CO2 Decomposition Research Articles

Unraveling novices' code composition difficulties

Unraveling novices' code composition difficulties

Unraveling novices' code composition difficulties

Unraveling novices' code composition difficulties

Unraveling novices' code composition difficulties

Unraveling novices' code composition difficulties

Adsorption and decomposition of CO2 on γ-Al2O3(1 0 0): First-principles investigation

The adsorption and dissociation of CO2 on perfect and oxygen-deficient γ-Al2O3(100) is comparatively studied using first-principles calculations. CO2 molecules are found to physically absorb at perfect γ-Al2O3(100) with a linear configuration without the tendency to decompose. By contrast, the presence of oxygen vacancies at the γ-Al2O3(100) surface results in direct CO2 decomposition at the oxygen vacancy sites or the CO2 adsorption at the Al site adjacent to the oxygen vacancy, followed by the CO2 molecular rotation to the oxygen vacancy site and subsequent decomposition. The charge transfer between adsorbed CO2 and the γ-Al2O3(100) surface is further analyzed to understand the oxygen deficiency effect on CO2 adsorption and decomposition. These results demonstrate the promoting effect of oxygen vacancies of the oxide catalysts on CO2 activation, which have practical importance in catalytic CO2 conversion to value-added chemicals and controlling the oxidation of alumina-forming alloys in CO2 containing atmospheres.

Synthesis of metal oxide nanoparticles by facile thermal decomposition of new Co(II), Ni(II), and Zn(II) Schiff base complexes- optical properties and photocatalytic degradation of methylene blue dye

Three new Co(II), Ni(II), and Zn(II) complexes of tridentate ONN ligand were synthesized from the reaction of 2-amino-3-hydroxypyridine and pyrole-2-carboxyaldehyde and characterized using physio-chemical and analytical methods such as NMR, elemental analyzer, FT-IR, ESI-MS, and magnetic moment measurement. The collected data indicated that prepared complexes have metal:ligand ratio of 1:1 and octahedral geometry for Co(II) and Ni(II) while tetrahedral geometry for Zn(II) complex. The synthesized complexes are utilized as precursors for synthesizing Co3O4, NiO, and ZnO NPs by thermal decomposition at 600 °C, and their structures were defined by PXRD, SEM, UV-DRS, FT-IR, and EDAX. By using Scherrer equation, the average crystallite size calculated for Co3O4, NiO, and ZnO nanoparticles are 22, 18, and 24 nm, respectively. The energy band gap of Co3O4, NiO, and ZnO nanoparticles are 1.67, 3.34, and 3.12 eV, respectively, according to the Tauc baseline calculation, revealing their semiconducting nature. Co3O4, NiO, and ZnO nanoparticles were employed for photocatalytic degradation of methylene blue dye in sunlight. After 105 min., the maximum percentage of MB dye degradation for Co3O4, NiO, and ZnO was found to be 80 %, 81.2 %, and 86.68 %, respectively.

Evidence for older carbon loss with lowered water tables and changing plant functional groups in peatlands.

A small imbalance in plant productivity and decomposition accounts for the carbon (C) accumulation capacity of peatlands. As climate changes, the continuity of peatland net C storage relies on rising primary production to offset increasing ecosystem respiration (ER) along with the persistence of older C in waterlogged peat. A lowering in the water table position in peatlands often increases decomposition rates, but concurrent plant community shifts can interactively alter ER and plant productivity responses. The combined effects of water table variation and plant communities on older peat C loss are unknown. We used a full-factorial 1-m3 mesocosm array with vascular plant functional group manipulations (Unmanipulated Control, Sedge only, and Ericaceous only) and water table depth (natural and lowered) treatments to test the effects of plants and water depth on CO2 fluxes, decomposition, and older C loss. We used Δ14 C and δ13 C of ecosystem CO2 respiration, bulk peat, plants, and porewater dissolved inorganic C to construct mixing models partitioning ER among potential sources. We found that the lowered water table treatments were respiring C fixed before the bomb spike (1955) from deep waterlogged peat. Lowered water table Sedge treatments had the oldest dissolved inorganic 14 C signature and the highest proportional peat contribution to ER. Decomposition assays corroborated sustained high rates of decomposition with lowered water tables down to 40 cm below the peat surface. Heterotrophic respiration exceeded plant respiration at the height of the growing season in lowered water table treatments. Rates of gross primary production were only impacted by vegetation, whereas ER was affected by vegetation and water table depth treatments. The decoupling of respiration and primary production with lowered water tables combined with older C losses suggests that climate and land-use-induced changes in peatland hydrology can increase the vulnerability of peatland C stores.

