Carbon-Nitride Popcorn-A Novel Catalyst Prepared by Self-Propagating Combustion of Nitrogen-Rich Triazenes

The interest in development of non-graphitic polymeric carbon nitrides (PCNs), with various C-to-N ratios, having tunable electronic, optical, and chemical properties is rapidly increasing. Here the first self-propagating combustion synthesis methodology for the facile preparation of novel porous PCN materials (PCN3-PCN7) using new nitrogen-rich triazene-based precursors is reported. This methodology is found to be highly precursor dependent, where variations in the terminal functional groups in the newly designed precursors (compounds 3-7) lead to different combustion behaviors, and morphologies of the resulted PCNs. The foam-type highly porous PCN5, generated from self-propagating combustion of 5 is comprehensively characterized and shows a C-to-N ratio of 0.67 (C₃ N_4.45 ). Thermal analyses of PCN5 formulations with ammonium perchlorate (AP) reveal that PCN5 has an excellent catalytic activity in the thermal decomposition of AP. This catalytic activity of PCN5 is further evaluated in a closer-to-application scenario, showing an increase of 18% in the burn rate of AP-Al-HTPB (with 2 wt% of PCN5) solid composite propellant. The newly developed template- and additive-free self-propagating combustion synthetic methodology using specially designed nitrogen-rich precursors should provide a novel platform for the preparation of non-graphitic PCNs with a variety of building block chemistries, morphologies, and properties suitable for a broad range of technologies.

Facile synthesis of MgCo2O4 nanosheets and its catalysis effect on the decomposition of ammonium perchlorate

The catalysis effects of MgCo2O4 nanosheets on the thermal decomposition of ammonium perchlorate (AP) were investigated. The MgCo2O4 nanosheets were synthesized with a facile free-template hydrothermal method. The chemical structure and micro morphology of MgCo2O4 nanosheets were characterized. Moreover, the catalysis thermal decomposition properties of AP using composite metal oxides MgCo2O4 nanosheets with different contents (1wt%, 3wt%, and 5wt%) as catalysts were investigated. The results showed that the reducing decomposition temperature of AP was 155.9 °C from 431 °C to 275.1 °C with 5wt% MgCo2O4 added. The heat release of AP was increased of 907 J/g at least. In addition, the catalysis thermal decomposition mechanism of AP with the existence of MgCo2O4 nanosheets was explained. With the increasing temperature, the accumulated electrons (e-) and holes (h+) excited was activated at the surface of MgCo2O4 nanosheets, which accelerated H transfer from H atom of NH4+ to O atom of ClO4- and boosted AP decomposition.

A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing

g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4-metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4-metal-oxide-based heterojunctions.

Fast synthesis of MoO3-x and its catalytic effect on the thermal decomposition of ammonium perchlorate based molecular perovskite (DAP-4)

In this work, it is shown that MoO3-x has a positive effect on the thermal decomposition of ammonium perchlorate based molecular perovskite (H2DABCO)[NH4(ClO4)3] (DAP-4). MoO3-x was prepared by heat treatment, and the morphology, structure, and thermal decomposition performance were characterized. The morphology and structure characterization results showed that MoO3-x was an irregular layered structure material and the Mo element was mainly in the +6 chemical valence state, with a small amount of Mo5+. Thermal analysis results showed that the thermal decomposition peak temperature of DAP-4 was effectively reduced from 394.4 °C to 353.7 °C, 321.4 °C, and 312.5 °C in the presence of 1%, 5%, and 10% MoO3-x, respectively. It is particularly worth noting that the maximum heat release rate of the DAP-4/10% MoO3-x mixture was increased by 4.9 times compared with pure DAP-4. Through the two classic thermal decomposition kinetic methods, Kissinger and Starink, the reliable kinetic parameters of DAP-4/MoO3-x were obtained. The increase of the reaction rate constant k indicated that the maximum thermal decomposition reaction rate of DAP-4 was effectively improved. This work provided a feasible technology for using MoO3-x as an effective catalyst to improve the thermal performance of DAP-4.

