Oxygen Enrichment Research Articles

Flexible Ce-doped WO3 nanowire arrays with enriched oxygen vacancies for soft-packaged asymmetric supercapacitor

Tungsten trioxide (WO3) is recognized as a promising anode material for asymmetric supercapacitors (ASCs), yet its low conductivity and stability as well as energy density greatly limit its development. Herein, a flexible Ce-doped WO3 (Ce1.5%-WO3) nanowire array with rich oxygen vacancies is grown on carbon cloth by a solvothermal synthesis. The specific capacitance of Ce1.5%-WO3 is 493F g−1 at 4 A/g and remains 90.4 % after 5000 cycles, superior to that of WO3 nanowire arrays (416F g−1, 80.3 %). The improved performance mainly stems from the synergistic effects of more oxygen vacancies, higher specific surface area, wider lattice spacing, faster ion diffusion, and electron transport generated by Ce doping. As-prepared ASC device can reach an energy density of 31.7 Wh kg−1 at a power density of 700 W kg−1. Furthermore, two flexible soft-packaged ASCs connected in series can illuminate different electronic devices. This strategy proves the great application prospect of Ce-doped WO3 nanowire arrays flexible electrodes in supercapacitors.

Dielectric properties of the Ca0.25Cu0.75-xAlxTiO3 ceramics: experimental and computational investigations

In this study, we employed a solid-state reaction method to synthesize Ca0.25Cu0.75-xAlxTiO3 ceramics, investigating the impact of Al doping at concentrations of x = 0 and 0.0125. Notably, all ceramics exhibited a primary phase of Ca0.25Cu0.75TiO3. The addition of Al3+ induced a significant increase in grain size. Density functional theory analyses revealed a preferential occupation of Cu sites by Al, leading to liquid-phase sintering processes attributed to excess Cu. Moreover, it was also found from DFT that the Al dopant cannot induce an oxygen vacancy in the lattice. Charge density analysis revealed that Cu+ and Ti3+ observed via XPS originate from the presence of an oxygen vacancy. The Ca0.25Cu0.7375Al0.0125TiO3 ceramic exhibited a very high dielectric permittivity of 9.23 × 104 and a low dielectric loss tangent of 0.057 at 1 kHz and room temperature. Importantly, the dielectric permittivity exhibited impressive stability over a temperature range of −60 °C to 110 °C, perfectly meeting the practical requirements for utilization in X5R ceramic capacitors. Our investigation indicates that the improved dielectric properties may be attributed to enhanced grain boundary responses, influenced by oxygen enrichment and the presence of metastable insulating layers at grain boundaries. Combining experimental findings with theoretical evidence, our study elucidates that the excellent dielectric properties of the Ca0.25Cu0.7375Al0.0125TiO3 ceramic originate from an extrinsic effect arising from grain boundary enhancement. This work not only contributes to advancing the understanding of the underlying mechanisms governing dielectric behavior in doped ceramics, but also emphasizes the potential of Ca0.25Cu0.7375Al0.0125TiO3 as a promising material for applications demanding superior dielectric performance.

Detection of Metal Enrichment by SN 2011jm in NGC 4809

Cosmic metals are believed to originate from stellar and supernovae (SNe) nucleosynthesis, dispersed into the interstellar medium (ISM) through stellar winds and supernova explosions. In this paper, we present the clear evidence of metal enrichment by a Type Ic SN 2011jm in the galaxy NGC 4809, utilizing high spatial resolution integral field unit observations obtained from the Very Large Telescope/Multi Unit Spectroscopic Explorer. Despite SN 2011jm being surrounded by metal-deficient ISM (∼0.25 Z ⊙) at a scale about 100 pc, we clearly detect enriched oxygen abundance (∼0.35 Z ⊙) and a noteworthy nitrogen-to-oxygen ratio at the SN site. Remarkably, the metal pollution is confined to a smaller scale (≲13 pc). We posit that the enhanced ionized metal stems from stellar winds emitted by massive stars or previous SN explosions. This observation may represent the first direct detection of chemical pollution by stellar feedback in star-forming galaxies beyond the Local Volume.

