Search

Hydrogen peroxide (H2O2) is a green oxidant widely used in various fields, from water treatment to rocket propellant. Currently, H2O2is predominantly manufacturedviathe anthraquinone process, which requires large infrastructure investments and high energy consumption. In this study, an argon plasma-catalytic bubble process was designed to generate underwater plasma bubbles for efficient delivery of reactive species for H2O2synthesis, using only water as a reactant and solar radiation as the renewable energy source. The process demonstrates unprecedented energy efficiency by employing a plasma-bubble catalytic reactor capable of operation in two discharge modes,i.e., glow and spark discharges, and using dual reactors within a single AC-circuit to mitigate energy losses around the ground electrode. The results suggest that the principal route of H2O2generation is from the combination of dissolved ˙OH radicals at the plasma-liquid interface (PLI) of the forming bubbles. The dissolution of H2O2formed in the gas phase also contributes to aqueous H2O2generation, especially when employing humid argon. By employing a secondary reactor to utilise the lost energy around the low-voltage electrode and integrating a strongly interfacial-coupled 2D-TiO2/2D-g-C3N4photocatalyst in the glow discharge area, the achieved H2O2production rate and energy efficiency of the system are 164.6 mg h−1and 9.0 g kW h−1, respectively. This study provides new insights for sustainable and decentralised H2O2production, and the proposed strategy can be further developed as a stand-alone or auxiliary technology in green and sustainable chemistry.

Complete degradation of mixtures of organic pollutants is a major challenge due to their diverse degradation pathways. In this work, a novel microplasma bubble (MPB) reactor was developed to generate plasma discharges inside small forming bubbles as an effective mean of delivering reactive species for the degradation of the target organic contaminants. The results show that the integration of plasma and bubbles resulted in efficient degradation for all azo, heterocyclic, and cationic dyes, evidenced by the outstanding energy efficiency of 13.0, 18.1 and 22.1 g/kWh with 3 min of processing, in degrading alizarin yellow (AY), orange II (Orng-II) and methylene blue (MB), individually. The MPB treatment also effectively and simultaneously degraded the dyes in their mixtures such as AY + Orng-II, AY + MB and AY + Orng-II + MB. Scavenger assays revealed that the short-lived reactive species, including the hydroxyl ([rad]OH) and superoxide anion ([rad]O2−) radicals, played the dominant role in the degradation of the pollutants. Possible degradation pathways were proposed based on the intermediate products detected during the degradation process. The feasibility of this proposed strategy was further evaluated using other common water pollutants. Reduced toxicity was confirmed by the observed increases in human cell viability for the treated water. This work could support the future development of high performance- and energy-efficient wastewater abatement technologies.

A permission to reproduce was missing in the legend of Figure 2. This change does not affect any results or conclusions of this paper. Figure 2. SEM images of S. cerevisiae cells exposed to the APCP jet for different treatment times. Parts of the pictures are enlarged to clearly show the cell response to the APCP jet. Some parts of the figures are reprinted from ref 19.

A plasma's working gas is a significant factor affecting their discharge characteristics and the induced chemistries during plasma–water interactions. However, the effects on the discharge mode and discharge stability have not been fully investigated. This study focuses on the discharge mode transition and stability with nitrogen and oxygen gases. Compared with the oxygen discharge, the nitrogen discharge remained stable over a larger voltage range and long duration time. A diffuse mode discharge had better stability and lower plasma activity for both nitrogen and oxygen gases, whereas a transient spark mode in nitrogen and filament mode in oxygen had lower stability but a higher plasma activity. This study improves the understanding of the physicochemical processes of plasma–water interactions.

In this study, we demonstrate that atmospheric air plasma bubbles are an effective, energy-efficient, residue-free alternative to current decontamination techniques. Five to fifteen minutes of plasma-bubble treatments of inoculated chicken skin led to a significant reduction in colony-forming units (CFUs). We show that the activation efficiency is dependent on the plasma discharge frequency, with a higher one (2,000 Hz) leading to a higher CFU reduction (1.4 log) as compared with a lower (0.3 log) reduction at 1,000 Hz. Scanning electron microscopy pictures of treated bacteria reveal damage to the cells. An evaluation of the physicochemical properties of the generated plasma-activated water revealed an increase in conductivity and in ozone, nitrite, nitrate, hydroxyl, and peroxide concentrations with higher frequencies, all contributing to the observed antimicrobial effect.

Sustainable ammonia synthesis at ambient conditions that relies on renewable sources of energy and feedstocks is globally sought to replace the Haber–Bosch process. Here, using nitrogen and water as raw materials, a nonthermal plasma catalysis approach is demonstrated as an effective power-to-chemicals conversion strategy for ammonia production. By sustaining a highly reactive environment, successful plasma-catalytic production of NH3 was achieved from the dissociation of N2 and H2O under mild conditions. Plasma-induced vibrational excitation is found to decrease the N2 and H2O dissociation barriers, with the presence of matched catalysts in the nonthermal plasma discharge reactor contributing significantly to molecular dissociation on the catalyst surface. Density functional theory calculations for the activation energy barrier for the dissociation suggest that ruthenium catalysts supported on magnesium oxide exhibit superior performance over other catalysts in NH3 production by lowering the activation energy for the dissociative adsorption of N2 down to 1.07 eV. The highest production rate, 2.67 mmol gcat.−1 h−1, was obtained using ruthenium catalyst supported on magnesium oxide. This work highlights the potential of nonthermal plasma catalysis for the activation of renewable sources to serve as a new platform for sustainable ammonia production.

