High CH4 Research Articles

Characteristics and mechanism of MBT anomaly of Karakum desert related with the Hindu Kush earthquake

AbstarctThe Hindu Kush is seismically active zone locates to the southwest of Pamir Plateau. Earthquakes are frequent here, but very a few relevant studies on earthquake anomalies was found. We investigated the abnormal change of satellite microwave brightness temperature (MBT) related with the recent Mw 6.4 earthquake occurred on January 11, 2024 near the Karakum Desert, Hindu Kush. We found a significant positive MBT anomaly appeared in the eastern part of Karakum Desert, on the immediate west of the epicenter, from three days before and two days after the earthquake. The temporal characteristics of the positive MBT anomaly can be described in sequence as follows: pre-earthquake (pre-EQ) rising, near-earthquake (near-EQ) enhancing, co-earthquake (co-EQ) peaking, after-earthquake (after-EQ) persisting and dissipating eventually. Validating with multi-source auxiliary data such as surface temperature (ST), microwave polarization difference index (MPDI), soil moisture (SM), rainfall and snowfall, we confirmed the positive MBT anomaly appeared in the Karakum Desert from January 10 to January 13 was attributed to the seismic activity but not meteorological factors. The upward transfer of P-hole particles, activated in the deep hypocenter area by accumulated crustal stress during the pre-, co- and after-EQ period, to the Quaternary surface along the stress gradient, was believed to have reduced the local ground surface dielectric constant and amplified the microwave radiation, which leading subsequently to the positive MBT anomalies. In addition, we found there was also abnormal locally high CH4 concentration occurred near the epicenter one day before the earthquake, which was probably related to the fault relaxing and CH4 releasing before the impending earthquake. This study has reference significance for identifying potential MBT anomalies during the seismogenic period and for the earthquake early warning in Hindu Kush region.

An Investigation of the Catalytic Activity of Inconel and Stainless Steel Powders in Reforming Primary Syngas

Biomass is perhaps the only renewable resource on the planet capable of delivering molecules similar to those derived from petroleum, and one of the most developed technologies to achieve this is gasification. When it comes to biomass conversion into fuels and commodities, supercritical water gasification (SCWG) could offer promising solution for producing hydrogen-rich syngas. However, the presence of methane (CH4) and carbon dioxide (CO2) in the syngas could negatively impact downstream processes, particularly when carbon monoxide is also required. Hence, improving the quality of the syngas produced from biomass gasification is essential for promoting the sustainability of several industrial processes. In this context, understanding the principles of the dry reforming of methane (DRM) becomes essential for upgrading syngas with high CH4 and CO2 content, especially when the carbon monoxide content is low. In addition to the experimental conditions used in such process, it has been reported that the material composition of the reactor can impact on reforming performance. Hence, this work aims at comparing the catalytic efficacy of Inconel and stainless steel for reforming syngas derived from SCWG under standard DRM conditions. In this specific work, the metals were directly used as catalyst and results showed that when using Inconel powder, CH4 conversion increased from 3.03% to 37.67% while CO2 conversion went from 23.16% to 51.48% when compared to stainless steel. Elemental and structural analyses revealed that the Inconel’s superior performance might be due to its high nickel content and the formation of active oxide compounds, such as FeNiO, FeCrO3, Fe3O4, Cr2O3, and Cr2NiO4, during the reaction. In contrast, Fe3O4 was the only oxide found in stainless steel post-reaction. Additionally, increasing the total gas feed flow rate was shown to reduce CH4 and CO2 conversions, supporting the known impact of residency time on catalytic efficiency.

Gold Single Atom Doped Defective Nanoporous Copper Octahedrons for Electrocatalytic Reduction of Carbon Dioxide to Ethylene.

