Pure Gas Research Articles

Microbial hydrogen sinks in the sand-bentonite backfill material for the deep geological disposal of radioactive waste.

The activity of subsurface microorganisms can be harnessed for engineering projects. For instance, the Swiss radioactive waste repository design can take advantage of indigenous microorganisms to tackle the issue of a hydrogen gas (H2) phase pressure build-up. After repository closure, it is expected that anoxic steel corrosion of waste canisters will lead to an H2 accumulation. This occurrence should be avoided to preclude damage to the structural integrity of the host rock. In the Swiss design, the repository access galleries will be back-filled, and the choice of this material provides an opportunity to select conditions for the microbially-mediated removal of excess gas. Here, we investigate the microbial sinks for H2. Four reactors containing an 80/20 (w/w) mixture of quartz sand and Wyoming bentonite were supplied with natural sulfate-rich Opalinus Clay rock porewater and with pure H2 gas for up to 108 days. Within 14 days, a decrease in the sulfate concentration was observed, indicating the activity of the sulfate-reducing bacteria detected in the reactor, e.g., from Desulfocurvibacter genus. Additionally, starting at day 28, methane was detected in the gas phase, suggesting the activity of methanogens present in the solid phase, such as the Methanosarcina genus. This work evidences the development, under in-situ relevant conditions, of a backfill microbiome capable of consuming H2 and demonstrates its potential to contribute positively to the long-term safety of a radioactive waste repository.

Corrosion and carburization of Ni3Al‐based superalloys in high‐temperature carbon dioxide

AbstractTo investigate the application of Ni3Al‐based superalloys in gas turbine cycle systems, this experiment exposed Ni3Al‐based superalloys to a 600°C/5 MPa environment with 99.995% pure CO2 gas. The corrosion and carburization behaviors and mechanisms were investigated in detail. The results reveal that with prolonged thermal exposure, the surface oxides of the samples tend to develop a continuous and homogeneous transition state alumina layer. This layer serves as a protective barrier, preventing the penetration and corrosion of external carbon‐containing and oxygen‐containing substances into the matrix. A small amount of carbon‐containing hazardous substances still penetrates the oxide layer or grain boundaries through highly diffusive pathways such as nanochannels, pores, and cracks, because the transition state of alumina is not completely dense. This leads to carbon deposition at the interface between the oxide layer and the matrix, where a mixture of alumina and amorphous carbon is formed at the interface.

Effect of Ar pressure on phase transition characteristics and charge transport mechanism in VO2 films grown by RF sputtering of V2O5

In this study, we report the growth and characterization of VO2 films deposited on YSZ (001) substrate employing RF magnetron sputtering of vanadium pentoxide (V2O5) target in pure Ar gas ambient. The VO2 film growth has been carried out at ∼700 °C for ∼15 min at ∼100 W RF power with a flow rate of ∼20 sccm at Ar gas deposition pressure of ∼3, ∼6, ∼20, and ∼40 mTorr. x-ray diffractometry and Raman spectroscopy show that the nearly pure VO2 phase achieved at lower Ar pressure, e.g., ∼3 and ∼6 mTorr transform into a multiphase V-O system at ∼20 and ∼40 mTorr. This pattern is also supported by the electrical transport measurements through the occurrence of hysteretic IMT in films grown at ∼3 and ∼6 mTorr and the absence of this signature in these films deposited at ∼20 and ∼40 mtorr Ar pressure. The most pronounced with the strongest hysteresis is seen in the Y6 film, and therefore, the optimum growth pressure in the present study is ∼6 mTorr. The suppression of IMT in Y20 and Y40 is attributed to the appearance of other V-O phases, which smear out the phase transition. The activation energy of the insulating phase is estimated from the Arrhenius fit to the ρ-T data is found to be ∼0.223 eV at ∼3 mTorr Ar pressure which increases to ∼0.311 eV for ∼6 mTorr film in the cooling cycle. The low temperature (120K≤T≤300K) transport conduction in all VO2 films is governed by Efros-Shklovskii’s variable range hopping (ES-VRH) mechanism with a systematic relation between growth conditions and phase transition characteristics. Thus, Argon gas pressure plays a critical role in growth and brings out the feasibility of VO2 films growth by RF sputtering of oxide V2O5 target under Argon ambient only.

