CO Molar Ratio Research Articles

Effect of Molar Ratio Modulation of Cobalt Precursors on Supercapacitor Behavior of Engineered Co–Co3O4 Nanocomposite Electrodes

Nanostructured Co–Co3O4 composite thin films deposited on nickel foam (NF) using combined cyclic voltammetry (CV) and pulse reverse potential (CV PRP) modes of electrodeposition from an electrolyte composed of CoCl2 and Co(CH3COO)2 precursor salt solutions with varied molar ratios demonstrated a dependency of the supercapacitance performance over the precursor components’ molar ratios. The specific capacity and its retention were found to increase with increasing CoCl2 in the electrolyte with a starting value of 474.6 C/g (791 F/g) at an applied current load of 1 A/g for a molar ratio of Co(CH3COO)2:CoCl2 of 100:0. High specific capacity of 1548 C/g (2580 F/g) and large retention (90.5%) were obtained at a critical molar ratio of Co(CH3COO)2:CoCl2 of 20:80. However, with 100% CoCl2 in the electrolyte, the specific capacity lowered to 276 C/g (460 F/g) with poor retention of only 60%. Crystallinity and morphological features, driven by the electrolyte concentration with molar variations of the deposited films, have been found to influence the specific capacitance performance. The degree of crystallinity, and the presence of Co and Co3O4 phases for the different molar ratios have been revealed by X-ray diffraction (XRD) studies. The diverse morphological features obtained by scanning electron microscopy (SEM) and the varying quantities of Co and O in the Co–Co3O4 nanocomposite thin films as confirmed by energy-dispersive X-ray spectroscopy (EDX) spectra correlate well with the electrochemical performance. The phase composition was further confirmed by the presence of Co–O bonds via the attenuated total reflection–Fourier transform infrared (ATR-FTIR) spectra obtained on these films.

Biogas Upgrading by CO2 Methanation with Ni-, Ni–Fe-, and Ru-Based Catalysts

This piece of work dealt with the concept of ‘biogas upgrading’ or enrichment of the CH4 contained in a sweetened biogas to proportions and features comparable to those of synthetic natural gas (SNG). For this, the behavior of three lab made catalysts (Ni/Al2O3, Ru/Al2O3, and Ni–Fe/Al2O3) was tested in a CO2 methanation reaction (Sabatier reaction) under different feeding conditions (with and without methane). In the first set of experiments (without methane), the good catalytic behavior of the solids was validated. All three catalysts offered similar and increasing CO2 conversions with increasing temperature (range studied from 250 to 400 °C) at a constant WHSV of 30 × 103 STPmL·gcat−1·h−1. The CH4 selectivity remained close to one in all cases. Considering their total metallic load, the Ru (3.7 wt%)-based catalyst stood out remarkably, with TOF values that reached up to 5.1 min−1, this being six or three times higher, than those obtained with the Ni (10.3 wt%) and Ni–Fe (7.4–2.1 wt%) catalysts, respectively. In the second set (cofeeding methane), and also for the three catalysts, a high correspondence between the conversions (and selectivities) obtained with both types of feeds was observed. This indicated that the addition of CH4 to the system did not severely modify the reaction mechanism, resulting in the possibility of taking advantage of the ‘biogas upgrading’ process by using H2 produced off-peak by electrolysis. In order to maximize the CH4 yield, temperatures in the range from 350–375 °C and a H2:CO2 molar ratio of 6:1 were determined as the optimal reaction conditions.

Atomically dispersed Co/C3N4 for boosting aerobic cyclohexane oxidation

The atomically-dispersed and high-loading Co on graphitic carbon nitrogen (Co/C3N4-w, w representing the molar ratio of Co to melamine in the synthesis recipe) was synthesized by coupling the one-pot strategy with the electrostatic adsorption method and used for the solvent-free aerobic oxidation of cyclohexane. The characterization results of Co/C3N4-w revealed that the single-atom Co with the positive charge existed in the sixfold cavities of C3N4 and was stabilized by the CoN interaction along with the electron transfer from Co atoms to C3N4. The catalytic activity of Co/C3N4-w presented the positive correlation with the loading of the single-atom Co, and the superior catalytic performance with 21 % conversion and 95 % overall selectivity was obtained over Co/C3N4-0.02, which also exhibited the excellent universality to the aerobic oxidation of other cycloalkanes and alkyl aromatics. Experiments combined with density functional theory calculations demonstrated that the favored O2 dissociation and intermediate cyclohexylhydroperoxide decomposition on the low-coordinated single-atom Co, and the promoted adsorption of cyclohexane on the electron-rich C3N4 surface, synergically boosted the cyclohexane oxidation. Distinctively, the high stability of Co/C3N4-0.02 in the cyclohexane oxidation originated from the robust single-atom Co structures and hydrophobic C3N4 surface.

