Thermal Condensation Research Articles

The Structure of Boron Monoxide.

Boron monoxide (BO), prepared by the thermal condensation of tetrahydroxydiboron, was first reported in 1955; however, its structure could not be determined. With the recent attention on boron-based two-dimensional materials, such as borophene and hexagonal boron nitride, there is renewed interest in BO. A large number of stable BO structures have been computationally identified, but none are supported by experiments. The consensus is that the material likely forms a boroxine-based two-dimensional material. Herein, we apply advanced 11B NMR experiments to determine the relative orientations of B(B)O2 centers in BO. We find that the material is composed of D2h-symmetric O2B-BO2 units that organize to form larger B4O2 rings. Further, powder diffraction experiments additionally reveal that these units organize to form two-dimensional layers with a random stacking pattern. This observation is in agreement with earlier density functional theory (DFT) studies that showed B4O2-based structures to be the most stable.

Triazine-based covalent organic polymer as a high aerobic oxidative desulfurization performance catalyst under mild reaction conditions

Aerobic oxidative desulfurization (AODS) has attracted significant attention due to the utilization of environmentally friendly and safe O2 as an oxidizing agent. However, it is still a great challenge to design metal-free catalysts that activate O2 effectively at low temperature. In this study, a triazine-based covalent organic polymer (MC-TCOP) was prepared through thermal condensation reaction, and the basic characteristics of the catalyst were analyzed by different characterization methods. The MC-TCOP was applied into the AODS reaction, and the catalytic performance reached to 99.6% under mild reaction conditions (T = 50 ℃, t = 150 min, gas flow = 90 mL/min, catalyst dosage = 0.04 g). Theoretical calculation showed O2 and dibenzothiophene (DBT) were co-adsorbed on the active sites of the catalyst, and the reaction mechanism indicated the O2 was activated into •O2− (by the charge difference between the nitrogen and carbon atoms), then the DBT was oxidized to corresponding sulphone. Moreover, reusability experiment confirmed the catalyst performance was still higher than 95% after 9 times of reusing. The MC-TCOP can be used as a metal-free and eco-friendly catalyst in AODS reaction.

Fabrication and application of novel magnetic polyethylene oxide/ polyacrylamide /graphitic carbon nitride nanocomposite by gamma irradiation for metal ion removal from waste water

ABSTRACT In this study, a facile thermal condensation method was employed to prepare graphitic carbon nitride (g-C3N4) nanoparticles, and characterised by different advanced techniques. The TEM results proved that g-C3N4 had an average size of 49.7–89.3 nm. The EDX analysis of g-C3N4 confirms the existence of only C and N elements. Polyethylene oxide/polyacrylamide (PEO/PAAm) hydrogel and PEO/PAAm/g-C3N4 nanocomposite of different ratios of g-C3N4 (5, 10, and 15%) were synthesised by gamma irradiation-induced crosslinking reaction. In addition, novel magnetic (PEO/PAAm/g-C3N4/Fe3O4) nanocomposite was successfully fabricated by alkaline co-precipitation of swollen PEO/PAAm/g-C3N4 in Fe3+/Fe2+ solutions for use in the removal of Sr2+, Zn2+, and Cd2+ ions from wastewater. The PEO/PAAm/g-C3N4/Fe3O4 nanocomposite was characterised by FTIR, XRD, SEM, EDX, and VSM techniques. The XRD of PEO/PAAm/g-C3N4/Fe3O4 nanocomposite showed the presence of the typical peaks of both g-C3N4 and Fe3O4 nanoparticles. The VSM analysis indicated that the saturation magnetisation value of the nanocomposite was 18.96 emu/g, which is suitable for magnetic separation and adsorption processing. The uptake ability of PEO/PAAm/g-C3N4/Fe3O4 nanocomposite towards the Sr2+, Zn2+, and Cd2+ was examined under the effect of pH, reaction time, pH, and adsorbent dosage as well as different adsorption kinetics and isotherms models were applied. The maximum removal percentage of Cd2+, Zn2+, and Sr2+ ions was 89.8%, 97.3%, and 91.5% and achieved after 25 min at the optimum pH of 6 for Cd2+ and Zn2+, and pH 4.0 for Sr2+ ions. The fast and easy uptake of PEO/PAAm/g-C3N4/Fe3O4 nanocomposite adsorbent for the pollutants owing to the synergistic effect of existing functional groups of PEO/PAAm as well as g-C3N4 and Fe3O4 improved the removal performance of metal ions for great application in environmental remediation of wastewater treatments.

