Interference Effect of Alcohol on Nessler's Reagent in Photocatalytic Nitrogen Fixation

Photocatalytic ammonia synthesis is another important reaction to mimic natural nitrogen fixation, which has attracted more and more attention. In recent reports, sacrificial agents are often used to promote charge separation, and high-activity photocatalysts are discovered by using Nessler's reagent method as a detection technique of ammonia production. However, there is an open question on the rationality and accuracy of the ammonia production amount in the presence of the sacrificial agent and Nessler's reagent detection method. In this report, P25 TiO2 is employed as a model photocatalyst and alcohol as sacrificial agent, and both Nessler's reagent and cation exchange chromatography are employed as ammonia detection methods. The different ammonia production amount was found by the different detection method. HPLC and H-1 NMR results indicate that carbonyl compounds (formaldehyde, acetaldehyde, and acetone) are produced in the reaction. When the carbonyl compound was added to the ammonia standard solution, the interference effect on the detection of ammonia was found in the Nessler's reagent method. No interference effect was found in the cation exchange chromatography. Thus, the Nessler's reagent is not suitable for ammonia detection in the presence of alcohol as the sacrificial agent.