Dielectric Barrier Discharge Research Articles

Evaluating BTEX in vehicle exhaust gas: A fast and efficient approach using SPME and GC-BID

Benzene, toluene, ethylbenzene, and the xylene isomers (m, p, and o-xylene) (BTEX) are known for their harmful effects on human health and have been extensively studied across various environmental matrices. However, quantifying BTEX in exhaust gases poses challenges due to the complexity of the matrices. In this study, we investigated a method development strategy involving solid-phase microextraction (SPME) and gas chromatography coupled with a dielectric barrier discharge ionization Detector (BID) for quantifying BTEX emitted from internal combustion engines operating at idle. Sampling was conducted using 1.0 L Tedlar bags, followed by withdrawal of aliquots and dilution with atmospheric air using a novel device (graduated vial) designed for gaseous samples. The SPME-GC-BID method was developed and validated for the conditions: BTEX extraction in CAR/PDMS 75 μm fiber at a contact time of 5.0 min at a temperature of 27 °C, followed by GC-BID analysis. Method validation to ensure the reliability of quantitative results used the merit figures e.g., limits of detection (LOD) and quantification (LOQ), precision, and accuracy (recovery). LOD varied from 0.194 to 0.340 mg m−3, LOQ varied from 0.587 to 1.03 mg m−3, precision ranged from 1.47 to 7.14 %, and recovery varied from 82.34 to 109.5 %. BTEX concentration in vehicle exhaust varied from 3.40 to 16.4 mg m−3. The results showed, concerning the figures of merit analyzed, that the SPME-GC-BID method provides good sensibility, precision, and accuracy for evaluating the presence of BTEX in the exhaust of internal combustion engines, contributing to the understanding of health risks associated with vehicle emissions.

Effects of Dielectric Barrier Discharge Cold Plasma on the Extraction of Bioactive Compounds from Colombian Arabica Coffee Powder

Effects of Dielectric Barrier Discharge Cold Plasma on the Extraction of Bioactive Compounds from Colombian Arabica Coffee Powder

Surface charge characteristics in a three-electrode surface dielectric barrier discharge

The surface charge characteristics in a three-electrode surface dielectric barrier discharge (SDBD) are experimentally investigated based on the Pockels effect of an electro-optical crystal. The actuator is based on the most commonly used SDBD structure for airflow control, with an exposed electrode supplied with sinusoidal AC high voltage, a grounded encapsulated electrode and an additional exposed electrode downstream supplied with DC voltage. The ionic wind velocity and thrust can be significantly improved by increasing DC voltage although the plasma discharge characteristics are virtually unaffected. It is found that the negative charges generated by the discharge of the three-electrode structure accumulate on the dielectric surface significantly further downstream in an AC period compared to the actuator with a two-electrode structure. The negative charges in the downstream region increase as the DC voltage increases. In addition, the DC voltage affects the time required for the positive charge filaments to decay. The positive DC voltage expands the ionic acceleration zone downstream to produce a greater EHD force. The amplitude of the DC voltage affects the electric field on the dielectric surface and is therefore a key factor in the formation of the EHD force. Further research on the surface charge characteristics of a three-electrode structure has been conducted using a pulse power to drive the discharge, and the same conclusions are drawn. This work demonstrates a link between surface charge characteristics and EHD performance of a three-electrode SDBD actuator.

Enhancing wetting and adhesion of stainless steel (SS304) surfaces with dielectric barrier discharge (DBD) plasma jet treatment

Enhancing the adhesion of coatings to metallic surfaces can be achieved through decontamination and increased surface energy. Among the various techniques used for functionalizing metallic surfaces, such as chemical etching, laser etching, flame treatment, and ultraviolet radiation; dielectric barrier discharge (DBD) plasma stands out as a promising option. It offers low-power, cost-effective, room-temperature operation and provides treatment with minimal alteration of subsurface properties. This study investigates using a DBD plasma jet to increase the treatment area, surface wettability, organic decontamination, and paint adhesion on stainless steel (SS304). The impact of different plasma treatments and aging times on the liquid contact angles and corresponding surface energies are experimentally examined. The results indicate that the surface energy of SS304 increases with treatment time. X-ray photoelectron spectroscopy (XPS) measurements are carried out to correlate this increase in surface energy to an increase in oxide bonds and decontamination of organic species, resulting in surface activation. However, it is observed that the plasma-treated surfaces exhibit no significant alterations in surface morphology, as confirmed through analyses of surface roughness and micro-hardness. Cross-hatch adhesion tests are carried out to demonstrate that the plasma surface treatment results in a significant improvement in surface adhesion to external coatings. Furthermore, the study evaluates the impact of DBD plasma jet treatment speed and dose on coating adhesion, providing valuable insights for making a trade-off between treatment quality and energy efficiency. The findings could extend the applicability of the DBD plasma jet to various areas, including anti-fogging surfaces, water harvesting, paints and coatings, and organic decontamination of surfaces.

