Search Results (354)

The electrochemical reduction of carbon monoxide (COER) offers a promising route for generating value-added multi-carbon (C₂₊) products, such as ethanol, but achieving high catalytic performance remains a significant challenge. Herein, we performed comprehensive density functional theory (DFT) computations to evaluate CO-to-ethanol conversion on single metal atoms anchored on graphitic carbon nitride (TM/g–CN). We showed that these metal atoms stably coordinate with edge N sites of g–CN to form active catalytic centers. Screening 20 TM/g–CN candidates, we identified V/g–CN and Zn/g–CN as optimal catalysts: both exhibit low free-energy barriers (<0.50 eV) for the key ^*CO hydrogenation steps and facilitate C–C coupling via an Eley–Rideal mechanism with a negligible kinetic barrier (~0.10 eV) to yield ethanol at low limiting potentials, which explains their superior COER performance. An analysis of d-band centers, charge transfer, and bonding–antibonding orbital distributions revealed the origin of their activity. This work provides theoretical insights and useful guidelines for designing high-performance single-atom COER catalysts. Full article

The combustion of gaseous fuels in condensing boilers contributes to the greenhouse gas and toxic compound emissions in exhaust gases. Hydrogen, as a clean energy carrier, could play a key role in decarbonizing the residential heating sector. However, its significantly different combustion behavior compared to hydrocarbon fuels requires thorough investigation prior to implementation in heating systems. This study presents experimental and theoretical analyses of the co-combustion of natural gas with hydrogen in low-power-output condensing boilers (second and third generation), with hydrogen content of up to 50% by volume. The results show that mixtures of hydrogen and natural gas contribute to increasing heat transfer in boilers through convection and flue gas radiation. They also highlight the benefits of using the heat from the condensation of vapors in the flue gases. Other studies have observed an increase in efficiency of up to 1.6 percentage points compared to natural gas at 50% hydrogen content. Up to a 6% increase in the amount of energy recovered by water vapor condensation was also recorded, while exhaust gas losses did not change significantly. Notably, the addition of hydrogen resulted in a substantial decrease in the emission of nitrogen oxides (NOx) and carbon monoxide (CO). At 50% hydrogen content, NO_x emissions decreased several-fold to 2.7 mg/m³, while CO emissions were reduced by a factor of six, reaching 9.9 mg/m³. All measured NO_x values remained well below the current regulatory limit for condensing gas boilers, which is 33.5 mg/m³. These results highlight the potential of hydrogen blending as a transitional solution on the path toward cleaner residential heating systems. Full article

For PEM fuel cell operation, high-purity hydrogen gas containing only trace amounts of carbon monoxide is a prerequisite. The water–gas shift reaction (WGSR) is an industrially applied mature operation mode to convert CO with H₂O into CO₂ (making it easy to separate, if necessary) and H₂. Since the WGS reaction is an exothermic equilibrium reaction, low temperatures (below 200 °C) lead to full CO conversion. Thus, highly active ultra-low-temperature WGSR catalysts have to be applied. A homogeneous Ru SILP (supported ionic liquid phase) catalyst based on the precursor complex [Ru(CO)₃Cl₂]₂ has been identified to operate at such low temperature levels. However, in a hydrogen rich atmosphere, transition metal complexes are prone to form nanoparticles (NPs) when dissolved in ionic liquids (ILs). In this article, the behavior of an anionic SILP WGSR catalyst, i.e., [Ru(CO)₃Cl₃]⁻ dissolved in [BMMIM]Cl, in an H₂-rich CO environment is described. The data reveal that during the WGSR, Ru nanoparticles form in the catalyst when very low CO concentrations are reached. The Ru NPs formation has been confirmed by transmission electron microscopy imaging and X-ray diffraction (XRD). Full article