Facile synthesis of all carbon-based cocatalyst assists carbon nitride nanotubes with effective photocatalytic H2 evolution

All carbon-based CG/M − CN rectangular nanotubes have been constructed by a facile molten salt thermal condensation of melamine and glucose. In the molten salt fluid, the glucose is carbonized into graphene-like (CG) nanosheets acting as an electron acceptor, and the melamine thermally condenses into carbon nitride (M − CN) rectangular nanotube acting as an electron donor. The 0.5 wt% CG/M − CN nanotubes display a photocatalytic H2 evolution rate of 2345 μmol h−1 g−1, which is 1.52 times higher than that of M-CN. Moreover, without loading Pt co-catalyst, the 0.5 wt% CG/M − CN nanotubes show a 12.75 times higher photocatalytic H2 evolution rate than that of M-CN. It is revealed that the graphene-like CG nanosheets not only can act as an electron acceptor boosting charge carrier separation, but also function as a HER cocatalyst for M-CN. Our work provides a new insight for the development of all carbon-based photocatalysts for energy-related applications.

Synthesis of Phosphotungstic acid/S-doped g-C3N4 Photocatalyst and Its Photocatalytic Degradation of Organic Pollutants in Aqueous Solutions

The S-doped g-C3N4 (SCN) was prepared by thermal condensation method using thiourea as a precursor, and then the phosphotungstic acid (PTA)/SCN composite photocatalytic material was prepared by reflux adsorption method. The photocatalytic degradation experiments of Rhodamine B showed that SCN20 had the highest photocatalytic degradation rate (74 %), which was 1.9 times and 3.5 times higher than that of PTA (39 %) and SCN (21 %), respectively. The photocatalytic degradation rate of SCN20 was increased by 5 times compared to that of SCN, indicating that the photocatalytic degradation performance of the composite material was significantly improved. The photocatalytic degradation mechanism study revealed that O2- was the main active species in the photocatalytic degradation of Rhodamine B, and the addition of PTA helped the effective separation of electrons-hole and improved the photocatalytic degradation rate. Our PTA/SCN is proposed as an environmental safety tool due to several advantages, such as low cost, convenient preparation, and efficient photocatalytic degradation of Rhodamine B.

Electrochemical detection of nitrazepam using leaf-like graphitic carbon nitride nanosheets

Benzodiazepines like nitrazepam are extensively used, both as prescribed medications and as illicit drug substitutes, and therefore detection is of prime importance. In this work, the electrochemical detection of nitrazepam using a graphitic carbon nitride (g-C3N4) modified electrode was investigated. The nitrogen-rich carbon material i.e., g-C3N4 was easily synthesized by the thermal condensation method using melamine as a precursor. The platinum electrode was modified by synthesized material and its electrochemical activity was tested using a three-electrode set-up. The cyclic voltammetry and electrochemical impedance spectroscopy confirmed the effective detection of nitrazepam. The detection at different concentrations was analyzed using CV and differential pulse voltammetry (DPV). The detection limit of 0.02 μM was found with the linear dynamic range of nitrazepam. A repeatability experiment was conducted to check the stability of the proposed electrode. This study confirms the potential use of g-C3N4 as an effective and stable electrode material for the detector in the field of pharmaceuticals and health care.