Transport of microplastics treated with dielectric barrier discharge (DBD) plasma in saturated porous media

The performance of discharge plasma in treating organic pollutants and micro-organisms in water is impressive. When discharge plasma is used to treat polluted water containing organic pollutants and microorganisms, the presence of a certain amount of microplastics (MPs) in the water is unavoidable due to the complexity of the components contained in the water and the prevalence of MPs. MPs, as one of the pollutants that are difficult to be degraded by discharge plasma, undergo physical and chemical changes that increase their risk in the environment after treatment. Therefore, it is necessary to understand the fate of MPs after being treated with discharge plasma. In this study, the surface morphology of plastics before and after discharge plasma treatment was observed by scanning electron microscopy (SEM). The plastics after discharge plasma treatment were characterized by Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) to determine the changes in oxygen-containing functional groups on the surface. The recovery of microplastics (MPs) in saturated porous media under different physicochemical and plasma oxidation conditions was investigated by column experiments. It has been shown that MPs exhibit increased recovery under conditions of increased flow rate and pH. A decrease in recovery was observed at elevated ionic strength and co-existing cation valence. High voltages and low air flow rates increase the oxidation of MPs by increasing the thermal effects of the dielectric barrier discharge (DBD) plasma system, the amount of reactive oxygen species (ROS) and the intensity of ultraviolet ray (UV) irradiation. The mobility of MPs is enhanced by a combination of these factors. The advection–dispersion equation (ADE) fits the transport data of MPs well. The interaction energy between quartz sand and MPs was calculated using the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. This study provides a new perspective on the potential risks of discharge plasma in water treatment.

Sequential DBD plasma-assisted tandem tri-electrodes Fenton process for enhanced antibiotics treatment and denitrification

Ozone generated by dielectric barrier discharge (DBD) plasma has the potential for water treatment; however, its limitations, including water solubility, performance in complex matrices, and resistance to some pollutants. This study explored a sequential DBD plasma assisted by a tandem tri-electrode Fenton (S-PEF) process, using a three-stage treatment approach for degrading antibiotics (sulfamethoxazole, SMX; amoxicillin, AMX; and norfloxacin, NOF) in continuous flow mode for 220-bed volumes. Initially, antibiotics such as SMX and AMX underwent degradation in DBD plasma gas, which housed the mixing chamber. The more resilient NOF was removed by hydroxyl radicals (OH) in the following anodic chamber of the tandem trielectrodes by Fenton assisted oxidation. The continuous cyclic redox regeneration of Fe in tandem trielectrodes prevents secondary Fe sludge pollution. Finally, NO3-N and NO2-N were denitrified into N2 with 95 % selectivity in a cathodic chamber using copper oxide nanowires. This sequential treatment is crucial to mitigating the competitive effects of CO32− and humic acid in wastewater since O3 is less susceptible to them compared to OH. The S-PEF completely degraded all antibiotics regardless of water temperature (10 and 25 °C) compared to sole plasma treatment. Finally, toxicity assessments using an ecological structure–activity relationship (ECOSAR) and E. coli disinfection assays showed a significant reduction in toxicity. This study highlights the promising potential of the S-PEF as an advanced technology for wastewater treatment.

