N2 Vapor Research Articles

Amino-Functionalizing Ce-Based MOF UiO-66 for Enhanced CO2 Adsorption and Selectivity.

Metal-organic frameworks (MOF) hold great promise for CO2 adsorption due to their high surface areas, tunable pore sizes, and the ability to modify their chemical properties to enhance CO2 affinity. MOFs tagged with functional groups either at linker or metal sites have shown improved CO2 uptake capacity and selectivity. This study focuses on investigating the potential of selective CO2 adsorption using amino functionalization of linker forming Ce-UiO-66. The physicochemical properties and characteristics of MOFs to determine the degree of amino functionalization and structural stability were examined using powder X-ray diffraction (PXRD), Fourier transformer infra-red (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2 porosimetry and specific surface area (BET). This work unveils a novel array of results on CO2, N2 and water vapour adsorption on Ce-UiO-66-NH2. The amino-functionalized Ce-UiO-66-NH2 shows 63 % higher CO2 uptake and 84 % higher CO2/N2 selectivity at 273 K and 1 bar over Ce-UiO-66. Ce-UiO-66-NH2 also shows excellent structural stability after gas and vapour sorption making Ce-UiO-66-NH2 potential adsorbent for CO2 capture.

Continuous adsorption process of [formula omitted]/[formula omitted]/[formula omitted] from [formula omitted] flow using type A zeolite adsorbents in the presence of ultrasonic waves

In this study, the adsorption capacity of different types of zeolite (3A, 4A, and 5A) for adsorbing CO2 from a mixture of CH4, N2, and water vapor was investigated with and without the use of ultrasonic waves. In this study, functional groups of O–H, Si–O–Al and Si–O–Si bands were identified in Fourier transform infrared (FTIR) spectroscopy of these adsorbents. X-ray diffraction patterns (XRD) for zeolite 3A and 5A showed the structure of chabazite and for zeolite 4A the structure of sodalite. In the Brunauer-Emmett-Teller (BET) test, the specific surface area of zeolites was measured as 16, 11.96 and 437 m2g−1, respectively. Ultrasonic waves increased the adsorption capacity of zeolites to adsorb CO2 at lower temperatures 80.64 to 175.44 mgg−1. Zeolite 5A has a higher affinity for CO2 than CH4 or N2, the selectivity of CO2/ N2 and CO2/ CH4 were 19.55 and 24.17, respectively. Data from adsorption experiments were used to learn an artificial neural network (ANN), and the ANN provided acceptable results for predicting the adsorption process.

Reasonable design of Sm-modified Cu-based catalyst for NH3-SCO: Role of the amide intermediates

The selective catalytic oxidation of ammonia (NH3-SCO) is currently the most effective method used to eliminate NH3. However, one of the major challenges for NH3-SCO is the development of catalyst capable of completely converting NH3 into harmless N2 and water vapor. In this paper, a high N2 selective catalyst prepared by the sol-gel method using TiO2 as the support, Cu as the active species, and Sm as the auxiliary agent is presented. Compared to traditional Cu/TiO2 catalyst, the 4SmCu/TiO2 catalyst has higher catalytic activity and N2 selectivity at low temperatures. The NH3 conversion can reach 100%, and the selectivity of N2 can be maintained at 100% at 275 °C. The excellent catalytic activity is attributed to the highly dispersed active species, abundant Lewis acid sites (LASs), and the generation of large amounts of surface-adsorbed oxygen. In addition, doping Sm species will cause TiO2 lattice distortion, and at the same time load the distorted TiO2 with more active material. Moreover, in-situ DRIFTS analysis suggests that both the 4SmCu/TiO2 and Cu/TiO2 catalysts follow the "internal" selective catalytic reduction (iSCR) mechanism during NH3-SCO reactions. The 4SmCu/TiO2 catalyst generates more amides (-NH2), which reduces the non-selective oxidation of the catalysts and promotes the formation of N2. This provides a new idea and method for the selective catalytic oxidation of NH3 to N2 and water vapor using Cu-based catalysts.

Design, Preparation, and High Intrinsic Proton Conductivity of Two Highly Stable Hydrazone-Linked Covalent Organic Frameworks.