Dual modulation on peroxymonosulfate activation site and photocarrier separation in carbon nitride for efficient photocatalytic organics degradation: Efficacy and mechanism evaluation

Herein, sulfur and sodium co-doped cyano-rich polymeric carbon nitride (NaCNS) have been designed to boost photocatalytic atrazine (ATZ) degradation with peroxymonosulfate (PMS) assistance. The NaCNS was fabricated via a two-step thermal condensation with the existence of sodium chloride and cysteine, and the ATZ degradation in the system was evaluated via batch experiments. Compared to pristine carbon nitride, the reaction rate constant of NaCNS was dramatically enhanced nearly sixfold (47.66 ×10−3·min−1). Given the experiments and theoretical calculation, the ATZ degradation in the system was mainly dominated by the electrophilic attack of O21, leading to the production of 11 intermediates with reduced ecotoxicity. The promoted photocatalytic performance was originating from the dual modulation of NaCNS, where the sodium act as a PMS activation site while the cyano and sulfur construct an electronic push-pull system for better photocarrier separation. Hopefully, this study can inspire the rational design of catalysts for efficient photocatalytic PMS activation.

Facile method for improving the catalytic performance of g-C3N4 by electrostatic self-assembled with Bi2MoO6/kaolinite composite

In order to overcome the shortcoming of g-C3N4 as a photocatalyst with high electron-hole pair recombination rate, an efficient photocatalyst of g-C3N4/Bi2MoO6/kaolinite composite was constructed in this work. Depending on the electrostatic self-assembly, g-C3N4 prepared by thermal condensation and Bi2MoO6/kaolinite by hydrothermal method were combined closely. The results showed that composite with multilevel structure was built, which proves that the collaboration of three components was successfully realized. When the mass ratio of Bi2MoO6/kaolinite and g-C3N4 was 0.25:0.75, the composite showed excellent photocatalytic performance. By constructing the interface in close contact and layered assembly, the synergistic effect between kaolinite and Bi2MoO6/g-C3N4 heterostructure was in favor of producing the excellent photocatalytic performance.

Thermal performance and condensation analysis of insulated concrete panels using a thermal-meta structure

Sandwich panels are widely employed in warehouses and factories due to their cost-effectiveness and workability. However, recent major fires in Korea, caused by the combustion of sandwich panels, have necessitated the development of limited combustible panels wgyith comparable thermal performance. In this study, we introduce an innovative panel that satisfies both fire resistance and insulation performance requirements. The panel comprises a fire-resistant concrete-based material and a honeycomb insulation material for enhanced insulation. The experimental results demonstrate that the developed honeycomb-meta precast concrete panel exhibits excellent insulation and fire resistance, outperforming traditional panels with an 18% higher flame retardancy. The panel effectively mitigates common issues typically encountered in prefabricated panels, such as decreased insulation performance and condensation at connection points. These findings highlight the potential of the developed panel in various construction applications, particularly in buildings requiring superior fire resistance and insulation performance.

Microwave-assisted synthesis of edge-grafted carbon nitride by triazole rings for efficient photocatalytic hydrogen evolution

Copolymerization of conjugated nitrogen heterocycles within carbon nitride nowadays is proven to be a successful strategy to promote charge separation. Here, a novel edge-grafted carbon nitride nanosheets by triazole rings were synthesized from the copolymerization of dicyandiamide and 3-amino-1, 2, 4-triazole via microwave-assisted heating with improved yield. Based on the building of a feasible donor-acceptor (D-A) system by such edge grafting, the rapid charge transfer pathways were formed. Benefiting from the thin-layer structure of carbon nitride via microwave-assisted heating and abundant π electrons by intramolecular doping, the system showed enhanced visible light absorption from n-π∗ electrons transition, facile charge separation and transfer, and then an increased H2 evolution rate (637.58 μmol h−1 g−1), which is 17.43 times than the triazole modified sample from conventional thermal condensation method. This work enlightens an innovative pathway for the regulation of carbon nitride photocatalysts by conjugated nitrogen heterocycles for efficient solar energy conversion applications.

Rational Design of Monolithic g-C3N4 with Floating Network Porous-like Sponge Monolithic Structure for Boosting Photocatalytic Degradation of Tetracycline under Simulated and Natural Sunlight Illumination.