Electric field components within a micro-scaled DBD measured by Stark shifting and splitting of helium lines

Abstract Atmospheric pressure dielectric barrier discharges (DBDs), such as the micro cavity plasma array (MCPA), have emerged as promising technologies for the conversion of volatile gases. These conversion processes’ effectiveness can be enhanced by integrating catalytically active surfaces. To deepen the understanding of the plasma-catalyst interaction, it is crucial to study the transport dynamics of charged species to the catalytic surface, which, due to collisions with neutrals, also directly affects the transport of reactive species to the catalyst. Thereby the transport of the charged species is in particular influenced by the electric field perpendicular to the catalytic surface. However, experimental data on the component-wise electric field strength within SDBDs are rare. To address this issue, we performed polarized optical emission spectroscopy on the shifting and splitting of the allowed 492.19 nm (1D → 1P0) and forbidden 492.06 nm (1F0 → 1P0) helium line pair. This diagnostic approach requires a non-radially symmetric geometry, which leads to an adapted reactor design of the MCPA allowing the side-on observation of the discharge. The discharge operates in pure helium at atmospheric pressure, utilizing a triangular excitation voltage with a frequency of 15 kHz and an amplitude of 600 V. We performed phase-resolved measurements of the electric field components with a temporal resolution of 1 µs. Our results revealed an electric field strength of approximately 22 kV cm−1 for the component perpendicular to the dielectric surface, while the component parallel to the dielectric surface is about 5 kV cm−1 larger during the decreasing potential phase of the applied voltage.

Plasma-mediated mercury vapor generation after microwave-induced combustion of fish tissue with detection by atomic absorption spectrometry

Mercury determination in fish tissues by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) was performed using microwave-induced combustion (MIC) for sample preparation, and plasma-mediated vapor generation (PMVG) in a tubular dielectric barrier discharge (DBD) as a sample introduction system. The main goal was to develop a method for Hg determination using very low amount of reagents being at the same time virtually free of interferences. The operational parameters of the PMVG step in the DBD reactor were optimized as follows: 70 mL min−1 Ar as the discharge gas, 20 mm electrode distance, primary voltage at 60 V and 50 μL as digested sample volume (in 0.1 mol L−1 HNO3 matrix). The effect of HNO3 concentration on the PMVG efficiency was studied. No differences in signal intensity were observed for HNO3 concentration up to 0.1 mol L−1, while a signal decrease by 25 % and 40 % was observed when the acid concentration increased to 1 and 5 mol L−1, respectively. Accuracy of the proposed method was evaluated using certified reference material (CRM) of dogfish liver (DOLT-4) and by Hg spikes on the sample prior to MIC. By using 500 mg of sample (or 250 mg of CRM) and 6 mL of 0.5 mol L−1 HNO3 as absorbing solution in MIC, recoveries of 104 % and 97 % were observed for spikes and CRM values, respectively. A limit of detection of 0.16 μg g−1 Hg (160 pg Hg absolute) was obtained. A comparison of the results for Hg determination in the CRM by PMVG-AAS and chemical cold vapor generation inductively coupled plasma mass spectrometry (CVG-ICP-MS) was performed with no significant differences in the results. Finally, an efficient, low-cost and low-volume reagent consumption sample introduction system for Hg determination by AAS was successfully combined with the advantages of MIC and subsequent PMVG by DBD.

The impact of catalyst structure and loading material on the dynamics of plasma propagation in dielectric barrier discharges

Abstract Based on a two-dimensional particle-in-cell/Monte Carlo collision model, the spatiotemporal dynamics of streamers in patterned dielectric barrier discharges are investigated. The influence of coating materials with high dielectric constant (similar to catalysts) on pellets embedded in the bottom electrode is evaluated through numerical analysis. Upon interaction with the streamers, the coating material is polarized, leading to significant changes in potential and electric field at various positions near its surface. This effect results in drastic changes in discharge behavior, even triggering the formation of new streamer branches at the edges of the coating. Electrons display diverse energy distributions at various spatial positions and times during the streamer evolution, potentially impacting catalytic reaction rates. The plasma's penetration into pores of dielectric pellets is contingent upon the sizes of the pores, affecting the electron density, energy, and the velocity of surface streamers. The revealed mechanisms are advantageous for controlling discharge characteristics and optimizing plasma treatment applications.

