Abstract
Yield validation of dinitrogen reduction reaction (N(2)RR) catalysts with (15)N isotope labeling experiments is frustrated by the high cost of (15)N(2) and the frequent occurrence of (15)NH(3) and (15)NO (x) impurities in commercial (15)N(2) sources. Also, gas diffusion electrode (GDE) cell architectures are relevant to scaling N(2)RR but underexplored and limited by ex situ product analysis methods. To overcome these obstacles, we develop and demonstrate a protocol for N(2)RR catalyst testing using a scalable GDE cell architecture and specialized test station that facilitates in-line product analysis with multiturn time-of-flight mass spectrometry. This approach provides robust yield measurements through real-time monitoring of (15)NH(3) with ultrahigh mass resolution. The (15)N-containing impurities are also monitored, allowing their influence to be mitigated. A minimum detectable yield of 6 pmol·cm(-2)·s(-1) (at 2.00 sccm and utilizing a 5 cm(2) electrode) for real-time (15)NH(3) yield rate measurements is achieved while using a cost-effective amount of (15)N(2) (<100 mL).