Binding Energy Of Nitrogen Research Articles

Theoretical Approach toward a Mild Condition Haber-Bosch Process on the Zeolite Catalyst with Confined Dual Active Sites.

The Haber-Bosch (H-B) process is today's dominant technology for ammonia production, but achieving a mild reaction condition is still challenging. Herein, we combined density functional theory (DFT) calculations and microkinetic modeling (MKM) to demonstrate the feasibility of conducting the H-B process under ambient conditions on a zeolite catalyst with confined dual active sites. Our designed dual Mo(II) cation-anchored ferrierite [2Mo(II)-FER] catalyst shows an energy barrier of only 0.58 eV for N≡N bond breaking due to the enhanced π-back-donation. Meanwhile, the three hydrogen sources (BH, FMH, and NMH) within 2Mo(II)-FER greatly enrich the hydrogenation mechanisms of NHx species, resulting in barriers of <1.1 eV for NHx (x = 0-2) hydrogenations. This dual-site catalyst properly decouples the N2 dissociation and NHx hydrogenation steps, which elegantly circumvents the linear scaling relation between the N2 dissociation barrier and the nitrogen binding energy. It is worth noting that our MKM results show 4 orders of magnitude higher reaction rates on 2Mo(II)-FER than the stepped sites of the FCC Ru catalyst at low temperatures, paving a solid basis to conduct the H-B process at low temperatures. We believe that our strategy will provide crucial guidance for synthesizing state-of-the-art zeolite catalysts to achieve the near-ambient condition H-B process and other chemical reactions in heterogeneous catalysis.

Toward Sabatier Optimal for Ammonia Synthesis with Paramagnetic Phase of Ferromagnetic Transition Metal Catalysts.

The Sabatier principle defines the essential criteria for being an ideal catalyst in heterogeneous catalysis, while approaching the Sabatier optimal is a major pursuit in catalyst design. The Haber-Bosch (H-B) process, converting nitrogen (N2) and hydrogen (H2) to ammonia (NH3), is a holy grail reaction for humans and also a great model reaction for fundamental research, where the established volcano plot between ammonia synthesis activity and nitrogen binding energy among metals has successfully guided new catalyst design. However, reaching the top of the activity volcano is still very challenging. Herein, we identify an elegant strategy to promote the ferromagnetic (FM) catalysts to be the Sabatier optimal of ammonia synthesis via a second-order ferromagnetic-paramagnetic phase transition, which represents an ideal and novel interdisciplinary of the aforementioned century-old classic principle, reaction, and theory in chemistry, physics, and material science. The paramagnetic (PM) Co and Ni metals could have 2-4 orders of magnitude higher ammonia synthesis activity than their ferromagnetic counterparts, holding the potential to achieve a near-ambient H-B process. We believe that our discovery will open a novel avenue for revisiting the catalytic performances of paramagnetic phases of ferromagnetic materials in heterogeneous catalysis.

Lithium‐based Loop for Ambient‐Pressure Ammonia Synthesis in a Liquid Alloy‐Salt Catalytic System

The Haber-Bosch process for ammonia (NH3 ) production in industry relies on high temperature and high pressure and is therefore highly energy intensive. In addition, the activity of the solid transition metal-based catalysts used is typically limited by the scaling relation between activation barrier for N2 dissociation and nitrogen-binding energy. Here, an innovative Li-based loop in a liquid alloy-salt catalytic system for ambient-pressure NH3 synthesis from N2 and H2 was developed. The looping process consisted of three reaction steps taking place simultaneously. The first step was the nitrogen fixation by Li in the liquid Li-Sn alloy to form lithium nitride (Li3 N), which floated up and dissolved into the molten salt. The second step was the hydrogenation of the Li3 N to produce NH3 and lithium hydride (LiH) in the molten salt. The third step was the decomposition of the LiH to regenerate Li in the presence of Sn. An average NH3 yield rate of 0.025 μg s-1 was achieved in an 81 h test at 510 °C and ambient pressure. The floating and dissolution of Li3 N realized in the liquid catalytic system enabled circumventing the scaling relation exerted on Li, and the remarkable properties of liquid alloy and molten salt offered extraordinary advantages for NH3 synthesis at ambient pressure.

