Search Results (159)

This study examines the surface chemistry of platinum, palladium, rhodium, and ruthenium-substituted lanthanum strontium cobaltate perovskite catalysts in the context of the dry reforming of methane (DRM). The catalysts were synthesized by the solution combustion method and characterized by using a series of techniques. To explore the effect of noble metal ion substitution on the DRM, surface reaction was probed by CH₄/CO₂ TPSR using mass spectroscopy. It was recognized that La_1−xSr_xCo_1−yPd_yO₃ show the best activities for the reaction in terms of the temperature but became deactivated over time. CH₄/CO₂ temperature-programmed surface reactions (TPSRs) were set up to unravel the details of the surface phenomena responsible for the deactivation of the DRM activity on the LSPdCO. The CH₄/CO₂ TPSR analysis conclusively demonstrated the importance of lattice oxygen in the removal of carbon, which is responsible for the stability of the catalysts on the synthesized perovskites upon noble metal ion substitution. Full article

Anaerobic digestion (AD) for food waste (FW) treatment has faced many challenges, especially ammonia nitrogen, acid, and salinity inhibition at a high organic loading rate (OLR). Therefore, a systematic understanding of the issues arising during the FW AD process is a necessity under a high OLR (over 3 g-VS/L d). Primarily, in terms of ammonia nitrogen inhibition, ammonia ions inhibit methane synthesis enzymes, and free ammonia (FAN) contributes to the imbalance of microbial protons. Regulation strategies include substrate C/N ratio regulation, microbial domestication, and ammonia nitrogen removal. In addition, with regard to acid inhibition, including volatile fatty acid (VFA) and long-chain fatty acid (LCFA) accumulation, the elevated acid concentration can contribute to reactive oxygen species stress, and a solution to this includes the addition of alkaline agents and trace elements or the use of microbial electrochemical and biofortification technology and micro-aeration-based AD technology. Furthermore, in terms of salinity inhibition, high salinity can result in a rapid increase in cell osmotic pressure, which can cause cell rupture, and water washing and bio-electrochemical AD are defined as solutions. Future research directions are proposed, mainly in terms of avoiding the introduction of novel containments into these regulation strategies and applying them in large-scale AD plants under a high OLR. Full article

The present study aims to investigate a Pd catalyst on a complex multi-oxide medium-entropy support interlayer La₂O₃-CeO₂-ZrO₂-Al₂O₃ and its possible use as catalysts for methane abatement applications. The low-temperature N₂-adsorption, XRD, TEM, XPS, TPD, and TPR techniques were used to characterize the catalyst. The palladium deposition on the supports leads to the formation of PdO. After the catalytic tests, the metal-Pd phase was observed. The complete oxidation of methane on Pd/La-Ce-Zr-Al catalyst takes place at temperatures above 250 °C, and in the presence of water vapor, the reaction temperature increases to about 70 °C. The careful choice of constituent oxides provides a balance between structural stability and flexibility. The alumina and lanthanum oxide ensure the high specific surface area, while the simultaneous presence of zirconia and ceria leads to the formation of a mixed-oxide phase able to interact with palladium ions by incorporating and de-incorporating them at different conditions. The mechanism of Mars–van Kerevelen was considered as the most probable for the reaction of complete methane oxidation. The possibility of the practical application of Pd-modified La-Ce-Zr-Al catalyst is evaluated. The use of a mix of multiple rare and abundant oxides makes the proposed catalyst a cost-effective alternative. Full article

