Pitfalls of Using Nessler’s Reagent for Ammonia Detection in Photocatalytic Nitrogen Fixation Studies: Leveraging ¹H NMR for Enhanced Accuracy and Precision

Photocatalytic nitrogen fixation has emerged as a promising method for sustainable ammonia production, holding great potential for green solar fuel synthesis. In this study, we attempted to replicate the reported yields of two nitrogen fixation catalysts, but the results were not reproducible upon systematic investigation. Accurately detecting and quantifying ammonia in aqueous solutions are major challenges in nitrogen fixation research. This is primarily due to the inherent complexities of the reaction solution and the limitations of available detection methods. To address these issues, we comprehensively investigated the widely used ammonia detection method involving Nessler’s reagent. Our study revealed that several factors, such as residual solvents on catalysts, nitrogen-containing surfactants, and reaction scavengers, can significantly influence the estimated ammonia production, leading to potentially misleading results. Consequently, a critical question arises regarding the reliability and validity of reported ammonia yields in the existing literature, as most studies solely rely on Nessler’s test. To ensure accurate and meaningful reporting of photocatalytic ammonia production, we propose guidelines emphasizing the essential parameters to be considered and standardized methods for quantification. Implementing these guidelines will enhance the reproducibility and credibility of future research in this field, facilitating the development of efficient and sustainable solar fuel production systems.