Transition metal oxynitride catalysts for electrochemical reduction of nitrogen to ammonia

DFT calculations predict a volcano-like relationship between limiting potential and nitrogen binding energy on TMNOs.

The Adsorption Capabilities of Methylene Blue Using Coconut Fibers in Order to Develop the Aquatic Environment

To decrease the amount of waste biomass and develop a useful application. Coconut fiber (CF) was used to prepare a novel adsorbent to remove methylene blue (MB), which is a recalcitrant organic compound in the water environment. We were able to produce novel adsorbents such as CCF500 and CCF1000 by the calcination treatment of CF. The specific surface area and pore volume of CCF1000 were higher than those of CF or CCF500. Quantity of MB adsorbed was in the order; CCF500<CF<CCF1000 under our experimental condition. Additionally, the specific surface area and pore volume were strongly related to the adsorption of MB (Correlation coefficient: >0.986). The adsorption mechanism of MB using CCF1000 was demonstrated in this study. The intensities of carbon (C), nitrogen (N), and sulfur (S) onto CCF1000 surface increased after adsorption of MB. In addition, the binding energies of nitrogen (1s) at approximately 400 eV and sulfur (2s and 2p) at approximately 165 and 230 eV which were generated after adsorption. Therefore, the adsorption of MB from aquatic solution was strongly involved with the physicochemical properties of CCF1000 surface. Our findings showed that CCF500 and CCF1000 could be produced from CF by calcination treatment, which demonstrates that the amount of waste biomass decreased. In particular, CCF1000 displays the capability to adsorb MB from aquatic solution. These results showed that CCF1000 could be a useful adsorbent for aquatic environment purification.

Contribution of Nitrogen Vacancies to Ammonia Synthesis over Metal Nitride Catalysts.

Ammonia is one of the most important feedstocks for the production of fertilizer and as a potential energy carrier. Nitride compounds such as LaN have recently attracted considerable attention due to their nitrogen vacancy sites that can activate N2 for ammonia synthesis. Here, we propose a general rule for the design of nitride-based catalysts for ammonia synthesis, in which the nitrogen vacancy formation energy (ENV) dominates the catalytic performance. The relatively low ENV (ca. 1.3 eV) of CeN means it can serve as an efficient and stable catalyst upon Ni loading. The catalytic activity of Ni/CeN reached 6.5 mmol·g-1·h-1 with an effluent NH3 concentration (ENH3) of 0.45 vol %, reaching the thermodynamic equilibrium (ENH3 = 0.45 vol %) at 400 °C and 0.1 MPa, thereby circumventing the bottleneck for N2 activation on Ni metal with an extremely weak nitrogen binding energy. The activity far exceeds those for other Co- and Ni-based catalysts, and is even comparable to those for Ru-based catalysts. It was determined that CeN itself can produce ammonia without Ni-loading at almost the same activation energy. Kinetic analysis and isotope experiments combined with density functional theory (DFT) calculations indicate that the nitrogen vacancies in CeN can activate both N2 and H2 during the reaction, which accounts for the much higher catalytic performance than other reported nonloaded catalysts for ammonia synthesis.

Selectivity Control in Catalytic Reductive Amination of Furfural to Furfurylamine on Supported Catalysts

AbstractAmines are widely used in the manufacture of pharmaceuticals, agricultural chemicals, polymers, and surfactants. However, amines are mostly produced via petrochemical means, which motivates amine production from renewable resources, such as biomass. However, biomass compounds present added challenges involving poor carbon balances. We show that furfural reacts homogeneously with ammonia to produce reactive primary imines, which form large side products and leads to significant carbon losses. The carbon balance is improved by mixing furfural with furfurylamine prior to reaction to form a secondary imine for use as the reaction substrate. While controlling the primary to secondary amine selectivity is a common challenge in reductive amination, supported metal catalysts, including Ni/SiO2, Co/SiO2, and Ru/SiO2 optimize the primary amine yield to 90 to 94 % by using the secondary imine as the reaction substrate. A qualitative correlation between the primary to secondary amine selectivity with the nitrogen binding energy of metals is identified.

Theoretical Investigation on the Single Transition-Metal Atom-Decorated Defective MoS2 for Electrocatalytic Ammonia Synthesis.

