Electrochemical Sensors for Ammonia Detection: Principles, Progress, and Prospects

Ammonia pollution threatens environmental quality, industrial safety, public health, and agricultural production, creating a need for rapid, sensitive, and stable monitoring. Electrochemical sensors are well suited to this task owing to their simple operation, fast response, miniaturization potential, and compatibility with real-time measurement. This review summarizes recent progress in electrochemical ammonia sensors. First, electrode platforms and fabrication methods, including solution deposition, hydrothermal growth, electrochemical deposition, screen printing, photolithography, and laser processing, are discussed. Then, performance-enhancement strategies, including heterojunction construction, hierarchical microstructuring, interfacial chemical regulation, catalyst anti-poisoning design, and machine learning-assisted signal decoupling, are examined. The main sensing methods, including amperometric, potentiometric, impedimetric, biosensing, and photoelectrochemical sensors, are compared in terms of their detection mechanisms, representative materials, detection ranges, limits of detection, and application scenarios, with the results summarized in tabular form. The practical performance of these sensors is also assessed against regulatory thresholds and in terms of long-term stability, application in real matrices, and reproducibility between devices. Finally, the main challenges, including the limited intrinsic selectivity, humidity and environmental interference, catalyst poisoning and interfacial fouling, and scalable fabrication, are identified, and future directions for the development of selective, stable, and field-deployable ammonia sensors, enabled by single-atom catalysis, molecular imprinting, interface engineering, and machine learning, are proposed.