Electrocatalytic CO2 reduction into high-value multicarbon products offers a sustainable approach to closing the anthropogenic carbon cycle and contributing to carbon neutrality, particularly when renewable electricity is used to power the reaction. However, the lack of efficient and durable electrocatalysts with high selectivity for multicarbons severely hinders the practical application of this promising technology. Herein, a nanoporous defective Au1Cu single-atom alloy (De-Au1Cu SAA) catalyst is developed through facile low-temperature thermal reduction in hydrogen and a subsequent dealloying process, which shows high selectivity toward ethylene (C2H4), with a Faradaic efficiency of 52% at the current density of 252 mA cm-2 under a potential of -1.1 V versus reversible hydrogen electrode (RHE). In situ spectroscopy measurements and density functional theory (DFT) calculations reveal that the high C2H4 product selectivity results from the synergistic effect between Au single atoms and defective Cu sites on the surface of catalysts, where Au single atoms promote *CO generation and Cu defects stabilize the key intermediate *OCCO, which altogether enhances C-C coupling kinetics. This work provides important insights into the catalyst design for electrochemical CO2 reduction to multicarbon products.

Isoreticular Tolerance and Phase Selection in the Synthesis of Multi-Module Metal-Organic Frameworks for Gas Separation and Electrocatalytic OER.

Although metal-organic frameworks are coordination-driven assemblies, the structural prediction and design using metal-ligand interactions can be unreliable due to other competing interactions. Leveraging non-coordination interactions to develop porous assemblies could enable new materials and applications. Here, we use a multi-module MOF system to explore important and pervasive impact of ligand-ligand interactions on metal-ligand as well as ligand-ligand co-assembly process. It is found that ligand-ligand interactions play critical roles on the scope or breakdown of isoreticular chemistry. With cooperative di- and tri-topic ligands, a family of Ni-MOFs has been synthesized in various structure types including partitioned MIL-88-acs (pacs), interrupted pacs (i-pacs), and UMCM-1-muo. A new type of isoreticular chemistry on the muo platform is established between two drastically different chemical systems. The gas sorption and electrocatalytic studies were performed that reveal excellent performance such as high C2H2/CO2 selectivity of 21.8 and high C2H2 uptake capacity of 114.5 cm3/g at 298 K and 1 bar.

Isoreticular Tolerance and Phase Selection in the Synthesis of Multi‐Module Metal‐Organic Frameworks for Gas Separation and Electrocatalytic OER

Although metal‐organic frameworks are coordination‐driven assemblies, the structural prediction and design using metal‐ligand interactions can be unreliable due to other competing interactions. Leveraging non‐coordination interactions to develop porous assemblies could enable new materials and applications. Here, we use a multi‐module MOF system to explore important and pervasive impact of ligand‐ligand interactions on metal‐ligand as well as ligand‐ligand co‐assembly process. It is found that ligand‐ligand interactions play critical roles on the scope or breakdown of isoreticular chemistry. With cooperative di‐ and tri‐topic ligands, a family of Ni‐MOFs has been synthesized in various structure types including partitioned MIL‐88‐acs (pacs), interrupted pacs (i‐pacs), and UMCM‐1‐muo. A new type of isoreticular chemistry on the muo platform is established between two drastically different chemical systems. The gas sorption and electrocatalytic studies were performed that reveal excellent performance such as high C2H2/CO2 selectivity of 21.8 and high C2H2 uptake capacity of 114.5 cm3/g at 298 K and 1 bar.