Influence of the Molar Ratio of Co and V in Bimetallic Oxides on Their Pseudocapacitive Properties.

Bimetallic oxides have significant attraction as supercapacitor electrode materials due to their highly reversible redox processes, which are commonly associated with their surface chemistry and morphological features. Here, we report the synthesis, characterization, and electrochemical evaluation of bimetallic oxides with different molar compositions of Co and V (Co0.6V0.4, Co0.64V0.36, Co0.68V0.32, and Co0.7V0.3 denoted as S1, S2, S3, and S4 samples, respectively). The materials were synthesized by a modified solvothermal method using glycerol as a stabilizing agent, characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, N2 adsorption isotherms, cyclic voltammetry, and galvanostatic charged/discharged in a three-electrode cell. The role of the CoV oxide compositions on the pseudocapacitive properties was studied through the analysis of the energy storage mechanism following the power law and Dunn's methodology to obtain the b values. An important finding of this work is that CoV oxides exhibited electrochemical characteristics of a pseudocapacitive electrode material even though the charge storage occurs in bulk. This behavior is consistent with the pseudocapacitance generated by redox processes, showing b values of 0.67, 0.53, 0.75, and 0.84, with a capacitive current contribution of 74, 74, 63, and 70% analyzed at a scan rate of 1 mV s-1, for S4, S3, S2, and S1 samples, respectively. Co0.7V0.3 (S4) oxide presented the highest specific capacitance of 299 F g-1 at 0.5 A g-1 with a Coulombic efficiency of 93% tested at 4 A g-1. The better electrochemical performance of this sample was attributed to the synergistic effect of the Co and V atoms since a minimum amount of V in the structure may distort the crystal lattice and improve the electrolyte diffusion, in addition to the formation of several oxidation states due to reduction of V5+, including V3+ and V4+ as well as to the formation of the metastable V4O9.

Construction of different metamorphic degree coal models and corresponding adsorption characteristics based on molecular simulation

Coal samples with different metamorphic degrees have different gas-adsorption capacities. Most of the existing studies analyze differences in gas-adsorption characteristics from a macro perspective, based on experimental methods, and there has been limited research on the micro level. Using industrial and elemental analyzes, Fourier-transform infrared spectroscopy, 13C-NMR, and X-ray photoelectron spectroscopy, we tested and analyzed the molecular-structure characteristics, such as elemental composition, atomic ratio, and functional-group type and distribution, of three coal samples: anthracite (WYM), coking coal (JM), and lignite (HM), with different metamorphic degrees and constructed their macromolecular-structure models. The carbon contents and densities of the models were consistent with the measured values. We also constructed a coal matrix model using a molecular simulation based on the constructed coal molecular model. By comparing and analyzing the trends of adsorption amount, isosteric heat, and selective adsorption coefficient, we explored the differences in the adsorption characteristics of single and binary mixtures on coals with different metamorphic degrees. The adsorption of CH4 and CO2 on the coal matrix conformed to the Langmuir adsorption model. With increasing metamorphic degree, the adsorption amount increased in the order WYM > JM > HM, and the adsorption capacity of the coal matrix for CO2 was higher than that for CH4. The isosteric adsorption heat of CH4 was proportional to the degree of coal metamorphism; however, its relationship with pressure was not clear. Under different temperature and pressure conditions, the selective adsorption of CH4/CO2 on coal with various metamorphic degrees decreased with an increasing CO2 molar ratio. Conditions of 303.15 K (30 °C), 2–4 MPa, and CH4/CO2 = 0.1 were more conducive to the competitive adsorption of CO2 than that of CH4.