Assembling crystalline materials with high stability and high proton conductivity as a potential alternative to the Nafion membrane is a challenging topic in the field of energy materials. Herein, we concentrated on the creation and preparation of hydrazone-linked COFs with super-high stability to explore their proton conduction. Fortunately, two hydrazone-linked COFs, TpBth and TaBth, were solvothermally prepared by using benzene-1,3,5-tricarbohydrazide (Bth), 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (Tp), and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (Ta) as monomers. Their structures were simulated by Material Studio 8.0 software and confirmed by the PXRD pattern, demonstrating a two-dimensional framework with AA packing. The presence of a large number of carbonyl groups as well as -NH-NH2- groups on the backbone is responsible for their super-high water stability as well as high water absorption capacity. AC impedance tests demonstrated a positive correlation between the water-assisted proton conductivity (σ) of the two COFs and the temperature and humidity. Under 100 °C/98% RH, the highest σ values of TpBth and TaBth can reach 2.11 × 10-4 and 0.62 × 10-5 S·cm-1, which are among the high σ values of the reported COFs. Their proton-conductive mechanisms were highlighted by structural analyses as well as N2 and H2O vapor adsorption data and activation energy values. Our systematic research affords ideas for the synthesis of proton-conducting COFs with high σ values.

Construction of Water Vapor Stable Ultramicroporous Copper-Based Metal–Organic Framework for Efficient CO2 Capture

It is quite essential to obtain an excellent CO2 adsorption capacity, CO2 adsorption selectivity and water vapor stability at the same time for practical CO2 capture after combustion. Through the combination of ultramicropore and the high density of CO2-philic sites without OMSs, an ultra-microporous Cu-based metal–organic framework has been designed and synthesized, featuring a high CO2 capacity (99 cm3 g−1 and 56.6 cm3 g−1 at 273 K and 298 K, respectively), high selectivity over N2 (118 at a scale of CO2/N2 15/85, 298 K) and excellent water vapor stability, simultaneously. Theoretical calculations indicate that neighboring ketonic O atoms with suitable distance play vital roles in boosting CO2 selective capture.

Interaction of molecular nitrogen with vanadium oxide in the absence and presence of water vapor at room temperature: Near-ambient pressure XPS.

Interactions of N2 at oxide surfaces are important for understanding electrocatalytic nitrogen reduction reaction (NRR) mechanisms. Interactions of N2 at the polycrystalline vanadium oxide/vapor interface were monitored at room temperature and total pressures up to 10-1 Torr using Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS). The oxide film was predominantly V(IV), with V(III) and V(V) components. XPS spectra were acquired in environments of both pure N2 and equal pressures of N2 and H2O vapor. In pure N2, broad, partially resolved N1s features were observed at binding energies of 401.0 and 398.7eV, with a relative intensity of ∼3:1, respectively. These features remained upon subsequent pumpdown to 10-9 Torr. The observed maximum N surface coverage was ∼1.5 × 1013cm-2-a fraction of a monolayer. In the presence of equal pressures of H2O, the adsorbed N intensity at 10-1 Torr is ∼25% of that observed in the absence of H2O. The formation of molecularly adsorbed H2O was also observed. Density functional theory-based calculations suggest favorable absorption energies for N2 bonding to both V(IV) and V(III) cation sites but less so for V(V) sites. Hartree-Fock-based cluster calculations for N2-V end-on adsorption show that experimental XPS doublet features are consistent with the calculated shake-up and normal, final ionic configurations for N2 end-on bonding to V(III) sites but not V(IV) sites. The XPS spectra of vanadium oxide transferred in situ between electrochemical and UHV environments indicate that the oxide surfaces studied here are stable upon exposure to the electrolyte under NRR-relevant conditions.

PENGARUH PERBEDAAN WAKTU EKUILIBRASI TERHADAP KUALITAS SEMEN BEKU BABI LANDRACE DALAM PENGENCER DURASPERM MODIFIKASI DENGAN AIR BUAH LONTAR (Effect of different equilibration time on the quality of landrace boar frozen semen on modification diluent....

