Ammonia Gas Sensor Fabricated by Multifunctional ZnO/GO Nanocomposites for Long-Term, Self-Powered Monitoring.

Abstract

As a promising hydrogen carrier for low-carbon energy cycling, ammonia also represents the most abundant alkaline gas in the atmosphere, impacting environmental quality through diverse geophysical and chemical processes. Hence, developing NH₃ sensing materials with high sensitivity and stability under self-powered operation is essential. A one-step in situ polymerization method is demonstrated to synthesize zinc oxide/graphene oxide (ZnO/GO) nanocomposites, serving as a gas-sensitive film for ammonia sensing and as high-performance electrode materials in supercapacitors, simultaneously. For the supercapacitor, the specific capacitance of 131 F g^-1 at 1 A g^-1 is achieved. The ammonia sensor featured a low detection limit (0.1 ppm) and fast response/recovery time (17 s/26 s @ 10 ppm NH₃), surpassing standards set by the US Occupational Safety and Health Administration (50 ppm), while outperforming commercial NH₃ gas sensors. By integrating the sensor into a detection instrument for fixed-point monitoring, the response relative standard deviation of below 1% over 210 days of continuous testing is achieved. In addition, a wearable contact-separated TENG is developed to harvest mechanical energy from a contact-separation setup that mimicked human footsteps, achieving a maximum output power of 4.1 mW to directly drive the ammonia gas sensor. The multi-scenario applications enhanced the spatial coverage and operational flexibility of NH₃ concentration monitoring.