This study investigates the partial oxidation of methane in a non-thermal plasma environment using an innovative plasma–catalysis reactor, where copper-based geopolymer materials are directly deposited onto the inner electrode. This original configuration enhances the plasma–catalyst interfacial contact, promoting efficient interaction between reactive plasma species and catalytic active sites. Two synthesis strategies were developed to tailor the nature and dispersion of copper species within the geopolymer matrix: (i) direct incorporation of CuO during geopolymer formation and (ii) post-synthesis copper ion exchange. While CuO incorporation exhibits limited influence on methane and oxygen conversions, product selectivity, and carbon balance, the ion-exchange approach significantly enhances catalytic performance.,Methane conversion increases from 8% for CuO-incorporated samples (2 wt%) to 19.6% for ion-exchanged catalysts. Concurrently, CO selectivity improves from 39.7% to 55.5%, indicating a more efficient pathway toward syngas-oriented products. Notably, the energy efficiency of CO production is markedly improved, with the specific energy input decreasing from 14.6 kJ·mol⁻¹ to 4.7 kJ·mol⁻¹. These results highlight the critical role of copper speciation and dispersion in plasma–catalytic systems. The superior performance of ion-exchanged copper geopolymers is attributed to enhanced accessibility of active sites and improved synergy with plasma-generated reactive species. This work demonstrates a promising and energy-efficient strategy for methane valorization through optimized plasma–catalyst coupling.

The use of ammonia as a hydrogen carrier is a fast-growing research area due to ammonia's high weight percentage of H2 (17.6 %) and its safer to handle features. Therefore, a higher demand for ammonia in energy applications is expected in the near future. Electric field-assisted ammonia synthesis is one way to meet the growing demand for ammonia, both for energy purposes and for industrial applications, mainly in fertilizer production. This study highlights the use of electric current for ammonia production by using NiO/La2O3 catalysts in a fixed-bed flow reactor. The operating conditions were maintained at a pressure of 5 bars and a current of 9 mA. The catalytic activity was analyzed in terms of ammonia concentration (ppm), synthesis rate RNH3 (mu mol. min-1.gcat-1) and energy efficiency EE (g-NH3 [kWh.gcat-1]-1). Good catalytic activity was obtained at 200 degrees C for the 10 wt% NiO/La2O3 catalyst, withRNH3 and EE values reaching 5.7 mu mol.min-1.gcat-1 and 4.5 g-NH3 [kWh.gcat-1]- 1, respectively. Characterization of the catalysts by powder X-Ray Diffraction (XRD) revealed the formation of La (OH)3 from La2O3 in the presence of electric field, and an altered reaction mechanism was observed. The temperature-dependent study showed an increase in NH3 production at 150 degrees C and 200 degrees C with an apparent activation energy of 30 kJ.mol-1.

In this work, we explore the possibility to harness the energy released during the implosion of acoustic cavitation bubbles to activate and selectively convert NH3 in water without the assistance of any catalyst. Two primary products, hydrazine and ammonium nitrite, were identified in the liquid phase. Hydrazine was formed as a result of the cleavage of the N─H bond of NH3 at the cavitation bubble collapse time, while ammonium nitrite was formed through oxidation of NH3 with HO● radicals stemming from the sonolysis of water. By adjusting the gas atmosphere, the generation of HO● radicals can be suppressed or enhanced, thereby enabling selectivity control over the sonochemical conversion pathway of NH3 toward either hydrazine or ammonium nitrite. For instance, we show that under H2 atmosphere, NH3 is predominantly converted to hydrazine, while under oxygen atmosphere ammonium nitrite becomes the major product formed. Finally, we discuss the unexpected beneficial role of salts (mono-, di-, and trivalent), which influence the efficiency of this sonochemical activation of NH3.