Two sequences of spiral galaxies with different shapes of the metallicity gradients

We considered two sequences of spiral galaxies with different shapes of the radial gas-phase oxygen abundance distributions from the galaxies in the survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA): (1) Galaxies in which the gradient is well approximated by a single linear relation across the whole disc, that is, galaxies with an S (slope) gradients, (2) galaxies in which the metallicity in the inner region of the disc is at a nearly constant level and the gradient is negative at larger radii, that is, galaxies with level-slope (LS) gradients. We also selected galaxies with a nearly uniform oxygen abundance across the whole galaxy, that is, galaxies with level (L) gradients (or O/H uniform galaxies) with a high oxygen abundance that can be the final evolutionary stage of the two galaxy sequences described above. The radial nitrogen abundance distributions in galaxies with LS oxygen abundance distributions also show breaks at radii smaller than the O/H distribution breaks. The observed behaviour of the oxygen and nitrogen abundances with radius in these galaxies can be explained by the time delay between the nitrogen and oxygen enrichment together with the variation in the star formation history along the radius. These galaxies clearly show the effect of the inside-out disc evolution model, which predicts that the galactic centre evolves more rapidly than the regions at greater galactocentric distances. We find that the shape of the radial abundance distribution in a galaxy is not related to its macroscopic characteristics (rotation velocity, stellar mass, isophotal radius, and star formation rate) and is independent of its present-day environment. The correlations between the gradient slopes and macroscopic characteristics of galaxies are weak in the sense that the scatter of the points in each diagram is large. The galaxies with different abundance distributions (S, LS, or L) in our sample are located within the main sequence of the star-forming galaxies in the diagram of star formation rate–stellar mass. We also examined the properties of the Milky Way in the context of the considered galaxy samples.

Highly efficient peroxymonosulfate activation by Fe[sbnd]Co bimetallic modified metal-organic frameworks-derived polyhedron with enriched oxygen vacancy for tetracycline degradation

It is important to propose a targeted solution strategy for the rate-limiting step in peroxymonosulfate activation in order to promote its wider application in advanced oxidation processes. In this study, a novel catalyst with FeCo bimetal doping, rich oxygen vacancy and porous polyhedral structure was prepared by using Fe, Co-doped Metal-Organic Framework as the precursor, which strategically enhanced the abundance and stability of active sites and promoted the adsorption of contaminates and PMS molecules. The M-450 (oxygen vacancy-rich)/PMS system demonstrated superior catalytic activity and interference resistance, in which 100 % of TC could be removed within 5 min. The corresponding reaction rate constant is 1.119 min−1, which is much higher than that of M-0 (without oxygen vacancy). Moreover, a series of studies proved that nonradical pathway (singlet oxygen) accompanied free radicals (sulfate radicals and hydroxyl radicals) collectively contributed to the tetracycline degradation. This study provides new ideas for the design and improvement of the functional catalyst for application in sulfate radicals based advanced oxidation processes.

Rich oxygen vacancies in confined heterostructured TiO2@In2S3 hybrid for boosting solar-driven CO2 reduction

Solar energy driving CO2 reduction is a potential strategy that not only mitigates the greenhouse effect caused by high CO2 level in atmosphere, but also yields carbon chemicals/fuels at the same time. Herein, a facile way to design the heterogeneous TiO2@In2S3 hollow structures possessing robust light harvesting in both ultraviolet and visible regions is proposed and exhibits a higher generation rate of 25.35 and 1.24 μmol·g−1·h−1 for photocatalytic CO2 reduction to CO and CH4, respectively. The excellent photocatalytic catalytic performance comes from i) the confined heterostructured TiO2@In2S3 possesses a suitable band structure and a broadband-light absorbing capacity for CO2 photoreduction, ii) the rich interfaces between nanosized TiO2 and In2S3 on the shell can significantly reduce the diffusion length of carriers and enhance the utilization efficiency of photogenerated electron-hole pairs, and iii) enriched surface oxygen vacancies can provide more active sites for CO2 adsorption.

Influence of oxygen enrichment method on the state of blast furnace raceway

The numerical simulation is applied to compare the effect of the oxygen enrichment rates under different injection methods on the flow and combustion features. The alteration in the gas velocity follows a congruous pattern for constant air and oxygen enrichment (CAOE) method and the reduced air and oxygen enrichment (RAOE) method. The oxygen enrichment rate increases by 1% and the velocity at the tuyere increases by 2.92 and 0.78 m s−1. The CAOE method has a more significant influence on the temperature and burnout of coal particles than that of the RAOE method. Furthermore, the burnout of coal particles at the exit of the raceway is 79.45% and 78.95%, at an oxygen enrichment rate of 12% under the conditions of the CAOE method and RAOE method. To improve the penetration capacity of the hearth and achieve higher burnout of pulverised coal, the CAOE method is recommended to enrich oxygen.