The influence of Zn content in Cu/ZnO/SBA-15/kaolinite catalyst for methanol production by CO2 hydrogenation

The capture and utilization of carbon dioxide (CO2) has been attracting increasing interest. Producing methanol from captured CO2 and renewable hydrogen is one promising route for CO2 utilization because it would introduce recycled carbon to a vast global fuels and chemicals market. It is known that the Cu or Pd based catalysts are highly active for methanol synthesis. In this study, Cu/ZnO/SBA-15/kaolinite catalysts were prepared with Zn loading varying – 2.4, 1.6 and 0.5 wt% – to find the optimum amount of Zn in this catalytic system. The catalysts have been characterized using XRD analysis, N2 adsorption–desorption analysis and SEM-EDX analysis. The performance of catalysts was evaluated in a fixed-bed tubular micro-activity reactor at 20 bar 250 °C with H2 to CO2 molar ratio 3 to 1. The activity tests showed that the amount of Zn loaded has a significant impact on methanol yield-catalysts with Zn loading 2.4 and 1.6 have approximately 1.7 times higher space–time yield of methanol than catalyst with Zn loading of 0.5 wt%.

Influence of the Molar Ratio of Co and V in Bimetallic Oxides on Their Pseudocapacitive Properties

Bimetallic oxides have attracted significant attention as supercapacitor electrode materials due to their highly reversible redox processes, which are commonly associated with their surface chemistry and morphological features. In this work, bimetallic oxides with different molar compositions of Co and V, denoted Co0.6V0.4, Co0.65V0.35, and Co0.7V0.3, were synthesized by a modified solvothermal method using glycerol as stabilizing agent. The electrochemical characterizations were measured in a three-electrode cell. The role of the composition of CoV oxides on the pseudocapacitive properties was studied through the analysis of the energy storage mechanism following the power - law and Dunn's methodology (Wang et al., 2007), to obtain the b values. The synthesized CoV oxides were observed to be small conglomerate particles with undefined morphology and crystal structure corresponding to Co3V2O8 with small shifts due to crystal lattice distortion as was evidenced by TEM and XRD characterizations (Fig.1). These results indicated that the bimetallic oxides with a molar composition of Co0.6V0.4, Co0.65V0.35 and Co0.7V0.3 showed values of b of 0.91, 0.73, and 0.82 and a capacitive current contribution of 68, 63, and 66% analyzed at a scan rate of 1 mVs-1, respectively. In addition, the Co0.7V0.3 oxide showed a specific capacitance of 299 F g-1 at a current density of 0.5 A g-1 using 1 mol L-1 of KOH, and a high-rate capability of 81% at current densities of 0.5 - 6 A g-1. The better electrochemical performance of this sample is attributed to the synergistic effect of the Co and V atoms, since a minimal amount of V atoms may distort the crystal lattice and improve the electrolyte diffusion. Keywords: Co-V oxides; capacitance; pseudocapacitive; supercapacitors; rate capability. References Wang, J., Polleux, J., Lim, J. & Dunn, B. (2007). Pseudocapacitive contributions to electrochemical energy storage in TiO2 (anatase) nanoparticles. The Journal of Physical Chemistry C, 111(40), 14925–14931. Figure 1

Quantitative Raman Spectroscopic Determination of the Composition, Pressure, and Density of CO2-CH4 Gas Mixtures

The Raman spectra for pure CO2 and CH4 gases and their ten gas mixtures were collected at pressures and temperatures ranging from 2 MPa to 40 MPa and room temperature (∼24°C) to 300°C, respectively. A systematic analysis was carried out to establish a methodology for the quantitative determination of the composition, pressure, and density of CO2-CH4 mixtures. The shift in the peak position of the υ1 band for CH4 was sufficiently large to enable the accurate determination of the pressure of pure CH4 and CH4-dominated fluids (>50 mol% CH4). An equation representing the observed relationship of the peak position of the υ1 band of CH4, density, and composition was developed to calculate the density of CO2-CH4 mixtures. The Raman quantification factor F (CH4)/F (CO2) was demonstrated to be near a constant value of 5.048 ± 0.4 and was used to determine the CH4 to CO2 molar ratio in an unknown CO2-CH4‐bearing fluid with high internal pressure (>10 MPa) based on the Raman peak area ratio. The effect of temperature on the variation in Raman spectral parameters was also investigated at temperatures up to 300°C. The results showed that the effect of temperature must be considered when Raman spectral parameters are used to calculate the pressure, density, and composition of CO2-CH4 gas mixtures. Raman spectroscopic analysis results obtained for six samples prepared in fused silica capillary capsules were validated by comparison with the results obtained from microthermometry measurements.

