Chemisorption Properties Research Articles

Adsorption and Gas Sensing Properties of the Pt3-MoSe2 Monolayer to SOF2 and SO2F2.

SF6 acts as an insulation gas in gas-insulated switchgear (GIS), which inevitably decomposes under partial discharge caused by insulation defects. This work is devoted to finding a new gas-sensing material for detecting two characteristic SF6 decomposition products: SOF2 and SO2F2. The platinum-cluster-modified molybdenum diselenide (Pt3-MoSe2) monolayer has been proposed as a gas sensing material. Based on first-principles calculations, the adsorption properties and the mechanism were studied by analyzing the adsorption structures, adsorption energy, charge transfer, density of states, and molecular orbitals. The adsorption ability of Pt3-MoSe2 to SO2F2 is stronger than that to SOF2 due to its chemisorption property. The obvious change of conductivity of the adsorption system during the gas adsorption process shows that Pt3-MoSe2 is sensitive to both of the gas molecules. In addition, the modest adsorption energy signifies that the gas adsorption process can be reversible, which confirms the feasibility of Pt3-MoSe2-based gas sensors. Our calculation suggests that Pt3-MoSe2-based gas sensors can be employed in GIS for partial discharge detection.

Highly efficient adsorption of Pb(II) by cubic nanocrystals in aqueous solution: Behavior and mechanism

As one of the most toxic heavy metal ions, lead pollution has become an urgent problem. Here, a cubic crystal nanoparticle (Prussian blue analogue, PBA), referred to as potassium manganese ferrocyanide (KMFC) was synthesized and used as a highly-effective sorbent for removing Pb(II) from aqueous solution. KMFC is a mesoporous material that has excellent ion exchange properties, which was confirmed by a series of characterizations. This paper investigated the adsorptive attributes of KMFC for lead ions in aqueous solution. The influences of temperature, contact time and pH on adsorption were studied in batch experiments. The KMFC possessed a robust adsorption capacity for resident lead ions in aqueous solution, which attained 1075.27 mg g−1 at room temperature (25 °C), based on the Langmuir model, which was far higher than any previously reported values. The adsorption process was well fitted to a pseudo-second-order kinetic model, as well as Langmuir and Temkin isotherm models, and was endothermic and spontaneous on the basis of thermodynamic analysis. The adsorption of Pb(II) on the surface of KMFC started with electrostatic attraction, due to the electronegativity of KMFC. Further, ion exchange was the dominant mechanism in this adsorption process, which was confirmed by FTIR, XPS, and other supplementary experiments. The good chemisorption (K+ exchange) properties of KMFC suggested that it likely has excellent prospects in applications for heavy metal ions adsorption. This study not only provided a new perspective for the design and development of heavy metal sorbents but provided a deep insight into the mechanism of adsorption of heavy metal ions by PBA.

Vertically aligned graphene nanosheets on multi-yolk/shell structured TiC@C nanofibers for stable Li–S batteries

Maintaining structural stability and alleviating the intrinsic poor conductivity of cathode materials are of great importance for practical application of Li–S batteries. Introducing void space and a highly conductive host to accommodate the volume changes and enhance the conductivity would be a smart design to achieve robust construction; effective electron and ion transportation, thus, lead to prolonged cycling life and excellent rate performance. In this regard, we report the design of carbonaceous hybrid with vertically aligned graphene assembled on multi-yolk/shell structured TiC@C nanofibers to afford synergistic properties of enough space, strong chemisorption and active electrocatalysis, high electrical conductivity as a sulfur host. Thus, the as-prepared sulfur cathode delivers an excellent cyclability over 800 cycles, a high areal capacity of 6.81 ​mA ​h ​cm2 at a high sulfur loading (10.5 ​mg). More importantly, soft package battery was also prepared with a capacity of 530 ​mAh g−1 and 46.5 ​mAh in the first cycle at a sulfur loading of 4.5 ​mg ​cm−2, which reveals its potential in promoting the practical application of Li–S batteries.