Using density functional theory calculations, we explored the potential of defective MoS2 sheets decorated with a series of single transition-metal (TM) atoms as electrocatalysts for the N2 reduction reaction (NRR). The computed reaction free-energy profiles reveal that the introduction of embedded single TM atoms significantly reduces the difficulty to break the N≡N triple bond and thus facilitates the activation of inert nitrogen. Onset potential close to -0.6 V could be achieved by anchoring various TMs, such as Sc, Ti, Cu, Hf, Pt, and Zr, and the formation of the second ammonia molecule limits the overall process. The Ti-decorated nanosheet possesses the lowest free-energy change of -0.63 eV for the potential determining step. To better predict the catalysis performance, we introduced a descriptor, φ, which is the product of the number of valence electron and electronegativity of the decorated TM. It shows a good linear relationship between the d-band center and binding energy of nitrogen, except for those metals with less than half-filled d-band. Although the metals in Group IIIB and IVB have strong adsorption interactions with N atoms, the Gibbs free-energy changes for desorption of the second ammonia are unexpectedly low. The selectivity of these systems toward nitrogen reduction reaction (NRR) is also significantly improved. Therefore, those defective MoS2 decorated with Sc, Ti, Zr, and Hf are suggested as promising electrocatalysts for NRR, for their both high efficiency and selectivity.

Development of Nanoparticle Catalysts for Electrochemical Ammonia Production

Ammonia is one the most common industrial chemicals produced in the United States. It has a strong foothold in the agricultural, plastic, and textile industries. A process termed Haber-Bosch, named for its inventors, is the current method used for ammonia based fertilizer production in the agricultural industry. The process requires high temperatures of 400-500°C and high pressures of 150 – 200 atm to convert nitrogen into ammonia [1]. These extreme conditions only result in a 15% conversion at equilibrium [1]. Another problem associated with the Haber-Bosch process is the reforming of hydrocarbons, like coal and natural gas, resulting in the consumption of 3 to 5% of the world’s natural gas production and the release of large amounts of CO2 [2]. The total energy consumption for an ammonia plant is about 7.9 MW h tNH3 -1, and 13.5 MW h tNH3 -1 for natural gas and coal, respectively [1], and the energy use for the entire ammonia industry is approximately 2% of the world’s energy consumption [2]. The extreme conditions, low efficiency, environmental pollution, and energy consumption of the Haber-Bosch process have helped to push research efforts towards a more economically and environmentally viable electrochemical catalyst approach. The focus of this project is to develop a suitable nanoparticle catalyst for a solid state electrolyte electrochemical process. Electrochemical reduction of nitrogen to ammonia has been performed over non-precious monometallic and multi-metallic combinations, such as iron (Fe) and nickel (Ni). These metals are chosen because they have theoretical nitrogen binding energies that are close to the theoretically-predicted optimum [3]. However, thus far, most electrocatalysts have resulted in low Faradaic efficiencies due to the affinity of the catalyst surface for preferential hydrogen binding [4]. A catalyst made up of a combination of the metals at the nano-scale could balance the need for low applied potential while keeping hydrogen binding to a minimum. In particular, recent work by Licht and co-authors demonstrated that an iron oxide nanoparticle catalyst can be used at elevated temperature (200 oC) to achieve Faradaic efficiencies of greater than 30% [2]. In our initial work, nano-sized catalysts of Fe, Ni, and Fe-Ni were screened for efficiencies over a three hour span. Monometallic Fe nanoparticles showed a drastic decrease in efficiencies over time, whereas the efficiency of the monometallic Ni nanoparticles increased with time. The bimetallic Fe-Ni nanoparticles resulted in a combination of both Fe and Ni properties, depending on the composition and morphology of the nanoparticles. A low surface area, larger diameter Fe-Ni nanoparticle material had decreasing efficiencies over time, whereas a high surface area, nanoparticle cluster Fe-Ni sample had increasing efficiencies over time. In this presentation, we will show recent results on our continued work to develop Fe-Ni bimetallic nanoparticles as an electrocatalyst for nitrogen reduction. In particular, we will discuss progress on controlling nanoparticle size, morphology, and composition to optimize efficiency benefits of Fe while being able to gain stability due to Ni. Experimentally, we will discuss our efforts to investigate the role of certain synthesis parameters on nanoparticle morphology and catalytic performance by changing the timing of synthesis steps to control changes in Fe oxidation state, nickel deposition, and core morphology. Also the effects of changing the molar ratio of Ni to Fe in synthesis and molar ratio of ligand to metal to influence particle size will be explored. References K. Kugler, B. Ohs, M. Scholz, and M. Wessling, Phys.Chem.Chem.Phys., 16, 6129 (2014)S. Licht, B. Cui, B. Wang, F. Li, J. Lau, and S. Liu, Science, 345, 637 (2014)E. Skulason, T. Bligaard, S. Gudmundsdottir, F. Studt, J. Rossmeisl, F. Abild-Pedersen, T. Vegge, H. Jonsson, and J. K. Norskov, Phys. Chem. Chem. Phys., 14, 1235-1245 (2012)Xu, G.C., R.Q. Liu, and J. Wan, Science in China Series B: Chemistry, 52, 8 (2009)