Crystal‐Facet Engineering of Mesoporous CuS Cascade Nanoreactors Enhances Photocatalytic C‐C Coupling of CO2‐to‐C2H4

Crystal‐facet heterojunction engineering of mesoporous nanoreactors with highly redox‐active represents an efficacious strategy for the transformation of CO2 into valuable C2 products (e.g., C2H4). Herein, hollow mesoporous cube‐like CuS nanoreactors (~860 nm) with controlled anisotropic crystal‐facets are prepared through an interfacial‐confined ion dynamic migration‐rearrangement strategy. The regulation of the S2‐ ion concentration facilitates the modulation of the highly active (110) to (100) crystal‐facet ratios from 0.119 to 0.288, and induces the formation of anisotropic crystal‐facet heterojunctions. The controllable crystal‐facet heterojunctions trigger the directional charge carrier migration, and are accompanied with the formation of tandem S‐defect sites (Cu0‐S1@S3). Both of them promote the efficient electron‐hole pair dissociation and attain asymmetric C‐C coupling. The hollow mesoporous CuS nanoreactors with optimized crystal‐facet ratio of 0.224 (HMe‐CuS‐3) deliver a high selectivity of 72.7% for the photocatalytic reduction of CO2 to acetylene (C2H2). Further constructed Au‐(110) and Co3O4‐(100) spatially separated cascade nanoreactors (SS‐Au@Co3O4‐CuS) achieve CO2‐C2H4 photoreduction, in which the Co‐sites enhance H2O dissociation to provide protons and the protonation of *CO to *COH. The *COH is further captured by Au‐sites to accomplish the asymmetric *CO‐*COH coupling and subsequent protonation, ensuring a high C2H4 generation rate of 4.11 μmol/g/h with a selectivity as high as 90.6%.

Crystal-Facet Engineering of Mesoporous CuS Cascade Nanoreactors Enhances Photocatalytic C-C Coupling of CO2-to-C2H4.

Crystal-facet heterojunction engineering of mesoporous nanoreactors with highly redox-active represents an efficacious strategy for the transformation of CO2 into valuable C2 products (e.g., C2H4). Herein, hollow mesoporous cube-like CuS nanoreactors (~860 nm) with controlled anisotropic crystal-facets are prepared through an interfacial-confined ion dynamic migration-rearrangement strategy. The regulation of the S2- ion concentration facilitates the modulation of the highly active (110) to (100) crystal-facet ratios from 0.119 to 0.288, and induces the formation of anisotropic crystal-facet heterojunctions. The controllable crystal-facet heterojunctions trigger the directional charge carrier migration, and are accompanied with the formation of tandem S-defect sites (Cu0-S1@S3). Both of them promote the efficient electron-hole pair dissociation and attain asymmetric C-C coupling. The hollow mesoporous CuS nanoreactors with optimized crystal-facet ratio of 0.224 (HMe-CuS-3) deliver a high selectivity of 72.7% for the photocatalytic reduction of CO2 to acetylene (C2H2). Further constructed Au-(110) and Co3O4-(100) spatially separated cascade nanoreactors (SS-Au@Co3O4-CuS) achieve CO2-C2H4 photoreduction, in which the Co-sites enhance H2O dissociation to provide protons and the protonation of *CO to *COH. The *COH is further captured by Au-sites to accomplish the asymmetric *CO-*COH coupling and subsequent protonation, ensuring a high C2H4 generation rate of 4.11 μmol/g/h with a selectivity as high as 90.6%.

The role of rumen microbiome in the development of methane mitigation strategies for ruminant livestock.

Ruminants play an important role in global food security and nutrition. The rumen microbial community provides ruminants with a unique ability to convert human indigestible plant matter, into high quality edible protein. However, enteric CH4 produced in the rumen is both a potent GHG and a metabolizable energy loss for ruminants. As the rumen microbiome constitutes 15-40% of the inter-animal variation in enteric CH4 emissions, understanding the microbiological mechanisms underpinning ruminal methanogenesis and its interaction with the host animal, is crucial for developing CH4 mitigation strategies. Variation in the relative abundance of different microbial species has been observed in cattle with contrasting residual CH4 emission and CH4 yield with up to 20% of the variation in inter-animal CH4 emissions attributable to the presence of a small number of microbial species. The demonstration of ruminotypes associated with high or low CH4 emissions suggests that interactions within complex microbial consortia and with their host are a major source of variation in CH4 emissions. Consequently, microbiome-assisted genomic approaches are being developed to select low CH4 emitting cattle, with breeding values for enteric CH4 being included as part of national breeding programmes. Generating rumen microbiome data for use in selection programs is expensive, therefore, identifying microbial biomarkers in milk or plasma to develop predictive models which include microbial predictors in equations based on animal related data, is required. A better understanding of the rumen microbiome has also aided the development and refinements of anti-methanogenic feed additives. However, these strategies, which increase the amount of reducing equivalents in the rumen ecosystem, do not generally result in an enrichment of propionate or an improvement in animal performance. Current research aims to provide alternative sinks to reducing equivalents and to stimulate activity of commensal microbes or the supplementation of direct fed microbials to capture lost energy. Furthering our knowledge of the rumen microbiome and its interaction with the host, will aid in the development of CH4 mitigation strategies for ruminant livestock.