Microscopic simulation study on the penetration property of pure hydrogen sulfide gas in polyethylene and polyvinylidene fluoride

The H2S penetration in the nonmetallic biogas pipelines and reinforced thermoplastic composite pipelines can lead to severe environmental pollution and disrupt the regular operations of oil and gas fields. Thus, delving into and comprehending the H2S penetration in polyethylene (PE) or polyvinylidene fluoride (PVF2) holds immense significance for both environmental preservation and industrial progress. In this study, Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) are employed to investigate and contrast the H2S penetration property within PE and PVF2 at 300–360 K and 0.1–1.5 MPa. The results indicate the diffusion and penetration coefficients decrease with decreasing temperature and pressure, while the solubility coefficient increases with decreasing temperature. Compared to PE, PVF2 demonstrates stronger resistance to H2S penetration, mainly due to H2S is difficult to diffuse in PVF2. The relationship between penetration coefficient and temperature is consistent with Arrhenius law. In 0.1 MPa, the activation energy of H2S in PE and PVF2 are 31,911 and 42,247 J/mol, respectively. Moreover, the relationship between activation energy and pressure is power function. The study also reveals the H2S diffusion in both PE and PVF2 follows the leap mechanism. These research findings can offer valuable guidance for reducing environmental pollution and ensuring industrial development.

Time-resolved investigations of a glow mode impulse dielectric barrier discharge in pure ammonia gas by means of E-FISH diagnostic

Time-resolved electric field strength measurements have been performed, using an electric-field induced second harmonic (E-FISH) diagnostic, in a nanosecond glow discharge of an impulse dielectric barrier discharge, in an ammonia gas environment. A temporal resolution of 2 ns and a spatial resolution estimated at 70 µm (given by laser waist) have been achieved. The comparative study of E-FISH measurements with and without a plasma discharge, operated at 4 kHz, reveal the presence of a persistent counter electric field, which is assumed to be caused by charge accumulation in between the AlN dielectrics used. Furthermore, by studying the influence of the applied voltage, the pressure, and the inter-dielectric distance, measurements seem to indicate the presence of charges remaining also in the post-discharge volume from the previous discharge to the next one.

Deux cents ans d’histoire des usages et mésusages du protoxyde d’azote

Deux cents ans d’histoire des usages et mésusages du protoxyde d’azote

Tuning the assembly of MgNiO2 nanoparticles-infused polysulfone membranes for efficient gas separation: The selectivity-permeability conundrum

The persistent surge in global energy demand, coupled with escalating environmental apprehensions, has underscored the imperative for adept and sustainable gas separation technologies. Mixed matrix membranes (MMMs) have surfaced as a promising avenue to confront these multifaceted challenges, synergistically harnessing the strengths of conventional polymeric membranes and nanoparticle reinforcements. In this work, MMMs have been tailored for gas separation applications by incorporating MgNiO2 nanoparticles as an additive into the polysulfone (PSf) matrix as they provide additional space (in the form of nanoscale voids) for gas diffusion, facilitating faster gas transport, promoting selective permeation of specific gases, and enhancing membrane stability, in addition to their versatility, ease of preparation, cost-effectiveness and high activity. The crystalline nature of MgNiO2 nanoparticles, as characterized by finely tuned grain sizes, has been validated by powder X-ray diffraction (XRD) analysis. Gas permeation experiments on the developed MMMs encompassing a diverse range of pure gases and gas mixtures have been performed. Among the different MMMs investigated, PSM1 with a composition of 100 mg MgNiO2 nanoparticles has yielded substantial enhancements in permeability and selectivity. The PSM1 membrane exhibits remarkable permeance of 56.9 for H2, 16.3 for CH4, and 15 GPU for CO2, having ideal selectivity ratios of 3.5 and 3.8 for H2/CH4 and H2/CO2, respectively. Finally, this work provides new directions for improving the trade of relationship between the selectivity and permeability of gas mixtures under relevant process conditions.