Anaerobic digestion (AD) converts organic waste into methane-rich biogas but often faces performance issues due to organic acid and ammonium nitrogen accumulation. This hinders methanogen growth and reduces methane production. Recent studies show that incorporating conductive materials (CMs) into the AD matrix can mitigate these issues by facilitating electron transfer between microorganisms. This process accelerates the oxidation of organic acids and ammonium ions, enhancing methane recovery. The effectiveness of CMs depends on their type, porosity, surface morphology, and conductivity, which foster a symbiotic microbial community. This comprehensive review paper aimed to (i) describe the influence of CMs on the growth and enrichment of the AD microbial community, (ii) quantify the enhancement of biodegradation and methane generation, and (iii) observe syntrophic interactions and interspecies electron transfer. The review also summarized the impact of different conductive materials on methane generation and the effect of operational parameters, e.g., dose, size, and external voltage application, on the conductive electrodes. The study summarized that the different conductive materials have different influences, and their application in the AD matrix has to be realistic based on availability and economic benefits. Full article

Petroleum hydrocarbon contamination has emerged as a significant global environmental issue, severely impacting soil microbial communities and their functions. This study employed high-throughput sequencing to systematically analyze the bacterial community structure and functional genes in soils with varying levels of petroleum hydrocarbon contamination. The results demonstrated that petroleum contamination led to a significant decline in microbial diversity, while enhancing the abundance of specific functional genes, such as those involved in polycyclic aromatic hydrocarbon (PAH) degradation, methane production, and denitrification. Phylogenetic analysis further revealed that microbial communities in highly contaminated soils tended to form highly clustered and specialized groups, while simultaneously promoting the coexistence of phylogenetically distant microorganisms. The Mantel test identified significant correlations between ammonium ion concentration, soil moisture content, and microbial metabolic pathways, particularly those related to petroleum hydrocarbon degradation and denitrification. These findings suggest that petroleum contamination not only disrupts the carbon and nitrogen metabolism balance but also has profound implications for greenhouse gas emissions and nitrogen cycling, potentially destabilizing the ecosystem. This study provides novel insights into the ecological functions of microbial communities in petroleum-contaminated soils and highlights potential key factors for pollution management and ecological restoration. Full article

Methane is the second most prevalent greenhouse gas after carbon dioxide in global climate change, and catalytic oxidation technology is a very effective way to eliminate methane. However, the high reaction temperature of methane catalytic oxidation is an urgent problem that needs to be solved. In this work, a series of MnCo₂O_4.5 catalysts were prepared using carbon spheres as templates, combined with metal ion adsorption and calcination processes. Excitingly, the catalytic oxidation activity of MnCo₂O_4.5 spherical catalyst with irregular nanoparticles on the surface for lean methane (T₉₀ = 395 °C) is higher than that of pure phase Co₃O₄ (T₉₀ = 538 °C) and Mo₃O₄ (T₉₀ = 581 °C) spherical catalysts and even surpasses most precious metal catalysts. The main reasons are as follows: (1) The spherical core with irregular nanoparticle morphology significantly increases the specific surface area, creating abundant active sites; (2) through the optimized distribution of oxygen vacancies, rapid oxygen migration through this structure can quickly enter the catalytic zone; (3) the hierarchical wall structure expands the interface and provides spatial accommodation for the catalytic process. Meanwhile, the structure of the ball wall further expands the reaction interface, providing sufficient space for the occurrence of reactions. Rich and highly active oxygen vacancies are evenly distributed on the surface and inside of the ball. The extraordinary performance of low-temperature methane combustion catalysts has opened a promising new path, which is expected to inject strong impetus into the global energy transition and environmental protection. Full article

The venting process is one of the most important events during the thermal runaway (TR) of lithium-ion batteries (LIBs) in determining fire accidents, while different ambient pressures will exert an influence on the venting events as well as the TR. Ternary nickel–cobalt–manganese (NCM) batteries with a 75% state of charge (SOC) were employed to conduct TR tests under different ambient pressures in a sealed chamber with dilute oxygen. It was found that elevated ambient pressure results in milder ejections in terms of jet temperature and mass loss. Gas venting characteristics were also obtained. Additionally, the amount of carbon dioxide (CO₂), hydrogen (H₂), methane (CH₄), and ethylene (C₂H₄) released increase with ambient pressure, while carbon monoxide (CO) varies inversely with ambient pressure. The higher the ambient pressure is, the greater the flammability risk is. The molar amount of C, H, O, and total gases released shows a positive correlation with the maximum battery temperature and ambient pressure. This study will support the design of safety valves and help reveal the effects of venting events on the evolution of TR. Full article