Investigating the Biomethane Production Potential of Blends of Bovine Manure with Switchgrass (Panicum Virgatum L.) and Sugar Beet (Beta Vulgaris L.) Foliage

The research aimed to evaluate the biomethane (CH4) content of biogas generated from various combinations of cattle waste (CW), three different varieties of Switchgrass (SG) (Panicum virgatum L.) plants (Kanlow (SG1), Shawne (SG2), Alamo (SG3), and sugar beet (Beta Vulgaris L.) leaves (BL). A laboratory-scale biomethane application setup was established to determine the biomethane potential. Three different experimental designs were implemented as the 1st application group, 2nd application group, and 3rd application group within the research framework. Biogas produced in the setup was stored using valves and balloons under optimal storage conditions. The Optima Biogas - Portable Biogas Analyzer device was employed to analyze the biomethane content of biogas samples from the materials and mixtures in the application groups. Biogas values were recorded, and glass reactor-specific methane production values were calculated. The highest glass reactor-specific methane production value was found to be 7.28 m3CH4 m-3 Reactor day in the CW (50%)-SG (20%)-BL (30%) mixture. The components of the biogas produced from the treatment groups were identified, and the highest CH4 (biomethane) yield was obtained from BL (beet leaves) at 58.86% in materials and from the CW-BL mixture at 53.76% in mixtures. Biomethane yields of the materials in other mixtures ranged from 53.42% to 43.12%.

A Scalable Pore-space-partitioned Metal-organic Framework Powered by Polycatenation Strategy for Efficient Acetylene Purification.

Efficient separation of acetylene (C2H2) from carbon dioxide (CO2) and ethylene (C2H4) is a significant challenge in the petrochemical industry due to their similar physicochemical properties. Pore space partition (PSP) has shown promise in enhancing gas adsorption capacity and selectivity by reducing pore size and increasing the density of guest binding sites. Herein, we firstly employ the 2D→3D polycatenation strategy to construct a PSP metal-organic framework (MOF) Ni-dcpp-bpy, incorporating functional N/O sites to enhance C2H2 purification. The polycatenated framework with optimized pore size and regularity, exhibiting significant improvements over traditional PSP MOFs by resolving the critical contradiction of balancing C2H2 uptake (98.5 cm3 g-1 at 298 K, 100 kPa) and selectivity of C2H2/CO2 (3.4), C2H2/C2H4 (5.9), and C2H2/CH4 (96.4) in a MOF. Breakthrough experiments confirm high-purity C2H4 (>99.9 %) and high C2H2 productivity from binary and ternary mixtures. Notably, Ni-dcpp-bpy exhibits excellent water stability, scalability, and regenerability after 20 cycles for separating C2H2/CO2. Theoretical calculations verify that the strong binding of C2H2 is mainly attributed to the C-H⋅⋅⋅O/N interactions between host Ni-dcpp-bpy and guest C2H2 molecules. The polycatenation strategy not only improved industrial C2H2 purification efficiency but also enriched the design diversity of customized MOFs for other gas separation applications.