Experimental control of the flow separation behind a backward facing step using deep reinforcement learning

In this experimental study, a value-based reinforcement learning algorithm (deep Q-network, DQN) is used to control the flow separation behind a backward facing step at a Reynolds number of 2.9 × 104. The flow is forced by a dielectric barrier discharge (DBD) plasma actuator pasted at the upstream of the step edge, and the feedback information of the separation zone is provided by a hotwire sensor submerged in the downstream shear layer. The control law represented by a deep neural network is implemented on a field programable gate array (FPGA), able to execute in real-time at a frequency as high as 1000 Hz. Results show that both open-loop periodical control and DQN control can effectively reduce the reattachment length and the recirculation area. Compared with the former, which requires dozens of trail-and-error measurements lasting for hours, the latter is able to find an optimal control law in only two minutes, achieving a long-term reward 7% higher. Moreover, by introducing a weak penalty term for plasma actuation, the mean actuator power consumption in DQN can be cut down to only 60% of that in the optimal open-loop control, meanwhile sacrificing a negligible amount of control effectiveness. Physically, the open-loop periodical control destabilizes the shear layer earlier, increasing both the area and the peak amplitude of the high turbulent kinetic energy (TKE) zone, whereas under DQN control, only a slight increase in the TKE peak is observed, and the overall spatial distribution remains the same as baseline.

Ozone Plasma Nanobubble (OPN) Reactor Combined with Coagulation-Flocculation Process: A Promising Technology for Leachate Treatment

According to World Bank data, approximately 2.01 billion tons of urban waste is produced annually, with approximately 33% of waste being improperly managed, leading to concentrated and toxic leachate. This poses a global challenge due to its varied characteristics influenced by climate, landfill age, and waste composition, resulting in groundwater and surface water pollution with severe impacts on human health, ecosystems, and biodiversity, necessitating stringent treatment measures. To address this, a study integrated coagulation-flocculation and advanced oxidation processes (AOPs) using a dielectric barrier discharge (DBD) ozone plasma nanobubble (OPN) reactor to degrade leachate. Gas flow rate, plasma voltage, and gas sources are variated. This research uses O2 or air as a gas source that produces plasma. The leachate is fed into the DBD reactor, so the bubble will burst and produce further ROS. Optimal results were observed after 60 min, with oxygen gas feed reducing total suspended solids (TSS), chemical oxygen demand (COD), and biological oxygen demand (BOD) by 100, 93.93, and 74.12%, respectively, alongside a decrease in pH. This study indicates the promising potential of this technology for leachate treatment and demonstrates the potential for nitrate production using both types of gas feed.

Dielectric barrier discharge cold plasma alleviated the immunoreactivity of egg white proteins with improved digestibility and functional properties

With the increasing number of children allergic to egg worldwide, there is an urgent need to develop strategies for effectively utilizing egg protein. As a novel food processing that can effectively reduce allergenicity and enhance protein quality and functional properties, cold plasma (CP) is gaining attention. The study investigated the impacts of the dielectric barrier discharge CP on the immunoreactivity, in vitro digestibility, functional properties, and structural changes of egg white protein (EWP). The results showed that the EWP treated with CP for 30 min had a significant decrease in immunoglobulin (IgG)-binding capacity by approximately 20% and improved in vitro digestibility. Further studies demonstrated that the decrease in the IgG-binding capacity of EWP correlated well with the alterations in the secondary and tertiary structures. The content of α-helix was decreased by 6.5% and the surface hydrophobicity increased by 2.5 folds after the 30-min treatment, compared with the untreated samples. The oxidation of peptide amino groups induces structural changes, accompanied by the oxidation of amino acid residues. This phenomenon has been validated through surface hydrophobicity and multispectral analysis. Additionally, CP also improved the foaming and emulsifying capacity of EWP by 140% and 8.03%, respectively. These findings suggest that CP treatment could be served as a potential technology to reduce the immunoreactivity, and improve the in vitro digestibility and functionality of EWP.

Citric acid modulated strong magnetic CoFe-LDH/CoFe2O4 coupled dielectric barrier discharge plasma for efficient levofloxacin degradation: Enhanced internal electric field and accelerated electron migration

A novel citric acid (CA) modulation strategy was developed to prepare strong magnetic CoFe-LDH/CoFe2O4-C composites, which were combined with dielectric barrier discharge (DBD) to effectively degrade levofloxacin (LEV) in wastewater. Kelvin probe force microscopy (KPFM) test showed that CA modulation facilitated a more powerful internal electric field to drive rapid charge migration. The addition of CoFe-LDH/CoFe2O4-C increased LEV degradation from 78.2% to 98.6% and reduced energy efficiency from 24.77 to 8.93 kWh m–3. Quenching experiments and electron paramagnetic resonance (EPR) spectra showed the CoFe-LDH/CoFe2O4-C could take full advantage of the active substances originating from DBD plasma and highlighted the role of 1O2 and ·O2–. Density functional theory (DFT) calculation revealed that the heterojunction can not only drive faster electron migration but also reduce the energy barrier of O3 decomposition. Possible degradation pathways for LEV were proposed. This study opened up a new avenue for the synthesis of applicable catalysts for plasma systems in water treatment areas.