High mobility and high stability glassy metal-oxynitride materials and devices.

In thin film technology, future semiconductor and display products with high performance, high density, large area, and ultra high definition with three-dimensional functionalities require high performance thin film transistors (TFTs) with high stability. Zinc oxynitride, a composite of zinc oxide and zinc nitride, has been conceded as a strong substitute to conventional semiconductor film such as silicon and indium gallium zinc oxide due to high mobility value. However, zinc oxynitride has been suffered from poor reproducibility due to relatively low binding energy of nitrogen with zinc, resulting in the instability of composition and its device performance. Here we performed post argon plasma process on zinc oxynitride film, forming nano-crystalline structure in stable amorphous matrix which hampers the reaction of oxygen with zinc. Therefore, material properties and device performance of zinc oxynitride are greatly enhanced, exhibiting robust compositional stability even exposure to air, uniform phase, high electron mobility, negligible fast transient charging and low noise characteristics. Furthermore, We expect high mobility and high stability zinc oxynitride customized by plasma process to be applicable to a broad range of semiconductor and display devices.

Effect of Metal in M3(btc)2 and M2(dobdc) MOFs for O2/N2 Separations: A Combined Density Functional Theory and Experimental Study

Computational screening of metal–organic framework (MOF) materials for selective oxygen adsorption from air is used to identify new sorbents for oxyfuel combustion process feedstock streams. A comprehensive study on the effect of MOF metal chemistry on gas binding energies in two common but structurally disparate MOFs has been undertaken. Dispersion-corrected density functional theory (DFT) methods were used to calculate the oxygen and nitrogen binding energies with each of 14 metals, respectively, substituted into two MOF series, M2(dobdc) and M3(btc)2. The accuracy of DFT methods was validated by comparing trends in binding energy with experimental gas sorption measurements. A periodic trend in oxygen binding energies was found, with greater oxygen binding energies for early transition-metal-substituted MOFs compared to late transition metal MOFs; this was independent of MOF structural type. The larger binding energies were associated with oxygen binding in a side-on configuration to the metal, with con...

Isotopic Chains Around Oxygen from Evolved Chiral Two- and Three-Nucleon Interactions

We extend the formalism of self-consistent Green's function theory to include three-body interactions and apply it to isotopic chains around oxygen for the first time. The third-order algebraic diagrammatic construction equations for two-body Hamiltonians can be exploited upon defining system-dependent one- and two-body interactions coming from the three-body force, and, correspondingly, dropping interaction-reducible diagrams. The Koltun sum rule for the total binding energy acquires a correction due to the added three-body interaction. This formalism is then applied to study chiral two- and three-nucleon forces evolved to low momentum cutoffs. The binding energies of nitrogen, oxygen, and fluorine isotopes are reproduced with good accuracy and demonstrate the predictive power of this approach. Leading order three-nucleon forces consistently bring results close to the experiment for all neutron rich isotopes considered and reproduce the correct driplines for oxygen and nitrogen. The formalism introduced also allows us to calculate form factors for nucleon transfer on doubly magic systems.