A simple approach to quantifying whole‐lake methane ebullition and sedimentary methane production, and its application to the Canadian Lake Pulse dataset

AbstractAquatic sediments represent a key component for understanding CH4 dynamics and emission to the atmosphere. Once produced in the sediments, CH4 is released either by diffusion at the sediment–water interface or by bubbling out to the atmosphere when total gas pressure in the sediment exceeds local ambient pressure due to high CH4 production. Although bubbling is one of the dominant CH4 emission pathways in lakes, direct measurements of this flux are hampered by its high spatiotemporal variability and methodological limitations. Here, we develop a conceptual approach to quantify CH4 production in lake sediments and particularly its release as bubbles based on simple measurements of bubble gas content and depth. Its main assumptions were empirically tested using > 200 long‐term bubble trap deployments collected from 4 temperate lakes. We then applied the developed methodology to a suite of 408 Canadian lakes to produce the first standardized large‐scale assessment of lakes CH4 ebullitive flux during summer. Our results show that lake sediments produced CH4 at a median rate of 3.3 mmol m−2 d−1 (ranged from 0.2 to 11.8 mmol m−2 d−1), releasing 33% via ebullition to the atmosphere. These rates are remarkably similar in magnitude to other regional estimates in the literature. Moreover, our approach revealed that catchment slope was an important determinant of both the lake‐wide ebullitive fluxes and the fraction of sediment CH4 production released as bubbles.

Polarization-Induced Internal Electric Field-Dominated S-Scheme KNbO3-CuO Heterojunction for Photoreduction of CO2 with High CH4 Selectivity.

The polarization-induced internal electric field (IEF) in ferroelectric materials could promote photogenerated charge transfer across the heterojunction interface, but the effect of polarization-induced IEF on the mechanism of photogenerated charge transfer is ambiguous. In this study, a KNbO3-CuO heterojunction was synthesized by depositing copper oxide (CuO) onto KNbO3. Incorporating CuO broadens the light absorption of KNbO3, thereby enhancing the dissociation of the photogenerated charges. The results show that the polarization-induced IEF in KNbO3 determines that the charge transport mechanism in the KNbO3-CuO heterojunction follows the S-scheme. Owing to the S-scheme heterojunctions and efficient CO2 capture and activation by CuO, the CH4 production rate of KNbO3-CuO increased by nearly 26 times compared to KNbO3. Additionally, the CH4 selectivity of KNbO3-CuO could reach up to 97.80%. This research offers valuable insights into enhancing the photogenerated charge separation and constructing heterojunctions.

A Rollar‐Type Resonant Photoacoustic Spectroscopy for Trace Gas Detection

ABSTRACTThis paper presents a miniature Rollar‐type resonant photoacoustic cell (RRPAC), consisting of two cylindrical resonant cavities and a buffer chamber. The finite element analysis of the acoustic field distributions for the RRPAC and T‐type resonant photoacoustic cell (TRPAC) is utilized, demonstrating that RRPAC can produce a greater photoacoustic signal than the conventional TRPAC. A high sensitivity trace C2H2 photoacoustic spectroscopy (PAS) system is successfully developed by combining a cantilever beam‐based acoustic sensor as the acoustic sensing unit and a high‐speed spectrometer as the demodulation unit with the RRPAC. The experimental results indicate that the 2f signal of the RRPAC at the first‐order resonance mode is approximately 1.5 times of the TRPAC with the same C2H2 concentration. The gas detection limit of the RRPAC PAS system for C2H2 is 40.7 ppb at an averaging time of 100 s. In comparison with the conventional TRPAC, the RRPAC exhibits higher sensitivity, thus providing a novel solution for the advancement of the PAS system.

