Plasma Decomposition Research Articles

Plasma Deposition of Parylene-like Films with Chemical Functional Groups for Immunoassays.

Parylene-like films obtained via the plasma decomposition of parylene precursors with functional groups (amino and formyl) are proposed as an alternative to those obtained via the thermal method. To analyze the chemical functional groups after plasma deposition, a surface analysis of the parylene films using the two different deposition methods was performed via Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). The FT-IR analysis revealed that the featured peaks of the chemical functional groups were maintained in the parylene-like films obtained via the plasma deposition method. The XPS analysis revealed that the featured chemical functional groups of parylene-AM and parylene-H were maintained after plasma deposition. The surface energy of the parylene films was estimated by using contact angle measurements. The plasma-deposited parylene films were then employed for protein immobilization via the functional groups using horseradish peroxidase (44 kDa) and green fluorescent protein (25 kDa) as model proteins. The parylene-AM and parylene-H films obtained via plasma deposition exhibited higher immobilization efficiencies than did the same parylene films obtained via thermal deposition. Finally, a competitive immunoassay was obtained by immobilizing the Fv-antibodies on plasma-deposited parylene-AM and parylene-H films via covalent bonding. Using heat-deactivated SARS-CoV-2 as a real sample, the limit of detection at the feasible level for the medical diagnosis of COVID-19 was achieved using a competitive immunoassay based on immobilized Fv-antibodies on plasma-deposited parylene films.

Enhanced hydrogen production through cracking of ammonia water using liquid plasma on titanate-based perovskite catalysts

In this study, a mass production of hydrogen was studied through cracking of ammonia water using liquid plasma. A new FexNi1-xTiO3 perovskite composite with significantly improved visible-light sensitivity was synthesized to further improve the photochemical reaction activity. It is applied to hydrogen production from the decomposition of ammonia water using liquid plasma. In this reaction, a large amount of hydrogen is produced with a small amount of nitrogen gas; moreover, oxygen is produced by liquid plasma discharge and no CO2 byproduct is produced. Titanate-based perovskite catalysts have also been used in decomposition reactions. Titanate-based perovskite catalysts exhibiting high rates of hydrogen production during decomposition were obtained for the plasma and photocatalytic decomposition of aqueous ammonia. FexNi1-xTiO3, which is a newly synthesized ABTiO3-type titanate, showed a higher rate of hydrogen production (approximately 140 L/(g·h)) than other titanate-based perovskites. Furthermore, the FexNi1-xTiO3 exhibited the highest sensitivity to UV and visible light. Its high photosensitivity helped improve the photocatalytic activity in the decomposition of ammonia in water using plasma.

Non-thermal atmospheric-pressure positive pulsating corona discharge in degradation of textile dye Reactive Blue 19 enhanced by Bi2O3 catalyst

In this work, monoclinic Bi2O3 was applied for the first time, to the best of our knowledge, as a catalyst in the process of dye degradation by a non-thermal atmospheric-pressure positive pulsating corona discharge. The research focused on the interaction of the plasma-generated species and the catalyst, as well as the role of the catalyst in the degradation process. Plasma decomposition of the anthraquinone reactive dye Reactive Blue 19 (RB 19) was performed in a self-made reactor system. Bi2O3 was prepared by electrodeposition followed by thermal treatment, and characterized by x-ray diffraction, scanning electron microscopy and energy-dispersive x-ray techniques. It was observed that the catalyst promoted decomposition of plasma-generated H2O2 into •OH radicals, the principal dye-degrading reagent, which further attacked the dye molecules. The catalyst improved the decolorization rate by 2.5 times, the energy yield by 93.4% and total organic carbon removal by 7.1%. Excitation of the catalyst mostly occurred through strikes by plasma-generated reactive ions and radical species from the air, accelerated by the electric field, as well as by fast electrons with an energy of up to 15 eV generated by the streamers reaching the liquid surface. These strikes transferred the energy to the catalyst and created the electrons and holes, which further reacted with H2O2 and water, producing •OH radicals. This was indentified as the primary role of the catalyst in this process. Decolorization reactions followed pseudo first-order kinetics. Production of H2O2 and the dye degradation rate increased with increase in the input voltage. The optimal catalyst dose was 500 mg∙dm−3. The decolorization rate was a little lower in river water compared with that in deionized water due to the side reactions of •OH radicals with organic matter and inorganic ions dissolved in the river water.