Nitrogen‐Doped Carbon Nanotubes: Growth, Mechanism and Structure

Nitrogen-doped bamboo-structured carbon nanotubes have been successfully grown using a series of cobalt/molybdenum catalysts. The morphology and structure of the nanotubes were analysed by transmission electron microscopy and Raman spectroscopy. The level of nitrogen doping, as determined by X-ray photoelectron spectroscopy, was found to range between 0.5 to 2.5 at.%. The growth of bamboo-structured nanotubes in the presence of nitrogen, in preference to single-walled and multi-walled nanotubes, was due to the greater binding energy of nitrogen for cobalt in the catalyst compared to the binding strength of carbon to cobalt, as determined by density functional theory.

Ammonia decomposition activity on monolayer Ni supported on Ru, Pt and WC substrates

Catalyst design for specific reactions currently involves using atomic or molecular descriptors to identify promising catalysts. In this paper, we explore three surfaces that have similar computed nitrogen binding energies, which is a descriptor for the ammonia decomposition reaction. The surfaces studied include a monolayer of Ni on Pt(111), Ru(0001) and tungsten monocarbide (WC). The activity of these surfaces toward the ammonia decomposition reaction was compared using density functional theory and temperature programmed desorption. It was found that while the NHx–H bond scission is similar on each of the surfaces, the temperature of nitrogen desorption is very different. The differences are explained and the implications for ammonia decomposition activity and catalyst design are discussed.

Experimental and theoretical studies of ammonia decomposition activity on Fe-Pt, Co-Pt, and Cu-Pt bimetallic surfaces

We investigate the decomposition of ammonia on bimetallic surfaces prepared by the deposition of a monolayer of Fe, Co, or Cu on a Pt(111) surface computationally and experimentally. We explore the correlation between predicted activities based on the nitrogen binding energies with experimental decomposition activity on these bimetallic and corresponding monometallic surfaces. Through density functional theory calculations and microkinetic modeling, it is predicted that the Fe-Pt-Pt(111) and Co-Pt-Pt(111) surfaces, with a monolayer of Fe or Co on top of Pt(111), are active toward decomposing ammonia. In contrast, the corresponding subsurface configurations, Pt-Fe-Pt(111) and Pt-Co-Pt(111) are inactive. These predictions were confirmed experimentally through temperature programmed desorption experiments. Decomposition was seen at temperatures below 350 K for the Fe-Pt-Pt(111) and Co-Pt-Pt(111) surfaces. For the Cu∕Pt(111) system, the surface, subsurface and parent metals were each predicted to be inactive, consistent with experiments, further validating the model predictions. The stability of these bimetallic surfaces in the presence of adsorbed nitrogen is also discussed.

Using first principles to predict bimetallic catalysts for the ammonia decomposition reaction

The facile decomposition of ammonia to produce hydrogen is critical to its use as a hydrogen storage medium in a hydrogen economy, and although ruthenium shows good activity for catalysing this process, its expense and scarcity are prohibitive to large-scale commercialization. The need to develop alternative catalysts has been addressed here, using microkinetic modelling combined with density functional studies to identify suitable monolayer bimetallic (surface or subsurface) catalysts based on nitrogen binding energies. The Ni-Pt-Pt(111) surface, with one monolayer of Ni atoms residing on a Pt(111) substrate, was predicted to be a catalytically active surface. This was verified using temperature-programmed desorption and high-resolution electron energy loss spectroscopy experiments. The results reported here provide a framework for complex catalyst discovery. They also demonstrate the critical importance of combining theoretical and experimental approaches for identifying desirable monolayer bimetallic systems when the surface properties are not a linear function of the parent metals.

A modified embedded-atom method interatomic potential for the Fe–N system: A comparative study with the Fe–C system

A modified embedded-atom method (MEAM) interatomic potential for the Fe–N binary system has been developed using previously developed MEAM potentials of iron and nitrogen. The potential parameters were determined by fitting to the dilute heat of solution and migration energy of nitrogen atoms, the vacancy–nitrogen binding energy and its configuration in body-centered cubic iron, and the enthalpy of formation and lattice parameter of Fe 4N. The potential reproduces very well the known physical properties of nitrogen as an interstitial solute element in body- and face-centered cubic iron and of various nitrides. The similarity and difference between nitrogen and carbon as equally important interstitial elements in iron are also examined. The applicability of the potential to atomistic approaches for investigating interactions between nitrogen atoms and other defects such as vacancies, dislocations, and grain boundaries, and also for investigating the effects of nitrogen on various deformation and mechanical behaviors of iron is demonstrated.