ABSTRACT This study investigates the synergy between nonthermal plasma and Ni/CeO 2 catalysts for efficient CO 2 methanation, with a particular focus on the roles of the synthesis route and nickel loading (1–15 wt.%). Catalysts prepared via sol‐gel and impregnation methods were characterized and evaluated under plasma‐assisted reaction. Among the series, the 15 wt.%Ni@CeO 2 ‐gel catalyst led to the highest specific activity (7.3 µmol CH 4 .g −1 .s −1 ). This performance is was attributed to the formation of a defective Ce 1‐x Ni x O 2‐γ solid solution possessing a high density of oxygen vacancies (≈16% Ce 3+ ), which provides basic and defect associated sites for CO 2 adsorption and activation. In contrast, surface basicity was not identified as a determining factor under nonthermal plasma activation. Electrical diagnostics based on Lissajous figures indicated that all catalysts possess a low capacitance (∼5‐35 pF), which is consistent with a discharge propagation on the catalyst surface rather than being localized at contact points. However, this parameter did not directly correlate with catalytic activity. Overall, the results of this study show that the performance of plasma assisted CO 2 methanation relies primarily on the surface defect chemistry, metal‐support interactions, and accessible hydrogenation sites.

Water vapour isotopes are important tools to better understand processes governing the atmospheric hydrological cycle. Their measurement in polar regions is crucial to improve the interpretation of water isotopic records in ice cores. In situ water vapour isotopic monitoring remains challenging, especially in dry places of the East Antarctic Plateau, where water mixing ratios can be as low as 10 ppm. We present in this article new commercial laser spectrometers based on the optical-feedback cavity-enhanced absorption spectroscopy (OF–CEAS) technique, adapted for water vapour isotopic measurements in dry regions. We characterise a first instrument adapted for Antarctic coastal monitoring with an optical cavity finesse of 64 000 (ring-down time of 54 µs), installed at Dumont d'Urville Station during the summer campaign 2022–2023, and a second instrument with a high finesse of 116 000 (98 µs ring-down time), to be deployed inland of East Antarctica. With a drift calibration every 24 h, the stability demonstrated by the high-finesse instrument allows one to study isotopic diurnal cycles down to 10 ppm humidity for δD and 100 ppm for δ18O.

CH4 reforming with CO2 was investigated using nanosecond pulsed DBD plasma, focusing on pulse parameters (pulse width and repetition frequency), discharge power, residence time and molar ratios on reaction performance. Furthermore, the impact of oxygen addition to the feed gas mixture was evaluated. At a constant power of 16 W and flow rate of 40 ml. min-1, the increase in pulse width from 150 ns to 175 ns enhanced CH4 conversion from 18.6 to 21.1

This paper presents an original one-dimensional statistical model designed to complement experimental data from a practical dielectric barrier discharge (DBD) reactor. The experimental setup consists of a plasma-assisted reactor with gas injection composed solely of CH4 and O2. The numerical procedure uses electrical measurements to provide a realistic description of the power consumption and the current flowing through the gas, in a complex scenario where approximately one hundred current peaks are measured per electrical half-period. A plasma kinetic model is then used to analyze the chemistry and characteristic times of both isolated discharges and a representative train of discharges occurring within the reactor. These times are used to optimize the computational costs and to select the most appropriate kinetic schemes for the gas phase, whether in a plasma or quasi-thermodynamic equilibrium state. This approach also allows the separation of fast transformations (plasma) occurring at constant volume, from slower transformations occurring at constant pressure. The statistical approach, based on a Monte Carlo method, clearly identifies the assumptions required to reduce the real complexity of the DBD reactor to a 1D flow model. The combination of chromatographic measurements at the reactor outlet and numerical simulations provides the heterogeneity factor of the discharges, which is identified as a key parameter in the model. Although the flow can be considered stationary on average, the obtained value reveals a highly heterogeneous spatial distribution of the discharges within the reactor. Thus, the numerical results suggest that the gases passing through the reactor are rarely in a plasma state.

Hydrogen is rapidly emerging as a pivotal clean energy carrier for both stationary and transport applications. However, the storage of hydrogen as compressed gas at high pressures poses significant challenges in terms of cost, transportation, and safety. Chemical storage, particularly using compounds like ammonia, has emerged as a viable alternative due to its high hydrogen content and narrow flammable range. This study investigates the catalytic decomposition of ammonia under an electric field using Ni based La2O3 catalysts. The catalytic performance is evaluated in terms of ammonia conversion and energy efficiency. High catalytic activity is obtained in the presence of 15 wt%NiO/La2O3, the energy efficiency is 0.29 mmol/kJ. This is attributed to the semiconducting properties of NiO. Catalyst characterization techniques, including X-ray diffraction, transmission electron microscopy, and photoelectron spectroscopy, provide insights into catalyst morphology, chemical composition before and after reaction. It is shown that hydroxylation of La2O3 proceeds during ammonia decomposition and a reaction mechanism is provided.