Evaluating the carbon footprint of sulphur recovery unit: A comprehensive analysis

Desulphurising of oil based fuels and industrial gases is a widespread practice. The combustion process in the sulphur recovery unit (SRU) involves the reaction of H2S with oxygen to produce SO2, which is then converted to elemental sulphur through a series of catalytic reactions. Oxygen enrichment is a technique used to enhance the performance and efficiency of the SRU. By introducing a higher concentration of oxygen into the combustion process, the overall combustion reaction can be optimised, resulting in an increased sulphur recovery from sour gas and reduced emissions of sulphur compounds. The present study analyses the gate-to-gate comparative environmental impact of air versus oxygen enriched air used for combustion to recover 1.0 ton sulphur using GaBi software (8.5.0.79 version). The primary data was collected from the literature. The GaBi Indian extension database is used for the secondary data source. The results are reported using midpoint impact assessment methods CML 2001. The global warming potential for oxygen-enriched SRU is 232 kg CO2 eq. compared to 276 kg CO2 eq. for air enriched SRU. Similarly, the potential for abiotic depletion (elements + fossil), acidification, eutrophication, human toxicity, freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, photochemical ozone creation and terrestric ecotoxicity are higher for air based SRU than oxygen-enriched SRU. The analysis concludes that oxygen enrichment technology is a highly effective way to reduce the environmental impact of the SRU.

Techno-economic analysis of carbon molecular sieve membranes to produce oxygen enrichment air

Oxygen Enriched Air (OEA) is essential for medical applications, metal production, chemical production, the petrochemical industry, and energy processes. In this work, carbon molecular sieve membranes (CMSM) and membrane systems are analyzed concerning their technical and economic feasibility to produce OEA for medical, post-combustion, and oxy-combustion applications. Process parameters, such as stage-cut, feed-to-permeate pressure ratio, membrane area, and the number of stages, were studied to assess the technical and economic feasibility of this technology. In this work, it was observed that for each membrane, there is a permeating oxygen concentration that minimizes the specific oxygen cost. The production of 56 tonO2·day−1 for a combustion enhancement process with a concentration of 72 % was obtained in a single-stage with a specific cost of 61.0 €·tonO2−1. A single-stage is also effective for producing OEA for medical applications (required concentration of 82 %) at a minimum separation cost of 45.8 €·tonO2−1. However, a two-stage system is required to produce OEA with a concentration higher than 95 % for oxy-combustion with an OEA production cost of 83.8 €·tonO2−1. These production costs are lower than those obtained with two different commercial membranes and are competitive with medium-scale cryogenic distillation and pressure swing adsorption processes.

Influence of secondary air blade angle and oxygen-rich combustion characteristics of an improved Babcock swirl burner

Innovations in research methods and stable combustion technologies were urgent to enhance flexibility in faulty coal-fired boiler. Focusing boiler start-stop processes was vital for effective peak shaving in power plants. The integration of enriched oxygen stable combustion with swirling techniques showed promise in improving low-load performance. In the cold single–phase experiment, the influence of secondary blade angle on the flow field of an improved Babcock burner was observed. Industrial experiments were conducted on a 700 MW boiler, exclusively implementing the improved burners in the lower layer of the boiler front wall. Stable annular recirculation zones were observed at the burner outlet with blade angles of 30°, 45°, 60°, and 75° for the secondary air. Increasing the blade angle expanded the recirculation zone length and decreased the gas net flow ratio. The angle, between 45° and 60°, facilitated air mixing and protected against outlet slagging and high-temperature corrosion. During cold start–up process of the boiler, supplying 0 kg·s−1 of pure oxygen to a single improved burner increased the flue gas temperature by about 50 °C within 0.4 m of the primary air duct outlet. Increasing the oxygen flow rate to 0.2456 kg·s−1 steadily raised the flue gas temperature at 405 MW. The gas temperature in the burner central region was generally lower than the secondary air zone, resulting in a longer ignition distance for the pulverized coal. Higher oxygen levels intensified the heating rate and reduced the ignition distance in the central region.