In order to solve the problems of powder g-C3N4 catalysts being difficult to recycle and prone to secondary pollution, floating network porous-like sponge monolithic structure g-C3N4 (FSCN) was prepared with a one-step thermal condensation method using melamine sponge, urea, and melamine as raw materials. The phase composition, morphology, size, and chemical elements of the FSCN were studied using XRD, SEM, XPS, and UV-visible spectrophotometry. Under simulated sunlight, the removal rate for 40 mg·L-1 tetracycline (TC) by FSCN reached 76%, which was 1.2 times that of powder g-C3N4. Under natural sunlight illumination, the TC removal rate of FSCN was 70.4%, which was only 5.6% lower than that of a xenon lamp. In addition, after three repeated uses, the removal rates of the FSCN and powder g-C3N4 samples decreased by 1.7% and 2.9%, respectively, indicating that FSCN had better stability and reusability. The excellent photocatalytic activity of FSCN benefits from its three-dimensional-network sponge-like structure and outstanding light absorption properties. Finally, a possible degradation mechanism for the FSCN photocatalyst was proposed. This photocatalyst can be used as a floating catalyst for the treatment of antibiotics and other types of water pollution, providing ideas for the photocatalytic degradation of pollutants in practical applications.

A composite of biomass porous carbon supported g‐C3N4 by 2,4,6‐triaminopyrimidine modification for enhancing oxytetracycline removal

AbstractSince the traditional g‐C3N4 photocatalyst was severely affected by low charge transfer rates and light absorption capacity, which inevitably limited its application in environmental pollution treatment. Herein, mixing the 2,4,6‐triaminopyrimidine (TAP) doped melamine and biomass porous carbon (BPC), the TAP‐BPC/CN composite with desirable conductivity was synthesized by one step thermal condensation. That is, the carbon atom of TAP was used to partially replace the nitrogen atom of tri‐s‐triazine structure of g‐C3N4, and decreased the interlayer distance of graphite lamellar structure, then improved the electrical conductivity of the materials and suppressed the recombination of photogenerated carriers. At the same time, the incorporation of BPC also contributed to increase the active sites of the material and enhance the separation efficiency of photogenerated carriers. Furthermore, the formation of p‐n homojunction in TAP‐BPC/CN built the construction of an internal electric field at the interface, which induced the band bending and improved charge separation and transfer effectively. As a result, the sample of TAP‐BPC/CN exhibited an excellent adsorption and photocatalytic activities in the degradation of oxytetracycline (OTC). This research provides a new strategy for efficient photocatalysts with high absorption and photocatalysis in the antibiotic wastewater treatment.

One-step cladding metal oxide nanowires with a carbon-dots-embedded ZnO amorphous layer toward boosted photoelectrochemical water oxidation

An effective method was proposed for constructing carbon dots (CDs)-sensitized multijunction composite photoelectrodes via one-step cladding a CDs-embedded ZnO amorphous overlayer on vertically aligned metal oxide nanowires. This strategy involved the double role of hexamethylenetetramine (HMTA) in the ethylene glycol (EG) solvent mixed with a controllable trace amount of water. In the water-deficient synthetic system, a limited portion of HMTA served as the pH buffer and hydroxyl source to force the hydrolytic process of zinc ions for the production of ZnO. The precipitated ZnO clusters were instantly capped by EG molecules through the activated alkoxidation reaction, and further crosslinked into an amorphous network surrounding the individual nanowires. Meanwhile, the excess HMTA was simultaneously depleted as the precursor for producing CDs in the EG solution through thermal condensation, which were packed in the gradually formed aggregates. We revealed that a CDs-embedded amorphous ZnO overlayer with an appropriate proportion of ingredient could be tailored through an optimal tradeoff between hydrolysis and condensation of HMTA. Benefiting from the synergy of the amorphous ZnO layer and the embedded CDs, the multijunction composite photoanodes exhibited significantly improved PEC performance and stability for water oxidation.