An experiment was carried out to recognize the effect of long equilibration time on the quality of spermatozoa and to obtain optimal equilibration time in the process cryopreservation of landrace pig semen. Semen was obtained from a landrace boar aged 2-3 years using glove hand method. The semen was than evaluated macroscopically and microscopically, good quality semen was diluted in a basic diluent, than kept for two hours at a temperature of 27-28oC. The semen were then centrifuged at 2000 rpm for 15 minutes, the supernatant was discarced and the pellets was re-diluted into basic diluent with a ratio of 1:1. Then, semen was diluted in treatment diluent with modified durasperm + 6% lactose + 4% glycerol with a concentration of 500 x 106/0.5 mL. Furthermore, the semen was packaged in 0.5 ml straws, then equilibrated at a temperature of 3-5oC appropriate to treatment, with 1 hour equilibration (T1), 2 hours equilibration (T2) and 3 hours equilibration (T3). After equilibration, the straws was frozen horizontally 5 cm above the liquid N2 vapor for 10 minutes at a temperature of ± -110oC and then stored in a liquid N2 container (-196oC). To test frozen semen, it was done by stored frozen semen at 37oC for 30 seconds. The results showed that the highest quality of spermatozoa (P <0.05) was found in T2 and T3 when compared to T1 (P> 0.05), with the motility value was T2: 28.13 ± 2.39%; T3: 25.00 ± 4.08%; and T1 18,15±3,23%. It can be concluded that 2 hours and 3 hours equilibration time was able to maintain the quality of frozen semen landrace boars and the statistically was not significant.

Effective green ammonia synthesis from gaseous nitrogen and CO2 saturated-water vapour utilizing a novel photocatalytic reactor

The ammonia synthesis from nitrogen and hydrogen derived from water vapor in the photocatalytic process performed under mild conditions is presented. A new solution of a gas-phase photocatalytic reactor with the bed in the form of a UV transparent glass fiber cloth coated with AEROXIDE® P25 TiO2 was applied. The bed in the reactor is located just above the water surface. The gases circulate from above towards the water surface, where the produced ammonia is easily absorbed and continuously separated from the gas phase, shifting the ammonia synthesis equilibrium towards the product. The highest amount of ammonia (about 1.3 mmol NH4+/g TiO2 after 6 h) was obtained at 20 °C, and with the use of the gaseous mixture containing CO2 (15%), N2 (85%), and water vapour derived from water located at the bottom of the reactor. Carbon dioxide in the reaction environment is simultaneously reduced to carbon monoxide and methane.

A Modified Surgical Face Mask to Improve Protection and Wearing Comfort

Wearing face masks is essential for reducing infection during the COVID-19 pandemic. However, ordinary surgical face masks can provide only moderate protection. The N95 face masks should provide sufficient protection but may impose complaints about breathing difficulty or even impair respiratory health. This investigation proposed a novel face mask modified from the surgical face mask to improve both protection and comfort. The filter material of the surgical face mask was covered and sealed on a cardboard support frame but with openings for air permeating through. The modified face masks were worn by a test subject for measuring the air contents inside the face masks. The protection performance was evaluated by the overall PM1 filtration efficiency. The concentrations of CO2, O2, N2, and water vapor were adopted to evaluate the breathing comfort. The performance of the proposed face mask was compared with the market-available surgical and N95 face masks. In addition, CFD modeling was adopted to investigate the dynamic air exchange of the face mask with respiration and the surrounding air. Impacts of the air sampling tube positions on the measurement results were also examined. The results revealed that the overall PM1 filtration efficiency of the modified face mask could reach 96.2%, which was much higher than that of the surgical face mask and only slightly lower than the N95 face mask. As compared with the N95 face mask, the modified mask reduced the respiratory flow resistance and the concentrations of CO2 and water vapor and thus increased the O2 content and breathing comfort.

Superhydrophobic Pt@SBA-15 catalyst for hydrogen water isotope exchange reactions

In this work, Santa Barbara amorphous-15 (SBA-15) mesoporous silica was modified to fabricate hydrophobic microscopic reaction environments that enhanced the catalytic activity of the liquid phase catalytic exchange (LPCE) reaction. The hydrophobicity or hydrophilicity of the environments synthesized using modified SBA-15 was verified by conducting N2 and water vapor adsorption-desorption experiments. A porous composite catalyst, Pt@SBA-15-x/PVDF, was synthesized via a two-solvent method. The water contact angle of Pt-modified SBA-15 was 152°, proving its superhydrophobicity and granting it excellent catalytic performance for LPCE techniques in hydrogen-water isotope exchange processes. The catalytic performance of the hydrophobic catalyst did not decrease significantly after 30 days of usage.