Wave function and molecular reactivity study of char with different edges and the chemisorption properties of nitric oxide

Molecular reactivity of simplified char models with armchair and zigzag edges and chemisorption properties of nitric oxide were studied with wave function theory and density functional reactivity theory. By comparing the electronegativity, electrophilicity and nucleophilicity of different models, it was concluded that chemisorptions of nitric oxide onto carbon models were electrophilic reactions. Electrons transferred to nitric oxide during chemisorption processes. The lowest unoccupied molecular orbital (LUMO), the highest occupied molecular orbital (HOMO), value of electron localization function, electrostatic potential distribution on van der Waals surface and electron density difference of char models with armchair and zigzag edges were analyzed. Zigzag edges were packed with more lone pair electrons, making them more vulnerable to electrophilic attacks. Double descriptors of different models were analyzed to elucidate why NO was more inclined to be chemisorbed at edges rather than onto carbon plane. The specific adsorption sites at edges were predicted by comprehensive analyses of atomic charge, condensed local electrophilicity, condensed local softness and the contribution to HOMO/LUMO orbital of each atom. Energies released from NO chemisorptions in different modes were calculated with and without considering London dispersion interaction. The thermodynamic results were consistent with the predictions of wave function theory and density functional reactivity theory. The dispersion effect should be considered when simulating carbon-based material systems.

A New Type of Strong Metal-Support Interaction Caused by Antimony Species

Interactions between metals and supports are of fundamental interest in heterogeneous catalysis, Noble metal particles supported on transition metal oxides (TMO) may undergo a so-called strong metal-support interaction via encapsulation. This perspective addresses catalytic properties of the metal catalysts in the SMSI state which can be explained on the basis of complementary studies. The electronic geometric and bifunctional effects originating from strong metal-support interactions (SMSI) that are responsible for the catalyst’s activity, selectivity, and stability are key factors that determine performance. A series of Pd-Sb supported on different metal oxide (i.e. SiO2, γ-Al2O3, TiO2, and ZrO2) were prepared by the impregnation method. The catalysts were characterized by N2 adsorption (BET-SA and pore size distribution), TEM (transmission electron microscope), TPR (temperature-programmed reduction), CO-chemisorption, the structural characterization of Pd (dispersity, surface area), interaction between Pd and Sb2O3 and also the influence of the nature of the support were investigated. SiO2 supported Pd catalyst exhibited the highest surface area (192.6 m2/g) and pore volume (0.542 cm3/g) compared to the other supported oxides catalysts. The electron micrographs of these catalysts showed a narrow size particle distribution of Pd, but with varying sizes which in the range from 1 to 10 nm, depending on the type of support used. The results show almost completely suppressed of CO chemisorption when the catalysts were subjected to high temperature reduction (HTR), this suppression was overcome by oxidation of a reduced Pd/MeOx catalysts followed by re-reduction in hydrogen at 453 K low temperature reduction (LTR), almost completely restored the normal chemisorptive properties of the catalysts, this suppression was attributed by SbOx species by a typical SMSI effect as known for other reducible supports such as TiO2, ZrO2, CeO2, and Nb2O5.

An experimental and theoretical approach to investigate correlation between electromagnetic properties of doped ferrites & its interfacial reactivity with dopamine