H2 Production from NH3 in a BaTiO3 Moderated Ferroelectric Packed-Bed Plasma Reactor

Plasma decomposition reactions are used for various gas phase chemical processes including the decomposition of ammonia. In this work we show that pure ammonia can be effectively decomposed at atmospheric pressure and ambient temperature using a packed-bed plasma reactor moderated with BaTiO3 ferroelectric pellets without catalyst. The decomposition rate and energy efficiency of this ferroelectric barrier discharge reactor have been monitored as a function of applied voltage (up to a maximum value of 2.5 kV) and flow rate. For each operating condition reaction efficiencies have been correlated with the parameters defining the electrical response of the reactor. It is found that plasma current and volume inside the reactor and hence the energy efficiency of the process and the decomposition rate vary with the applied voltage and the flow of ammonia (a maximum decomposition rate of 14% and an energy efficiency of 150 LH2/kWh has been determined under optimized operation conditions). The role of back reactions (i.e. N2 + 3H2 → 2NH3) in decreasing reactor performance is another key effect affecting the overall efficiency for the ammonia decomposition. The possibilities of ferroelectric barrier discharge reactors to induce the decomposition of ammonia and the importance of keeping the operating temperature below the Curie temperature of the ferroelectric material are highlighted.

MOF Enhanced Dielectric Barrier Discharge Plasma Decomposition of H2S in the Presence of Low Alkanes

MOF Enhanced Dielectric Barrier Discharge Plasma Decomposition of H2S in the Presence of Low Alkanes

Paramagnetic Properties of Carbon Films

This research paper presents the results of obtaining carbon films on various substrates (quartz, mica, and silicon) at temperatures from 0 °C (initial) to 800 °C through plasma chemical vapor deposition. The carbon films obtained on various films were studied using the method of electron paramagnetic resonance (EPR). EPR measurements were carried out on twenty samples at a perpendicular and parallel arrangement of the sample plane concerning the orientation of the magnetic field. When measuring the resonance conditions by changing the magnetic field, an EPR signal appeared in all of the deposited samples. The paper presents a general view of the EPR spectrum in all of the samples, including the signal intensity, g-factor, line widths, and normalized signal intensity of the carbon films on various substrates at temperatures from 0 °C to 800 °C. Studies show that with an increase in temperature, the normalized intensity of the EPR signal line increases during the deposition of a carbon in all deposited substrates (quartz, mica, and silicon) using the method of plasma decomposition of a mixture of methane and hydrogen.

Contribution of electron density to plasma decomposition rate of methane

Hydrogen extraction from methane will be a common and useful technique in hydrogen production systems and fuel cycle systems of deuterium-tritium fusion reactors. Since tritium is a precious fuel, it needs to be extracted from impurity gases such as tritiated methane contained in the exhaust gas from the plasma vessel of a fusion reactor. An experimental work was conducted in this study to investigate the electron collision of methane decomposition reaction in helium plasma. A special attention was placed on the electron density distribution in a plasma chamber, and the dependence of the decomposition rate on the methane/helium ratio. The experimental results showed that methane decomposition rate and electron density tended to increase linearly with increasing RF power. This suggests that a strong dependence of electron collision on methane decomposition. Eventually, the dependence of methane decomposition rate on electron density, total pressure, and inlet methane concentration in a gas flow-type helium plasma reactor was successfully formulated. This study provides new sight for demonstrating the contribution of electron density in RF plasma assisted methane decomposition, and the summarized equation offers potential for reactor design on promising energy utilization.