Two stable phenyl acyl thiourea carboxylate-based MOFs: Syntheses, crystal structures and proton conductive properties

The phenyl-substituted acylthiourea-carboxylic acid ligand has several coordination sites and strong coordination ability. The MOFs constructed by these ligands are flexible and stable, which is very beneficial to the study of proton conductivity. In this paper, we designed and synthesized two MOFs, [Mn(H2BBT)2(H2O)2]n (H3BBT = N-benzoyl-N′-(4-benzoxy)thiourea) (1), and [Cd(H2BBT)2]n (2) by the solvent evaporation method. Their molecular structures were characterized by single-crystal X-ray diffraction. The high water and chemical stability of the two MOFs were confirmed by X-ray powder diffraction. The AC impedance spectra of them show that the proton conductivity increases with the increase in temperature and humidity. The best proton conductivities of 1 and 2 are 1.69 ​× ​10-5 and 1.79 ​× ​10-4 ​S ​cm-1 under 98% RH and 100 ​°C, respectively. The proton conduction mechanisms of the two MOFs were highlighted based on the calculated activation energy, structural characteristics, N2 and H2O vapor adsorption determinations, and so on.

High Protonic Conductivity of Three Highly Stable Nanoscale Hafnium(IV) Metal-Organic Frameworks and Their Imidazole-Loaded Products.

Attracted by the exceptional structural rigidity and inherent porous structures of the Hf-based metal-organic frameworks (MOFs), we adopted a rapid synthesis approach to preparing three nanoscale MOFs, Hf-UiO-66 (1), Hf-UiO-66-(OH)2 (2), and Hf-UiO-66-NH2 (3), and systematically explored the water-assisted proton conductivities of the original ones and the post-modified products. Interestingly, the proton conductivities (σ) of all three MOFs exhibit significant temperature and humidity dependence. At 98% RH and 100 °C, their optimal σ values can reach up to 10-3 S·cm-1. Consequently, imidazole units are loaded into 1-3 to obtain related MOFs, Im@1, Im@2, and Im@3, and the σ values of the imidazole-loaded products are boosted to 10-2 S·cm-1. Note that these modifications not only do not change the frameworks of the pristine MOFs but also do not affect their high chemical and water stability. The proton-conductive mechanisms of these MOFs before and after modification have been thoroughly discussed based on structural analyses, N2 and H2O vapor adsorptions, and activation energy values. The excellent structural stability as well as the durability and stability of their proton conduction ability indicate that these MOFs can be used in the field of fuel cells and so on.

Specific Surface Area of Nanopowders from Argon Adsorption at 77 and 87 K: Zeta Adsorption Isotherm Approach

The surface characterization of nanopowders is widely attempted by both N2 and Ar vapor adsorption methods. They are used as complementary probe molecules because of their similarities and certain differences. However, the respective reported analyses, using the Brunauer–Emmett–Teller method, suffer from inconsistencies between the determined values of the specific surface areas, As. We examine this issue by using the zeta adsorption isotherm approach on the reported data for both vapors on two different samples from the same batch of a nanopowder material. By assuming the equivalence of the As determined by both of the vapors, we obtain the average occupied area of an adsorbed argon atom, σA(Ar), on silica and carbon black at the solid- and liquid-state temperatures of 77 and 87 K, respectively. We then examine the determined value of σA(Ar) by obtaining As for other samples of the same material with varying specific areas. By transforming the adsorption data from mass-specific to area-specific, the respective thermodynamic isotherms, nSV, of Ar vapor adsorbing on silica and carbon black are obtained. The determined nSV are then used with the Gibbs adsorption equation to determine the solid surface energy, γS0, and solid–vapor interface energy, γSV, for both substrates. The obtained γSV(xV) on both substrates is used to interpret the phase transition state of the Ar adsorbate at 77 K. The determined thermodynamic isotherms for Ar and N2 vapors are further used in a comparative study to show that the Ar vapor adsorption is negligibly affected by the change in silanol concentration on the silica surface in contrast with N2 vapor adsorption.