Magnetic nanoparticles have attained considerable attention in the field of biomedicine. It can acquire single magnetic domain when particle size is scaled down to few nanometers and exhibit high coercivity and magnetization. At diameter less than 30 nm it exhibits superparamagnetism which makes it an attractive candidate for biosensing, magnetic resonance imaging and targeted drug delivery applications. However colloidal instability limits its application. The use of bifunctional linkers not only stabilizes nanoparticles but also provides one-step synthesis system in which linker has an attachment site for magnetic nanoparticles and another site bearing COOH−/NH2+ which allows binding of functional proteins or drugs. In this study, we selected dopamine for functionalization of Magnetite, Cobalt and Zinc Ferrite nanoparticles to understand how introduction of bivalent cations affects the chemisorption properties. Changes in its interfacial reactivity towards dopamine were first determined theoretically and interacting species were identified through Fourier Transform Infra-red Spectroscopy/FTIR. Dopamine binds with Fe+2 at octahedral positions through its -OH group in bidentate bridging configuration while addition of Zn+2 shifts its reactivity towards amine groups. A correlation between interfacial reactivity & electromagnetic properties of doped Iron oxides determined using combinations of pseudopotential and relativistic treatment methods, has also been established.

Synthesis, characterisation and CO2 adsorption potential of NaA and NaX zeolites and hydrotalcite obtained from the same coal fly ash

Hydrotalcites and zeolites are materials characterised by a high capacity for CO2 adsorption and can therefore be useful adsorbents for the capture of CO2 from flue gases. In this study, two types of zeolites (NaXFA and NaAFA) were successfully synthesised from South African coal combustion fly ash. Their CO2 adsorption properties, as well as those of a hydrotalcite (HTFA) synthesized from the same fly ash in our previous work, were investigated and compared. In addition, this paper reports the CO2 adsorption capacity of a novel hierarchical morphology NaX-type zeolite (NaXFA) made from fly ash. This material was characterized by plate-like structures arranged in ball-like clusters with crystal widths of between 63 nm and 99 nm. NaXFA was characterised by very high CO2 physisorption properties and was therefore the most suitable candidate for low temperature and pressure swing adsorption generally required in short-term CO2 adsorption applications. In contrast, both physisorption and chemisorption properties were observed for NaAFA and HTFA. However, HTFA was the most suitable material for chemisorption of CO2. The findings demonstrated the suitability of utilising HTFA for both short- and long-term capture of CO2.

Facile Synthesis of Mordenite Nanoparticles for Efficient Removal of Pb(II) Ions from Aqueous Media

The current research presents the fabrication of mordenite nanoparticles via a hydrothermal technique using low-cost mixed organic templates. The utilized templates such as (polyethylene glycol 200 and glycerol), (polyethylene glycol 200 and ethylene glycol), (ethylene glycol and glycerol), and (ethylene glycol, polyethylene glycol 200, and glycerol) were named PEG-GL, PEG-EG, EG-GL, and EG-PEG-Gl, respectively. Characterization of the fabricated nanoparticles was carried using FE-SEM, HR-TEM, FT-IR, XRD, and BET techniques. XRD confirmed that the average crystallite sizes of PEG-GL, PEG-EG, EG-GL, and EG-PEG-Gl were 86.78, 38.75, 98.70, and 45.96, respectively. Also, HR-TEM confirmed that the average diameters of the previous samples were 80.42, 35.50, 92.85, and 44.73, respectively. In addition, FE-SEM confirmed that the previous samples consist of (spherical and cup), (tree leaves and cylindrical rods), (cylindrical rods and spherical), and (spherical and rods) shapes, respectively. Besides, characteristic vibrations of mordenite such as internal symmetric, external symmetric, internal asymmetric, external asymmetric, and bending were detected using FT-IR at 690–705, 780–795, 1025–1030, 1222–1235, and 447–464 cm−1, respectively. The PEG-EG sample efficiently removed Pb(II) ions from aqueous media where 17.40 mg/g is the capacity value. Pore diffusion, intra-particle diffusion, pseudo-first-order, and liquid film diffusion kinetic models successfully described the removal of Pb(II) ions in the view of the kinetic study. In addition, Langmuir isotherm successfully described the removal of Pb(II) ions in the view of the equilibrium study. Moreover, the exothermic and chemisorption properties of the removal of Pb(II) ions were confirmed in the view of the thermodynamic study. The capacity of the PEG-EG sample or % removal of Pb(II) ions was not greatly affected after five desorption-adsorption cycles.