Plasma decomposition of methanol to produce hydrogen with an atmospheric-pressure nitrogen microwave plasma torch

An atmospheric-pressure microwave plasma torch is employed to generate hydrogen by injecting methanol aerosols into the near afterglow region of a nitrogen microwave plasma. Two types of reaction chambers are proposed to study the influence of different boundary conditions of reaction chambers on hydrogen production by comparison. Fourier transformation infrared spectrometer and gas chromatography are used to measure and determine the hydrogen production rate, energy efficiency, and hydrogen yield. Also, the effects of conditions of methanol injection and discharge parameters on methanol decomposition are investigated, respectively. It is found that the active species originated from collision with the excited and ionized N2 in the high gas temperature in the plasma discharge plays an important role in the conversion of methanol to hydrogen. The gas flow pattern in the reaction chamber is closely related to boundary conditions and significantly affects the reaction time of methanol in it, which is analyzed with the software of computational fluid dynamics. The achievements of hydrogen production in our work are as follows: production rate up to 921 l/h, energy yield up to 371 l/kWh, and hydrogen yield up to 70%, respectively. Furthermore, the reaction mechanism is discussed in detail with respect to the formation of outlet products.

Long and flexible atmospheric pressure plasma jet probes for operation in humid environments

Herein, we describe a new flexible atmospheric pressure plasma jet device composed of hollow-core optical fibers and introduce two potential applications of the device: endoscopic plasma treatment and decomposition of aqueous phosphorus compounds. The proposed device is 1.6 m long and highly flexible, has a small probe size of several hundred micrometers, and spatially separates the plasma jet from the electrical input, making it very suitable for treatment through the biopsy channel of a conventional endoscope. Because the wire electrode of the fabricated atmospheric pressure plasma jet device is thoroughly isolated inside the hollow of the optical fiber, the device produces a plasma column in an identical discharge state regardless of external environmental conditions. As a result, the device can operate safely and steadily in highly humid environments, such as underwater, which can be utilized to decompose phosphorus compounds in fresh water.

Benchmarking plasma and electrolysis decomposition technologies for ammonia to power generation

Ammonia is a promising energy and hydrogen carrier due to its ease of liquification, high hydrogen content, and potential to be synthesized without carbon feedstocks. Despite its widespread use in agriculture, the utilization of ammonia to deliver hydrogen or for direct power generation is still under development. Sometimes referred to as “cracking”, the standard approach for recovering hydrogen from ammonia relies on harsh reaction conditions that limit its suitability for low-carbon transitions. This work investigates the technology development status and potential cost of plasma and electrolysis-based ammonia decomposition, benchmarks them with thermal-chemical decomposition, and further compares them with direct ammonia-to-power solid oxide fuel cell systems. Results suggest that in order to reach cost parity with cracking technologies, plasma-based decomposition must achieve one order of magnitude improvement in energy efficiency (to 10 kWh/kg or lower), while electrolysis decomposition must achieve enhanced durability using cheap electrolytes.

Plasma assisted dry reforming of methane: Syngas and hydrocarbons formation mechanisms

Plasma reactions of CO2 + CH4 mixtures have been proposed as a suitable process for the dry reforming of methane. Without specific catalysts, most studies report the formation of CO and H2 as main reaction products and arise the question whether CHx radicals coming from CH4 may interact with intermediate species formed by electron impact dissociation of CO2, a critical step for the formation of high added value oxygenated compounds. We have addressed this question studying the CO2 + CH4 plasma reaction in a ferroelectric-moderated packed-bed reactor varying the reactants ratio. Analysis of the reaction products by mass spectrometry and the plasma reaction intermediates by optical emission spectroscopy suggest that few direct cross-link interactions exist between intermediate plasma species issued from CH4 or CO2. This preliminary evidence is corroborated by experiments using 13CO2 instead 12CO2 as reactant. The isotope labeling procedure has proved that plasma reaction mechanisms of CO2 and CH4 molecules proceed almost independently, with the formation of small amounts of water and the removal of carbon deposits resulting CH4 plasma decomposition as sole evidences of cross reactions. These results highlight the need of using catalysts to promote specific surface reactions for a better control of the selectivity of the process.