Single-Atom Cu Channel and N-Vacancy Engineering Enables Efficient Charge Separation and Transfer between C3N4 Interlayers for Boosting Photocatalytic Hydrogen Production

Polymeric carbon nitride (C3N4) has attracted great attention in photocatalysis due to its low-cost, visible-light response, and environment-friendly merits. However, the catalytic efficiency of pristine bulk C3N4 is severely limited by its poor photoinduced electron/hole pair separation and interlayer charge transport. Herein, single-atom Cu is bridged into C3N4 sheet interlayers through the thermal condensation of self-assembly supramolecules of Cu precursors and melamine–cyanuric acid monomers. Simultaneously, N vacancies are engineered into C3N4 only by gradient temperature. The single-atom Cu bridges serve as electron channels to promote photoinduced electron/hole pair separation and interlayer charge transport. The experimental results and calculations demonstrate that N vacancies break the symmetry of pristine C3N4, allowing more electrons to pass through the delocalized π-conjugated network of C3N4 to Cu sites, which facilitates charge transfer between C3N4 layers, resulting in more effective separation of electron/hole pairs, optimal charge distribution, and lower hydrogen evolution barrier. As a result, the photocatalyst at a stationary point with a 1 wt % Pt cocatalyst presents a high visible-light photocatalytic hydrogen production rate (11.23 mmol g–1 h–1), reaching a high apparent quantum yield of 31.60% at 420 nm. It is noted that the photocatalyst still exhibits a high hydrogen production rate of 605.15 μmol g–1 h–1 in the absence of the Pt cocatalyst.

Nanoarchitecture engineering of crumpled polymeric carbon nitride nanosheets for efficient visible-light photocatalytic CO2 reduction

Polymeric carbon nitride nanosheets with few layers have emerged as a new category of semiconductor materials which are promising for photocatalytic applications because of their unique optical and electronic characteristics. The texture and optical–electronic properties of the nanosheets significantly influence the photocatalytic activities. In this study, a series of crumpled polymeric carbon nitride nanosheets was prepared via a facile stepwise pyrolytic strategy and a time-dependent pyrolysis process. The as-obtained nanosheets exhibit a sequential change in morphology from a continuous-aggregation architecture to discrete nanosheets with prolonged thermal-treatment time. The nanosheets with the continuous-aggregation architecture, consisting of small curved nanosheet subunits are laterally large; thus, they can provide numerous reactive sites for surface reactions and awaken intrinsic n → π* electron transitions to promote photocatalytic activity. The optimum crumpled polymeric carbon nitride nanosheet is formed after 2 h of thermal condensation, and it demonstrates efficient CO2-conversion performance with the highest CO-evolution rate of 1287 µmol g−1h−1, which is 7 times more than that of pristine polymeric carbon-nitride nanosheets. This work provides an opportunity to significantly understand the roles of texture and optical–electronic properties in improving the photocatalytic activities of polymeric carbon-nitride nanosheets.

The mitigation of pitch-derived carbon with different structures on the volume expansion of silicon in Si/C composite anode

The microstructures of carbon precursors significantly affect the electrochemical performance of Si/C composite anodes. However, the interaction between Si and carbon materials with different structures is still unclear. Pitch-based materials undergoing different thermal treatments are superior sources for synthesizing carbons with different structures. Herein, different types of mesophase pitch (domain, flow-domain and mosaic structure) obtained from controllable thermal condensation are utilized to prepare Si/C composite materials and the corresponding models are established through finite element simulation to explore the correlation between the lithium storage properties of Si/C composites and the structures of carbon materials. The results indicate that the flow-domain texture pitch P2 has a better ability to buffer the volume expansion of silicon particles for its highly ordered arrangement of carbon crystallites inside could disperse the swelling stress uniformly alongside the particle surface. The sample Si@P2 exhibits the highest capacity of 1328 mA h/g after 200 cycles at a current density of 0.1 A/g as well as the best rate performance and stability. While sample Si@P3 in which the mosaic texture pitch P3 composed of random orientation of crystallites undergoes the fastest capacity decay. These findings suggest that highly ordered carbon materials are more suitable for the synthesis of Si/C composite anodes and provide insights for understanding the interaction between carbon and silicon during the charging/discharging process.