γ-Graphyne nanotube as nanofilter for cigarette smoke based on chemisorption properties – A first-principles study

The chemisorption behavior of tobacco smoke molecules (TSMs) such as acrolein, acrylamide, and nicotine on γ-graphyne nanotube (GNT) was studied by means of density functional theory (DFT) technique. The geometric solidity of pristine γ-GNT is verified in terms of cohesive energy with phonon-band structure. The prime motivation of this research article is to filter TSMs using γ-GNT. The chemisorption of different preferential interaction sites of TSMs on γ-GNT is explored in connection with the energy gap, adsorption energy, and Bader charge transfer. Importantly, the high negative value of adsorption energy is perceived upon the chemisorption of TSMs on γ-GNT. The novel aspects of the present research suggest that the γ-GNT can be efficiently utilized as nanofilter to remove TSMs.

High-throughput calculations of catalytic properties of bimetallic alloy surfaces

A comprehensive database of chemical properties on a vast set of transition metal surfaces has the potential to accelerate the discovery of novel catalytic materials for energy and industrial applications. In this data descriptor, we present such an extensive study of chemisorption properties of important adsorbates - e.g., C, O, N, H, S, CHx, OH, NH, and SH - on 2,035 bimetallic alloy surfaces in 5 different stoichiometric ratios, i.e., 0%, 25%, 50%, 75%, and 100%. To our knowledge, it is the first systematic study to compile the adsorption properties of such a well-defined, large chemical space of catalytic interest. We propose that a collection of catalytic properties of this magnitude can assist with the development of machine learning enabled surrogate models in theoretical catalysis research to design robust catalysts with high activity for challenging chemical transformations. This database is made publicly available through the platform www.Catalysis-hub.org for easy retrieval of the data for further scientific analysis.

(Invited) Mixed-Metal-Oxide Based Electrocatalysts for Efficient Reduction of Carbon Dioxide

Of particular interest to the preparation of advanced catalytic materials is efficient utilization of catalytic sites (metal and metal oxide nanostructures, their stabilization and intentional activation, as well as organization into two-dimensional arrays, ultra-thin films or three-dimensional networks (e.g. through sequential deposition) on electrode surfaces. They can form nanosized materials with well-defined composition, structure and thickness that exhibit desirable electrocatalytic properties (e.g. toward reduction of CO2). We explore here the ability of polynuclear inorganic metal oxo systems to stabilize and functionalize metal (e.g. copper) nanostructures. Here certain nanostructured metal oxides of zirconium, titanium, zinc or tungsten have been demonstrated to influence supported metal centers in ways other than simple dispersion over electrode area. Evidence is presented that the support can modify activity (presumably electronic nature) of catalytic metal nanoparticles (e.g. Cu, Ag, Au, Pd, Ru) thus affecting their chemisorptive and catalytic properties. Metal oxide nanospecies can generate –OH groups at low potentials that induce proton mobility at the electrochemical interface. Our research interests concern development of systems for the electrocatalytic reduction of carbon dioxide not only in neutral but also in acid media. For example, nanosized Cu or Ru naoparticles immobilized within ultra-thin films of tungsten oxide or zirconia have been considered. Selectivity of the catalytic systems largely depends on the activing adsorptive (CO2) phenomena and the affinity of catalytic centers to the adsorbed carbon monoxide (CO) type intermediates leading to their protonation or hydrogenation. Reduction of carbon dioxide begins now at less negative potentials and is accompanied by significant enhancement of the CO2-reduction current densities relative to the competitive hydrogen evolution.