Hydrogen production by microwave plasma decomposition of H2S at atmospheric pressure with cooling implemented in its afterglow

In this work, H2S is decomposed with the use of a N2 microwave (MW) plasma torch at atmospheric pressure with hydrogen as the main product as well as elemental sulfur. The variation of the conversion rate of H2S into H2 is investigated with respect to various dilution ratios of H2S to N2 as the carrier gas, MW power, total flow rate, and arrangement of the cooling rods in the reaction chamber. It is experimentally found that direct cooling of the afterglow by introducing a cooling rod downstream in the reaction chamber enhances the conversion rate, and an optimum for each conversion curve is determined, which is dependent of MW power, gas flow rate, and relative distance of the cooling rod in the afterglow.

Non-thermal plasma approach for conversion of greenhouse’s gases to hydrogen and valuable chemical fuels: A short review

An effective alternative energy source as a substitute for fossil-based fuels has become a major area of research for sustainable energy development. It is undeniable that there has been a decline in fossil fuel reserves as the primary energy which forces the development of new energy sources to meet requirements of both renewable and ecological aspects. In both of these aspects, hydrogen (H2) is one of the most promising renewable and environmentally friendly energy sources. Besides being able to be used to produce heat through combustion because it has a high calorific value (142 kJ/g), hydrogen can also be used to activate fuel cells to produce electrical energy without toxic gas emissions. Various applications of hydrogen gas led to the discovery of new sources and methods of producing hydrogen, including from the feedstock of greenhouse gases which has main component of CH4 and CO2. This review describes plasma dry reforming of greenhouse gas along with plasma decomposition of greenhouse components, namely CO2 and CH4 as an alternative process for hydrogen gas formation. Plasma-assisted decomposition of each compound, CO2 and CH4 from the view of plasma parameters and the effect of additional of catalyst are also discussed.

A comparison of the most promising low-carbon hydrogen production technologies

The energy transition to be successful requires an increasing share of renewable electricity and large amounts of low-carbon hydrogen. This paper presents a comparison of the following promising low-carbon hydrogen production technologies. Typical electrolyzer technologies, namely alkaline electrolysis (AEL), polymer electrolyte membrane electrolysis (PEMEL), and high-temperature electrolysis (HTEL), as well as methane pyrolysis systems based on thermal, plasma and catalytic decomposition along with steam methane reforming (SMR) with carbon capture utilization or storage (CCUS) are discussed and evaluated. These hydrogen technologies are then compared on the basis of assessment criteria such as the technology readiness level (TRL), scalability, levelized cost of hydrogen (LCOH), the impact of by-products and their carbon footprint. Compared to the other two low-carbon hydrogen production technologies mentioned in this paper, methane pyrolysis performed well and was found to be a promising alternative. Using exclusively renewable electricity for the required process heat yields lower CO2 emissions than currently operating SMR-CCUS systems can achieve and shows competitive LCOH. Moreover, in the course of decarbonization and due to its inadequate CO2 capture rates, the SMR-CCS technology should serve exclusively as an interim solution to the rapid market ramp-up of the low-carbon hydrogen economy. With respect to the ambitious green hydrogen targets, it was determined that electrolysis is indispensable, but still needs to be scaled up as it currently does not produce sufficient amounts of hydrogen. Furthermore, the LCOH of methane pyrolysis was lower than the one of electrolysis using renewable electricity. Therefore, methane decomposition is considered a promising low-carbon hydrogen production technology that needs to be implemented alongside green and blue hydrogen to contribute to a successful energy transition.