Cu-doped In₂O₃ nanocomposites with copper compositions of 1–3 wt.% are synthesized by a hydrothermal method using water or alcohol as a solvent. Cubic In₂O₃ is formed when water is used for synthesis, while composites synthesized in alcohol contain rhombohedral In₂O₃. This trend is independent of the amount of copper introduced. The Cu ions are shown to be uniformly distributed in the In₂O₃ nanoparticles without significant destruction of the indium oxide structure. All the composites exhibit a porous structure that depends on the solvent used for the synthesis. The addition of copper to both crystalline forms of indium oxide increases the resistance of the films and reduces the operating temperature. The phase state of indium oxide also affects the conductivity of the composites. There is an increase in sensory response to H₂ and CO with the introduction of Cu into samples with cubic structure, but a reduction in response in samples with the rhombohedral phase of indium oxide. Full article

This study evaluated the economic feasibility of producing hydrogen from natural gas via thermal degradation in a plasma reactor. Plasma pyrolysis, where natural gas passes through the space between electrodes and serves as the working medium, enables high hydrogen yields without emitting carbon monoxide or carbon dioxide. Instead, the primary products are hydrogen and solid carbon. Unlike conventional methods, this approach requires no catalysts, addressing a major technological limitation. A thermodynamic equilibrium model based on Gibbs free energy minimization was used to analyze the process over a temperature range of 500–2500 K. The results indicate an optimal temperature of approximately 1500 K, which achieved a 99.5% methane conversion by mass. Considering the capital and operating costs and profit margins, the hydrogen production cost was estimated at 3.49 EUR/kg. The sensitivity analysis revealed that the price of solid carbon had the most significant impact, which potentially raised the hydrogen cost to 4.53 EUR/kg or reduced it to 1.70 EUR/kg. Full article

Unmanned aerial vehicles, also termed as unarmed aerial vehicles, are used for various purposes in and around the environment, such as delivering things, spying on opponents, identification of aerial images, extinguishing fire, spraying the agricultural fields, etc. As there are multi-functions in a single UAV model, it can be used for various purposes as per the user’s requirement. The UAVs are used for faster communication of identified information, entry through the critical atmospheres, and causing no harm to humans before entering a collapsed path. In relation to the above discussion, a UAV system is designed to classify and transmit information about the atmospheric conditions of the environment to a central controller. The UAV is equipped with advanced sensors that are capable of detecting air pollutants such as carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), ammonia (NH₃), hydrogen sulfide (H₂S), etc. These sensors present in the UAV model monitor the quality of air, time-to-time, as the UAV navigates through different areas and transmits real-time data regarding the air quality to a central unit; this data includes detailed information on the concentrations of different pollutants. The central unit analyzes the data that are captured by the sensor and checks whether the quality of air meets the atmospheric standards. If the sensed levels of pollutants exceed the thresholds, then the system present in the UAV triggers a warning alert; this alert is communicated to local authorities and the public to take necessary precautions. The developed UAV is furnished with cameras which are used to capture real-time images of the environment and it is processed using the YOLO V3 algorithm. Here, the YOLO V3 algorithm is defined to identify the context and source of pollution, such as identifying industrial activities, traffic congestion, or natural sources like wildfires. Full article

Carbon monoxide (CO) is classified as a simple fuel that contains one carbon and one oxygen atom. The oxidation of CO with an oxidizer is relatively unusual, with the oxidation of CO having a slow reaction time. The addition of a small amount of “hydrogenous” species, such as H₂, H₂O, and CH₄, will substantially increase the reaction time. This study numerically investigated and compared the effects of different hydrogenous species addition on the premixed CO/air flames, which act as the initiation of a CO/air flame, on the adiabatic flame temperature, laminar flame speed, and heat release rates at standard conditions (298 K and 1 atm pressure) using San Diego Mechanism. The results showed that the addition of critical hydrogenous species distinguished the difference between dry and wet CO/air oxidation, in which different hydrogenous species have an identical critical value. Adding different hydrogenous species and different addition ratios has an indistinguishable adiabatic flame temperature, while adding CH₄ has a higher laminar flame speed distribution compared with H₂ and H₂O addition, respectively. Furthermore, the laminar flame speed positively correlates with the net heat release rate, which adding CH₄ has a noticeable increase on the net heat release rate. Adding more hydrogenous species makes the reactant more reactive and moves the reaction zone upstream. Finally, the dominant reactions to the heat release rate are identical in different hydrogenous species addition, where R23: CO + O (+M) ⇌ CO₂ (+M) becomes the most contributed reaction. Full article