Study of cryogenic CO2 capture with solar-assisted VAR system

One of the major contributors to the rise in global warming potential (GWP) is the continuous accumulation of carbon dioxide (CO2) in the atmosphere. Carbon capture and storage (CCS) is a modern approach to capture CO2 from various industrial processes and store it efficiently for further use. In the cryogenic carbon capture method, CO2 is liquefied by condensation and separated from the CO2 contained gas. The CO2 capture by the cryogenic method can yield high purity CO2 and negligible secondary emissions. However, huge energy is required for the condensation process. In the present study, a low energy penalty method for a post-combustion carbon capture process by the application of the cryogenic technique is performed using process simulation. To reduce energy consumption, a solar integrated vapor absorption refrigeration (VAR) system is designed. The designed solar VAR system provides the required refrigeration cooling load for condensing CO2 in a flue gas stream. For this purpose, the flue gas mixture composed of CO2, N2, and water vapor with respective molar fractions of 15%, 75%, and 10% is considered. The mass flow rate of the flue gas considered is 673.4 kg/s at 1.1 bar and 40 °C. CO2 is separated by condensing the gas at a pressure of 40 bar and temperature of −28 °C. The heat energy required to operate the VAR is 83.3 MW at 75 °C which is supplied by the solar collector. The simulation result indicates that for a post-combustion process, a high-grade electrical energy penalty is found to be about 1.26 MJ/kg CO2 captured, which is better than the most common approaches like absorption, adsorption, and membrane methods. It is also observed that with the increase in the CO2 concentration from 15 to 25 mol% in the flue gas, the energy penalty is reduced by about 37.5%. The performance analysis is also carried out by varying the CO2 recovery rate and purity. It is observed that the energy penalty is decreased by about 10.3% with the increase of CO2 recovery from 90% to 100%. Also, the energy penalty is increased by 4.2% with the increase of CO2 purity from 95% to 100%. The specific CO2 capture process cost is found to be about 1.008 million USD/(kg.s−1).

Atomic-level insights into the activation of nitrogen via hydrogen-bond interaction toward nitrogen photofixation

Summary As the activation of N2 molecules is generally regarded as the bottleneck in N2 reduction, it is of significant importance to develop promising strategies to efficiently activate N2 molecules. Herein, we discovered an innovative approach to activate N2 molecules via hydrogen-bond interaction in N2 photofixation. Porous Cu with surface modification of S atoms (3%-S/Cu) exhibited remarkable catalytic activity and stability in N2 photofixation. Further mechanistic studies revealed that surface S atoms directly participated in the catalytic process by accepting and donating H atoms. In addition, the forming S–H bond significantly promoted the activation of N2 molecules via hydrogen-bond interaction, contributing to the enhanced catalytic activity.

Thermodynamic N2 Vapor Isotherms of Materials: Zeta Adsorption Isotherm Approach

For N2 vapor adsorbing on a nanopowder at 77 K, we use a multicomponent canonical ensemble to determine the conditions for equilibrium between a contacting vapor phase and the adsorbed molecular clusters. Provided the substrate variations (heterogeneities) do not cause a phase transition, such as wetting or capillary condensation, we show that the equilibrium conditions allow an expression for an adsorption isotherm to be formed. The isotherm expression contains four constants that are to be obtained empirically from mass-specific adsorption measurements. The specific surface area of a substrate is expressed in terms of the specific number of adsorption sites and the cross-sectional area of an adsorbed N2 molecule on materials. This procedure is investigated by using the respective specific surface areas of different samples of a given material to transform the data into an area-specific basis. We pooled data sets from multiple samples with possibly different specific surface areas to form a single data set. The thermodynamic (zeta adsorption) isotherm is formulated after a regression analysis is performed on the pooled data set. This isotherm is used with the Gibbs adsorption equation to obtain the solid surface energy of a material as a function of the amount adsorbed. Five materials are examined: silica, α-alumina, γ-alumina, carbon black, and graphitized carbon. Their respective solid surface energies are each shown to be a material property.

Adsorption of Carbon Dioxide, Water Vapor, Nitrogen, and Sulfur Dioxide on Activated Carbon for Capture from Flue Gases: Competitive Adsorption and Selectivity Aspects