Honeycomb-like Nitrogen-Doped Carbon 3D Nanoweb@Li2s Cathode Material for Use in Lithium Sulfur Batteries

Current lithium-ion batteries have a low theoretical capacity that is insufficient for use in emerging electric vehicles and energy storage systems. The development of lithium-sulfur batteries utilizing Li2S cathodes would be a promising option to overcome the capacity limitation. In this work, novel three-dimensional (3D) honeycomb-like N-doped carbon nanowebs (HCNs) have been synthesized through a facile aqueous solution route for use as a cathode material in lithium-sulfur batteries. The Li2S@HCNs cathode delivers a high discharge capacity of ca. 815 mAh g-1 after 65 cycles at 0.1 C, along with a superior rate capacity of ca. 568 mAh g-1 even at 2 C. The outstanding electrochemical rate performance is ascribed to their unique 3D honeycomb-like nanoweb structure, consisting of nanowires derived from polypyrrole. These properties greatly enhance the electrochemical reaction kinetics by providing efficient electron pathways and hollow channels for electrolyte transport. Nitrogen doping in the carbon nanowebs also considerably improves the chemisorption properties by tuning affinity between sulfur and oxygen functional groups on the carbon framework. The simple synthesis strategy and the resulting unique electrode structure could present a new avenue in nanostructure research for high performance lithium-sulfur batteries.

Low operating temperature and highly selective NH3 chemiresistive gas sensors based on Ag3PO4 semiconductor

Developing of novel chemiresistive gas sensing materials with desired unique gas chemisorption properties is of great important. In this work, motivated by the special electronic structure, Ag3PO4 semiconductor is systematically investigated as gas sensing material for the first time. Encouragingly, the Ag3PO4 nanoparticles based gas sensors exhibit high selectivity to NH3 at near room temperature of 50 °C with negligible responses to the other gases (including H2, CO, ethanol, acetone, NO2 and SO2). Furthermore, the responses decreased with the increase of operating temperature from 50 to 100 °C, indicating the superior NH3 sensing activity. The in-situ infrared characterization and theoretical calculations reveal that the lone pair of NH3 coordinate with the superficial silver atoms of Ag3PO4 accompanied with strong adsorption energy, efficient quantities electron migration and thermodynamic favorable, explained the origin of the high selectivity. Our work indicates that Ag3PO4 based materials are very promising low operating temperature and highly selective NH3-sensing materials.

Energetics of Au Adsorption and Film Growth on Pt(111) by Single-Crystal Adsorption Calorimetry

Bimetallic catalysts are an important class of heterogeneous catalysts with catalytic properties distinct from either of their bulk metal constituents. The structural, electronic, chemisorptive, and catalytic properties of bimetallic surfaces have been widely studied. Surface reactivity often correlates with adsorption energy of one metal on a single-crystal surface of the other as measured using temperature-programmed desorption (TPD). However, TPD only works for systems where the metals are immiscible. For bimetallic systems that form an alloy or intermetallic compound, TPD generally fails because the adsorbed metal penetrates into the bulk upon heating. The metal-on-metal adsorption energy is unmeasured for all but one such system previously but often calculated because these adlayers often have interesting catalytic properties. We report here calorimetric measurements of the adsorption energy versus coverage of an adlayer of one metal on another for such a bimetallic system, where the metals prefer to alloy: Au on Pt(111). This bimetallic combination is important in catalysis and electrocatalysis. The first monolayer (ML) of Au grows pseudomorphically with the Pt(111) surface at 300 K, with an average heat of adsorption of 389, ∼21 kJ/mol greater than the bulk heat of sublimation of Au. The heat increases with coverage by ∼11 kJ/mol in the first 0.03 ML and then by another ∼2 kJ/mol up to a maximum of 395 kJ/mol at 0.7 ML, and it then decreases to near the bulk heat of sublimation (368 kJ/mol) at 1 ML. The increase in heat is attributed to the increase in size of the two-dimensional Au islands that nucleate at a very low coverage and their corresponding increase in the average number of Au–Au nearest neighbor bonds. The high-coverage decrease in heat is attributed to the buildup of strain associated with the 4% Au/Pt lattice mismatch. The second and possibly third layers of Au show similar but much smaller oscillations in heat around 370 kJ/mol, attributed to the same two effects.