Preparation of In2O3/ZrO2 catalyst via DBD plasma decomposition of Zr(OH)4 for CO2 hydrogenation to methanol

In2O3/m-ZrO2 (monoclinic ZrO2) was recently confirmed to be active for hydrogenation of CO2 to methanol. In this work, an argon dielectric barrier discharge (DBD) plasma decomposition of Zr(OH)4, operated at atmospheric pressure and about 150 °C, was applied for the preparation of ZrO2. The catalyst characterization confirmed the DBD plasma decomposition causes a formation of amorphous ZrO2 (am-ZrO2). The obtained am-ZrO2 was used as a support for the preparation of In2O3/am-ZrO2 catalyst, which was found to be active for CO2 hydrogenation to methanol. The space-time yield of methanol over 10 wt.% In2O3/am-ZrO2 catalyst reaches 0.21 gMeOH gcat−1 h−1 under 5 MPa and 300 °C. The thermal treatment of the DBD generated am-ZrO2 further improves the activity of the In2O3/am-ZrO2 catalyst. The present study demonstrates that DBD plasma decomposition is a rapid and convenient way for the preparation of am-ZrO2, further facilitating the catalyst design for CO2 hydrogenation to methanol.

RE-NiOx (RE=Ce, Y, La) composite oxides coupled plasma catalysis for benzene oxidation and by-product ozone removal

Plasma-coupled catalysis is a promising volatile organic compounds (VOCs) removal technology because of its interactional principles of plasma decomposition and catalytic oxidation. However, the problem of harmful by-products is still in trouble. A series of rare earth doped RE-NiOx (RE = Ce, Y, La) composite oxides were synthesized by metal organic frameworks (MOFs)-derived method for coupled plasma oxidation of benzene and by-product ozone removal. Compared with plasma alone, the 1%La-NiOx catalyst shows the best enhancement of 50% for benzene conversion with complete removal of a maximum of 800 ppm ozone. The energy consumption for 90% benzene removal efficiency (η90%) is also reduced from 3600 to 1200 J/L. Characterization results of RE-NiOx catalysts indicate that the doping of La causes interaction and synergistic effect between La and Ni, and the surface oxygen and lattice oxygen with defects play crucial roles in benzene oxidation and ozone decomposition, respectively. In addition, the decomposition mechanism of benzene and ozone under plasma is proposed. Plasma is responsible for the indiscriminate bond breaking in benzene and oxygen to form a variety of organic intermediates and ozone, while the La-NiOx catalyst selectively oxidizes the intermediates to COx/H2O and decomposes the ozone into oxygen.

Effect of metal on corona discharge plasma in a honeycomb catalyst and optimization of the critical parameters for ethylene removal

This work focused on the factors affecting the effective generation of corona discharge plasma in a honeycomb catalyst reactor. Pd, Co, and Ag were used as the active metal catalysts to investigate the plasma formation and decomposition of ethylene. Unlike the Ag-coated honeycomb catalyst, which resulted in excessive arcing, the Co-coated honeycomb monolith was able to generate stable plasma, but the discharge power was insufficient to decompose ethylene at an acceptable level. The incorporation of a small amount of Pd with Co significantly enhanced the discharge power and the ethylene removal performance. The catalytic activity of the prepared catalyst for the removal of ethylene was evaluated using plasma catalytic oxidation and thermal catalytic oxidation. ANOVA was used to assess the effect of single process factors and their relationships in the plasma process. All the process factors such as specific energy input (SEI), ethylene concentration, and flow rate were found to affect the ethylene conversion, CO2 selectivity, and energy efficiency (EE). Under the optimal conditions, i.e., an SEI of 80 J/L, an ethylene concentration of 20 ppm, and a flow rate of 20 L/min, the ethylene conversion was 85 %, CO2 selectivity was 70 %, and EE was 0.86 g/kW h.