Magneto-Conductive and Magnetic Properties in La<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>MnO<sub>3 </sub>Thin Films on a-SiO<sub>2</sub> Substrates Produced by Metal Organic Decomposition Method

We have studied magneto-conductive and magnetic properties of La1-xSrxMnO3 (LSMO) thin films on a-SiO2 substrates produced by the metal organic decomposition (MOD) method. LSMO thin films for x = 0, 0.15 and 0.3 have been produced in a pure O2 gas atmosphere. Although LaMnO3 (LMO) single crystal is an antiferromagnetic insulator (AFI), LMO thin films we have produced show ferromagnetic metal (FM) properties for suitable heat treatment conditions. We consider that the excess of O2- ions in LMO thin films produced in a pure O2 gas atmosphere induces the strong hole self-doping into those and the LMO thin films change from AFI to FM. Whereas, the ordinary hole doping is also occurred in LSMO thin films at x > 0. Thus, the carrier doping for LSMO thin films at x > 0 is caused by the hole self-doping by O2- ions and the ordinary hole doping by the replacement of La3+ ions by Sr2+ ones. To investigate the crystallographic and surface structures of the LSMO thin films, X-ray diffraction and SEM measurements have been performed, respectively. From the X-ray diffraction measurement, we have found that all LSMO thin films have perovskite structure and are polycrystalline. From the SEM measurement, we have seen that the LSMO thin films are formed of the aggregation of LSMO fine particles. Electrical resistivities (ERs) and magneto-resistivity (MR) ratios of the LSMO thin films have been measured on the temperature dependence (4K-300K). From MR ratio measurements, the coercive forces of them have been obtained as a function of temperature, and the Curie temperatures have been estimated from the temperature dependences of the coercive forces. We have discussed the origin of the magneto-conductive and magnetic properties of LSMO thin films.

Robust approximation rules for critical electric field of dielectric gas mixtures

A semi-analytic method for quickly approximating the density-reduced critical electric field for arbitrary mixtures of gases is proposed and validated. Determination of this critical electric field is crucial for designing and testing alternatives to SF6 for insulating high voltage electrical equipment. We outline the theoretical basis of the approximation formula from electron fluid conservation equations, and demonstrate how for binary mixtures the critical electric field can be computed from the transport data of electrons in the pure gases. We demonstrate validity of the method in mixtures of N2 and O2, and SF6 and O2. We conclude with an application of the method to approximate the critical electric field for mixtures of SF6 and HFO1234ze(E), which is a high interest mixture being actively studied for high voltage insulation applications.

A semi-rigid co-poly(imide) derived from an isomeric mixture of monomers. Assessing gas transport properties in self-standing polymer membrane