Honeycomb-Like Nitrogen-Doped Carbon 3D Nanoweb@Li2 S Cathode Material for Use in Lithium Sulfur Batteries.

Current lithium-ion batteries have a low theoretical capacity that is insufficient for use in emerging electric vehicles and energy-storage systems. The development of lithium-sulfur batteries utilizing Li2 S cathodes would be a promising option to overcome the capacity limitation. In this work, new three-dimensional (3D) honeycomb-like N-doped carbon nanowebs (HCNs) have been synthesized through a facile aqueous solution route for use as a cathode material in lithium-sulfur batteries. The Li2 S@HCNs cathode delivers a high discharge capacity of approximately 815 mAh g-1 after 65 cycles at 0.1 C, along with a superior rate capacity of approximately 568 mAh g-1 even at 2 C. The outstanding electrochemical rate performance is ascribed to their unique 3D honeycomb-like nanoweb structure, consisting of nanowires derived from polypyrrole. These properties greatly enhance the electrochemical reaction kinetics by providing efficient electron pathways and hollow channels for electrolyte transport. Nitrogen doping in the carbon nanowebs also considerably improves the chemisorption properties by tuning affinity between sulfur and oxygen functional groups on the carbon framework. The simple synthesis strategy and the resulting unique electrode structure could present a new avenue in nanostructure research for high-performance lithium-sulfur batteries.

Carbon Defect-Induced Reversible Carbon-Oxygen Interfaces for Efficient Oxygen Reduction.

It is a great challenge to fabricate a metal-free oxygen reduction reaction (ORR) electrocatalyst that can operate well in the acidic medium and fuel cells system. Here, a metal-free carbon material C-900 with abundant defect sites is fabricated by a self-sacrificed template and a solid-state reaction strategy. C-900 shows a superior performance to 20% Pt/C in alkaline medium and a performance closer to 20% Pt/C in acidic condition. It can thus be applied in air-breathing fuel cell (without extra operation pressure) as the cathode catalyst, which shows a high performance (1160 W L-1; ∼62% of 20% Pt/C) with excellent stability. By using oxygen temperature-programmed desorption, the strong selective chemisorption of O2 on C-900 has been revealed. The excellent chemisorption property of C-900 may originate from the large amounts of carbon defect sites, which have been confirmed by synchrotron radiation-based X-ray absorption spectroscopy. The rich defect sites and excellent chemisorption property can thus induce reversible carbon-oxygen interface for the excellent ORR activity.

Ultra-efficient removal of NO in a MOFs-NTP synergistic process at ambient temperature

In this work, a new MOFs-NTP synergistic method was first proposed in order to study the denitration performance. As a highly efficient MOFs material, CuBTC was synthesized by microwave method and combined with non-thermal plasma (NTP) which achieved an ultra-efficiency of 97.87% for NO removal. It was 76.77% and 64.43% higher than that of the CuBTC-alone process and NTP-alone denitration process. The influential factors and characterization analysis (SEM, XRD, N2 adsorption-desorption isotherms, ESR, XPS) were also investigated to study the synergistic effect of the MOFs-NTP denitration process. The results showed that CuBTC could be activated by NTP and generated the coordinatively unsaturated Cu(I)/Cu(II) sites which greatly enhanced the surface catalytic activity of CuBTC. NO was mainly reduced by Cu(I) sites to N2. Cu(II) species can also be reacted with NO to generate Cu2+⋯(NO) adducts. The increase of carbonyl groups (CO) and carboxyl groups (COO) content also improved the chemisorption property of CuBTC. The results have shown that MOFs can serve as an ultra-efficient gas pollution adsorption material and will be more widely to be used in the field of environmental protection in the future.