Research development on graphitic carbon nitride and enhanced catalytic activity on ammonium perchlorate

Recently, graphitic carbon nitride (g-C3N4) has attracted considerable attention due to its attractive features including excellent electrochemical performance, suitable band gap, nontoxicity, and high mechanical and thermal stability. Such unique advantages endow it with promising applications in batteries, photocatalysts, photodegradation, and so on. In particular, it has been applied to catalyze the thermal decomposition of ammonium perchlorate (AP) and has shown excellent performance. In this review, the structure, preparation methods and exfoliation strategies of g-C3N4 are comprehensively introduced. Furthermore, the enhanced catalytic mechanism for the thermal decomposition of AP is discussed in detail, and a future research direction is also proposed.

Facile synthesis of MXene-supported copper oxide nanocomposites for catalyzing the decomposition of ammonium perchlorate

MXene-supported CuO nanocomposites were synthesized by ice crystal templating and could effectively reduce the HTD temperature and increase the heat release of AP. A possible mechanism for the excellent catalytic performance was also proposed.

Single-Atom Pt Stabilized on One-Dimensional Nanostructure Support via Carbon Nitride/SnO2 Heterojunction Trapping

Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO₂ heterostructure. With the ultrahigh specific surface area (54.29 m² g^-1) of the nanostructure, we obtained maximized catalytic active sites, as well as further catalytic enhancement achieved with the heterojunction between carbon nitride and SnO₂. X-ray absorption fine structure analysis and HAADF-STEM analysis reveal a homogeneous atomic dispersion of Pt species between carbon nitride and SnO₂ nanograins. This Pt SAC system with the 1D nano-heterostructure support exhibits high sensitivity and selectivity toward detection of formaldehyde gas among state-of-the-art gas sensors. Further ex situ TEM analysis confirms excellent thermal stability and sinter resistance of the heterojunction-immobilized Pt single atoms.

Visible light-enhanced thermal decomposition performance of ammonium perchlorate with a metal–organic framework-derived Ag-embedded porous ZnO nanocomposite

An Ag-embedded porous ZnO nanocomposite (Ag–ZnO NC) fabricated using an MOF exhibits high catalytic activity for the thermal decomposition of AP under the assistance of visible light.

Direct Growth of CuO Nanorods on Graphitic Carbon Nitride with Synergistic Effect on Thermal Decomposition of Ammonium Perchlorate

Novel graphitic carbon nitride/CuO (g-C₃N₄/CuO) nanocomposite was synthesized through a facile precipitation method. Due to the strong ion-dipole interaction between copper ions and nitrogen atoms of g-C₃N₄, CuO nanorods (length 200–300 nm, diameter 5–10 nm) were directly grown on g-C₃N₄, forming a g-C₃N₄/CuO nanocomposite, which was confirmed via X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). Finally, thermal decomposition of ammonium perchlorate (AP) in the absence and presence of the prepared g-C₃N₄/CuO nanocomposite was examined by differential thermal analysis (DTA), and thermal gravimetric analysis (TGA). The g-C₃N₄/CuO nanocomposite showed promising catalytic effects for the thermal decomposition of AP. Upon addition of 2 wt % nanocomposite with the best catalytic performance (g-C₃N₄/20 wt % CuO), the decomposition temperature of AP was decreased by up to 105.5 °C and only one decomposition step was found instead of the two steps commonly reported in other examples, demonstrating the synergistic catalytic activity of the as-synthesized nanocomposite. This study demonstrated a successful example regarding the direct growth of metal oxide on g-C₃N₄ by ion-dipole interaction between metallic ions, and the lone pair electrons on nitrogen atoms, which could provide a novel strategy for the preparation of g-C₃N₄-based nanocomposite.

A facile one-pot solvothermal synthesis of CoFe2O4/RGO and its excellent catalytic activity on thermal decomposition of ammonium perchlorate

A novel catalyst CoFe₂O₄/RGO has been synthesized and shows enhanced catalytic activity on thermal decomposition of ammonium perchlorate.

Effects of metal organic framework Fe-BTC on the thermal decomposition of ammonium perchlorate

Fe-BTC effectively enhances the thermal decomposition of AP and improves the combustion properties of BAMO–THF propellant with AP as the oxidizer.