Plasma Etch of IGZO Thin Film and IGZO/SiO2 Interface Diffusion in Inductively Coupled CH4/Ar Plasmas

InGaZnO (IGZO) has recently gained considerable attention as a promising alternative channel material for semiconductor devices. Thoroughly investigating and precisely controlling the manufacturing processes, including plasma etching of IGZO material, become essential for the fabrication of IGZO-channel devices. In this work the etching characteristics of IGZO thin films were systemically investigated in inductively coupled CH4/Ar plasmas with various gas ratios, bias voltages, and surface temperatures. The ion flux in CH4/Ar plasmas were analyzed using bias power and voltage, and the relative densities of CH and H radicals were quantified through optical actinometry. The change in the density of CH3 radicals, considered as the primary etchant, is also estimated based on plasma kinetics analysis. O2 plasma step was applied after CH4/Ar plasma to mitigate hydrocarbon deposition during CH4/Ar plasma processing. At low CH4 ratios the IGZO etch rate increases with a higher CH4 proportion, aligning with the ascending trend of CH3 radical density, which suggests that CH3 radical density acts as a limiting factor (radical-limited regime). However, IGZO etch rate decreases at high CH4 ratios, corresponding to the reduction in ion flux, which indicates that ion flux becomes a limiting factor in this ion-limited regime. IGZO etch rate shows a linear relationship with bias voltage and follows the Arrhenius equation with varying surface temperature in plasmas without bias voltage. A spontaneous etch rate model was proposed for radical-limited etch regime. In this model, the etch rate is determined by CH3 radical density and IGZO surface reactivity, where both ion energy and surface temperature play important roles. IGZO thin film was deposited on SiO2 during the fabrication of a three-dimensional ferroelectric field-effect transistor (FerroFET) device, and the interaction between IGZO and SiO2 in CH4/Ar plasmas was investigated using time-of-flight secondary ion mass spectrometry. The efficacy of removing IGZO atoms that had diffused into the below SiO2 network was enhanced when subjected to CH4/Ar plasma with a bias voltage compared to the process without bias voltage. However, exposure to CH4/Ar plasma resulted in a deeper diffusion of IGZO atoms into SiO2 network, primarily attributed to ion bombardment rather than elevated surface temperature. A significant improvement in surface smoothness was achieved after IGZO and SiO2 etch by introducing BCl3 into the SiO2 etching chemistry.

Direct Observation of Intermediates for Carbon Dioxide Reduction Reaction in Concentrated Electrolytes

There is a growing need to utilize CO2 and realize a carbon-neutral society from the perspective of environmental problems caused by CO2 from fossil fuel-based processes. In this trend, electrochemical carbon dioxide reduction reaction (CO2RR), which converts CO2 to valuable fuels and chemicals with renewable energy, is attracting attention[1]. However, CO2RR has many challenges, including its low product selectivity. In particular, the hydrogen evolution reaction (HER), which occurs at the potential close to the standard electrode potential of CO2RR, reduces the selectivity of CO2RR, especially in aqueous electrolytes such as KHCO3 [2] [3]. Therefore, we focus on a concentrated electrolyte, which is used as a means of HER suppression in water-based Li-ion batteries[4], to improve the selectivity of CO2RR. A concentrated electrolyte is an electrolyte with a high salt concentration, which can improve the electrochemical stability of water by creating a specific water environment[5]. Furthermore, due to its high salt concentration, the effect of anions and/or cations may become significant[6][7]. However, there has been no detailed understanding of how the electrolyte concentration affects the complex reaction pathway of CO2RR.Here, we report the effect of concentrated electrolytes on the reaction process of CO2RR by directly observing reaction intermediates in situ while applying the potential. The product selectivity of CO2RR in 22.2, 42.0, and 61.7 mol kg– 1 of concentrated electrolyte was evaluated. Gas chromatography (GC) analysis confirms the suppression of HER in the series of concentrated electrolytes compared to 0.1 M KHCO3, a common aqueous electrolyte. In addition, an increase in the Faradaic efficiency of C2H4 was observed in ~ 42.0 mol kg– 1, implying a concentration-dependent change in the CO2RR reaction pathway (Fig.1). To elucidate the cause of the high C2H4 selectivity, in situ surface-enhanced infrared absorption spectroscopy (SEIRAS), which allows direct observation of the reaction intermediates, was performed. The results showed that as the electrolyte concentration was increased, the peaks at 1400 to 1500 cm– 1 region became more pronounced at low potential. We also observed the difference in the potential dependency for the intensity of CO adsorbates peak at 2100 cm–1 by electrolyte concentration. We will then discuss the effect of electrolyte concentration on the intermediates, unraveling the concentration-dependent change of the C2H4 selectivity. The work highlights the use of concentrated electrolytes to open up additional knobs for tuning the product selectivity of CO2RR, simply by designing an electrolyte component.[1] De Luna, P. et al, Science. 2019 364, 350.[2] Pan, F.; Yang, Y. Energy Environ. Sci. 2020, 13, 2275–2309.[3] Hori, Y. et al, Electrochim. Acta. 1994 39, 1833–1839.[4] Han, J. et al, Energy Environ. Sci. 2023 16, 1480.[5] Ko, S. et al, Electrochem. Commun. 2020 116, 106764.[6] Shin, S. J. et al, Nat. Commun. 2022 13, 5482.[7] Varela, A. S. et al, ACS Catal. 2016 6, 2136-2144. Figure 1

