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

Abstract

The nitrogen reduction reaction (NRR) is a promising pathway toward the decarbonization of ammonia (NH 3 ) production. However, unless practical challenges related to the detection of NH 3 are removed, confidence in published data and experimental throughput will remain low for experiments in aqueous electrolyte. In this perspective, we analyze these challenges from a system and instrumentation perspective. Through our analysis we show that detection challenges can be strongly reduced by switching from an H-cell to a gas diffusion electrode (GDE) cell design as a catalyst testing platform. Specifically, a GDE cell design is anticipated to allow for a reduction in the cost of crucial 15 N 2 control experiments from €100–2000 to less than €10. A major driver is the possibility to reduce the 15 N 2 flow rate to less than 1 mL/min, which is prohibited by an inevitable drop in mass-transport at low flow rates in H-cells. Higher active surface areas and improved mass transport can further circumvent losses of NRR selectivity to competing reactions. Additionally, obstacles often encountered when trying to transfer activity and selectivity data recorded at low current density in H-cells to commercial device level can be avoided by testing catalysts under conditions close to those in commercial devices from the start.

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

“…Furthermore, as highlighted by Kolen et al [474] in a recent perspective paper, detecting NH3 in NRR would necessitate experiments in a GDE cell rather than in H-cell. Future NRR research should focus on the relationships between the electrochemical reactors, reactor parameters, j, product detections and yields, corresponding reaction mechanisms, etc.…”

Electrochemical Generation of Catalytically Active Edge Sites in C2N‐Type Carbon Materials for Artificial Nitrogen Fixation

“…Besides, isotope labeling experiments with 15 N 2 as the feeding gas that also went through a scrubbing procedure have been performed to further validate the nitrogen source for ammonia. From the 1 H NMR spectra of pre-concentrated electrolyte after electrolysis with different N 2 gases employed (Figure 2d), distinct doublet peaks of 15 NH 4 + with a spacing of 73 Hz were observed, while triple peaks of 14…”

“…[ 10h,13 ] It can be anticipated that one of the most straightforward ways to overcome such experimental limitations in the future will be to move to reactor concepts with larger solid‐liquid‐gas interfaces and therefore intrinsically higher ammonia production rate. [ 14 ]…”

“…[10h,13] It can be anticipated that one of the most straightforward ways to overcome such experimental limitations in the future will be to move to reactor concepts with larger solid-liquid-gas interfaces and therefore intrinsically higher ammonia production rate. [14] Among the catalytic nanomaterials investigated, metal-free carbon-based materials have attracted a lot of attention because of their abundancy and low-cost. [15] Especially heteroatom-rich carbons (e.g., carbons doped with nitrogen) emerged as promising NRR catalysts recently and different mechanisms for the activation of N 2 on their surface have been proposed.…”

Enhanced Nitrogen Reduction to Ammonia by Surface- and Defect-Engineered Co-catalyst-Modified Perovskite Catalysts under Ambient Conditions and Their Charge Carrier Dynamics

“…In particular, ammonia (NH 3 ) possesses much higher energy storage density than that of highly efficient batteries, capacitors, and other storage devices. With the extra possibility of utilizing ammonia as an energy carrier in various applications, nitrogen reduction electrochemistry in particular has the potential to directly offset 1–1.4% of the worldwide CO 2 emissions, currently produced during the manufacturing of ammonia (NH 3 ). − However, the exceptionally stable nitrogen triple bond (NN), which has a bond energy of 940.95 KJ/mol, due to the lack of a permanent dipole moment, makes N 2 reduction exceedingly difficult under ambient conditions and thus limits the overall efficiency. , In order to accelerate the activation of NN in the electrocatalytic nitrogen reduction reaction (NRR), a variety of electrocatalysts are being designed. Electrocatalysts such as organometallic, doped carbon-based, and non-precious metal-based catalysts have been explored to design active and durable bifunctional catalysts.…”