LAUSR

Assessing novel electrocatalysts for the electrochemical ammonia synthesis (EAS) requires reliable quantitative trace analysis of electrochemically produced ammonia to infer activity and selectivity. In this study, we have developed and investigated an ion chromatography (IC) method for the quantitative trace analysis of ammonium in 0.1 M sulfuric acid electrolyte in detail and applied it successfully to EAS gas diffusion electrode (GDE) experiments with commercial chromium nitride as electrocatalyst. The developed IC method is highly sensitive, versatile and reliable achieving a limit of quantification (LOQ) of 6 µg l-1 (6 ppbmol) ammonium. The impacts of the sample matrix, dilution and neutralization as well as contamination on the quantitative analysis by IC were analyzed. Experimental constraints resulted in an effective LOQ including dilution of 60 µg l-1 for the determination of ammonium in 0.1 M sulfuric acid electrolyte due to necessary sample dilution. We believe that the practical guide presented here can be very relevant for the field of EAS as guideline and is applicable to both, a broad range of catalyst systems and ion chromatography devices.