Among biomass gasification syngas cleaning methods, non-catalytic reforming emerges as a sustainable and high-efficiency alternative. This study employed integrated experimental analysis and kinetic modeling to examine non-catalytic reforming processes of biomass-derived producer gas utilizing a synthetic tar mixture containing representative model compounds: naphthalene (C₁₀H₈), toluene (C₇H₈), benzene (C₆H₆), and phenol (C₆H₅OH). The experiments were conducted using a high-temperature fixed-bed reactor under varying temperatures (1100–1500 °C) and equivalence ratios (ERs, 0.10–0.30). The results obtained from the experiment, namely the measured mole concentration of H₂, CO, CH₄, CO₂, H₂O, soot, and tar suggested that both reactor temperature and O₂ content had an important effect. Increasing the temperature significantly promotes the formation of H₂ and CO. At 1500 °C and a residence time of 0.01 s, the product gas achieved CO and H₂ concentrations of 28.02% and 34.35%, respectively, while CH₄, tar, and soot were almost entirely converted. Conversely, the addition of O₂ reduces the concentrations of H₂ and CO. Increasing ER from 0.10 to 0.20 could reduce CO from 22.25% to 16.11%, and H₂ from 13.81% to 10.54%, respectively. Experimental results were used to derive a kinetic model to accurately describe the non-catalytic reforming of producer gas. Furthermore, the maximum of the Root Mean Square Error (RMSE) and the Relative Root Mean Square Error (RRMSE) between the model predictions and experimental data are 2.42% and 11.01%, respectively. In particular, according to the kinetic model, the temperature increases predominantly accelerated endothermic reactions, including the Boudouard reaction, water gas reaction, and CH₄ steam reforming, thereby significantly enhancing CO and H₂ production. Simultaneously, O₂ content primarily influenced carbon monoxide oxidation, hydrogen oxidation, and partial carbon oxidation. Full article

In rocketry today, conventional hypergolic propellant combinations typically use hydrazine-derived fuels and oxidizers based on nitrogen tetroxide. Due to their high toxicity and consequently expensive handling, safer alternatives, so-called “green hypergolics”, are currently being developed. The ionic liquid-based fuels [EMIM][SCN], HIP_11 and HIM_30, paired with highly concentrated hydrogen peroxide as an oxidizer, are three candidates for such green hypergolics, which are currently under research at the German Aerospace Center (DLR). These combinations have been shown to exhibit reliable hypergolic ignition. For a better understanding of the reaction process and to assess the risks in working with these propellants, it is desirable to determine their combustion products. A test setup was designed to extract the gaseous combustion products from hypergolic drop tests. The gas samples were analyzed using Fourier-transform infrared spectroscopy and the gaseous combustion products were determined from the infrared spectra. Additional tests with varied oxidizer concentration or alternative fuels were conducted to further investigate detailed aspects of the findings. It was concluded that [EMIM][SCN], HIP_11 and HIM_30 produce very similar sets of combustion products with hydrogen peroxide, including water vapor, carbon dioxide, carbon monoxide, hydrogen cyanide and sulfur dioxide. Finally, the combustion products were compared to the substances produced when thermally decomposing the fuels. This confirmed that the previously detected substances were caused by a reaction between hydrogen peroxide and the fuels, rather than by their thermal decomposition due to heating. Full article