Plasma coupled with ultrasonic for degradation of organic pollutants in water: Revealing the generation of free radicals and the dominant degradation pathways

This study explores the synergistic effects of dielectric barrier discharge (DBD) plasma coupled with ultrasound (US) in the degradation of organic pollutants in water. The optimal degradation conditions were determined to be 100W ultrasonic power, 190V DBD plasma voltage, and neutral pH. The combination of DBD plasma and US significantly enhances the generation of reactive species (·OH, ·O2-, and 1O2), leading to a 97.3% degradation efficiency of methyl orange (MO), which is 17.3% higher than DBD plasma alone. Electron spin resonance (ESR) identified ·OH, ·O2-, and 1O2 in DBD/US system, and radical scavengers were employed to elucidate their roles. The degradation process was assessed through changes in pH, conductivity, TOC and COD, with characterization and analysis via UV-Vis and LC-MS. By combining LC-MS with density functional theory (DFT) calculations, nine intermediates were identified and three degradation pathways dominated by free radicals were established. Additionally, the DBD/US system treated wastewater containing sulfamethoxazole (SMX), sulfadiazine (SDZ), tetracycline (TC), and ciprofloxacin (CIP), achieving degradation rates exceeding 80%. These findings suggest that the DBD/US coupled system holds promising potential for treating organic pollutant wastewater.

Numerical study on positive streamer in parallel-rod dielectric barrier discharge in atmospheric air

In this work, a parallel-rod dielectric barrier discharge (DBD) operating in atmospheric air is investigated through the two-dimensional plasma fluid model. The effects of applied voltage (Vp), secondary electron emission coefficient (γ), and photoionization are examined. Photoionization can significantly influence streamer dynamics by accelerating and broadening both volumetric and surface streamers and enhance the impact of the applied voltage. Without photoionization, the propagation distance of the surface streamer along the curved dielectric surface is limited to 0.1–0.2 mm under applied voltages of 8–8.5 kV. In contrast, with photoionization, this distance can extend to 0.3–0.6 mm. Achieving the same distance requires much higher voltages (10–11 kV) if without photoionization. The “double-layer” structure of the surface streamer is investigated, revealing that γ predominantly affects the surface branch with little impact on the volumetric branch. The critical charge density for streamer onset is found to be about 1018 m−3, and the volume-to-surface streamer transition is attributed to the lateral electric field provided by the space charges. This work provides insights into the regulation strategies and underlying mechanisms of streamer dynamics in parallel-rod DBDs in atmospheric air.

Constructing a hollow-cage nanoenzyme sensor for dual detection of thiamine hydrochloride and hydrogen peroxide based on dielectric barrier discharge microplasma etching

Constructing a hollow-cage nanoenzyme sensor for dual detection of thiamine hydrochloride and hydrogen peroxide based on dielectric barrier discharge microplasma etching

Enhancing degradation of PLA-made rigid biodegradable plastics with non-thermal plasma treatment

This study evaluated the efficacy of Dielectric Barrier Discharge Non-Thermal Plasma (DDBD-NTP) as a pretreatment method to enhance the degradation of rigid biodegradable plastics (RBP) during composting, specifically focusing on polylactic acid (PLA) products such as drinking cups (CS) and spoon handles (SH). Using a Single-Factor-At-A-Time (SFAT) design, the impact of NTP parameters, including input voltage and treatment duration, on the physicochemical properties was evaluated, and the subsequent degradation rate of RBP was assessed by measuring the degree of disintegration in a home-scale composter. The filamentary discharge mode of the DDBD plasma system selectively altered the surface characteristics of RBP without significantly affecting their bulk properties. High-voltage treatments significantly increased surface roughness and accelerated degradation rates, while low-voltage and short-duration treatments enhanced oxidation, as indicated by the increased O/C ratio (85.5% for SH and 66.1% for CS), showing a non-linear response to plasma intensity. Furthermore, NTP treatment reduced water contact angles (up to a 39.79% reduction for SH and 82.65% for CS), indicating enhanced hydrophilicity. All NTP-treated samples demonstrated significantly higher degradation rates compared to both untreated and thermally treated counterparts. Notably, ‘high-voltage for short-duration’ treatments, such as CS-3 and SH-3, exhibited the highest degradation rates among the samples. CS-3 achieved complete disintegration (100%) within 20 days, markedly exceeding the 2% observed in untreated CS samples. Similarly, SH-3 reached 36% disintegration after 35 days, considerably surpassing the 9% seen in untreated SH samples. The findings indicate that NTP treatment is a viable and sustainable method to enhance the biodegradation of plastic waste.

