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Benzylpentazole ( B) and its derivatives ( B-NH ~ B-NF ) with electron-donating group (−NH, −NHMe, −NMe, and−OH) and electron-withdrawing group (−NO, −CN, −CF and −NF) were studied using density functional theory to assess their potentials for replacing phenylpentazole ( PhN ) as cyclo-N precursor. The pyrolysis mechanisms of the N ring and the C─N bond connecting pentazole and benzyl, bond lengths, and atomic charge have been investigated for revealing the effects of substituents on stability and assessing the possibilities of benzylpentazoles as cyclo-N precursor. Substituents especially electron-withdrawing groups lower the N ring stability and the C─N bond stability of B simultaneously. Compared to PhN , benzylpentazoles mostly possess higher activation energy for the N ring decomposition (81.2 ~ 101.7 kJ/mol), lower C─N bond dissociation energy (385.6 ~ 452.8 kJ/mol), and higher chemical stability (7.83 ~ 8.49 eV). B and B- NMe with the highest N ring stability, appropriate C─N bond stability, and chemical stability are the most potential candidates for replacing PhN as cyclo-N precursor. [ABSTRACT FROM AUTHOR]

Structures of the salts I-IV formed by 3,6-dihydrazido-1,2,4,5-tetrazine with HNO3, HN(NO2)2, HClO4, and HC(NO2)3, respectively, were studied using dispersion-corrected density functional theory. The intramolecular hydrogen bond energies of I-IV were estimated using the quantum theory of atoms in molecules. The total hydrogen bond energies ( EH,tot) have the order of I (65.60 kcal/mol) > II (46.24 kcal/mol) > III (39.13 kcal/mol) > IV (19.68 kcal/mol). In addition, the charge transfer ( q), binding energy ( Eb), lattice energy ( HL), dispersion energy ( Edis), and second-order perturbation energy ( E2) were evaluated for studying the intramolecular interactions between the cation and anion. Linear relationships exist between any two of EH,tot, qtot, Eb, and E2,tot. HLs have the same variation trend as h50s (characteristic height) and may be used as the indicator of impact sensitivity. The HOMOs and LUMOs of I-IV are derived from the HOMOs of the isolated anions and the LUMOs of the isolated cations, respectively. Ultraviolet spectra of I-IV have the strongest absorptions at around 442, 445, 427, and 587 nm, respectively. The excitations HOMO→LUMO to HOMO-7→LUMO play important roles in the first three excited states. [ABSTRACT FROM AUTHOR]

Three high nitrogen compounds, 1,2-di(5H-pyrazolo[1,5-d]tetrazol-5-yl)diazene (DPyTD), 1,2-di(6H-[1–3]triazolo[1,5-e]tetrazol-6-yl)diazene (DTrTD) and 1,2-di(3H-tetrazolo[1,5-e]tetrazol-3-yl)diazene (DTeTD) with N 12 , N 14 or N 16 chain produced by the internal 1,3-dipolar cycloadditions of bis(azidoazolyl)diazenes (1,2-bis(3-azido-1H-pyrazol-1-yl)diazene, 1,2-bis(4-azido-1H-1,2,3-triazol-1-yl)diazene and 1,2-bis(5-azido-1H-tetrazol-1-yl)diazene), were studied using the density functional theory (DFT). The energies ( E a,1 and E a,2 ) required for the two internal cycloadditions of bis(azidoazolyl)diazenes were predicted at the B3LYP/6-311++G∗∗ (128.8–138.5 and 130.2–144.7 kJ/mol), B3PW91/6-311++G∗∗ (124.9–133.0 and 125.5–138.1 kJ/mol) and B3LYP/Aug-cc-pvdz (119.0–128.0 and 120.5–133.0 kJ/mol) levels of DFT. The bend of the azido group starts the 1,3-dipolar cycloadditions. Two 1,3-dipolar cycloadditions are independent. The IR, UV, and NMR spectra were simulated for characterization. The frontier orbitals cover the whole structure leading to small energy gaps (2.99–4.02 eV). The predicted impact sensitivities (17.3–22.1 J) show the acceptable stability of title compounds. [ABSTRACT FROM AUTHOR]

The salts formed by N and metallic cations (Na, Fe and Ni) may be potential candidates for superior energetic materials and were studied with the density functional theory B3LYP method and ab initio molecular orbital theory MP2 method using the 6-31G* and LanL2DZ basis sets. Thermal dissociations of these salts are initiated by breaking of the N ring, and those of Fe(N) and Ni(N) proceed sequentially through two transition states. In gas phase, the activation barriers ( Es, in kJ/mol) of thermal dissociations decrease in the order of N > NaN > HN > Ni(N) > Fe(N). Products of initial pyrolysis of these salts are N and metallic azide. The frontier orbital energy gaps (in eV) are N (8.27) > HN (7.40) > NaN (5.10) > Fe(N) (4.92) > Ni(N) (3.43). The more stable salt has the smaller electron transfer between the cation and anion. [ABSTRACT FROM AUTHOR]