Spatio-temporal analysis of decoupling and spatial clustering decomposition of CO2 emissions in 335 Chinese cities

• Spatio-temporal analysis of the decoupling of urban development levels and CO 2 emissions. • Spatial decomposition of CO 2 emissions for 335 cities. • Chinese cities can be clustered into nine types according to their development status and resource endowment. • The critical intra-group decomposition factors differed for the nine types of cities. • Population intensity is the most critical factor contributing to the inter-group differences in urban CO 2 emissions. The decoupling of urban development levels (UDL) and CO 2 emissions is an essential representation of sustainable urban development. The spatial decomposition of urban CO 2 emissions is an essential reference for achieving differential CO 2 emission reduction. This study first evaluates the UDL of 335 cities from 2009 to 2019 using the entropy weight-TOPSIS method. The Tapio decoupling method is used to analyze the spatio-temporal evolution of the decoupling relationship between UDL and CO 2 emissions. Second, the Logarithmic Mean Divisia Index (LMDI) method is used to spatially decompose urban CO 2 emissions and explore their key influencing factors. Finally, cities with the same development status and resource endowment are spatially clustered by density peaks. Moreover, the proposed spatial LMDI method is used for intra-group and inter-group decomposition of CO 2 emissions. The results show that the decoupling status can be divided into three stages. CO 2 emission intensity and electricity consumption intensity show mainly north–south differences, while other factors show mainly east–west differences. Cities can be classified into nine types by clustering, and the critical intra-group decomposition factors are different. Population intensity is the most critical factor contributing to the inter-group differences in urban CO 2 emissions, followed by land size and output intensity.

Decomposition of CO2 in a Glow Discharge (an Analytical Review)

Decomposition of CO2 in a Glow Discharge (an Analytical Review)

Influence of Gap Width on Temporal Nonlinear Behaviors in CO2 Dielectric Barrier Discharges under Martian Conditions

In recent years, the in situ resource utilization of CO2 on Mars for oxygen and carbon monoxide production has attracted increasing attention. Dielectric barrier discharges (DBDs) have great potential for large-scale industrial application of CO2 decomposition, and the nonlinear behaviors of DBDs are directly related to the discharge stability. In this paper, a fluid model is built to investigate the influence of gap width on temporal nonlinear behaviors in CO2 DBDs driven by tailored voltages under Martian conditions (the pressure and temperature are 4.5 Torr and 210 K, respectively). The simulation results show that, with the increase in the gap width, the discharge evolves from period-one state into period-two state, then changes into chaos, and finally undergoes an inverse period-doubling bifurcation from reverse period-two discharge to period-one discharge. After the CO2 discharge is extinguished, the electron density drops rapidly, and the dominant charged particles in the discharge region are heavy CO3− and CO2+ ions. As the gap width increases, the heavy ions produced by the previous discharge cannot be completely dissipated and stay in the sheath region, which makes the subsequent discharge easy to be ignited and reduces the breakdown voltage, leading to the evolution from period-one discharge to period-two discharge. When the gap width is increased to 5 mm, a lot of charged particles stay in the discharge gap, and these charged particles, especially electrons, are driven to the electrodes by the applied voltage, forming a reverse electric field, which inhibits the development of positive discharge and facilitates the formation of negative discharge. Then, as the gap width continues to increase, the density and spatial distribution of residual ions in the sheath region at the beginning of the negative discharge for two consecutive voltage periods are gradually equal, resulting in the discharge evolution from reverse period-two state to reverse period-one state. This study could deepen the understanding of the underpinning physics of nonlinear behaviors, and provide a groundwork for actively regulating the evolution of nonlinear behaviors.