Non-thermal plasma appears as a promising alternative technology to develop the electrification of the petrochemical industry. Non-thermal plasma has the advantage of operating at atmospheric pressure and room temperature in “on/off” mode. The high-energy electrons generated are able to activate many reactants allowing thermodynamically unfavorable reactions to occur. Methane coupling is particularly important to produce C2 hydrocarbons, especially ethylene known as a platform chemical for the synthesis of many products. In this review, the state-of-the-art of plasma and plasma-catalysis for methane coupling is described. Focus is given on plasma chemistry and the influence of different parameters related to plasma reactors and gas composition are discussed. The role of a catalyst coupled with plasma is detailed and synergies are explained for various catalytic compositions.

Modeling tritium content in water presents a meaningful way to evaluate the representation of the water cycle in climate models as it traces fluxes within and between the reservoirs involved in the water cycle (stratosphere, troposphere, and ocean). In this study, we present the implementation of natural tritium in water in the atmospheric general circulation model (AGCM) MIROC5-iso and its simulation for the period 1979-2018. Owing to recently published tritium production calculations, we were able to investigate, for the first time, the influence of natural tritium production related to the 11-yr solar cycle on tritium in precipitation. MIROC5-iso correctly simulates continental, latitudinal, and altitude effects on tritium in precipitation. The seasonal tritium content peaks, linked to stratosphere-troposphere exchanges, are accurately simulated in terms of timing, even though MIROC5-iso underestimates the amplitude of the changes. Decadal tritium concentration variations in precipitation owing to the 11-yr solar cycle are well simulated in MIROC5-iso, in agreement with the observations at Vostok in Antarctica for example, Finally, our simulations revealed that the internal climate variability plays an important role in tritium in polar precipitation. Owing to its influence on the south polar vortex, the Southern Annular Mode enhances the effect of the production component on tritium in East Antarctic precipitation. In Greenland, we found an east-west contrast in the detection of the 11-yr solar cycle in tritium in precipitation owing to the influence of the North Atlantic Oscillation on humidity conditions. Models used to simulate the future of our climate are still struggling to represent the water cycle adequately. To address this challenge, we have added the capability to simulate tritium in water into the atmospheric model MIROC5-iso. Tritium is a naturally occurring radioactive isotope produced by interactions of cosmic rays in the atmosphere. Because it decays away with a half-life of 12.32 years, it is a very powerful tracer of water exchanges within and between water cycle reservoirs, such as the stratosphere, the troposphere, and the ocean. We were also able to investigate the influence of the 11-year solar cycle on tritium in precipitation, as well as the impact of natural atmospheric circulation variations on an interannual time scale. MIROC5-iso can simulate decadal variations in tritium in precipitation related to solar cycles. The presence or absence of this cycle in our modeled tritium for polar regions is influenced by interannual variations in the atmospheric circulation, especially related to precipitation amount variations. Conclusively, we show that tritium is reliable complementary tracer for better constraining the water cycle representation in climate models. For the first time, natural tritium (HTO) is modeled in an atmospheric model by considering solar modulation over the period 1979-2018 MIROC5-iso correctly captures the observed spatial distribution of tritium in precipitation and its temporal variations Internal climate modes can enhance or hide changes in tritium in precipitation owing to the decadal tritium production variations

Valorization of carbon dioxide via the dry reforming of methane (DRM) reaction offers dual benefits, mitigating environmental issues and generating syngas as a valuable feedstock for the production of methanol. This chapter relates the advantages and drawbacks of the different technologies used in the dry reforming of methane, including thermally-driven, plasma-assisted, electro- and photo-assisted, membrane, and solar-driven DRM. Some technological challenges are furthermore addressed. All these processes show a promising future, but further investigations are required to overcome the major issues linked to carbon poisoning, catalyst deactivation, and energy efficiency.