Three stable conformations of salts formed from 3,6-diguanidino-1,2,4,5-tetrazine-1,4-di-N-oxide (DTDO) and HNO and HN(NO) were studied using the density functional theory. For two salts, free energies ( Gs) and total energies ( Es) of the three conformations increase in the same order. Intramolecular interactions in the three conformations, such as the hydrogen bonding interaction ( E), the charge transfer ( q), the binding energy ( E), the dispersion energy ( E) and the second-order perturbation energy ( E), decrease in completely opposite order to that of Gs and Es. Different conformations have distinct effects on the chemical stabilities and UV stabilities of two salts. Aromaticities of tetrazine in different conformations are slightly different. Although stabilities of the three conformations are different, their values are comparable. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Nitrogen-rich 1,2,4-triazole ( 1) and 1,2,3-triazole ( 2) react as bases with the oxygen-rich acids HNO3 ( a), HN(NO2)2 ( b), and HClO4 ( c) to produce energetic salts ( 1a, 1b, and 1c and 2a, 2b, and 2c, respectively) potentially applicable to composite explosives and propellants. In this study, these salts were studied with the dispersion-corrected density functional theory. For the isomers such as 1a and 2a, the more negative Δr Gm of the formation reaction leads to a higher thermally stable salt. The ability to form intramolecular hydrogen bonds predicted with the quantum theory of atoms in molecules has the order of 2 > 1. Different hydrogen bonds result in different second-order perturbation energies, redshifts in IR, and electron density differences. The charge transfer, binding energy, dispersion energy, lattice energy, and energy gap between frontier orbits in the salts of 1 are larger than those of 2, which is helpful for stabilizing the former, and 1 is more obviously stabilized than 2 by formation of salts. Different conformations of 1 and 2 hardly affect the frontier orbital distributions. Base 1 is a more preferred base than 2 to form salts. [ABSTRACT FROM AUTHOR]

The inefficient activated carbon (AC) air-cathode microbial fuel cell (MFC) is greatly constrained by the sluggish oxygen reduction reaction (ORR), which requires highly active and cost-effective catalysts to expedite the reaction kinetics. Herein, we propose an accessible and scalable method to prepare porous iron-nitrogen-doped carbon nanospheres (FFC/NG) by utilizing the inexpensive zinc-iron Prussian blue analogue as the precursor. Physicochemical characterization indicates that the evaporation of Zn is helpful to promote the surface area and mesopores volume. The maximum power density for the optimal sample (FFC/NG@AC-3) is 1913 ± 39 mW m−2, which is 200.3% higher than that of the bared AC and also outperforms the performance of the commercial Pt/C. The removing rate of chemical oxygen demand (COD) for FFC/NG@AC-3 can reach 80.2% after 72 h, 13.6% higher than that of bared AC. Density functional theory (DFT) confirms that the carbon atoms adjacent to graphitic nitrogen and pyridinic nitrogen on the graphene shell contribute to enhancing the oxygen adsorption energy. It can be well concluded that due to low cost, facile synthesis and remarkable performance, FFC/NG is a promising AC air-cathode modification reagent for MFC. [Display omitted] • A novel porous Iron-nitrogen-doped carbon nanosphere was derived from Zn–Fe PBA. • The evaporable Zn plays a leading role in formation of the porosity of FFC/NG. • The maximum power density is 1913 ± 39 mW m−2. • DFT calculation revealed that graphitic N and pyridinic N are favorable to ORR. [ABSTRACT FROM AUTHOR]

Heteroatom-doped porous carbon frameworks have attracted extensive attention as high-performance electrodes for capacitive applications. While their further development is still restricted by the inevitable concurrent dopant leaching effect and structural collapse during the high-temperature pyrolysis process. Therefore, developing a straightforward method for the synthesis of carbons simultaneously with plentiful multiple external defects and rational porous structure to satisfy high-performance capacitive applications is still a tremendous challenge. Herein, an emerging plerogyra sinuosa-like hierarchically porous carbon with plentiful N/P external defects is firstly prepared via an effective and in-site carbonization process, which shows great promise for supercapacitor and capacitive deionization applications. Due to the efficient N and P synergistic effects and 3D connected framework with prolific meso-microporous structure, the optimized carbon exhibits a large specific capacitance of 337 F g−1 at a current density of 1 A g−1 and maintains 239 F g−1 at 100 A g−1 in 6.0 M KOH electrolyte. For capacitive deionization tests, the carbon shows an excellent salt adsorption capacity of 19.3 mg g−1 in NaCl solution with a concentration of 500 mg L−1 at an applied voltage of 1.2 V. While from the kinetics analysis and density functional theory, we find that the coupling of multiple external defects has a positive influence on the distribution of electron density and surface condition, which is greatly beneficial to pseudocapacitance, quantum capacitance and the electrolyte-adsorption capacity. This work provides a new route for the preparation of emerging heteroatom-doped hierarchically porous carbon frameworks for further advanced applications such as water treatment, electrocatalysis, as well as energy storage. [ABSTRACT FROM AUTHOR]