There is extensive interest in postcombustion flue gas treatment for mitigating CO2 emissions and removal of acid gases. In this study we investigate the adsorption of the main flue gas components (CO2, N2, SO2, and water vapor) on Filtrasorb 400 activated carbon to understand adsorption characteristics of the main components and competitive adsorption effects. The adsorption isotherms of the pure components of flue gas, CO2 (273.15–318.15 K and 0–50 bar), N2 (298.15–313.15 K and 0–150 bar), SO2 (273.15–303.15 K and 0–3.6 bar), and water vapor (293.15–303.15 K and 0–41 mbar), were investigated. The isosteric enthalpies of adsorption were determined to be a function of surface excess. The enthalpies at zero surface coverage have the order SO2 > H2O > CO2 > N2. However, the SO2 isosteric enthalpy decreases with increasing surface excess and is lower than that of water vapor at high surface excess uptake values. The temperature range for CO2 adsorption covers the subcritical to supercritical gas transition. There was no evidence for isosteric enthalpy differences over this temperature range. The adsorption kinetics for SO2 (290.65–303.15 K) and H2O (293.15–303.15 K) adsorption were measured for each isotherm pressure increment. In both cases the adsorption kinetics followed the linear driving force model. The adsorption mechanisms for both SO2 and H2O kinetic trends are discussed in terms of the adsorption mechanisms. The water vapor adsorption kinetics showed a minimum in the region where water molecules form clusters around functional groups, which merge in the pores. The SO2 adsorption kinetics also show a minimum with increasing surface coverage, and this is attributed to dipole–dipole interactions. The activation energies for diffusion of both SO2 and H2O into F400 were very low. Both the N2 and CO2 adsorption kinetics were too fast to be measured accurately by the gravimetric method used in this study. Ideal adsorbed solution theory (IAST) was used to calculate competitive adsorption of SO2/CO2 and CO2/N2 from the isotherms of the pure components. The competitive adsorption of CO2/N2 was investigated by using the integral mass balance (IMB) experimental method, and this was used for validation of the IAST. The results provide an insight into the role of competitive adsorption in the capture of CO2 and SO2 from flue gases by adsorption from both thermodynamic and kinetic perspectives.

Control of the hydration layer states on phosphorus-containing mesoporous silica films and their reactivity evaluation with biological fluids.

Transparent phosphorus-containing MPS (PMPS) films were synthesized by the introduction and reaction of phosphoric acid into the silica framework during the sol-gel reaction. We then investigated the hydration layer structures formed on the PMPS films and achieved the selective adsorption of fibronectin (Fn). In particular, the surface analyses indicated that the P atom was distributed at the outermost surfaces of the PMPS films. The PMPS films exhibited a high transparency (e.g., averaged transmittance value in the visible light region: 79%), and the haze value (0.14%) decreased with the increasing P/Si molar concentration. Solid-state 29Si-NMR and Fourier transform infrared spectroscopy (FT-IR) spectra indicated the formation of Si-O-P bonds, suggesting that the condensation reaction between the Si-O- and P-O- groups effectively occurs in the silica framework. The larger amount of P-O- and P[double bond, length as m-dash]O groups at the Si-O-P bonding site on the films affects the water molecular adsorption states (i.e., formation of the hydration layer), which was supported by the Brunauer-Emmett-Teller (BET) surface areas of N2 and water vapor, leading to enhancement of the hydrogen bondability of the PMPS films with the increased formation of Si-O-P bonds. The deconvolution results of the FT-IR spectra demonstrated that the ratio of free water to bonding water increased significantly with an increase in the formation of Si-O-P bonding, and the resulting O-H stretching vibration in the hydration layer became more asymmetric. It is suggested that the water molecules are irregularly hydrogen-bonded with the different functional groups of Si-O-, P-O- and P[double bond, length as m-dash]O. In the immersion experiment of the PMPS films in phosphate buffer, the resultant P/Si molar concentration of the PMPS film decreased upon increasing the immersion time and the mesostructures were preserved. The amount of Fn adsorption significantly increased as the O-H stretching vibration of the water molecules became more asymmetric, whereas the adsorption of fibrinogen was completely suppressed by the films. Therefore, we found that the addition of phosphoric acid in the MPS film synthesis significantly affects the hydration layer structures on the film surfaces to provide the possibility of selective protein adsorption.

Fabrication and Characterization of Porous Core–Shell Graphene/SiO2 Nanocomposites for the Removal of Cationic Neutral Red Dye

Porous rGO/SiO2 nanocomposites with a “core-shell” structure were prepared as an efficient adsorbent for the liquid-phase adsorption of cationic neutral red (NR) dye. The samples were characterized with powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TG), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N2 and water vapor adsorption/desorption methods. The NR removal ability and kinetics of the adsorption process of SiO2 and the rGO/SiO2 nanocomposites were investigated at 298 K. The rGO/SiO2 nanocomposite SG 0.30 showed a superior adsorption of NR dye. In regard to NR at pH 5, we measured a superior adsorption capacity of 66.635 mg/g at an initial NR concentration of 50 mg/L. The experimental adsorption capacity of SG 0.30 was 3.791 times higher than that of SiO2. Then, we compared the results with similar materials used for NR removal. Moreover, the water adsorption sites provided by the nitrogen- and oxygen-containing groups might be one of the reasons for the increased adsorption of water vapor. The broad range of properties of the rGO/SiO2 nanocomposite, including its simple synthesis, ability to be mass prepared, and strong adsorption properties, makes it a truly novel adsorbent that can be industrially produced, and shows potential application in the treatment of wastewater-containing dyes.