Novel methods for determination and manipulation of surface charges performed on an atmospheric DBD microplasma

Abstract In photo- and electrocatalysis it is already well-established that surface charges can alter chemical adsorption and reaction paths of the catalyst. However, the novel realm of plasma catalysis lacks experimental exploration regarding the impact of plasma-induced surface charges on catalytic processes. This paper paves the way by introducing a straightforward method for precisely charging the dielectric (catalyst) in a dielectric barrier discharge microplasma at atmospheric pressure. It additionally enables the determination of this surface charge avoiding artifacts or volume charge interference. Through pre-charging of the dielectric, the charges’ impacts on re-ignition and forming of charge equilibria during the discharge are investigated. Moreover, a laser-assisted operando technique is introduced to generate up to 15% of either positive or negative additional surface charges (compared to the default operation) within 3.5 μs after irradiation and potential for even higher yields. The charges’ origin and the plasma’s response to these laser-induced surface charges are explored.

Enhanced degradation of aqueous caffeine via cylindrical dielectric barrier discharge plasma: Efficacy and toxicity insights

An environmentally friendly approach for caffeine degradation was explored in this study utilizing cylindrical dielectric barrier discharge (CDBD) plasma. The current-voltage characteristics and the plasma parameters of the CDBD, such as the electron temperature, electron density, density of nitrogen excited states, vibrational temperature, and rotational temperature, were assessed through electrical and optical characterization respectively. Fourier-transform infrared spectroscopy (FTIR) was employed to evaluate the reactive oxygen and nitrogen species (RONS) in the plasma-treated air. The physicochemical properties of deionized water (DW) were measured. To gain a deeper insight into the role of RONS in caffeine degradation, their concentrations in DW were analyzed. Furthermore, the effects of initial concentration, sample volume, and pH on caffeine degradation were investigated. The highest degradation of caffeine was 94% at initial concentration of 50 mg L-1, sample volume 50 mL and in neutral pH. Liquid chromatography–mass spectrometry (LC-MS) was then used to propose the degradation pathway for caffeine. The major reactive species involved in caffeine degradation was ozone. Finally, the phytotoxicity and cytotoxicity of caffeine were assessed before and after plasma treatment with plasma-treated caffeine (PTC) showing minimal toxicity to both plants and cells.

Plasma-Assisted Synthesis of Methanol Through Hydrogenation of Carbon Dioxide With Non-Noble Metal Mixed Oxide Catalysts.

The utilization of carbon dioxide through chemical conversion is a promising approach for the recycling of carbon resources. Despite well-developed industrial processes for CO2 hydrogenation to methanol, the effective use of CO2 as a feedstock remains challenging because of the costly requirements of high temperature and reaction pressure. In this paper, we report the methanol synthesis from CO2 and hydrogen using a dielectric barrier discharge (DBD) reactor under atmospheric pressure with a nickel-cerium-aluminum mixed oxide (Ni/Ce-Al MOx) catalyst. The combined use of plasma and the Ni/Ce-Al MOx catalyst was observed to yield 13.3±0.4 % of methanol, favorably compared to the 2.6±0.5 % yield of the case without catalyst. Microscopy images, selected area electron diffraction patterns, and energy-dispersive X-ray analysis confirmed the presence of fluorite-structured ceria, aluminium, nickel, and nickel oxide particles in the catalyst. The reaction mechanism for the plasma-assisted hydrogenation of CO2 was hypothesized to involve a carbide formation pathway due to the presence of carbide confirmed by X-ray photoelectron spectroscopic characterization.