Chemical structure and morphology of polymers are directly related with the membrane separation performance. Poly(imide)s (PIs) are the most widely used polymers in the preparation of membranes for gas separation applications; thus, research on the structural design of polymers is of great interest to develop new membranes. In the present work, we reported the synthesis, characterization, and measurement of the gas transport properties of a new co-poly(imide)s (PI-D2a-D2b-6FDA) prepared from a mixture of isomeric diamines. The co-poly(imide) synthetic route involved several steps, starting by a bromination reaction, followed by a double nucleophilic aromatic substitution giving an isomeric mixture of precursors, which suffered a Suzuki-Miyaura C–C cross-coupling reaction followed by the reduction of nitro groups to give two new isomeric diamines. Finally, diamines simultaneously reacted with the dianhydride 6FDA to obtain PI-D2a-D2b-6FDA. The co-poly(imide) had a Mn of 47.7 kDa and a Mw of 74.0 kDa with a PDI of 1.6. The sample exhibited a 10% weight loss at 540 °C, Tg of 280 °C, BET surface area of 110 m2 g−1, and wide-angle X-ray diffraction (WAXD) interchain d-spacing at 9.5 Å and 6.3 Å. Tensile strength, elongation at break and Young's modulus were 109.6 MPa, 6.66% and 2.18 GPa, respectively. co-Poly(imide) was soluble in various polar aprotic organic solvents such as DMSO, NMP, DMF, DMAc, THF, and chloroform, forming a self-standing dense film whose gas transport properties were measured. Pure gas permeability coefficients for H2, CO2, O2, N2, and CH4, were 47.28, 24.04, 4.35, 1.02, and 0.76 (Barrer), respectively, which follows a decreasing order by the increasing kinetic diameters of the respective gases. Ideal gas selectivities H2/N2, O2/N2, CO2/CH4, and CO2/N2 were 46.4, 4.3, 31.6, and 23.6, respectively. These gas transport properties were compared with the commercial polymer Matrimid®, showing higher gas permeability coefficients than Matrimid®.

Alkaline Earth Metal Aluminate Support for Selective Oxidative Coupling of Methane

AbstractThe oxidative coupling of methane (OCM) provides a direct route to transform methane into higher value products. The alkali metal tungstate catalysts have demonstrated high selectivity towards C2 products, ethane (C2H6) and ethylene (C2H4). However, the severe sintering of the SiO2 support limits the reaction rate requiring active site densification to compete with unselective gas phase combustion reaction especially at high pressure operations. This work studies alkaline earth metal oxides as supports for K2WO4 catalysts to maintain comparatively high surface area under OCM conditions. Among Mg, Ca, and Sr aluminates, the K2WO4/MgAl2O4 catalyst exhibited the highest C2 yields. To achieve high C2 product selectivity, a relatively large loading of K2WO4 (20 wt %) was required likely to cover the unselective surface sites of MgAl2O4 support. The catalyst further showed high levels of stability when utilized at high pressures (0.9 MPa) for over 60 h, without any change in product selectivity. The Mn/K2WO4/MgAl2O4 showed multifold higher CH4 conversion rate, compared with the SiO2 counterpart. The findings showcase the potential of the MgAl2O4 support as a viable candidate for alkali metal tungstate catalysts for OCM, which introduces high density of active components in given volume in the reactor, which induces high contribution of the catalyst relative to the pure gas phase oxidation.

Efficient adsorption separation of methane from C2–C3 hydrocarbons in a Co(II)-nodes metal–organic framework

Methane (CH4) as a substitute for other mineral fuels plays a crucial role in reducing energy consumption and preventing environmental pollution. The present study employs a solvothermal method to fabricate a porous framework Co-metal–organic framework (Co-MOF) containing two distinct secondary building units (SBUs): an anionic [Co2(μ2-OH)(COO)4(H2O)] and a neutral [CoN2(COO)2]. Notably, within the anionic SBUs, the coordinated water molecules induce the generation of divergent unsaturated Co(II) centers in the unidirectional porous channels, thereby creating open metal sites. The adsorption performance of Co-MOF towards pure component gases was systematically investigated. The results demonstrated that Co-MOF exhibits superior adsorption capacity for C2–C3 hydrocarbons compared to CH4, which offering the potential for efficient adsorption and separation of CH4 from C2–C3 hydrocarbons. The gas selectivity separation ratios of Co-MOF for C2H6/CH4 and C3H8/CH4 were calculated using the ideal adsorbed solution theory method at 273/298 K and 0.1 MPa. The results revealed that Co-MOF achieved remarkable equilibrium separation selectivity for CH4 and C2–C3 hydrocarbon gases among non-modified MOFs, signifying the potential of the synthesized Co-MOF for efficient recovery and purification of CH4 from C2–C3 hydrocarbons. Breakthrough experiments further demonstrate the ability of Co-MOF to purify methane from C2–C3 hydrocarbons in practical gas separation scenarios. Additionally, molecular simulation calculations further substantiate the propensity of anionic SBUs to interact with C2–C3 hydrocarbon compounds. This study provides a novel paradigm for the development of porous MOF materials in the application of gas mixture separation.

