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

Abstract

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 non-deuterated 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.