Electrochemical Devices with Ru Catalysts, Hydrogen-Permeable Membranes, and Phosphate Electrolytes for Ammonia Synthesis from Nitrogen and Water

Ammonia is an indispensable bulk chemical for artificial fertilizers and various industries, and it is now expected to be utilized as a chemical energy carrier. When ammonia is synthesized from nitrogen and water which are abundant in the atmosphere with electricity from renewable energies, ammonia is the most ideal chemical fuel utilizable to fuel cells, combustion engines, hydrogen converters, and so on. Conventional industrial ammonia synthesis, so called Haber–Bosch process, currently consumes 1 or 2% of human consumption energy which is mostly from fossil resources. The point is that the most part of consumed energy is for hydrogen production for Haber–Bosch process, since Haber–Bosch synthesis of ammonia is exothermic process releasing heat from high energetic hydrogen to form relatively lower energetic ammonia. Therefore, it is hard to reduce the energy consumption when ammonia is produced from hydrogen. On the other hand, because ammonia is essentially lower energetic chemicals than hydrogen, the energy consumption for ammonia synthesis can be reduced if ammonia is synthesized from nitrogen and water with minimum electricity. Furthermore, a small single electrochemical device has significant advantages over a combination of water electrolysis and Haber–Bosch process; the absence of operation and storage of hydrogen gas, easy start and stop of single devise, simple heating and cooling equipment, distributed small scale devises like fuel cells.The present work indicates that a combination of Ru ammonia catalysts, Pd hydrogen-permeable membranes, phosphate electrolytes enables ammonia synthesized from nitrogen and water at ~250ºC and ~1.0 MPa. The combination of endothermic water electrolysis and exothermic ammonia synthesis in an electrochemical cell leads thermally neutral process without heat loss. In the temperature range of 200~250ºC, the equilibrium of ammonia synthesis reaction shifts to ammonia formation with moderate pressurizing to ~1 MPa. Ammonia is intrinsically decomposed to nitrogen and hydrogen at higher temperature according to the equilibrium. The temperature of 200~250ºC is challenging for Ru ammonia catalysts, because they are typically used at 350~500ºC for typical ammonia synthesis. The presence of Pd hydrogen-permeable membranes blocks absorption of produced ammonia into proton-conductive electrolytes and penetration of water from the anode side into produced ammonia. The maximum ammonia formation rate was 11.1 nmol s-1 cm-2 at 20 mA cm-2, 250ºC, 1.0 MPa, 10 cm3 min-1 of N2 flow and vapor of 1 micro-L liquid H2O with 10 cm3 min-1 of Ar flow. At that time, current efficiency for ammonia formation was 16% and hydrogen was produced with the remaining 79% of current. According to the thermodynamic equilibrium of ammonia synthesis, 36% conversion of hydrogen to ammonia is the equilibrium limit at 250ºC and 1.0 MPa, so that attainment of equilibrium was 44%. As Ru ammonia catalysts, Ru/Cs+/MgO, Ru/Cs+/CeO2, and Ru/CeO2 were examined. Ru/Cs+/MgO showed the highest ammonia synthesis rate under elevated pressure conditions. The point of this cell for higher ammonia formation rates is the operation of H2/N2 ratio at 0.07 which is much lower than 3 of stoichiometry. Ammonia synthesis with Ru catalysts at the low temperature regime was strongly suppressed by the presence of hydrogen in spite of one of the reactants, so that the excess nitrogen need to be fed to the reactor. Suppression of nitrogen activation by the presence of hydrogen is found to be the key factor for further developments.For understanding the properties of adsorption of nitrogen and hydrogen, infrared spectroscopy and temperature programmed desorption measurements have been performed. The presence of Cs+ promoter has been known that it makes electron rich at the nitrogen adsorption sites of Ru. However, the present work found that the presence of Cs+ promoter affected the hydrogen adsorption to be weakened.The further strategy for the development of present electrochemical ammonia synthesis cell will be discussed in the presentation. Figure 1