Recent years have witnessed successful applications of non-thermal plasmas (NTPs) as efficient and flexible tools for direct conversion of liquid alcohols into higher-value energy carriers at mild or even near-room-temperature conditions. Better understanding of the fundamental physical properties of the liquid alcohol discharges is needed for development and optimization of NTP-based applications. Here we investigate the discharge characteristics of a plasma-based liquid ethanol conversion under different process parameters and reveal the general trends of the discharge behavior. Two discharge modes, namely the self-pulsed and direct current (DC) modes, are sustained during the in-liquid discharge. These two modes can be easily interchanged and flexibly controlled by adjusting the processing parameters. The behavior of the bubbles generated during the discharge plays an important role in the transition between the discharge modes. When the discharge is sustained with the diffusion and floating of the bubbles, the DC mode is observed. Otherwise, the discharge develops into the pulse mode. The production rates and composition of the gaseous products are also shown to depend on the discharge modes.

Sustainable and cost effective food preservation techniques are of industrial, environmental and public health significance globally. A promising means for the gentle but efficient sanitation of foods is the application of cold atmospheric plasma. Here, the preservation of fresh-cut apples was investigated using a gas phase surface discharge plasma (SDP) reactor within an exposure chamber. Results show that the microbial load reduction of the fresh-cut apples was found to be strongly dependent on the storage time and preservation method, e.g. refrigeration (control), SDP-room temperature and SDP-refrigeration (SDP-RF). After 6 d of storage, the microbe load on the apple pieces for the SDF-RF treated groups was found to be significantly lower compared to the refrigeration-stored (4 °C) and the SDP only-processed groups, with the lowest bacterial load on the 120 s SDP-RF stored apple pieces (1.76 CFU g-1). Furthermore, the effects of the preservation method on the quality attributes (weight loss, firmness, and physical appearance), and the surface chemistry directly after cutting and SDP processing, as well as the activities of polyphenol oxidase and peroxidase after the different duration of storage were evaluated. This study successfully demonstrates the feasibility of SDP for the effective preservation of fresh-cut apples and contributes to the fundamental understanding of surface plasma-induced effects on the microbial inactivation and postharvest quality of fresh-cut fruits.

Efficient and selective internalization of nanoscale diamonds (also termed nanodiamonds, NDs) by living cells is of fundamental importance for their bionanotechnological applications. The biocompatibility of NDs is well established and has been suggested to arise from the limited membrane perturbation during their cellular translocation. However, the latter may be affected when cells are subjected to external stress. This study shows that the oxidative stress generated by atmospheric pressure cold plasmas (APCP) alters cell sensitivity to NDs, and their cytotoxicity profile. Both positively and negatively charged NDs are nontoxic to cells, here Saccharomyces cerevisiae and human cell lines, i.e., near-normal human mammary epithelial cells (MCF-10A) and breast cancer cells (MDA-MB-468 and T47D), unless the APCP stress is introduced. A brief exposure of the cells to APCP leads to a significant increase in their ND affinity (uptake and/or surface attachment) and intracellular ROS accumulation, particularly for positively charged NDs and both yeast and cancer cells. A concomitant decrease in cell viability and yeast cell growth, reflected by longer lag phases and lower cell density after 24 h of incubation, demonstrates a considerably enhanced ND toxicity to these cells. These results suggest that chemo-radiative stress, such as that produced by plasma, may influence the toxicity of nanoparticles to different cells, with specificity achieved through controlling particle charges. Moreover, since oxidative stress is not only associated with the use of APCP but can arise unintentionally within an organism and/or in the environment, these findings may have broader implications for the use of nontoxic nanoparticles in bionanotechnology in general.

Thermodynamic and kinetic limitations can restrict the feasibility and scalability of conventional catalytic processes for CO2 methanation at the industrial level. Due to its nonequilibrium nature, nonthermal plasma (NTP) promises to reduce reaction barriers and make this gas conversion approach viable even at low temperatures. However, the current understanding of the fundamental chemical and physical behaviors in the hybrid plasma catalytic interactions is insufficient. This study demonstrates plasma-driven CO2 conversions approaching the reaction equilibrium with high methane yields even at low temperature (150 °C). It was observed that the addition of plasma to the catalytic bed enhanced the CO2 conversion around 20 times relative to thermal activity, whereas the CH4 selectivity increased around 5 times by introducing the nickel catalyst into plasma discharge compared to plasma only (at 150 °C). Moreover, the findings provide new insights into the gas phase activation of reactants (CO2 and H2) and the reaction over Ni0 to decouple the plasma and catalyst synergy. The catalyst did not undergo significant structural changes under plasma discharge, apart from a slight decrease in Ni crystallite size, while an enhanced metal dispersion was evident (24% to 42%, from CO pulse chemisorption). The optimized system achieved a CO2 conversion of 60% with a CH4 selectivity of over 97% at 150 °C, which required much higher temperatures (320-330 °C) to achieve equivalent conversion in thermal catalysis. This study is a step toward an understanding and effective control of the plasma enhanced catalytic CO2 transformation via low energy reaction pathways that utilize the NTP for low-temperature CO2 methanation with high conversion, selectivity, stability, and controllability.