Plasmas for in situ resource utilization on Mars: Fuels, life support, and agriculture

This work discusses the potential of combining non-thermal plasmas and conducting membranes for in situ resource utilization (ISRU) on Mars. By converting different molecules directly from the Martian atmosphere, plasmas can create the necessary feed-stock and base chemicals for processing fuels, breathing oxygen, building materials, and fertilizers. Different plasma sources operate according to different principles and are associated with distinct dominant physicochemical mechanisms. This diversity allows exploring different energy transfer pathways leading to CO2 dissociation, including direct electron-impact processes, plasma chemistry mediated by vibrationally and electronically excited states, and thermally driven dissociation. The coupling of plasmas with membranes is still a technology under development, but a synergistic effect between plasma decomposition and oxygen permeation across conducting membranes is anticipated. The emerging technology is versatile, scalable, and has the potential to deliver high rates of production of molecules per kilogram of instrumentation sent to space. Therefore, it will likely play a very relevant role in future ISRU strategies.

Oxidative removal of hexane from the gas stream by dielectric barrier discharge reactor and effect of gas environment

The removal of hexane from a gas stream using a dielectric barrier discharge (DBD) reactor was conducted at ambient temperature and atmospheric pressure. The role of N2, dry and humidified air carrier gases were investigated in terms of removal efficiency and product selectivity. The oxygen concentration was also varied over the range of 0 – 21% at constant power and residence time in an N2O2 mixture for further insight into oxygen's role. A semi-empirical model of NTP-decomposition in the presence of O2, N2 and H2O is proposed. It was observed that hexane removal efficiency and product selectivity increased with increasing plasma power, regardless of the carrier gas used. The maximum removal efficiency (hexane) was 94.4% in the humidified air carrier gas. The introduction of water vapour with a relative humidity of 25% at 20 °C in the plasma DBD system significantly increased the hexane removal efficiency and CO2 selectivity (84.7%) while eliminating the production of solid residue and O3. This was probably due to the action of OH radicals. Increasing O2 concentration from 0 to 21% increased the removal efficiency and CO2 selectivity due to the generation of oxygen radicals. The results imply that the decomposition of hexane by non-thermal plasma DBDs is dominated by the effect of OH and O radicals. A semi-empirical model shows that the non-thermal plasma decomposition of hexane is first order. The DBD reactor has been demonstrated to be an effective and promising technology for removing hexane emissions from air streams. The effects of N2, O2 and H2O have been quantified, and mechanisms for their action proposed.

A laser-induced breakdown spectroscopy method to assess the stochasticity of plasma-flame transition in sprays

An experimental approach is presented to evaluate the impact of plasma composition arising from pulse-to-pulse energy and mixture fluctuations on the non-resonant laser-induced ignition of sprays. This allows for spark events to be conditioned on the successful or failed establishment of a flame kernel, a phase dominated by plasma decomposition and recombination reactions and the on-set of combustion reactions, that is, independent of the subsequent flame growth phase controlled by propagation phenomena only, such as fuel availability and turbulent strain. For that, laser-induced breakdown spectroscopy of the spark-generated plasma is carried out, followed by OH high-speed imaging of the kernel. Exploratory experiments in spatially uniform and polydisperse kerosene droplet distributions in a jet suggest that the hydrogen concentration in the plasma deriving from the fuel dissociated by the spark is closely related to the generated OH radicals levels and, in turn, with the success of establishing a flame kernel. This suggests that the ignition process is heavily controlled by mixture fluctuations at the spark, inherent of spray flows. The instantaneous mixture at the spark is estimated with a stochastic model, with the probability density function of the equivalence ratio exhibiting values higher than twice the mean value, while the highest probability occurs at lean conditions between the gaseous equivalence ratio and the overall equivalence ratio. The findings corroborate insights on the early-phase ignition obtained from direct numerical simulations, and the framework paves the way for the development of smart online engine-health tools to assess relight capability in future aeroengines.