Atmospheric-pressure plasma discharges have attracted significant attention in recent years, owing to their potential for diverse applications in biomedicine, agriculture, food, and recently with us for green ammonia synthesis. The insights provided by this research into the mechanisms of mode transition and the factors that influence the generation of specific chemical products can support the development of new plasma technologies for efficient and sustainable ammonia synthesis. However, the mechanisms of the mode transition between the dominant O3 and NOx species in atmospheric-pressure plasma discharges remain poorly understood.
In a recent study, researchers from Queensland University of Technology (QUT) in Australia and Chongqing University in China investigated mode transition mechanisms in atmospheric-pressure dielectric barrier discharge (DBD) involving 63 species and 750 reactions. They developed a global chemical kinetics model for the atmospheric-pressure DBD and validated it with experimental results, accurately describing the mode transition between the O3 and NOx modes.
The researchers identified the essential transient intermediate species for the O3 and NOx production and loss reactions, which were N, O, O2(a), and O2(b). They also quantified the individual and synergistic effects of the specific discharge energy and the gas temperature on the species density and the relative contributions of the dominant reactions under increasing discharge voltage conditions.
The study showed that the gas temperature and specific discharge energy both contribute to the discharge mode transition, while the factors affecting the change of the O3 and NOx density differ in the respective modes. The specific discharge energy was found to be the key factor affecting the change of the NO density in both the O3 and NOx modes and the change of the O3 species density in the O3 mode. Furthermore, the decoupling study showed that a comprehensive account of the effect of the gas temperature and the specific discharge energy is required for a drastic reduction of the O3 density during the transition from the O3 to the NOx modes.
The findings of this study contribute to a better understanding of the mechanisms of mode transition in atmospheric-pressure plasma discharges, which is crucial for effectively controlling the dominant generation of targeted reactive species in diverse fields. The global chemical kinetics model developed in this study can be extended to other gas mixtures and discharge geometries, facilitating the design and optimisation of plasma devices for specific applications.
Overall, this research provides valuable insights into the physicochemical processes involved in atmospheric-pressure plasma discharges and can complement my hybrid plasma electrocatalysis process for ammonia synthesis.
The recent research into atmospheric-pressure plasma discharges and mode transition mechanisms could significantly benefit our hybrid method for ammonia synthesis using non-thermal plasma activation. Our process activates air with non-thermal plasma to produce soluble and reactive forms of nitrogen (NOx-), which are then passed through an electrochemical cell and converted into ammonia. By gaining a deeper understanding of the factors that influence the generation of nitrogen intermediates, we can optimise our electrochemical cell for higher efficiency and ammonia production yields. The insights gained from the global chemical kinetics model developed in this study can be applied to our hybrid plasma electrocatalysis process, leading to more sustainable and cost-effective ammonia synthesis. The findings of this research could help us refine our hybrid method and pave the way for further advancements in green ammonia synthesis.
The new research can be found at Kun Liu et al 2023 Plasma Sources Sci. Technol. 32 025005. DOI 10.1088/1361-6595/acb814
The hybrid plasma electrocatalysis method: J Sun et al 2021 Energy & Environmental Science 14 (2), 865-872. DOI: 10.1039/D0EE03769A