Molecular dynamics simulation of CO2-N2 dissolution and stripping of oil films on pore walls based on intermolecular interaction energy

The interaction between crude oil and pore surfaces is notable in the process of CO2 and N2 flooding, and some crude oil can hardly be displaced and remains on pore walls in the form of oil films. The reasons for residual oil retention and stripping from pore surfaces were studied. The results indicated that in hydrophilic systems, the gas phase exhibited the ability to dissolve oil films when the CO2 mole ratio in the gas phase was not lower than 25%, and oil films can be stripped from pore surfaces only when the CO2 mole ratio was not lower than 75%. In hydrophobic systems, when the CO2 mole ratio in the gas phase was higher than 50%, the gas phase exhibited the ability to dissolve oil films. Regardless of the proportion of CO2 in the mixed gas, the gas phase did not provide the ability to strip oil films.

Oxygen vacancy enhancing the Co3O4-CeO2 nanosheets as the cathode to activate peroxymonosulfate for degradation of ceftiofur sodium

Herein, the bimetallic oxides Co3O4-CeO2 with abundant oxygen vacancy (VO) were successfully prepared and applied to activate peroxymonosulfate (PMS) for degradation of ceftiofur sodium (CEF). By optimizing the molar ratio of Co and Ce, nanosheet structures were obtained, which had large surface area and rich oxygen vacancies. The degradation efficiency of CEF can reach 94.3 % and the corresponding TOC removal is as high as 50.3 % after 40 min under the optimum conditions with 10 mA−1 cm−2 current density, pH 3, 5 mM PMS and 25 ℃. 1O2 is the main reactive species and its formation is related with VO in the process of degradation CEF. In details, the abundant VO on the catalyst surface can not only accelerate electron transfer to promote the conversion of PMS → ·SO5-· → 1O2 but also act as electron transport channels to facilitate Co3+/Co2+ redox cycle. This study is of far-reaching significance for oxygen vacancy-activated PMS to promote the efficient degradation of refractory organic pollutants.

Enhanced Fenton-like catalysis for pollutants removal via MOF-derived CoxFe3-xO4 membrane: Oxygen vacancy-mediated mechanism.

Traditional batch configuration is not sustainable due to catalyst leaching and ineffective recovery. Herein, a novel membrane-based catalyst with oxygen vacancies is developed, which assembled metal-organic-framework cobalt ferrite nanocrystals (MOF-d CoxFe3-xO4) on polyvinylidene fluoride membrane to activate peroxymonosulfate (PMS) for catalytic degradation of emerging pollutants. MOF-d CoxFe3-xO4 are synthesized by one-step pyrolysis using Co/Fe bimetallic organic frameworks (CoxFe3-x bi-MOF) with tunable cobalt content as a template (x/3-x represented the molar ratio of Co and Fe in MOF). Intriguingly, MOF-d Co1.75Fe1.25O4 membrane exhibits excellent PMS activation efficiency as indicated by 95.12% removal of the probe chemical (bisphenol A) at 0.5mM PMS (∼100Lm-2h-1at the loading of 10mg), which is significantly higher than the traditional Co1.75Fe1.25O4 suspension system (34.16%). Experimental results show that the membrane has excellent anti-interference ability to anions and dissolved organic matter, and can effectively degrade a variety of emerging pollutants, and its performance is not inhibited by the change of solution pH (3-9) or the long-term (20h) continuous flow operation. EPR and quenching experiments show that catalytic degradation is the result of the synergistic effect of radicals and non-radicals. The oxygen vacancy-mediated mechanism can explain the formation of active substances, and the formation of 1O2 plays an important role in the degradation of bisphenol A. This study provides a membrane-based strategy for effective and sustainable removal of emerging pollutants.