Sustainability Assessment of the Utilization of CO2 in a Dielectric Barrier Discharge Reactor Powered by Photovoltaic Energy

The direct activation of diluted CO2 in argon was studied in a co-axial dielectric barrier discharge (DBD) reactor powered by photovoltaic energy. The influence of the initial CO2 and argon concentration on the CO2 decomposition to form CO was investigated using a copper-based catalyst in the discharge zone. It was observed that the CO2 conversion was higher at lower CO2 concentrations. The presence of the diluent gas (argon) was also studied and it was observed how it has a high influence on the decomposition of CO2, improving the conversion at high argon concentrations. At the highest observed energy efficiency (1.7%), the CO2 conversion obtained was 40.2%. It was observed that a way to enhance the sustainability of the process was to use photovoltaic energy. Taking into account a life cycle assessment approach (LCA), it was estimated that within the best-case scenario, it would be feasible to counterbalance 97% of the CO2 emissions related to the process.

Supercritical CO2-Induced Evolution of Alkali-Activated Slag Cements.

The phase changes in alkali-activated slag samples when exposed to supercritical carbonation were evaluated. Ground granulated blast furnace slag was activated with five different activators. The NaOH, Na2SiO3, CaO, Na2SO4, and MgO were used as activators. C-S-H is identified as the main reaction product in all samples along with other minor reaction products. The X-ray diffractograms showed the complete decalcification of C-S-H and the formation of CaCO3 polymorphs such as calcite, aragonite, and vaterite. The thermal decomposition of carbonated samples indicates a broader range of CO2 decomposition. Formation of highly cross-linked aluminosilicate gel and a reduction in unreacted slag content upon carbonation is observed through 29Si and 27Al NMR spectroscopy. The observations indicate complete decalcification of C-S-H with formation of highly cross-linked aluminosilicates upon sCO2 carbonation. A 20–30% CO2 consumption per reacted slag under supercritical conditions is observed.

Experimental and kinetic studies of NO reduction by ammonia injection into high-temperature reducing atmosphere

Experiments were conducted to investigate the NOx reduction performance by ammonia injection into a high-temperature reducing atmosphere and the integrated effects of temperature and oxygen concentration were discussed in detail. Ammonia oxidation was trivial at lower temperatures and the presence of oxygen facilitated the replenishment of OH radicals, enhancing the NOx reduction efficiency. The replenishment of OH radicals and ammonia oxidation were simultaneously promoted at higher temperatures. Therefore, trace amount of oxygen was preferred for higher temperatures to suppress the NOx formation from ammonia oxidation. A maximum NOx reduction efficiency of over 95 % was achieved at 1573 K and 0.0 vol% O2 with normalized stoichiometric ratio of 1.5 and residence time of 0.71 s. Furthermore, rate-of-production analysis was performed to provide insights into NH3/NO reaction pathways in the absence of oxygen. Results showed that the NOx reduction process was initiated by thermal decomposition of NH3 and CO2 acted the role of O2 when oxygen is absent, which could provide O atoms to react with H for the replenishment of OH radicals. The relatively high activation energy of NH3 decomposition accounted for the shift of the temperature window towards higher temperatures in the absence of oxygen.

Photoredox-Mediated Designing and Regulating Metal-Coordinate Hydrogels for Programmable Soft 3D-Printed Actuators.

Metal-organic coordination is widely applied for designing responsive polymers and soft devices. But it is still a challenge to prepare redox-responsive actuators with complicated structures, limiting their advanced applications in material and engineering fields. Here, we report a photoredox-mediated designing and regulating strategy to fabricate metal-coordinate hydrogels with the catalysis of Ru(II)/Co(III) under visible-light irradiation in seconds. Meanwhile, multiple polymer networks are formed and penetrated by each other, enabling as-prepared hydrogels excellent mechanical properties and toughness. This rapid, one-step, and controllable process is highly compatible with standard photography and printing techniques to make hierarchical 2D/3D structures. Importantly, the oxidization decomposition of Co(III) benefits the formation of cobalt cation-based redox-responsive networks, which have the potential for designing shape-memory materials and actuators by the regulation of Co3+/2+ states via tuning redox environmental conditions. As a proof-of-concept, a programmable air-driven actuator is successfully demonstrated to control cargo capturing/releasing by designing complicated, asymmetric structures and optimizing their performance with the combination of a typical extrusion 3D printing approach. In this Letter, we report a simple and general metal-organic coordination strategy for designing high-performance actuators, which shows promising applications in smart soft devices and electronics.

