried out directly in the gas phase with a gas chromatography (GC) method, previously developed in our group. Details of the detection method are available elsewhere. , The electrodes under investigation in this study were mounted in a two-compartment polyether ether ketone (PEEK) electrochemical flow cell (Figure a). One side of the electrode, in the liquid compartment, is in contact with the aqueous electrolyte (0.1 M KOH), while the other side, in the gas compartment, is in contact with only N 2 at ambient pressure flowing at 1 mL min –1 (the electrode geometrical active area is 2.5 cm 2 ).…”

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

“…With GC-MS, gaseous 14 NH 3 / 15 NH 3 can be detected in operando with no external sample manipulations and at very low NH 3 production rates (on the order of 10 –13 mol/s at 1 mL/min) which makes the detection more reliable and more sensitive than the commonly used NH 3 accumulation in an acid trap. 44 …”

“…We want to briefly highlight the opportunity of combining the low isotope labeling cost in a GDE cell with very sensitive 1 H NMR spectrometers or the recently developed, highly sensitive detection methods for aqueous and gaseous ammonia detection using ultrahigh performance liquid chromatography-mass spectrometry (UPLC-MS) and gas chromatography-mass spectrometry (GC-MS), respectively (see Figure 2a). 24,44,45 Unlike 14 NH 3, 15 NH 3 is not affected by contaminations, other than the ones coming from the 15 N 2 itself which can be removed with a proper gas purification step. Therefore, 15 NH 3 from NRR can be quantified accurately as soon as the detection limit of the detection method is reached which is 1 ppm for GC-MS and less than 1 μM for very sensitive 1 H NMR spectrometers and UPLC-MS, respectively .…”

“…Therefore, 15 NH 3 from NRR can be quantified accurately as soon as the detection limit of the detection method is reached which is 1 ppm for GC-MS and less than 1 μM for very sensitive 1 H NMR spectrometers and UPLC-MS, respectively . 24,44,45 By using these very sensitive detection methods, 15 N 2 experiments can become even shorter and cheaper so that catalysts could potentially be tested only with 15 N 2 instead of 14 N 2 requiring only a few milliliters of 15 N 2 per catalyst and consequentially enabling rapid, unambiguous NH 3 quantification. With GC-MS, gaseous 14 NH 3 / 15 NH 3 can be detected in operando with no external sample manipulations and at very low NH 3 production rates (on the order of 10 −13 mol/s at 1 mL/min) which makes the detection more reliable and more sensitive than the commonly used NH 3 accumulation in an acid trap.…”

“…With GC-MS, gaseous 14 NH 3 / 15 NH 3 can be detected in operando with no external sample manipulations and at very low NH 3 production rates (on the order of 10 −13 mol/s at 1 mL/min) which makes the detection more reliable and more sensitive than the commonly used NH 3 accumulation in an acid trap. 44 Electrochemical Benefits of a High Surface Area NRR Catalyst. The choice of cell design has several other implications for NRR research besides the ones discussed in the previous section.…”