XPS determination of the binding energies of phosphorus and nitrogen in phosphazenes

Phosphazenes are compounds in which repeating units -N = P(L1, L2)— are arranged in cyclic or linear structures including polymeric ones. Representatives are numerous due to the possibility of varying the ligands L1 and L2. This determines the wide spectrum of useful properties of the phosphazenes such as elasticity, thermal stability, biological compatibility etc. and, a consequence there is enhanced interest in these compounds [1–3]. Although the literature on phosphazenes is impressive [4–6], it seems that the nitrogenphosphorus bond and the effect of substituents on this bond are not yet sufficiently investigated [7]. Dake et al. [8] have used XPS and Raman spectroscopy to investigate the effect of electron-accepting substituents on the distribution of the electron charge in the nitrogen-phosphorus chains, comparing cyclic trimers and linear polymers when substitution is homogeneous (L1 = L2). The results of these authors confirm the assumptions based on theoretical considerations, according to which the N P bond is strongly polarized, this effect being more pronounced with polymers rather than with cyclic trimers. As to the influence of substituents on the binding energies of nitrogen and phosphorus, it is found to depend not only on the electromeric effect of the substituent but also on the conformation of the phosphazene molecule. The present paper is aimed at determining the binding energies of nitrogen and phosphorus in some cyclic phosphazene molecules in the cases of identical (L1 = L2) or different (L1 = L2) substituents as well as in linear polymers having electron-donating or electronaccepting ligands. The following 7 phosphazenes were investigated: Cyclic trimers (No1 hexachlorocyclotriphosphazene (NPCl2)3, No2 cis-bis-(dimethylamino)-tetrachlorocyclotriphosphazene N3P3[N(CH3)2]Cl4, No3 bis(dimethylamino)-bis-(trifluorethoxy)-dichlorocyclotriphosphazene and N3P3[N(CH3)2]2(OCH2CF3)2Cl2), Cyclic tetramert (No4 octabutylaminocyclotetraphosphazene N4P4[NH(C4H9)]8), Cyclomatrix polymer (No5 phospham [(NPNH)3]n) and Linear polymers (No6 poly-bis-(butylamino)phosphazene {NP[NH(C4H9)]2}n, No7 poly-bis-(trifluoroethoxy)phosphazene [NP(OCH2CF3)2]n). The compounds were prepared according to usual methods [9, 10]. Elemental analysis, IR and 31P-NMR spectra, X-ray phase analysis and measurement of the

Dislocation locking by nitrogen impurities in FZ-silicon

The locking of dislocations by nitrogen impurities in nitrogen-doped FZ-grown (NFZ) silicon crystals was investigated as a function of time in the temperature range 550–830°C. It was found that nitrogen impurities induce a strong locking effect on stationary dislocations after a sufficiently long anneal. The locking is similar in magnitude to that observed for oxygen atoms in Czochralski-grown crystals (Cz), although the nitrogen concentration in the NFZ samples (2.2×1015cm−3) is two orders of magnitude lower than the usual oxygen concentration in Cz silicon. The unlocking stress initially increases with annealing time and then saturates to a value of approximately 50MPa for all the temperatures investigated. Information concerning nitrogen diffusion is deduced and by making certain physically realistic assumptions, data is inferred regarding the binding energy of nitrogen and the dislocation pinning force per nitrogen atom at the dislocation core.

Study of Nitrogen Adsorbed on Open-Ended Nanotube Bundles

The adsorption of N2 on the open-ended single-walled carbon nanotube bundles was studied. The amount corresponding to the first coverage adsorbed on open-ended carbon nanotube bundles is three times larger than the amount adsorbed on closed-ended nanotube bundles. The isosteric heat of adsorption was obtained from the adsorption isotherm measurement performed at temperatures ranging from 117 to 130 K. The estimated heat of adsorption of nitrogen on the open-ended nanotube bundles is about twice as great as that on the closed-ended nanotube bundles. This leads directly to the conclusion that the binding energy of nitrogen on the open-ended nanotube is greater than that of nitrogen on the closed-ended nanotube bundles.