Our planet is currently facing dual challenges of global warming and energy crisis. The heavy reliance of the energy sector on fossil fuels significantly contributes to the accumulation of greenhouse gases, such as CH₄ and CO₂, in the environment atmosphere, exacerbating global warming. Stabilized zirconia-based material offer a promising solutions to address both challenges. As a catalytic support material, active sites incorporated stabilized-zirconia can facilitate the conversions of greenhouse gases like CH₄ and CO₂ into syngas (H₂ and CO). This reaction is popularly known as dry reforming of methane (DRM). Additionally, stabilized zirconia-based materials act as solid-state electrolyte in fuel cells enabling the electrochemical conversion of H₂ and O₂ to generate electricity. Both processes require high-temperature stability and oxide ionic conductivity, making “Ca, Mg, Sc, Y-stabilized zirconia” an optimal choice. In DRM, the key factors influencing catalytic efficiency include metal–support interaction, reducibility, and basicity. Meanwhile, for solid oxide fuel cells, performance is governed by factors such as size-fit, charge imbalance, dopant miscibility, ion conducting phases, densification, electrolyte thickness, and grain boundary volume. This compressive review explores the dual functionality of “Ca, Mg, Sc, Y-stabilized zirconia” as a catalyst’support for DRM and as an solid electrolyte for fuel cells. The most promising research outcomes are highlighted, and future research directions are outlined. By bringing together the catalytic and fuel cell research communities, this study aims to advance sustainable energy technologies and contribute to mitigating environmental and energy crisis through the development of stabilized zirconia-based materials. Full article

This study investigated the inhibitory effect and mechanism of modified ultrafine ABC powder on the explosion of a methane (CH₄)/coal dust mixed system. Through experiments, it was found that the addition of ABC powder significantly weakened the deflagration characteristics of the CH₄/coal dust mixture system. During decomposition, heat was absorbed to generate ammonia and phosphoric acid. Inert gases such as CO₂ and water vapor produced during decomposition could dilute the oxygen concentration. Phosphate ions produced during the decomposition of ammonium phosphate would bind with free radicals during combustion, reducing their reactivity. The explosion reaction was suppressed through a dual mechanism of physical cooling and chemical consumption of free radicals. The experimental results showed that the weight loss rate of modified ABC powder was 49% at 800 °C, while the weight loss rate of unmodified ABC powder was 78%. The modified ABC powder had better thermal stability and could absorb more heat at high temperatures, further suppressing explosive reactions. This study provides a new modification scheme for explosion suppressants for coal mine safety, which has important theoretical and practical application value. Full article

Background: The mixed type of irritable bowel syndrome (IBS-M) is characterized by recurrent constipation and diarrhea. The cause of the variability of these symptoms is not sufficiently understood. The aim of this study was to perform metagenomic and metabolic assessment of the gut microbiome in constipation and diarrheal period of IBS-M. Methods: This study included 30 women, aged 28–47 years old, with the symptoms which aligned with those of IBS-M, according to the Rome IV Criteria. Results: In both periods of the disease, the dysbiosis index (DI), the Shannon diversity index (SDI), the hydrogen–methane and ammonia breath tests, as well as the selected bacterial metabolites (-p-hydroxyphenyl acetic acid (HPA), 3-indoxyl sulfate (Indican, 3-IS)), and hippuric acid (A) in urine, were determined. The dysbiosis index (DI) in the period of constipation was 3.73 ± 0.90 points, and in the diarrheal period it did not change significantly 3.93 ± 0.75 points (p > 0.05). During the diarrheal period, the diversity of bacteria increases from 2.16 ± 0.59 to 2.74 ± 0.50 points on the Shannon dietary index (p < 0.001). The gut microbiome profile also changed, especially during the diarrheal period where an abundance of Bifidobacterium spp. and Lactobacillus spp. decreased significantly. In addition, during this period, the levels of hydrogen and ammonia in breath air increased, while the methane level decreased. The differences also concern the results of urinary metabolites, especially related to hippuric acid and indican. During the diarrheal period, the levels of hydrogen and ammonia ions increased, while the methane level decreased. The differences also concern the results of urinary metabolites, especially related to hippuric acid and indican. Conclusions: In patients with IBS-M, periodic changes in the profile and metabolism of the gut microbiome occur, which coexist with recurrent symptoms such as constipation and diarrhea. Full article