Review of Developed Methods for Measuring Gas Uptake and Diffusivity in Polymers Enriched by Pure Gas under High Pressure.

Gas emission and diffusion through polymeric materials play crucial roles in ensuring safety and monitoring gas concentrations in technology and industry. Especially, the gas permeation characteristics for O-ring material should be investigated for sealing application in a hydrogen infrastructure. To accommodate the requirements of different environments, we first developed four complementary effective methods for measuring the gas absorption uptake from polymers enriched by pure gas under high pressure and determining the gas diffusivity. The methods included the gravimetric method, the volumetric method, the manometric method, and gas chromatography, which are based on mass, volume, pressure, and volume measurements, respectively. The representative investigated results of the developed methods, such as gas uptake, solubility, and diffusivity are demonstrated. The measuring principles, measuring procedures, measured results, and the characteristics of the methods are compared. Finally, the developed methods can be utilized for testing transport properties, such as the leakage and sealing ability, of rubber and O-ring material under high pressure for hydrogen fueling stations and gas industry.

Preparation and characterisation of heat‐resistant fluorinated co‐polyimides and their gas transport characteristics

A series of fluorinated co-polyimide films based on the 6FDA-FTPPA/BAFL backbone were prepared from 4-(3-fluoro-4-(trifluoromethyl)phenyl)-2,6-bis(4-aminophenyl)pyridine (FTPPA),commercial 9,9-bis(4-aminophenyl)fluorene (BAFL), and 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), with varying ratios of FTPPA:BAFL units (3:1, 2:1, 1:1, 1:2, and 1:3). Co-polyimides not only exhibit high thermal stability ( Tg > 357°C), good optical properties (λcutoff > 327 nm) and hydrophobicity (contact angle >91.4°), but also favorable solubility properties in both high and low boiling organic solvents. The fractional free volume of the polymers was simulated using molecular mechanics and molecular dynamics and correlated with experimental gas separation data. The presence of bulky groups led to high FFVs (>17.8%) and the formation of large microcavities with diameters ranging from 5.48 to 5.72 Å, which efficiently increased gas permeability. In pure gas permeation experiments, the permeability coefficients of CO2 and He for the 6FDA-FTPPA/BAFL (3:1) film were 41.48 and 79.38 bar, respectively, which were superior to those of commercial Matrimid and Kapton in terms of gas permeability. In especial, the 6FDA-FTPPA/BAFL (1:2) and 6FDA-FTPPA/BAFL (1:3) in co-polyimide membranes exhibited the most attractive separation performance for O2/N2 gas pairs, approaching the 1991 Roberson upper limit.

The Four-Sinker Densimeter: A New Instrument for the Combined Investigation of Accurate Densities and Sorption Phenomena of Pure Gases and Gas Mixtures

An apparatus for high-accuracy gas density and adsorption measurements over the range of temperature from (193 to 423) K and pressure from (0 to 15) MPa is described. This instrument is based on the two-sinker densimetry principle and incorporates a magnetic suspension balance. In addition to the two “density sinkers”, two “sorption sinkers” are weighed to investigate density and adsorption of a gas sample simultaneously. The design of the sinkers increases the resolution of density and adsorption investigations and enables the correction of sorption effects on density measurements. The complete apparatus, including the sinkers, the temperature and pressure measuring systems, and the measurement procedure, is described. For the density range investigated, the uncertainty (k = 2) is between (0.0034 to 0.019) kg·\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot$$\\end{document}m−3, corresponding to (0.060 to 0.011)%. The uncertainty (k = 2) in adsorption load is (0.16 to 0.26) μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}g·\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot$$\\end{document}cm−2. Density measurements at T = (283 and 293) K and pressures up to 10 MPa of high-purity argon and nitrogen validate the instrument for density. Adsorption measurements of high-purity carbon dioxide and propane on a gold surface validate the instrument for adsorption investigation at T = (283 and 293) K and up to the saturation pressure of the investigated gas. The apparatus was used to measure the binary mixture (0.75 CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{CO}_2$$\\end{document} + 0.25 C3H8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{C}_3\ ext{H}_8}$$\\end{document}). In the future, the apparatus will also be used to accurately determine dew-point densities and pressures of pure gases and gas mixtures.