H2-rich syngas production from pyrolysis of agricultural waste digestate coupled with the hydrothermal carbonization process

A novel process to produce a H2-rich syngas from a high moisture-containing agricultural waste digestate is proposed. This process combines the use of hydrothermal carbonization (HTC), dewatering, pyrolysis, and catalytic reforming. Due to the feature of the high moisture content in the digestate, the effect of the HTC and dewatering on the process performance is of interest, and four scenarios were considered. Furthermore, three pyrolytic temperatures were chosen to understand the effect of pyrolysis conditions on the produced H2-rich syngas. A life cycle assessment was conducted to investigate the environmental impact of the proposed process. Results show that the application of HTC technology, increases the process efficiency, produces less syngas from one ton of digestate, lowers the cumulative energy demand and the negative carbon emissions. When the dewatering technology is used, the syngas yield is promoted but the H2 concentration in the syngas is reduced. The H2 to CO molar ratio reaches the maximum value of 9.2 when using a 450 ˚C pyrolysis temperature, by only using HTC. When the combining process of HTC and dewatering is used, it results in the highest process efficiency, but the smallest relative negative CO2 equivalent emissions by treating one ton of dry digestate.

Flower-like bimetal-organic framework derived composites with tunable structures for high-efficiency electromagnetic wave absorption

Recently, high-performance functional composites for electromagnetic wave absorption (EWA) with tunable nano/micro-structures have attracted extensive attention. Herein, the flower-like electrically conductive and magnetic cobalt-nickel@carbon (CoNi@C) composites derived from bimetallic metal-organic frameworks (MOFs) were fabricated via solvothermal method and pyrolysis. By adjusting the ratios of different precursors, different morphological features of composites were formed. When the molar ratio of Co and Ni was 1:2, the CoNi@C composites exhibited the optimal minimum reflection loss (RLmin) of −56.89 dB at 6.7 GHz with an effective absorption bandwidth of 4.7 GHz, due to the coordinated dielectric and magnetic loss caused by the electromagnetic properties of each component as well as the interactions between the unique three-dimensional (3D) interfaces of flower-like structures that promoted the absorption and dissipation of composites for microwaves. The composites are expected to become promising candidates as high-efficiency absorbers in the electromagnetic protection field.

The electron engineering of CeO2/Co(OH)2 hybrids to enhance the performance for overall water splitting in alkaline media

• CeO 2 -Co(OH) 2 was prepared through one-step electro-deposition strategy. • The content of oxygen vacancies increased by the introduction of CeO 2 into Co(OH) 2 . • The electron environment of Co and Ce can be tuned by adjusting Co to Ce ratio. • The optimized CeO 2 -Co(OH) 2 was active for HER and OER. To obtain highly active electrocatalyst for the whole electrochemical water splitting is of importance to generate hydrogen. Co(OH) 2 is used as electrocatalyst towards OER, however, the performance can be improved further. Usually, to construct the interface and adjust the electronic environment of electrocatalysts are regarded as powerful ways to improve the activity. Herein, CeO 2 -Co(OH) 2 sheets supported on copper foam (CF) are fabricated by electrodeposition method. The morphology and the electron structure of metals are adjusted by changing the molar ratio of Co to Ce, thus, resulting in different electrocatalytic activity. The optimal hybrids of CeO 2 -Co(OH) 2 exhibits lower overpotentials of 188, 269 mV to reach 10 mA cm −2 towards HER and OER, respectively, and good stability. Notably, it is found that the electroactivity is extremely superior to that of bare CF as well as the counterparts in the literature. Also, we try to employ M(OH) 2 (M = Fe, Ni) to substitute Co(OH) 2 to investigate the effect of species of hydroxides on the electron interaction between CeO 2 and hydroxides, the XPS results indicate that Ce and Co shows stronger electron interaction compared to other two control hydroxides. As electrocatalysts for alkaline full water splitting, CeO 2 -Co(OH) 2 requires a cell voltage of 1.62 V to drive 10 mA cm −2 . Experimental results prove the advantages of the electron engineering and morphology control.