Methane and carbon dioxide evasion from a mosaic of Amazon lakes, river channels, and inundated forests

Seasonally inundated forests are the largest type of wetland in the Amazon basin. Here we provide new data from inundated forests, a lake, and river channels during high water in the forested Anavilhanas archipelago (Negro River, Brazil). Evasion pathways of CH4 in flooded forests include tree trunks, diffusion from the water, and ebullition. Within flooded forest sites, diffusive CH4 fluxes were lowest (mean, 6.2 µmol m-2 h-1), ebullitive fluxes averaged 50 µmol m-2 h-1, and fluxes from the trees had the highest fluxes when expressed per inundated surface area (83 µmol m-2 h-1). The lake and river channels usually had higher CH4 and CO2 fluxes than inundated forests. Overall, mean CH4 fluxes from inundated forests in our study were lower than fluxes measured in nutrient-rich inundated forests. Our results contribute to understanding the heterogeneity of C fluxes from inundated forests. Water levels, currents and extent of inundated habitats contribute to variability in gas fluxes. Outgassing rates are expected to become more variable with projected periods of especially high and low water levels as the climate changes.

Regulating a sql layered coordination polymer into a rare fsc open framework with naphthalenedisulphonic acid pillar for C2H2/CO2 separation

The removal of carbon dioxide (CO2) from acetylene (C2H2) represents a pivotal industrial process for the production of high-purity C2H2. Nevertheless, the separation of C2H2 and CO2 is challenging due to their highly similar molecular sizes and physical properties. In this work, we report a fine regulation of a sql layered coordination polymer (termed NTU-107) into a rare fsc open framework (termed NTU-108) with naphthalenedisulphonic acid pillar for selective C2H2 capture from CO2-contained mixtures. NTU-107 was prepared by the reaction of 4-(1H-imidazol-1-yl)benzoic acid (L1) ligand and Cu2+ ion, showing a layered framework with a pore size of 4.2 Å. After inserting 1,5-naphthalenedisulphonic acid between the layers, a new pillar-layered open framework (5.8 Å) with sulphonic acid functional sites was prepared. Single-component gas adsorption experiments and breakthrough experiments demonstrated that NTU-108 with accessible sulphonic acid sites exhibits a high C2H2 absorption capacity and dynamic C2H2/CO2 separation performance at room temperature.