Biomass-derived carbon/γ-MnO2 nanorods/S composites prepared by facile procedures with improved performance for Li/S batteries

The promising prospects of the Li/S battery, due to its theoretical energy density of about 2500 Wh kg─1, are severely limited by two main weaknesses: the poor conductivity of S and the solubility of the polysulphides in the electrolyte. A combination of carbon and transition metal oxides is the best option for mitigating both of these shortcomings simultaneously. In this work, we use hydrothermally-tailored γ-MnO2 nanorods combined with an activated biomass-derived carbon, which is an inexpensive material and easy to prepare. This strategy was also followed for a AC/MnO2/S composite, a preparation of which was made by grinding; this is the simplest method for practical applications. More complex procedures for the formation of in situ hydrothermal MnO2 nanorods gave similar results to those obtained from grinding. Compared with the AC/S composite, the presence of MnO2 markedly increased the delivered capacity and improved the cycling stability at both low (0.1 C) and high (1 C) currents. This behavior results from a combination of two main effects: firstly, the MnO2 nanorods increase the electrical conductivity of the electrode, and secondly, the small particle size of the oxide can enhance the chemisorption properties and facilitate a redox reaction with polysulphides, more efficiently blocking their dissolution in the electrolyte.

Experimental identification and thermodynamic analysis of ammonia sorption equilibrium characteristics on halide salts

Solid–gas chemisorption based on metal ammine complexes is a kind of promising energy-saving and environment-friendly technology for various thermal engineering applications such as chemical heat pump, thermochemical energy storage, chemisorption refrigeration, etc. The accurate thermodynamic parameters of ammonia sorption on halide salts can allow a significant theoretical and experimental study on a solid–gas chemisorption system using halide salt–ammonia sorption working pairs. In this study, the thermodynamic properties of chemisorption between strontium chloride (SrCl2) and ammonia is firstly investigated by developing a facile methodology for sorption equilibrium measurement. The facile methodology involves the fabrication of incompact composite sorbent of expanded graphite/SrCl2 with high porosity and an optimized temperature-controlling method so as to weaken the adverse effect of heat and mass transfer on chemisorption and realize the chemical equilibrium and thermal quasi-equilibrium during the isobaric measurement process. Through the experimental measurement, the stoichiometric equations of chemisorption between SrCl2 and NH3 are updated, and thermodynamic parameters including reaction enthalpy, reaction entropy and hysteresis are identified. Similarly, the thermodynamic characteristics of chemisorption between ammonia and halide salts BaCl2, SrBr2, and MnCl2 are also investigated. The facile methodology is proved available for measuring the ammonia sorption equilibrium characteristics on halide salts. At last, the working performance of a cascade thermochemical energy storage system using four halides salts is analyzed based on the obtained thermodynamic parameters.

Tuning the electronic and chemisorption properties of hexagonal MgO nanotubes by doping – Theoretical study

Oxide materials offer a wide range of interesting physical and chemical properties. Even more versatile behavior of oxides is seen at the nanoscale, qualifying these materials for a number of applications. In this study we used DFT calculations to investigate the physical and chemical properties of small hexagonal MgO nanotubes of different length. We analyzed the effect of Li, B, C, N, and F doping on the properties of the nanotubes. We find that all dopants favor the edge positions when incorporated into the nanotubes. Doping results in the net magnetization whose value depends on the type of the impurity. Using the CO molecule as a probe, we studied the adsorption properties of pristine and doped MgO nanotubes. Our results show that the dopant sites are also the centers of significantly altered chemical reactivity. While pristine MgO nanotubes adsorb CO weakly, very strong adsorption at the dopant sites (B-, C-, and N-doped nanotubes) or neighboring edge atoms (F- and Li-doped nanotubes) is observed. Our results suggest that impurity engineering in oxide materials can be a promising strategy for the development of novel materials with possible use as selective adsorbents or catalysts.