Field-Deployable Ammonia Sensor for Assessment of Wastewater Feedstocks and Their Utilization for Ammonia Synthesis

Renewable energy-driven electrochemical ammonia synthesis using nitrates presents a promising pathway for producing ammonia while utilizing wastewater as a feedstock. This approach enables decentralized ammonia production and addresses environmental concerns related to nitrate pollution. If the broader goal is to use real wastewater as a feedstock, various anions and their influence on ammonia selectivity must be carefully studied. However, two significant challenges hinder its practical implementation: interference from common wastewater anions (sulfate, chloride, phosphate) and the lack of rapid, cost-effective ammonia monitoring methods suitable for process optimization. Here, an integrated solution combining fundamental studies of anion effects with an innovative paper-based detection platform is presented. This systematic investigation reveals how competing ions influence electrochemical ammonia selectivity, providing crucial insights for catalyst design. More importantly, a paper-based sensing protocol is developed that achieves sensitive ammonia quantification (10–500 µm range with 35 µm limit of detection) using merely 10 µL of sample. This field-deployable system eliminates the need for sophisticated instrumentation, delivering results three times faster than standard colorimetric assays while maintaining >90% accuracy. The sensor's robust performance enabled real-time monitoring of ammonia production from synthetic and real wastewater samples during electrochemical testing.