Peripheral artery disease (PAD) is a chronic progressive accumulation of atherosclerotic lesions with varying degrees of arterial obstruction determining ischemic symptoms of the involved extremities. PAD is associated with decreased bioavailable nitric oxide due to endothelial cell dysfunction and the development and progression of vascular arterial stiffening (VAS). Atherosclerosis also plays an essential role in the development and progression of vascular arterial stiffening (VAS), which is associated with endothelial cell activation and dysfunction that results in a proinflammatory endothelium with a decreased ability to produce bioavailable nitric oxide (NO). NO is one of three gasotransmitters, along with carbon monoxide and hydrogen sulfide, that promotes vasodilation. NO plays a crucial role in the regulation of PAD, and a deficiency in its bioavailability is strongly linked to the development of atherosclerosis, VAS, and PAD. A decreased arterial patency may also occur due to a reduction in the elasticity or diameter of the vessel wall due to the progressive nature of VAS and atherosclerosis in PAD. Progressive atherosclerosis and VAS promote narrowing over time, which leads to impairment of vasorelaxation and extremity blood flow. This narrative review examines how atherosclerosis, aging and hypertension, metabolic syndrome and type 2 diabetes, tobacco smoking, and endothelial cell activation and dysfunction with decreased NO and VAS with its increased damaging pulsatile pulse pressure result in microvessel remodeling. Further, the role of ischemia and ischemia–reperfusion injury is discussed and how it contributes to ischemic skeletal muscle remodeling, ischemic neuropathy, and pain perception in PAD. Full article

This study evaluates the potential of hydrogen as a clean additive to conventional diesel fuel. Experiments were carried out on a single-cylinder, air-cooled diesel engine under half- and full-load conditions, across engine speeds ranging from 1000 to 3000 rpm. Hydrogen, produced on site via a proton exchange membrane electrolyser, was supplied to the engine at a constant flow rate of 0.5 L/min. Compared to pure diesel, the hydrogen–diesel blend reduced specific fuel consumption by 10% and increased brake thermal efficiency by 10% at full load. Emissions of carbon monoxide and carbon dioxide decreased by 13% and 17%, respectively, at half load. Additionally, nitrogen oxide emissions dropped by 17%. These results highlight the potential of hydrogen to improve combustion efficiency while significantly mitigating emissions, offering a viable transitional solution for cleaner power generation using existing diesel infrastructure. Full article

Biogas is a crucial renewable energy source for green hydrogen (H₂) production, reducing greenhouse gas emissions and serving as a carbon-free energy carrier with higher specific energy than traditional fuels. Currently, methane reforming dominates H₂ production to meet growing global demand, with biogas/landfill gas (LFG) reform offering a promising alternative. This study provides a comprehensive simulation-based evaluation of Steam Methane Reforming (SMR) and Dry Methane Reforming (DMR) of biogas/LFG, using Aspen Plus. Simulations were conducted under varying operating conditions, including steam-to-carbon (S/C) for SMR and steam-to-carbon monoxide (S/CO) ratios for DMR, reforming temperatures, pressures, and LFG compositions, to optimize H₂ yield and process efficiency. The comparative study showed that SMR attains higher specific H₂ yields (0.14–0.19 kgH₂/Nm³), with specific energy consumption between 0.048 and 0.075 MWh/kg of H₂, especially at increased S/C ratios. DMR produces less H₂ than SMR (0.104–0.136 kg H₂/Nm³) and requires higher energy inputs (0.072–0.079 MWh/kg H₂), making it less efficient. Both processes require an additional 1.4–2.1 Nm³ of biogas/LFG per Nm³ of feed for energy. These findings provide key insights for improving biogas-based H₂ production for sustainable energy, with future work focusing on techno–economic and environmental assessments to evaluate its feasibility, scalability, and industrial application. Full article