A numerical study of NOX and soot emissions in ethylene-ammonia diffusion flames with oxygen enrichment

Blending ammonia with hydrocarbon fuels is gaining interest due to its potential to significantly reduce carbon emissions from the combustion of these blends. Additionally, studies have provided strong evidence of oxygen enhanced combustion to reduce soot emissions and improve flame stability. The present work attempts to leverage the benefits of both strategies, ammonia doping and oxygen enhanced combustion, by considering ethylene diffusion flames. Simulations are performed using the CHEMKIN-Pro software. A reaction mechanism with 372 species and 13,847 reactions is developed by combining gas phase chemistries for ethylene, NH3 and NOX, along with a detailed soot mode. The mechanism is extensively validated for a range of fuel blends in terms of flame structure, intermediate hydrocarbons, soot precursors and soot. Oxygen enrichment is achieved by removing certain amount of nitrogen from oxidizer stream and adding it to fuel stream, and thereby maintaining a nearly constant flame temperature. Extensive analysis is carried out to characterize the chemical and dilution effects of ammonia doping on flame structure, soot precursors, soot, and NOX in ethylene flames with varying levels of oxygenation. Further, dominant reaction pathways for several soot precursors and NOx are identified through detailed rate of production analyses. Results indicate that ammonia doping in ethylene flames leads to substantial increase in NOX emissions, while oxygenation has negligible influence on NOX emissions. In contrast, both NH3 doping and oxygenation provide significant reduction in the formation of soot precursors and soot. Oxygenation achieves this reduction through both hydrodynamic and flame structure effects, as the flame shifts from oxidizer side to fuel side. On the other hand, NH3 doping reduces the rates of important reactions for the formation of soot precursors, as the concentrations of relevant species (C2H2, C3H3, C3H3-P, C3H3-A etc.) decrease due to their consumption through reactions with species like NCO and CN formed from NH3. Moreover, the effectiveness of NH3 doping is further enhanced when combined with oxygenation. Hence, NH3 doping and oxygenation are found to be effective and synergistic strategies in reducing soot emissions, and their proper combination could provide near zero soot emissions.

Basic property and oxygen defect-enhanced nitrogen-doped layered hydroxide-derived oxides MAlO (M = Ni, Co) for carbonyl sulfide hydrolysis at low temperature

Catalytic hydrolysis has been considered the most efficient method for the removal of carbonyl sulfide (COS). However, high-efficiency catalyst was urgently desired. In the present work, nitrogen-doped layered hydroxide-derived oxides (Ni(Co)Al-N) were successfully prepared. It was revealed that N enriched basic sites and oxygen vacancies were well developed for the prepared catalyst. And the catalytic activity was improved significantly. Among the catalysts, the NiAl-N catalyst exhibited the best catalytic activity (can reach 780 min COS 100 % conversion) and lowest activation energy. The concept of OH generation potential was firstly proposed to evaluate the contribution of basic sites to the improvement of catalytic activity. The OH generation potential was greatly improved due to N doping. More importantly, the enhanced basic property and oxygen defect content jointly contributed to the enhancement of catalytic activity. Besides, COS cannot adsorb on the catalyst surface and the reaction obeyed an E-R mechanism. Namely, H2O first adsorbed on basic sites to form OH groups, then COS reacted directly with the formed OH groups, and to generate H2S and CO2 products. HCO3– and HSCO2− were the main intermediate species, and the rate-determining step was the reaction between OCOSH* and H* to form CO2 and H2S.

Study on the Effect of High-Concentration Oxygen Enrichment on Engine Performance and Exhaust Emissions Using Diesel Fuel and Palm Biodiesel Substitute Fuel

Air pollution remains a big issue in many countries. One form of air pollution comes from the use of fossil fuels as the primary fuel in the power generating and transportation sectors. Diesel engines are employed in a variety of industries due to their dependability, durability, and efficiency. Enhancing the availability of oxygen within the combustion chamber is one technique for reducing exhaust gas emissions and optimizing diesel engine combustion. The aim of this study is to investigate how oxygen enrichment in diesel engines with diesel fuel and biodiesel affects their performance and emissions. The modeling in this research was carried out using AVL BOOST version 2011 software based on experimental results of the YANMAR TF 155 R-DI diesel engine at 1200 rpm with and without oxygen enrichment. Modeling was performed based on the baseline parameter of a diesel engine with gradual loads at 50%, 75%, and 100%. The oxygen concentration was increased to 30.6%, 37.8%, 45%, and 54% by mass. The results show an increase in the maximum heat release rate (HRR) and the mass fraction burned (MFB) up to 90% for both fuels. The peak heat release rate of biodiesel shifts around 6 J/degree and the brake-specific fuel consumption (BSFC) is up to 0.0035 kg/kWh higher than that of diesel fuel. When compared to diesel fuel, the thermal efficiency and BSFC of biodiesel usage are around 0.3% and 0.028 kg/kWh, respectively. NOx emissions increase due to higher combustion temperatures and more oxygen availability. Biodiesel emits 50% less NOx than diesel fuel, presumably due to a lower combustion temperature. As a result, while high-concentration oxygen enrichment improves combustion and lowers soot emissions, it raises NOx emissions. Soot emissions were reduced as a result of the enhanced combustion process, while NOx emissions rose due to higher combustion temperatures and increased oxygen availability.