Functionalization of TiO2 inverse opal structure with atomic layer deposition grown Cu for photocatalytic and antibacterial applications

TiO2 inverse opal (IO) structure surfaces were functionalized with a sub-monolayer amount of Cu by atomic layer deposition (ALD) and tested for photocatalytic and antimicrobial applications. Decomposition of acetylene (C2H2) into CO2 and reduction of CO2 into CH4 were tested in the gas phase and photodegradation of methylene blue (MB) was tested in the liquid phase. Antimicrobial activity was tested against Gram-positive Staphylococcus aureus (S. aureus) bacteria. ALD Cu without any post-deposition heat treatment (HT) decreased the photo degradation rate of both C2H2 and MB but improved the activity towards CO2 reduction. ALD Cu increased MB photodegradation rate and antimicrobial activity only after HT at 550 °C, which was linked to the improved chemical stability Cu after the HT. The same HT decreased the activity towards CO2 reduction and decomposition of C2H2. The HT induced desorption of loosely bound ALD Cu+/2+ from the TiO2 IO surface and the remaining Cu+/2+ was reduced to Cu+. The photocatalytic and antimicrobial activity of TiO2 IO can be tailored by the addition of a sub-monolayer amounts of Cu with performance depending on the targeted reaction.

Study of the Effect of the Driving Force on the Kinetics of CO2 Hydrate Growth in Coal Particles

Coal and gas outbursts are geological disasters occurring in the process of coal mining that can cause serious casualties and economic losses, among which CH4 is the main component of coal mine gas. However, there are still many coal seams around the world that are dominated by CO2. Although the frequency of CO2 gas outburst accidents is relatively low, CO2 outbursts are very violent, notably difficult to control and highly dangerous. The application of hydration curing technology to reduce the pressure and gradient of CO2 gas in the coal can effectively reduce the occurrence of coal and CO2 outburst. Accordingly, in this paper, experimental studies on the growth kinetics of CO2 hydrate with three driving forces (2, 2.5, 3 MPa) were carried out under four different coal particle sizes (C1: 0.425–0.850 mm, C2: 0.250–0.425 mm, C3: 0.180–0.250 mm, C4: 0–0.180 mm) to obtain kinetic parameters such as gas consumption, growth rate, and heat of decomposition during the synthesis of CO2 hydrate. The results show that the hydrate nucleation time in the same particle size system does not follow the same decreasing trend with increasing driving force. Gas consumption of CO2 hydrates in the same particle size system increased with increasing driving force, and there exists a critical value regarding the effect of the driving force on CO2 hydrate generation in coal particles with the particle size. Under the same temperature conditions, increasing the driving force in the particle size system could increase the CO2 hydrate growth rate. With decreasing coal particle size and increasing driving force, the promoting effect gradually exceed the inhibiting effect, which promote CO2 hydrate formation. Through linear fitting, an equation of the average growth rate of CO2 hydrates versus the driving force for the C1-C4 systems is fitted to provide a reference to predict the average CO2 hydrate growth rate. In the same medium, with increasing driving force, more heat is required for complete decomposition, which remains relatively stable, and the heat of decomposition of CO2 hydrates is the highest in the C1 medium, indicating that the presence of CO2 hydrates in the C1 system represents the most stable state.

