Na Lu

A dual-chamber gas–liquid phase dielectric barrier discharge (DBD) reactor with tri-electrodes was designed for air-fed nitrogen fixation (NF). Air was activated in the gas-phase discharge chamber to produce nitrogen oxides (NO _x ), and these NO _x species continued to synthesize aqueous nitrate species in the gas–liquid discharge chamber. The effect of electrode configuration, applied voltage, air flow rate, initial solution pH and electric discharge duration on the concentration, selectivity of nitrate/nitrite/ammonia, total nitrogen concentration and energy yield (EY) of NF was studied. The results showed that the DBD reactor with tri-electrodes efficiently produced microdischarges for N ₂ fixation with high nitrate selectivity at a higher applied voltage. The initial pH of the water in the lower discharge chamber had little effect on the input power but a significant impact on the transfer and conversion of gaseous NO _x into aqueous nitrate, and a weak alkaline pH was more favorable for total nitrogen accumulation. Meanwhile, the input air flow rate in the DBD reactor and the water volume in the lower discharge chamber showed an optimum value, and the EY of total NF reached a maximum of 0.84 g kWh ⁻¹ at an initial solution pH 11 and water volume of 35 ml. The optical emission spectrum in the discharge regions indicated that the NF results at different applied voltages and air flow rates can be attributed to their influence on the production of N ₂ ^* , N ₂ ⁺ and •OH, and the experiments including electron quenching and dry air discharge indicated that NH ₄ ⁺ was mainly produced via the reduction of N ₂ by hydrated electrons.

This work presents a novel approach to enhance the discharge intensity and plasma-chemical reactivity of nanosecond pulsed streamer discharge through ultraviolet (UV)-induced cathode photoemission pre-ionization in atmospheric pressure air. The photoemission efficiency of three cathode materials—zinc (Zn), graphite, and stainless steel—was systematically quantified, revealing a clear hierarchy of Zn > graphite > stainless steel. The work function was identified as the primary factor governing electron emission efficiency, while surface microstructure and UV absorption characteristics were found to further modulate the photoemission dynamics. By establishing the correlation between cathode photoemission efficiency and discharge behavior, cathode photoemission is confirmed as the primary mechanism in discharge enhancement. The electron density multiplication driven by the electron avalanche is amplified by this process, resulting in a significant reduction in breakdown voltage thresholds, an enhancement in discharge intensity, and a prolongation of the discharge duration. Among the tested cathodes, the most pronounced enhancement effects were exhibited by Zn, with a 5.06 A increase in discharge current and an approximately 88.2% improvement in discharge energy, followed by graphite cathodes, while stainless steel cathodes have the weakest effect. Notably, the generation of reactive species is facilitated by this enhanced discharge regime, with the presence of O (3 p ⁵ P) in atmospheric pressure air, a species that remains undetectable under conventional pulsed discharge conditions.

Exploration of the interaction dynamics between plasma and fluidized particles in a plasma fluidized-bed holds practical importance for elucidating the mechanism of plasma treatment of powders. In this study, we employed a 2D fluid model to investigate the effects of particle diameter, dielectric constant, and inter-particle spacing, with the primary aim of simulating the specific consequences of variations in particle size, material type, and gas-to-powder ratio (GPR) on the powder processing effect. The results indicate that particles with diameters below 300 μm exert less impact on streamer propagation, enabling complete plasma wrapping of the particle surface (100%). However, particles with a diameter of 400 μm induce branching, leading to a reduction in the treatment area to 46%. These observations imply a critical particle size range of 300–400 μm for achieving effective plasma treatment of the fluidized particles. Plasma treatment ensures a comprehensive surface coverage on particles with low dielectric constants (εr8) exhibit a diminished plasma-treated surface area (80%), meaning that longer treatment durations for high dielectric constant materials may be required to achieve a comparable treatment effect. Furthermore, as the inter-particle spacing increases from 10 to 500 μm, the plasma-treated surface area undergoes an initial increment, followed by a subsequent reduction. Notably, at 300 μm spacing, the streamer channel displays a root-like branching pattern, leading to a substantial expansion of the plasma-treated surface area. This indicates that an optimal GPR in the fluidized-bed system can enhance the powder treatment effect.

A surface packed‐bed discharge reactor was designed to enhance the generation of reactive species in water. The pellets packed between discharge electrodes can intensify the electric discharge in water and produce reactive species of higher concentrations, and zirconia pellets had the highest energy efficiency for generating reactive species. Moreover, the degradation of sulfamethoxazole also demonstrated better performance of surface packed‐bed discharge than surface discharge on the generation of discharge plasma. At an applied voltage of 22 kV, the sulfamethoxazole degradation efficiency and energy efficiency of surface packed‐bed discharge were 2.1 and 1.6 times that of surface discharge.

In this study, a humidified air plasma was used to investigate the inactivation effect of Escherichia coli (E. coli) on fresh cabbage as well as the changes in physicochemical properties, which included changes in total phenolics, anthocyanin content, and antioxidant activity. The humidified air plasma is generated through the process of discharging within a surface dielectric barrier discharge (SDBD) system. The effects of cabbage tissues including cabbage leaf, upper epidermis and leaf flesh, and their water contents and sizes on E. coli inactivation were evaluated by changing the plasma treatment time. The experimental results showed that the exposure of E. coli to plasma inactivation on the upper epidermis had a high bactericidal efficacy, with 5.53 colony-forming units inactivated after 10 min of exposure. On the other hand, the presence of moisture in moderate amounts enhances the inactivation efficiency of the plasma against E. coli. The presence of the protein and the increased area of the sample, which is then in contact with the bacteria and exposed to the plasma, were found to inhibit the E. coli inactivation efficiency. Our analysis indicates that plasma-activated RONS, including H2O2 and HOONO, play a crucial role in the inactivation process of E. coli. Total phenols, proanthocyanidins and antioxidant properties on cabbage did not change significantly after plasma treatment for 10 min. Our study presents the feasible approach for the application of plasma in optimizing sterilization conditions for a range of fruits and vegetables.

Enhancing discharge energy in dielectric barrier discharge (DBD) is vital for various applications. This study establishes a theoretical formula for predicting enhanced discharge in multi‐needle‐plate (MP) DBD, accounting for factors like needle count, rotation speed, and voltage frequency. Experiments validate the formula's accuracy, showing that precisely matched parameters result in enhanced discharge power, heightened streamer luminosity, and curved streamer channels. Lissajous figures in MP DBD exhibit elliptical shapes due to residual discharges during voltage fall. Statistical analysis of current pulses and discharge images confirms that dielectric plate rotation increases discharges and extends their duration during voltage fall. Numerical simulations highlight surface charge movement's role in enhancing the electric field and affecting streamer propagation direction in the air gap.