Experimental and numerical investigation of methane combustion in a HCCI engine under enriched oxygen conditions

The challenge in the energy transition lies in the intermittent nature of renewable energy, requiring the development of effective storage methods. E-fuels are considered a promising solution, with potential applications to Homogeneous Charge Compression Ignition (HCCI) engines known for their high thermal efficiency and low nitrogen oxide emissions. However, HCCI engines face limitations such as low power density and a narrow operating range. To overcome these issues, oxygen-enriched combustion is proposed, aiming at enhancing the mixture reactivity and expanding the operating range by decreasing the intake temperature. As the potential of the expansion of the operating range has never been investigated, we performed an experimental campaign using a methane-fuelled HCCI engine at variable oxygen fractions in the oxidizer. To further elucidate the effects of oxy-fuel combustion, we also performed a kinetic analysis of the reactions driving the combustion behaviour. It has been experimentally found that increasing the oxygen content in the mixture, up to 90%, has a significant potential to decrease the needed intake temperature (up to 70 °C) of the charge to keep the Maximum Pressure Rise Rate (MPRR) below the safety threshold of 8 bar/CAD. Despite the notable IMEP increase achieved, operating the engine at high oxygen content presents significant technical challenges. Therefore, to make HCCI engines competitive with other combustion modes, it is essential to combine oxygen enrichment with additional power density enhancement techniques. The kinetic analysis has highlighted that the mixture is less sensitive to intake temperature changes at higher oxygen percentages (above 50%) and that the rates of the main reactions involved in methane and OH consumption are highly enhanced by oxygen addition.

Enhancing pure NH3 combustion: Impacts of O2 enrichment under MILD conditions in a 20-kW semi-industrial scale furnace

This experimental work provides insights into the effects of oxygen (O2) enrichment on pure ammonia (NH3) combustion in a 20-kW semi-industrial scale furnace featuring an industrial-grade burner operated under MILD/Flameless conditions. The impact of O2 enrichment on the NH3 combustion stabilization, the flame and furnace temperature, the exhaust emissions, and the OH* chemiluminescence were explored. The tests were conducted by varying O2 concentration in the oxidizer stream from 21 % to 50 % and using two different oxidizer injectors to achieve average inlet velocities of 80 m/s and 150 m/s while keeping the inlet power and the total oxidizer mass flow rate constant. Stable flameless combustion with a distributed reaction zone and a consistent and uniform temperature profile throughout the combustion chamber was achieved with O2 enrichments higher than 34 %. Nevertheless, high levels of NH3 slips were observed, which were drastically reduced to negligible concentrations at higher O2 enrichments. On the contrary, NO emissions increased with the O2 fraction with an opposite non-linear trend compared to that of NH3 slip. An optimum trade-off between NOx emissions and NH3 slip was achieved by co-firing NH3 with O2=37 % with ID16 and 36 % with ID20 injector. This study also compares the behavior of pure O2-enriched NH3 combustion under flame and MILD combustion conditions to highlight the advantages of oxygen-enhanced NH3 flameless combustion. While operating in flame mode ensured a stable ammonia oxidation process already at low O2 enrichment=30 %, NO emissions and NH3 slips were significantly higher than those measured under MILD conditions. Finally, the impact of varying industrial load and the related heat balance on the NH3 slip was assessed at different levels of O2 enrichments at a fixed equivalence ratio. The overall results show that O2-enriched flameless ammonia combustion can simultaneously expand the range of stable combustion and reduce NO and NH3 emissions.

