Ammonia Detection Methods in Photocatalytic and Electrocatalytic Experiments: How to Improve the Reliability of NH3 Production Rates?

The enzyme nitrogenase inspires the development of novel photocatalytic and electrocatalytic systems that can drive nitrogen reduction with water under similar low‐temperature and low‐pressure conditions. While photocatalytic and electrocatalytic N2 fixation are emerging as hot new areas of fundamental and applied research, serious concerns exist regarding the accuracy of current methods used for ammonia detection and quantification. In most studies, the ammonia yields are low and little consideration is given to the effect of interferants on NH3 quantification. As a result, NH3 yields reported in many works may be exaggerated and erroneous. Herein, the advantages and limitations of the various methods commonly used for NH3 quantification in solution (Nessler's reagent method, indophenol blue method, and ion chromatography method) are systematically explored, placing particular emphasis on the effect of interferants on each quantification method. Based on the data presented, guidelines are suggested for responsible quantification of ammonia in photocatalysis and electrocatalysis. The advantages and limitations of different detection methods for ammonia quantification in aqueous media are systematically examined in the context of photocatalytic and electrocatalytic N2 fixation. The results show that the accurate determination of NH3 concentration is challenging and a flowchart is constructed to assist researchers in the selection of the best detection method(s) for accurate NH3 quantification.