Selective CO2 reduction to methane catalyzed by mesoporous Ru-Fe3O4/CeOx-SiO2 in a fixed bed flow reactor

Development of a robust catalyst for selective reduction of CO2 directly into hydrocarbon fuels is very challenging from both energy and environmental perspectives as it offers a renewable and green route for the production of fuels. Herein, we report a novel catalyst synthesized via excess solution impregnation of Ru and Fe3O4 nanoparticles (NPs) on ceria promoted mesoporous silica SBA-15 support. The selective catalytic reduction of CO2 to methane was carried out in the presence of H2 over novel Ru-Fe3O4/CeOx-SiO2 (Ce3+/Ce4+, x=1.64) catalyst in a fixed bed reactor. The CO2 conversion was found to be 82% at 0.25 wt% ruthenium loading, 2.5 wt% iron loading, 575 K temperature, 20 bar pressure, 3000 mLg−1h−1 gas hour space velocity and H2 to CO2 mole ratio of 5:1. The close contact between ruthenium and Fe3O4 nanoparticles facilitated the reduction of CO2 through hydrogen spill-over effect at lower temperature, whereas ceria NPs acted as a promoter for this reduction reaction. The catalysts were characterized thoroughly using physicochemical techniques such as CO chemisorption, BET, TPR, TPD, XRD, SEM, HR- TEM, ICP-AES and XPS analyses. High surface area and large mesopores of silica support facilitated the fine dispersion of the active catalytic sites and oxygen vacancy as supported from the DFT study on the catalytic activity. Optimal process conditions could render much higher CO2 conversion efficacy for selective methane synthesis in comparison with previous investigations.

Design and validation of reactant feeding control strategies for the solar-autothermal hybrid gasification of woody biomass

Several hybridization strategies of a solar-autothermal biomass gasifier were examined for stable and continuous operation under variable solar irradiation. The ultimate objective was to demonstrate the feasibility of controlled syngas production, through the modification of oxygen, water, and biomass injection rates. Various hybridization strategies were probed by thermodynamic analysis and experimentally validated. Thermodynamic equilibrium calculations detailed the impact of both H2O and O2 injection rates on the produced syngas composition under constant wood feeding. Oxygen injection decreased the H2:CO molar ratio, while reducing the solar thermal power required to carry out the gasification reaction. Meanwhile, the total H2+CO production dropped by 1.36 mol of H2 and 0.64 mol of CO per mole of O2 added, independently of the quantity of water provided. Validation experiments were then carried out under real concentrated solar flux in a directly-irradiated conical spouted-bed reactor, following distinct hybridization paths. Maintaining constant the H2:CO ratio above 1 during hybridization required to provide high amounts of water steam with oxygen, which penalized the gasifier efficient heating. In contrast, minimizing the water injection rate throughout hybridization strongly altered the H2:CO ratio but decreased the CO2 production and the solar thermal power requirement. Finally, the successful control of the outlet H2+CO volume flow rate with simultaneous oxygen and wood injection was demonstrated (under constant water feeding rate). Solar-to-fuel efficiencies were kept around 20%, while hybridization decreased the cold-gas efficiency below 80%.

Techno-economic Analysis of Biogas Conversion to Liquid Hydrocarbon Fuels through Production of Lean-Hydrogen Syngas

Large-scale biogas plants are a viable source of CH4 and CO2 to be converted efficiently into high-value products. Specifically, production of liquid hydrocarbons can enhance the availability of green fuels while achieving significant CO2 reductions on site. In this study, the production of liquid hydrocarbons is simulated by dry reforming of biogas into lean-hydrogen syngas, further converted in CO hydrogenation and oligomerization reactors. The process was modeled by using CHEMCAD based on published experimental results with the projected feed composition. A high molar feed ratio of CO2/CH4 (>1.7) was set for the reformer to minimize steam requirement while avoiding carbon formation and reaching an optimal H2 to CO molar ratio (0.7). Two options were techno-economically evaluated based on a biogas plant with a capacity of 5000 N m3/h that produces between 13.8 and 15.7 million liters per year of blending stock for transportation fuels. The economics of the process depends mainly on the cost and availability of the biogas. The minimum selling price of the liquid fuels is $1.47/L and $1.37/L for options 1 (once-through conversion of syngas to liquid fuels) and 2 (recycle of tail gas from oligomerization reactor), respectively, and can be significantly reduced in case the biogas throughput is increased to >20 000 N m3/h. Recycling of the tail gas (option 2) yielded higher productivity, resulting in higher carbon yield (77.9% on the basis of methane) and energy efficiency (67.1%). The economic viability of the process can be improved by implementing CO2 tax or other incentives to reduce capital investment. It provides a potential route for efficient conversion of biogas into liquid hydrocarbons to meet the increased demand for renewable fuels as blending stock in the transportation sector while improving the sustainability of the plant.