Analysis of the Influence of Oxygen Enrichment in the Blast on Temperature Field and NO Generation near the Burner in Reheating Furnace

Analysis of the Influence of Oxygen Enrichment in the Blast on Temperature Field and NO Generation near the Burner in Reheating Furnace

An investigation of the structural and electronic origins of enhanced chemical looping air separation performance of B-site substituted SrFe1-xCoxO3-δ perovskites.

Chemical looping air separation (CLAS) is a promising process intensification technology for extracting oxygen from air for oxygen enrichment in process streams. Co-doped strontium ferrites (SrFe1-xCoxO3-δ) have been found to have outstanding activities for CLAS processes. In this study, we explore the underlying factors driving the enhancement in oxygen uptake and release performance of perovskite structured SrFe1-xCoxO3-δ oxygen carriers for CLAS. Phase-pure perovskites, with B site substituted by up to 75 mol% Co, were prepared by a sol-gel method and systematically investigated through a wide range of well controlled experimental and computational approaches. While all SrFe1-xCoxO3-δ oxygen carriers showed excellent cyclic stability and structural reversibility over CLAS cycles, increased B site occupancy by Co resulted in monotonic decrease in onset temperature for oxygen release and increase in oxygen carrying capacity. These experimental trends can be fundamentally explained by an increase in the structural tolerance factor, an elevation in transition metal d-band, as well as an increased degree of hybridization between the metal d-band and the O p band. Therefore, these ab initio structural and electronic descriptors are useful design rationales for the hypothesis-driven synthesis of high-performing oxygen carriers for CLAS.

Evaluation of the effects of oxygen enrichment on combustion stability of biodiesel through a PSO-EMD-RBF model: An experimental study

<abstract> <p>In this study, we processed the flame images of biodiesel combustion in industrial furnaces, classified and evaluated flame states using digital image processing techniques, and proposed a combustion stability index (CSI) using the particle swarm optimization (PSO) algorithm. In order to more accurately predict the combustion stability under different oxygen concentrations, we proposed a method that combines the Multi-Input Radial basis function neural network (RBF-NN) with empirical mode decomposition (EMD). Initially, the EMD method was employed to decompose the original time series of CSI. Subsequently, a decomposition model incorporating initial parameters and CSI was established using the radial basis function. The results of the computations indicate that the EMD-RBF-NN model significantly outperforms existing models in enhancing the accuracy of CSI.</p> </abstract>

Exploiting synergies between sustainable ammonia and nitric acid production: A techno-economic assessment

The decarbonization of the fertilizer industry is an important step towards a climate-neutral society. Nitric acid produced via the Ostwald process is a key precursor to nitrogen-based fertilizers, with the production of ammonia representing an important intermediate step. This work focuses on the search for synergies between the sustainable production of ammonia feedstocks – hydrogen and nitrogen – and nitric acid production in the Ostwald process: Oxygen a by-product of sustainable hydrogen and nitrogen production was considered for injection in the Ostwald process at 4 points. A techno-economic assessment was performed to identify the technical and economic potential of this air enrichment. In addition, the safety implications of applying a higher oxygen concentration in the ammonia combustion step of the Ostwald process was evaluated based on explosion limit simulations. The techno-economic assessment was based on a mono-pressure nitric acid plant with a plant capacity of 700t/d of pure nitric acid at a concentration of 60wt% in water. The investigations of injecting oxygen at four different points of the plant show that daily nitric acid production can be increased by 0.31% and final NOx concentration of the absorption column can be reduced by up to 43.6% by enriching the main air pipeline with oxygen. Optimal oxygen injection could reduce the capital costs by 0.41M€. Nevertheless, the operating costs dominated the final cash flow analysis with ammonia costs accounting for ca. 60% of the total operating costs. The CO2 price would need to increase to at least 233€/t to compensate for the higher green ammonia price and equalize the minimum selling price. As the oxygen injection at the main air line comes with safety risks due to the ammonia explosion limits, we evaluated the effect of O2-enrichment on the explosion limits of NH3-O2-N2 mixtures. The foreseen oxygen enrichment reduced the lower explosion limit only marginally. For a medium pressure plant at 5.8bar the lower explosion limit is reduced to 10.3% for the highest considered oxygen injection case, which is close to the applied ammonia concentration.

Plasma-engraved Co3O4 nanorods with enriched oxygen vacancies for efficient electrocatalytic ammonia synthesis

Plasma-engraved Co3O4 with enriched oxygen vacancies exhibits an FE of 98.9% and a noteworthy ammonia yield of 27.5 mg cm−2 h−1.