Study on Ammonia Response Characteristics of ZnO/MnO2/g-C3N4 Composites at Room Temperature

The ternary nanocomposite ZnO/MnO2/g-C3N4 was synthesized for room-temperature ammonia gas detection. Incorporation of g-C3N4 into the ZnO/MnO2 heterostructure significantly improved the composite’s sensing sensitivity at ambient conditions. g-C3N4 facilitated electron migration across the heterojunction interface, boosting conductivity, and provided abundant adsorption sites for ammonia molecules due to its layered structure. The ZnO/MnO2/g-C3N4 composite material exhibits outstanding ammonia sensing performance, with its detection sensitivity being 2.4 times that of the ZnO/MnO2 system. Notably, this material demonstrates rapid response and recovery characteristics, with recorded times of 7.3 and 1.6 s, respectively, thereby optimizing its functional performance and expanding its range of operational applications. The study found that the optimal doping ratio of ZnO/MnO2/g-C3N4 can effectively enhance the material’s specific surface area and electron mobility, thus improving its ammonia adsorption capacity and optimizing the sensor’s response and recovery characteristics. The synthesis employed a sequential two-step strategy: initial formation of a ZnO/MnO2 heterostructure followed by g-C3N4 integration. This approach effectively mitigated limitations of pure ZnO, including sluggish desorption kinetics and low response magnitude. Density functional theory (DFT) computations were employed to elucidate the atomic-level sensing mechanism, revealing significant charge redistribution at the ZnO/MnO2/g-C3N4 heterojunction interfaces upon ammonia adsorption.