Deep Eutectic Solvents and Layered Double Hydroxides in Solid‐Phase Extraction of Antidepressant Drugs

AbstractFor the first time, an acidic deep eutectic solvent (DES) comprised of malonic acid and ChCl was used to complete dissolution of Co‐Al, Ni‐Al, and Cu‐Al layered double hydroxides (LDHs) as sorbents in the vortex‐assisted in‐situ solid‐phase extraction of doxepin and amitriptyline followed by high‐performance liquid chromatography‐ultraviolet (HPLC‐UV). Moreover, the ability of urea:ChCl and ethylene glycol:ChCl was investigated to dissolve the LDH sorbents. The extraction conditions were optimized in terms of vortex time, molar ratio of Co2+:Al3+, NaOH concentration, and volume of DES based on the Box‐Behnen design. The linearity, limit of detection, and coefficient of determination R2 for both analytes were assessed as well. Recoveries of more than 93.1 % with relative standard deviations of less than 5.3 % were achieved for spiking urine and pharmaceutical formulation samples.

Effect of the Cu/ZnO/SBA‐15/kaolinite preparation method on the catalyst structural properties and catalytic performance at CO2 hydrogenation at low pressure

AbstractCarbon dioxide catalytic hydrogenation to methanol in the presence of nanocatalysts has been recognized as one of the most effective ways to fix and utilize the emitted CO2. In this study, Cu/ZnO/SBA‐15 catalyst has been synthesized by three different methods: “impregnation‐sol–gel autocombustion” method, impregnation method and direct synthesis method using triblock copolymer Pluronic P123 as a template. Cu/ZnO/SBA‐15 catalysts comprising kaolinite clay have been used in CO2 hydrogenation to methanol for the first time to make the methanol synthesis more cost‐effective. The performance of catalysts upon hydrogenation of CO2 was evaluated in a fixed‐bed tubular micro‐activity reactor at 20 bar with H2 to CO2 molar ratio 3 to 1 and 250°C. Results showed that the highest methanol production, with STY of 36 mg CH3OHh−1gcat−1, could be obtained using the catalyst prepared by “impregnation‐sol–gel autocombustion”. This synthesis method allowed to obtain catalyst with the smallest crystallite size and a good dispersion of the active phase over and into SBA‐15. The CO2 conversion reached 15.9%, which is close to conversion level provided by commercial Cu catalyst.

Synthesis of Co3O4@TiO2 catalysts for oxygen evolution and oxygen reduction reactions

The electrospinning method combined with high temperature thermal annealing was used to prepare TiO 2 fibers modified with different concentrations of Co 3 O 4 . Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), desktop scanning electron microscope (TM3030)-energy spectrometer (SwiftED3000), thermal analyzer (TGA), X-ray diffractometer (XRD), X-ray photoelectron energy Spectral analyzer (XPS), Brunauer–Emmett–Teller (BET) (BET) were used to study the influence of different cobalt oxide concentrations on the morphology of mesoporous TiO 2 fibers. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and continuous cycle method were used to evaluate the fiber's oxygen evolution reaction (OER) and oxygen reduction (ORR) reactivity. It was found that the fiber with a molar ratio of Co to Ti of 1:10 showed the best performance for both OER and ORR reactions in alkaline solution. The fiber showed an overpotential of 382 mV at a current density of 10 mA cm −2 , a Tafel slope of 58 mV·dec −1 , and a half-wave potential change of only 10 mV after 4000 CV cycles. It has an onset potential of 0.83 V (vs RHE) in the ORR reaction. The OER/ORR overpotential gap (E) of 0.85 V is significantly lower than commercial platinum/carbon and bulk TiO 2 analogs. Obviously, this catalytic activity stems from the synergy between Co 3 O 4 and TiO 2 fibers. In addition, the higher specific surface area and the presence of disordered mesopores provide a higher charge carrier density during the electrocatalytic process, which improves the reaction activity. • TiO 2 was adopted in present research to replace carbon as a catalyst support substrate. • The Co 3 O 4 @TiO 2 nanofiber possess an unique mesoporous structure, which provides more active sites for the reaction, and makes good catalytic performance for the reaction through the synergistic of TiO 2 and Co 3 O 4 . • The Co 3 O 4 @TiO 2 nanofibers show good catalytic performance for both the OERand ORR.