Research on Dual Fuel Combustion Characteristics of PFI Natural Gas +DI Gasoline in Large Cylinder Diameter Engine

A 3D simulation model of a single cylinder of a natural gas engine was established. PFI natural gas DI gasoline was used to control the time matching between injection and ignition, so that gasoline could form a small active stratified area near the spark plug. The combustion characteristics under different matching conditions were studied, and finally compared with pure natural gas. It is found that gasoline can be used in large cylinder diameter natural gas engine in a small range, which can accelerate the combustion of natural gas fuel, shorten the time used by CA0-CA5 by 77.6%, shorten the time used by CA5-CA90 by 26.5%, and increase the indicated thermal efficiency of natural gas engine by 1.4%.

Increasing biohydrogen production from swine wastewater influenced by anaerobic consortium and nickel ferrite nanoparticles

Screening of efficient microbial consortia and supplementing nanoparticles for pure hydrogen gas evolution have recently become urgent issues in the field of wastewater-derived hydrogen production. In this study, a newly isolated anaerobic consortium combining with nickel ferrite (NiFe2O4) nanoparticles (NPs) was applied to increase the biohydrogen production from swine wastewater. The suitable swine-wastewater-to-rice-straw-hydrolysate proportion was determined as 2:3, which corresponded to a cumulative hydrogen production of 1560.4 ± 10.3 mL/L. The addition of 200 mg/L NiFe2O4 NPs was found to be the most favorable for hydrogen gas evolution, resulting in a cumulative hydrogen production that was 21.8 % higher than that of the control (0 mg/L). Moreover, with the optimal dose (200 mg/L) of NiFe2O4 NPs, butyric acid was converted to the dominant volatile fatty acid, the microbialcommunity was dominated by Clostridium_sensu_stricto and Rummeliibacillus, and the relative expression of hydrogenase gene increased 175.4 ± 31.7-fold after 24 h of fermentation. The changes in microbial metabolism, distribution, and hydrogenase gene expression are helpful to increase the biohydrogen production with the addition of optimal dose of NiFe2O4 NPs.

Theoretical investigation of hydrogen sulfide capture from methane binary mixture using s-heptazine-based metal-organic framework.

MOFs are promising candidates for the capture of H2S and CO2 from raw biogas. The presence of H2S residues in natural gas pipelines can cause corrosive damage and reduce energy efficiency. H2S capture from biogas presents several challenges due to its high toxicity and its corrosiveness. Microporous MOFs incorporating Lewis basic sites have demonstrated efficient capture of small and polar gas molecules such as CO2 and H2S from gas binary mixtures. In the quest to design and investigate functional materials to support the energy transition, specifically for the purification of RNG gas, we theoretically investigated the potential of s-heptazine-based IRH-1 for H2S capture from CH4 mixtures. IRH-1 exhibited significantly higher adsorption capacities for H2S (2.60 mmol/g) and CO2 (2.68 mmol/g) compared to CH4 (0.98 mmol/g) at 100 kPa and 298 K simulated by GCMC. All computed average energies for H2S were below 20 kJ/mol, indicating an exothermic physisorption behavior within the pores of IRH-1. IAST revealed remarkable H2S selectivity of IRH-1 for CH4/H2S binary mixtures at 5%, 10%, 15%, and 20% of H2S at 100 kPa. GCMC simulations were performed with the BIOVIA Materials Studio 5.0 package using LJ potentials and UFF parameters to investigate the adsorption of pure H2S gas in the IRH-1 material. The IAST method was used to predict the adsorption behavior of H2S in different H2S/CH4 gas mixtures. The IAST calculations were performed using the Python package pyIAST, which allows the prediction of adsorption isotherms for mixed gases based on the adsorption isotherms for pure gases by numerical integration of the Gibbs adsorption approach.

Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen.

Herein, we propose an oxygen-containing species coordination strategy to boost CO2 electroreduction in the presence of O2. A two-dimensional (2D) conjugated metal-covalent organic framework (MCOF), denoted as NiPc-Salen(Co)2-COF that is composed of the Ni-phthalocyanine (NiPc) unit with well-defined Ni-N4-O sites and the salen(Co)2 moiety with binuclear Co-N2O2 sites, is developed and synthesized for enhancing the CO2RR under aerobic condition. In the presence of O2, one of the Co sites in the NiPc-Salen(Co)2-COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO2 molecules and stabilize the key intermediate *COOH of the CO2RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni-N4-O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO2RR. Thus, NiPc-Salen(Co)2-COF exhibits high oxygen-tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) of 97.2 % at -1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm-2 at -1.1 V in the presence of 0.5 % O2, which is superior to that in pure CO2 feed gas (FECO=94.8 %, jCO=19.9 mA cm-2). Notably, the NiPc-Salen(Co)2-COF achieves an industrial-level current density of 128.3 mA cm-2 in the flow-cell reactor with 0.5 % O2 at -0.8 V, which is higher than that in pure CO2 atmosphere (jCO=104.8 mA cm-2). It is worth noting that an excellent FECO of 86.8 % is still achieved in the presence of 5 % O2 at -1.0 V. This work provides an effective strategy to enable the CO2RR under O2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.

Boosting CO2 Electroreduction over a Covalent Organic Framework in the Presence of Oxygen

AbstractHerein, we propose an oxygen‐containing species coordination strategy to boost CO2 electroreduction in the presence of O2. A two‐dimensional (2D) conjugated metal‐covalent organic framework (MCOF), denoted as NiPc‐Salen(Co)2‐COF that is composed of the Ni‐phthalocyanine (NiPc) unit with well‐defined Ni−N4−O sites and the salen(Co)2 moiety with binuclear Co−N2O2 sites, is developed and synthesized for enhancing the CO2RR under aerobic condition. In the presence of O2, one of the Co sites in the NiPc‐Salen(Co)2‐COF that coordinated with the intermediate of *OOH from ORR could decrease the energy barrier of the activation of CO2 molecules and stabilize the key intermediate *COOH of the CO2RR over the adjacent Co center. Besides, the oxygen species axially coordinated Ni−N4−O sites can favor in reducing the energy barrier of the intermediate *COOH formation for the CO2RR. Thus, NiPc‐Salen(Co)2‐COF exhibits high oxygen‐tolerant CO2RR performance and achieves outstanding CO Faradaic efficiency (FECO) of 97.2 % at −1.0 V vs. the reversible hydrogen electrode (RHE) and a high CO partial current density of 40.3 mA cm−2 at −1.1 V in the presence of 0.5 % O2, which is superior to that in pure CO2 feed gas (FECO=94.8 %, jCO=19.9 mA cm−2). Notably, the NiPc‐Salen(Co)2‐COF achieves an industrial‐level current density of 128.3 mA cm−2 in the flow‐cell reactor with 0.5 % O2 at −0.8 V, which is higher than that in pure CO2 atmosphere (jCO=104.8 mA cm−2). It is worth noting that an excellent FECO of 86.8 % is still achieved in the presence of 5 % O2 at −1.0 V. This work provides an effective strategy to enable the CO2RR under O2 atmosphere by utilizing the *OOH intermediates of ORR to boost CO2 electroreduction.