Electrochemical NH3 production: In-situ evaluation of the activity and durability of nitrogen-reduction catalysis using scanning electrochemical microscopy (SECM)

Abstract

Developing efficient electrochemical processes for ammonia (NH3) production is a significant challenge that needs to be met to realize a carbon-neutral chemical industry. Recently, electrocatalytic nitrogen-reduction has been actively investigated under ambient conditions. However, the evaluation of electrodes for NH3 production using ex-situ NH3 detection methods only provide time-and space-averaged catalytic information. When investigating the transient activity of electrodes with spatiotemporal information, the real-time detection of NH3 near the electrode with high analytical resolution is essential. In this study, in-situ detection of electrochemically generated NH3 was first demonstrated using scanning electrochemical microscopy. A low NH3 flux of 6.6 nmol cm-2 s- 1 generated from an Fe-CuS/C electrode was detected using NH3 oxidation current detected at a poly-crystalline Pt ultramicroelectrode. This observation provides invaluable information on catalysis, including transient activity and durability. The advantages and limitations of the proposed in-situ NH3 detection method are demonstrated in an evaluation of nitrogen-reduction electrolysis.