. The EPICA (European Project for Ice Coring in Antarctica) Dome C (EDC) ice core drilling in East 19 Antarctica reaches a depth of 3260 m. The reference EDC chronology (AICC2012) provides an age vs depth 20 relationship covering the last 800 kyr (thousands of years) with an absolute uncertainty rising up to 8,000 years at 21 the bottom of the ice core. The origins of this relatively large uncertainty are threefold: (1) the δ 18 O atm ,δO 2 /N 2 22 and total air content (TAC) records are poorly resolved and discontinuous over the last 800 kyr, (2) the three orbital 23 tools are not used simultaneously and (3) large uncertainties are associated with their orbital targets. Here, we 24 present new highly resolved δ 18 O atm ,δO 2 /N 2 and δ 15 N measurements for EDC ice core covering the last five 25 glacial - interglacial transitions as well as novel absolute 81 Kr ages. We have compiled chronological and 26 glaciological information including novel orbital age markers from new data on EDC ice core as well as accurate 27 firn modeling estimates in a Bayesian dating tool to construct the new AICC2023 chronology. The average 28 uncertainty of the ice chronology is reduced from 2,500 years to 1,800 years in AICC2023 over the last 800 kyr. 29 The new timescale diverges from AICC2012 and suggests age shifts reaching 3,800 years towards older ages over 30 Marine Isotopes Stages (MIS) 5, 11 and 19. But, the coherency between the new AICC2023 timescale and 31 independent chronologies of other archives (Italian Lacustrine succession from Sulmona Basin, Dome Fuji ice 32 core and northern Alpine speleothems) is improved by 1,000 to 2,000 years over these time intervals.

A series of four catalysts, CeO2, CePO4 and LaPO4 in a nanorod structure and CePO4 nanospheres were assessed for the oxidative coupling of methane (OCM) reaction in an electric field at room temperature. The applied current of 3 mA was kept constant throughout the study. The cerium and lanthanum phosphates showed similar and high activity for OCM in the electric field, while CeO2 was not active for OCM reaction, and led only to total oxidation into CO2. C2 selectivity was improved as methane content increased in the feed and reached 27.6 % at a CH4/O2 ratio of 3. Switching the polarity of the current from positive to negative shifted the C2 selectivities to acetylene (18.2 %) for CePO4. It was suggested that this shift was related to the deposited power due to the polarity switch rather than the polarity effect on the electric field. Changing the structure of the CePO4 catalyst from nanorod to nanosphere did not alter the conversion or selectivities, indicating that the morphology does not compromise the reactivity.

The coupling of methane to C2 hydrocarbons by means of non-thermal plasma is a recognized process as it is performed at room temperature, through the generation of radical species, but it still presents a major disadvantage of carbon deposition. The main goal of the study is to better control the chemistry and avoid C deposit. For that purpose, the addition of hydrogen as co-feed in a Dielectric Barrier Discharge plasma reactor was proposed. Experiments were carried out at a fixed deposited power of 8 W in the presence and absence of helium. As expected the conversion of methane was low without helium (6.5% for pure CH 4 against 22.3% for He/CH 4 : 30/10 mL min −1 ). A high selectivity into hydrocarbons was achieved by adding H 2 to CH 4 (75% for H 2 /CH 4 = 1 against 62% without H 2 ), the main product being ethane (selectivity of 60%). An increase of the deposited power from 8 to 21 W favoured methane transformation and the hydrocarbons yield reached 9.1%. Surprisingly, the carbon deposition was limited at high deposited power. It could result from the hydrogenation of coke precursor (ethylene, acetylene) or reaction of H 2 with C deposit. The beneficial action of hydrogen on the reaction to reach high C2 selectivity has been demonstrated and a reaction mechanism is proposed.

Electric field-induced decomposition of ammonia into hydrogen and nitrogen was investigated over CeO2, Fe-, Ru- deposited CeO2, CePO4 and Sr-doped CePO4, and CeZrO4 in a packed bed down-flow reactor. The effect of applied current, concentration of ammonia in a feed, and residence time was examined using CeO2 alone. The conversion of ammonia was also studied with respect to a reduction temperature, loading and a type of the deposited metal. The activity results have been analyzed in terms of surface, morphological and electrical characterization of the catalysts. Among metal-deposited catalysts, ammonia decomposition result at 4 mA was the best for 1 wt % Fe/CeO2 reduced at 550 degrees C, showing 22 % of conversion with 0.18 mmol of converted ammonia per kJ of energy consumed. The activity of studied Ce-based catalysts normalized per mass of loaded catalyst showed an accordance in activity-porosity relation.