The DIR (Dirigent) gene family plays a multifaceted role in plant growth, development, and stress responses, making it one of the key gene families for plant adaptation to environmental changes. However, research on ZmDIRs in maize remains limited. In this study, we identified a member of the maize DIR gene family, ZmDIR5, whose promoter region contains numerous elements associated with responses to abiotic stresses. ZmDIR5 is upregulated in response to waterlogging, salt, and drought stresses, and its protein is localized in the endoplasmic reticulum. Subsequent studies revealed that ZmDIR5-EMS (ethyl methane sulfonate) mutant lines exhibited reduced growth compared to WT (wild-type) plants under waterlogging, salt, and drought stress conditions. The mutant lines also demonstrated a relatively higher accumulation of malondialdehyde and reactive oxygen species, lower synthesis of proline and total lignans, and decreased antioxidant enzyme activity under these stress conditions. Additionally, the mutant lines displayed impaired sodium and potassium ion transport capabilities, reduced synthesis of abscisic acid and zeatin, and decreased expression of related genes. The mutation of ZmDIR5 also inhibited the phenylpropanoid biosynthesis pathway in maize. These results indicate that ZmDIR5 serves as a positive regulator of maize tolerance to waterlogging, salt, and drought stresses. Full article

The reaction between methanol radical cations and methane, producing methyl radicals and protonated methanol, is pivotal to both astrochemical and atmospheric processes. Methanol and methane are the most abundant organic molecules in space and Earth’s atmosphere and central to molecular synthesis under different environmental conditions. Here, we present a combined experimental and theoretical investigation of the ion–molecule reaction between CH₃OH^•+ and CH₄. The study explores the reaction mechanism and energetics under ionized conditions utilizing quantum chemical methods and experimental data. The findings reveal that the reaction’s non-thermal behavior becomes pronounced when CH₃OH^•+ is vibrationally excited by photon absorption above the ionization threshold, as can happen in the presence of ionizing agents like cosmic rays. Conversely, in thermal equilibrium conditions, the reaction accelerates as temperatures decrease, as suggested by canonical rate coefficient calculations. The products can initiate further chemical reactions, shaping molecular networks in the interstellar medium and affecting atmospheric trace gas balances. Full article

Calcium orthophosphate material (Ca_1-xCu_x)HPO₄.nH₂O (0.4 ≤ x ≤ 1) with the gradual replacement of Ca²⁺ with Cu²⁺ ions were synthesized by a chemical precipitation technique. Samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Then, the prepared powders were deposited onto an alumina substrate with interdigitated Pt electrodes by the spin coating method and polyvinyl alcohol (PVA) as a binder. Successively, the sensors were investigated from 0% to 90% at room temperature under various conditions, including humidity, nitrogenous oxide, methane, carbon dioxide and ammonia. The results evidenced that at 90% RH, the sensitivity of sensors significantly increased with the increase in the Cu content. Moreover, the sensors exhibited good repeatability and, after 1 year of aging, the sensor response was equal to 34% that of the freshly prepared sensor. Finally, there was no interference in the presence of other gases (nitrogenous oxide 2.5 ppm, methane 10 ppm, carbon dioxide 500 ppm and ammonia 4 ppm). Full article