Combustible gas leakage remains a critical safety concern in industrial and indoor environments, necessitating the development of detection systems that are both accurate and practically deployable. This study presents a wireless gas detection system that integrates a gas sensor array, a low-power microcontroller with Zigbee-based communication, and a Back Propagation (BP) neural network optimized via a sequential hybrid strategy. Specifically, Particle Swarm Optimization (PSO) is employed for global parameter initialization, followed by Dung Beetle Optimization (DBO) for local refinement, jointly enhancing the network’s convergence speed and predictive precision. Experimental results confirm that the proposed PSO-DBO-BP model achieves high correlation coefficients (above 0.997) and low mean relative errors (below 0.25%) for all monitored gases, including hydrogen, carbon monoxide, alkanes, and smog. The model exhibits strong robustness in handling nonlinear responses and cross-sensitivity effects across multiple sensors, demonstrating its effectiveness in complex detection scenarios under laboratory conditions within embedded wireless sensor networks. Full article

Methanol, a renewable and sustainable fuel, provides an effective strategy for reducing greenhouse gas emissions when synthesized through carbon dioxide hydrogenation integrated with carbon capture technology. The incorporation of hydrogen into methanol-fueled engines enhances combustion efficiency, mitigating challenges such as pronounced cycle-to-cycle variations and cold-start difficulties. A simulation framework was developed using Python 3.13 and the Cantera 3.1.0 library to model the combustion system of a four-stroke spark-ignited (SI) methanol–hydrogen engine. This framework integrates a fractal turbulent combustion model with chemical reaction kinetics, complemented by early flame development and near-wall combustion models to address limitations during the initial and terminal combustion phases. The model was validated by using experimental data measured from a spark-ignited methanol engine. The effects of varying Hydrogen Energy Rates (HER) on engine power performance, combustion characteristics, and emissions (like formaldehyde and carbon monoxide) were subsequently analyzed under different operating loads, whilst the knock limit boundaries were established for different operational conditions. Findings demonstrate that increasing HER improves the engine power output and thermal efficiency, shortens the combustion duration, and reduces the formaldehyde and carbon monoxide emissions. Nevertheless, under high-load conditions, higher HER increases the knocking tendency, which constrains the maximum permissible HER decreasing from approximately 40% at 15% load to 20% at 100% load. The model has been developed into a Python library and will be open-sourced on Github. Full article

Asphalt binder flue gas emits irritating odors and poses health and environmental hazards. To promote the sustainable development of asphalt pavement construction, this study investigates the flue gas odor-reducing effectiveness and performance impacts of deodorizing materials on asphalt binders. A specialized asphalt binder flue gas collection device was designed, coupled with an evaluation protocol tailored for asphalt deodorants, to systematically evaluate the odor-reducing effectiveness of materials B and C on both 70# pure asphalt binder and SBS-modified asphalt binder. Finally, the impacts of two kinds of deodorizing materials on the high-temperature and low-temperature performance of different asphalt binders were discussed. The results show that the odor-reducing effectiveness of tert-butyl-co-aldehyde-acting material C on odorous volatile organic compounds (VOCs), hydrogen sulfide (H₂S), and carbon monoxide (CO) in 70# pure asphalt binder flue gas is the best, reaching 66.7%, 49.1%, and 44.0%, respectively. The odor-reducing effectiveness of conjugated double bonds and aldehyde group synergistic material B on odorous VOCs, H₂S, and CO in SBS-modified asphalt binder is the best, reaching 78.7%, 52.9%, and 51.0%, respectively. Both materials B and C can improve the high-temperature deformation resistance of 70# pure asphalt binder and SBS-modified asphalt binder. The anti-cracking properties of SBS-modified asphalt binder at low temperatures were improved to some extent by materials B and C, but the anti-cracking properties of 70# pure asphalt binder at low temperatures were not good. These asphalt binders all meet the specification requirements of a stiffness modulus not more than 300 MPa and a creep rate not less than 0.3. Full article