Dry reforming of methane was investigated by non-thermal plasma coupled with different metal oxides: BaO, La2O3, ZnO, CaO, alpha-Al2O3, MgO, gamma-Al2O3, TiO2 and CeO2. The deposited power was fixed at 8 W and the total gas flow at 40 mL.min 1 (75 % helium as diluent). Electrical characterization showed that the CO2 and CH4 conversions were enhanced (from 5.6 to 30.6 % for CH4 and from 1.9 to 16.1 % for CO2) when the permittivity was reduced from 2903 to 4.1, respectively. Methanol selectivities were favored for the oxides presenting low permittivities, indicating that reaction is favored under a low electric field, thus low density of reactive species. The effect of reaction temperature was evaluated on MgO catalyst. The increase of the temperature favored CH4 conversion, while reducing methanol selectivity. The oxide characterization by TGA revealed the rehydroxylation of MgO at low temperature, which was correlated to the improved oxygenated compounds selectivities.

Succession of cold glacials and warm interglacials during the Quaternary results from large global climate responses to variable orbital configurations, accompanied by fluctuating greenhouse gas concentrations. Despite the influences of sea ice and atmospheric and ocean circulations in the Southern Ocean on atmospheric CO2 concentrations and climate, past changes in this region remain poorly documented. Here, we present the 800 ka deuterium excess record from the East Antarctica EPICA Dome C ice core, tracking sea surface temperature in evaporative regions of the Indian sector of the Southern Ocean from which moisture precipitated in East Antarctica is derived. We find that low obliquity leads to surface warming in evaporative moisture source regions during each glacial inception, although this relative temperature increase is counterbalanced by global cooling during glacial maxima. Links between the two regions during interglacials depends on the existence of a temperature maximum at the interglacial onset. In its absence, temperature maxima in the evaporative moisture source regions and in East Antarctica were synchronous. For the other interglacials, temperature maxima in the source areas lag early local temperature maxima by several thousand years, probably because of a change in the position of the evaporative source areas. Interglacial temperature coupling between East Antarctica and the Southern Ocean was set by the position of moisture source regions, according to an 800,000-year-long deuterium-excess ice-core record from East Antarctica.

Interface optimisation for continuous hemp reinforcements in epoxy resin is a current challenge for the development of biocomposites. A chemical treatment based on hydrogen peroxide and a physical one using a non-thermal plasma have been tested to optimise interface adhesion, by varying several parameters. FTIR analysis and FE-SEM observations have shown the effects of the treatments on chemical and morphological aspects of the treated yarns. Tensile tests on hemp yarns have allowed the selection of the treatment parameters leading to the best strength. Fragmentation tests results showed that the two treatments lead to a decrease in the fragment lengths and thus, an enhancement of the Interfacial Shear Strength (IFSS) values in comparison with the untreated yarn. This is confirmed by the micro-CT observations of the debonding lengths in the vicinity of each yarn fragment extremity. Finally, the plasma treated samples exhibit a better interface adhesion quality (IFSS = 44.7 ± 4 MPa) than the chemically treated ones (IFSS = 24.2 ± 4 MPa), which are better than the non-treated ones (IFSS = 13.5 ± 4 MPa).

The transformation of methane and carbon dioxide by coupling plasma and catalysis was investigated using a fluidized bed reactor and the results, in terms of reactant conversion and yields in products, were compared with those obtained in a fixed bed reactor. A series of alumina, including a commercial sample and various mesomacro materials synthesized in the laboratory, was tested in this study. Their surface areas varied from 260 to 312 m(2) g(-1) depending on their calcination temperature. A correlation between reactant conversion and surface area of alumina was highlighted for the plasma-fluidized bed, the best conversions being reached with the alumina presenting the highest surface area. CH4 conversion increased from 8.5 to 12.1% for S = 260 and 312 m(2) g(-1) respectively and the CO2 conversion from 3.4 to 6.2% for a deposited power of 4 W, in an excess of CO2. This correlation was not corroborated for the fixed bed reactor. It proves that an efficient coupling of plasma and catalysis can be expected as soon as solid particle are moving in the gas flow, enhancing the plasma-surface interaction.