The development of state-of-the-art gas sensors based on metal oxide semiconductors (MOS) to monitor hazardous and greenhouse gas (e.g., methane, CH₄, and carbon dioxide, CO₂) has been significantly advanced. Moreover, the morphological and topographical structures of MOSs have significantly influenced the gas sensors by means of surface catalytic activities. This work examines the impact of morphological and topological networked assembly of zinc oxide (ZnO) nanostructures, including microparticles and nanoparticles (0D), nanowires and nanorods (1D), nanodisks (2D), and hierarchical networks of tetrapods (3D). Gas sensors consisting of vertically aligned ZnO nanorods (ZnO–NR) and topologically interconnected tetrapods (T–ZnO) of varying diameter and arm thickness synthesized using aqueous phase deposition and flame transport method on interdigitated Pt electrodes are evaluated for methane detection. Smaller-diameter nanorods and tetrapod arms (nanowire-like), having higher surface-to-volume ratios with reasonable porosity, exhibit improved sensing behavior. Interestingly, when the nanorods’ diameter and interconnected tetrapod arm thickness were comparable to the width of the depletion layer, a significant increase in sensitivity (from 2 to 30) and reduction in response/recovery time (from 58 s to 5.9 s) resulted, ascribed to rapid desorption of analyte species. Additionally, nanoparticles surface-catalyzed with Pd (~50 nm) accelerated gas sensing and lowered operating temperature (from 200 °C to 50 °C) when combined with UV photoactivation. We modeled the experimental findings using a modified general formula for ZnO methane sensors derived from the catalytic chemical reaction between methane molecules and oxygen ions and considered the structural surface-to-volume ratios (S/V) and electronic depletion region width (L_d) applicable to other gas sensors (e.g., SnO₂, TiO₂, MoO₃, and WO₃). Finally, the effects of UV light excitation reducing detection temperature help to break through the bottleneck of ZnO-based materials as energy-saving chemiresistors and promote applications relevant to environmental and industrial harmful gas detection. Full article

Optimizing forest management requires a comprehensive understanding of how soil properties and microbial communities evolve across different plantation ages. This study examines variations in soil nutrient dynamics, enzyme activities, and bacterial communities in Schima superba Gardn. & Champ plantations of 10, 15, 27, 55, and 64 years. By analyzing soil from depths of 0–20 cm, 20–40 cm, and 40–60 cm, we identified significant age-related trends in soil characteristics. Notably, nutrient contents, including total organic carbon (TOC), total phosphorus (TP), total carbon (TC), total nitrogen (TN), and nitrate nitrogen (${\mathrm{NO}}_3^{-}$-N), as well as soil water content (SWC), peaked in 55-year-old mature plantations and decreased in 64-year-old over-mature plantations. Enzyme activities, such as urease, sucrase, and acid phosphatase, decreased with soil depth and exhibited notable differences across stand ages. Microbial community analysis indicated the predominance of Acidobacteria, Chloroflexi, Proteobacteria, Actinobacteria, and Verrucomicrobiota in nutrient cycling, with their relative abundances varying significantly with age and depth. Mature and over-mature plantations exhibited higher absolute abundances of functional genes related to methane metabolism, nitrogen, phosphorus, and sulfur cycling. Reduced calcium ion levels were also linked to lower gene abundance in carbon degradation, carbon fixation, nitrogen, and phosphorus cycling, while increased TOC, ${\mathrm{NH}}_4^{+}$-N, ${\mathrm{NO}}_3^{-}$-N, and AP correlated with higher gene abundance in methane metabolism and phosphorus cycling. Our findings suggest that long-term cultivation of Schima superba enhances soil nutrient cycling. Calcium ion was identified as a significant factor in assessing soil properties and microbial dynamics across different stand ages, suggesting that extended plantation rotations can improve soil health and nutrient cycling. Full article