Oxygen/nitrogen co-doped flexible ultramicroporous carbon monolith with a high CH4 adsorption capacity for CH4/N2 separation from low-concentration coalbed methane

Developing novel carbon adsorbents with high CH4 adsorption capacity for CH4/N2 separation is always an imperative and challenging process, which could effectively mitigate global warming and fully utilizes low-concentration coalbed methane (CBM). Herein, a green and effective method is proposed to synthesize flexible porous carbon monolith without using binder and toxic/corrosive agents. Melamine sponge is selected as carbon source and nitrogen source, simultaneously as a three-dimensional flexible supporting framework, and glucose is used as second carbon source. The environment-friendly chemical agent potassium oxalate monohydrate (K2C2O4·H2O) is used as activator to control the ultramicroporous structure and O&N co-doped property via changing the activation temperature and the amount of K2C2O4·H2O. The optimal sample exhibits a record-high CH4 adsorption capacity of 1.95 mmol/g and a good IAST CH4/N2 selectivity of 5.58 at 25 °C and 1.0 bar, outperforming many other adsorbents. Above results originate from the synergistic effect of its high ultramicropore volume (0.26 cm3 g−1), suitable ultramicropore size (centered at 0.55 nm), abundant –OH groups and a certain amount of –COOH groups, as well as N-6 and N-5 species. Dynamic breakthrough experiments further approve that CH4/N2 mixture can be well separated on this carbon material under realistic condition. This work introduces a new pathway to prepare O&N co-doped flexible ultramicroporous carbon monolith adsorbent for efficient capture of CH4 from low-concentration CBM.

Dual‐Site NiO/Bi3O4Br Heterojunction Catalyst for High‐Efficiency CO2‐to‐CH4 Conversion

AbstractSolar light‐driven conversion of CO2 into chemicals with high calorific value is regarded as an upcoming carbon utilization technology for alleviating the energy crisis. This technique faces the challenge of low CO2 conversion and product yield due to charge recombination in the catalyst. In this paper, a dual‐reaction site heterojunction catalyst was designed and fabricated by combining NiO with Bi3O4Br nanosheets, for the separation of CO2 reduction and H2O oxidation semireactions, which effectively promoted electrons and holes separation. The resulting catalyst exhibited a high CH4 production rate (8.12 µmol/g) and selectivity (94.69%). Electron distribution and band structure were investigated to explain the satisfactory catalytic performance. In addition, combining the in‐situ DRIFTS results, a formic acid‐intermediated CO2‐to‐CH4 reaction pathway was proposed. This work aims to pave the way for CH4 production via CO2 photoreduction with high efficiency and selectivity.

Unexpected inhibition roles of methane nanobubbles on hydrate decomposition

Uncontrolled hydrate decomposition poses extraordinary risks, such as submarine landslides during hydrate exploitation, and gas leakage during hydrate storage/transportation. Previous studies suggested inhibitors can effectively prevent hydrate decomposition by adsorbing onto the hydrate surface. However, herein, we find inhibitors have very limited adsorption coverages on hydrate, which cannot fully explain their good performance. In this study, by combining experiments and molecular simulations, a new inhibition mechanism is proposed, in which nanobubbles act as the primary factor in inhibiting hydrate decomposition. Specifically, when PVP (a typical inhibitor) is added into the solution, its hydrophobic groups interact strongly with CH4, thereby increasing CH4 solubility and inducing the formation of CH4 nanobubbles. These nanobubbles are then encapsulated within the hydrate and inhibit hydrate decomposition by the following process: nanobubbles gradually become exposed to the aqueous phase during hydrate decomposition and release CH4 to the region near the nanobubble-hydrate interface. The high local CH4 concentrations near the nanobubble-hydrate interface would promote the formation of microstructures necessary for hydrate nucleation, thereby amplifying the driving force toward nucleation and consequently inhibiting hydrate decomposition. Our proposed “nanobubble inhibition mechanism” can provide a theoretical foundation for developing and applying inhibitors to prevent hydrate decomposition in various industrial applications.