Preparation of carbon nitride nanotubes with P-doping and their photocatalytic properties for hydrogen evolution

Various carbon nitride (C3N4) materials show great potential as an eco-friendly, visible-light-active photocatalyst for hydrogen evolution reaction (HER). In this work, a new route to produce one-dimensional (1D) P-doped carbon nitride nanotubes is developed via supramolecular self-assembly. The nanotubes are produced by thermal condensation of melamine and cyanuric acid. The addition of an ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) improves the uniformity of the nanotubes. It is revealed that the C3N4 nanotubes are formed by thermal condensation of rod-shaped intermediates. The nanotubes show an excellent photocatalytic HER activity under visible light irradiation and are a superior catalyst to 3D C3N4 samples. From thorough structural and photophysical characterizations, it is found that the nanotubes contain larger surface areas, more amine bridges, better crystallinity, and more visible-light-absorption ability than control samples. These structural features are reasons for the enhanced photocatalytic performance.

Palmitic acid-based amide as a corrosion inhibitor for mild steel in 1M HCl

Due to growing environmental concerns and regulations limiting the use of harmful and toxic synthetic corrosion inhibitors, there is a high demand for sustainable corrosion inhibitors. In this study, a green and rapid technique was used to synthesize amide N-(4-aminobutyl)palmitamide (BAPA) which yielded 91.17% of the product within 2 min, compared to a low yield of 75–80% and a very long 8–10 h reaction time with the conventional thermal condensation method. The chemical structure of BAPA was analyzed by FT-IR, 1HNMR and 13CNMR spectra, as well as CHNS elemental analysis. When applied to mild steel exposed to 1 M HCl, BAPA delayed and reduced corrosion by adsorbing to the steel surface to form a protective layer. The inhibition efficiency increased with increasing amide concentration, and maximal inhibition of 91.5% was observed at 0.5 mM BAPA. The adsorption of BAPA on mild steel in an acidic solution was studied and inhibition performance was correlated with the calculated adsorption-free energy ΔGads, indicating good agreement between the experimental and adsorption findings. Surface morphology of untreated and treated mild steel coupons was evaluated by SEM, and based on density functional theory (DFT) computations and atomic charges analysis, a stronger interaction was observed between BAPA and mild steel surface leading to the formation of a compact protective film on the metallic surface. This protective film is attributed to the presence of nitrogen atoms and carbonyl group in the chemical structure of BAPA.

An Origin of Narrow Extended Structure in the Interstellar Medium: An Interstellar Contrail Created by a Fast-moving Massive Object

We investigate the thermal condensation caused by a massive object that passes through the interstellar medium with high velocity, and propose a mechanism for creating a filamentary gaseous object, or interstellar contrail. Our main result shows that a long interstellar contrail can form with a certain parameter; a compact object more massive than 104 M ☉ can make a filament whose length is larger than 100 pc. Observation of interstellar contrails may provide information on the number, masses, and velocities of fast-moving massive objects, and can be a new method for probing invisible gravitating sources such as intermediate-mass black holes.

MoO3/S@g-C3N4 Nanocomposite Structures: Synthesis, Characterization, and Hydrogen Catalytic Performance.

Hydrogen production as a source of clean energy is high in demand nowadays to avoid environmental issues originating from the use of conventional energy sources i.e., fossil fuels. In this work and for the first time, MoO3/S@g-C3N4 nanocomposite is functionalized for hydrogen production. Sulfur@graphitic carbon nitride (S@g-C3N4)-based catalysis is prepared via thermal condensation of thiourea. The MoO3, S@g-C3N4, and MoO3/S@g-C3N4 nanocomposites were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FESEM), STEM, and spectrophotometer. The lattice constant (a = 3.96, b = 13.92 Å) and the volume (203.4 Å3) of MoO3/10%S@g-C3N4 were found to be the highest compared with MoO3, MoO3/20-%S@g-C3N4, and MoO3/30%S@g-C3N4, and that led to highest band gap energy of 4.14 eV. The nanocomposite sample MoO3/10%S@g-C3N4 showed a higher surface area (22 m2/g) and large pore volume (0.11 cm3/g). The average nanocrystal size and microstrain for MoO3/10%S@g-C3N4 were found to be 23 nm and -0.042, respectively. The highest hydrogen production from NaBH4 hydrolysis ~22,340 mL/g·min was obtained from MoO3/10%S@g-C3N4 nanocomposites, while 18,421 mL/g·min was obtained from pure MoO3. Hydrogen production was increased when increasing the masses of MoO3/10%S@g-C3N4.