Comprehensive study on plasma chemistry and products in [formula omitted] pulsed discharges under Martian pressure

With the development of Mars exploration, the In-Situ resource utilization on Mars has been drawn significant attention in recent years. The abundant CO2 in the Martian atmosphere makes it possible to decompose CO2 to produce high-value platform chemicals by plasma technology. In this comprehensive study, the discharge characteristics, products distribution, and reaction pathways in CO2 pulsed discharges under Martian pressure are investigated, and the effects of pulsed waveforms on discharge characteristics and produced species are also discussed. The simulation results show that electrons and CO2+ ions are the main components of charged particles in the discharge region; CO and O are mainly produced by the electron impact dissociation and electron impact attachment reactions with ground state and vibrationally excited state of CO2 during the power-on phase and consumed by the ion–neutral reactions. The recombination reaction of electrons and CO2+ ions is very important for the formation of O2. The simulation data also give the main generation and consumption pathways of vibrationally excited CO2 molecules, and indicate that the vibrational energy of excited CO2 molecules can lower the energy barrier of the reaction and facilitate the decomposition of CO2. In addition, the experimental and computational data also suggest that the pulsed waveforms could affect the discharge characteristics and plasma chemistry in CO2 pulsed discharges under Martian pressure, the densities of product species in CO2 plasma increase with the pulse rise rate and pulse rise duration of pulsed voltage. This study provides an enhanced understanding of discharge characteristics and plasma chemistry in the CO2 pulsed discharges under Martian pressure, and suggests optimized ways to utilize the CO2 on Mars.

Enhanced CO2 conversion by frosted dielectric surface with ZrO2 coating in a dielectric barrier discharge reactor

The direct conversion of CO2 into CO and O2 by dielectric barrier discharge (DBD) non-thermal plasma is effective with simple setup, easy on/off operation and flexibility to the CO2 source. Herein, we demonstrated the frosted dielectric surface without and with ZrO2 coating can significantly improve the conversion and energy efficiency of the plasma CO2 decomposition in a DBD reactor, compared to the conventional un-frosted dielectric surface without ZrO2 coating. The use of the frosted dielectric surface increases the dielectric capacitance, mean electron energy and micro-discharge channels, leading to increased CO2 conversion and energy efficiency. The coating of ZrO2 of a high dielectric constant further improves the discharge performances with further increased CO2 conversion and energy efficiency. The highest energy efficiency of 7.7% was achieved within the tested conditions. The effect of CO2 adsorption on ZrO2 coating is negligible because of the low coating amount.

Measurement of CO, HCN, and NO productions in atmospheric reaction induced by femtosecond laser filament

It is proved that the chemical reaction induced by femtosecond laser filament in the atmosphere produces CO, HCN, and NO, and the production CO and HCN are observed for the first time. The concentrations of the products are measured by mid-infrared tunable laser absorption spectroscopy. In the reduced pressure air, the decomposition of CO2 is enhanced by vibration excitation induced by laser filament, resulting in the enhanced production of CO and HCN. At the same time, the CO and HCN generated from the atmosphere suffer rotation excitation induced by laser filament, enhancing their absorption spectra. It is found that NO, CO, and HCN accumulate to 134 ppm, 80 ppm, and 1.6 ppm in sealed air after sufficient reaction time. The atmospheric chemical reaction induced by laser filament opens the way to changing the air composition while maintaining environmental benefits.

Enhancing the low-temperature CO2 methanation over Ni/La-CeO2 catalyst: The effects of surface oxygen vacancy and basic site on the catalytic performance

This work reports a strategy to promote the low-temperature CO2 methanation on the Ni-based catalyst by tuning the surface oxygen vacancy and medium-strength basic sites of the CeO2 support and thus changing the reaction pathway. La species was introduced into CeO2 support and calcined at 600 °C (CeO2-La-600) to form a La-Ce-O solid solution with a thin La2O2CO3 layer on the surface, generating more basic sites and oxygen vacancies. This unique structure facilitated the adsorption and direct dissociation of CO2. Over Ni/CeO2-La-600, the reaction follows the HCOO* and *CO pathways, while over Ni/CeO2-600, the reaction occurs via the HCOO* pathway only. The decomposition of CO2 * to *CO is energetically more favorable than hydrogenation to HCOO* on Ni/CeO2-La-600, resulting in its higher catalytic performance at low temperatures. This work unravels the complex interplay among oxygen vacancy, basic site, and reaction pathway in CO2 methanation over the Ni-based catalysts.

Thermal Decomposition of Co–Cu Double Salicylate Complex under Argon Atmosphere Resulting in Metal–Carbon Compositions

Thermal Decomposition of Co–Cu Double Salicylate Complex under Argon Atmosphere Resulting in Metal–Carbon Compositions