Toward reliable and accessible ammonia quantification in the electrocatalytic reduction of nitrogen

Nitrogen electroreduction may alleviate fossil energy requirements to produce fertilizers, but efficient catalysts must still be developed. The development of accurate and accessible ammonia quantification tools is key to accelerate this process. This article provides guidelines to optimize sensitivity of UV-vis spectroscopy and the ion-selective electrode for initial catalyst screening. However, confirmation of the catalytic origin of ammonia is only feasible through 1H-NMR, which is much less frequently applied largely due to the high expertise and expensive apparatuses needed. We introduce a protocol accessible to catalyst practitioners applicable to widely available 300 MHz NMR spectrometers. To this end, we adapted the WATERGATE suppression method to accomplish high signal-to-noise ratios even in nondeuterated samples. It was demonstrated for a relevant concentration of 1 ppm, enabling qualitative and quantitative analysis in 2 and 15 min, respectively. By making 1H-NMR quantification more accessible, this study facilitates the application of state-of-the-art catalytic assessments.

Automated summary

Nitrogen electroreduction shows potential in reducing fossil energy requirements for fertilizer production, but efficient catalysts are still needed. This article introduces guidelines for using UV-vis spectroscopy and ion-selective electrodes for initial catalyst screening, highlighting the importance of 1H-NMR for confirming the catalytic origin of ammonia. The study also presents a protocol for making 1H-NMR quantification more accessible, allowing for qualitative and quantitative analyses in a timely manner.