MWCNTs@NHBut/PTA: New efficient solid acid catalyst for solvent free synthesis of benzochromenopyrimidines

In this study, a novel and eco‐friendly synthesis of benzochromenopyrimidines catalyzed by phosphotugstic acid immobilized on aminated multiwalled carbon nanotubes (MWCNTs@NHBut/PTA) is reported. New solid acid catalyst was prepared through a simple process with good percentage of organo metallic groups and characterized with FTIR, TEM, SEM, EDX and TGA techniques. Reusable catalytic system provides a convenient, safe and green pathway to generate a variety of benzochromenopyrimidines under mild conditions.     

Covalent Grafting of BPin functions on Carbon Nanotubes and Chan–Lam–Evans Post-Functionalization

The chemical functionalization of carbon nanotubes is often a prerequisite prior to their use in various applications. The covalent grafting of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (BPin) functional groups directly on the surface of multi- and single-walled carbon nanotubes, activated by nucleophilic addition of nBuLi, was carried out. Thermogravimetric analysis (TGA) coupled with mass spectrometry, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ions mass spectrometry (ToF-SIMS) confirmed the efficiency of this methodology and proved the integrity and covalent grafting of the BPin functional groups. These groups were further reacted with various nucleophiles in the presence of a copper(II) source in the conditions of the aerobic Chan–Lam–Evans coupling. The resulting materials were characterized by TGA, XPS and ToF-SIMS. This route is efficient, reliable and among the scarce reactions that enable the direct grafting of heteroatoms at carbonaceous material surfaces.     

First principles investigations of Fe,Co, Ni in model honeycomb carbon networks

The behaviors of ferromagnetic transition metals of the first period: Fe, Co and Ni are examined within density functional theory calculations in two dimensional carbon extended networks using model structure LiC₆. Around geometry optimized structures, the energy-volume equations of states considering non magnetic and spin polarized configurations established ferromagnetic ground states with magnetizations –reduced with respect to the metals’– of 2 μ_B for FeC₆ and 1 μ_B for CoC₆ while no magnetic solution could be identified for NiC₆. In the D_6h point group of the P6/mmm space group l_m decomposition of the d states results with increasing energy into doublet state E_1g with d(x²-y²) and d(xy); singlet state A_1g d(z²) and doublet state E_2g d(xz) and d(yz) lying on E_F and responsible of the onset of magnetic moments. This was mirrored via molecular orbital approach with a construct of Fe embedded between two extended carbon networks thus validating the model structure proposed for TC₆ compounds. The 100% polarization in one spin channel allows proposing potential uses in spintronics applications.     

BiVO4/TiO2 heterojunction with rich oxygen vacancies for enhanced electrocatalytic nitrogen reduction reaction

The large-scale production of ammonia mainly depends on the Haber–Bosch process, which will lead to the problems of high energy consumption and carbon dioxide emission. Electrochemical nitrogen fixation is considered to be an environmental friendly and sustainable process, but its efficiency largely depends on the activity and stability of the catalyst. Therefore, it is imperative to develop highefficient electrocatalysts in the field of nitrogen reduction reaction (NRR). In this paper, we developed a BiVO₄/TiO₂ nanotube (BiVO₄/TNT) heterojunction composite with rich oxygen vacancies as an electrocatalytic NRR catalyst. The heterojunction interface and oxygen vacancy of BiVO₄/TNT can be the active site of N₂ dynamic activation and proton transition. The synergistic effect of TiO₂ and BiVO₄ shortens the proton transport path and reduces the over potential of chemical reaction. BiVO₄/TNT has high ammonia yield of 8.54 μg·h⁻¹·cm⁻² and high Faraday efficiency of 7.70% in −0.8 V vs. RHE in 0.1 M Na₂SO₄ solution.     

Sonochemical conversion of CO2 into hydrocarbons: The Sabatier reaction at ambient conditions

In this study, we investigated an alternative method for the chemical CO₂ reduction reaction in which power ultrasound (488 kHz ultrasonic plate transducer) was applied to CO₂-saturated (up to 3%) pure water, NaCl and synthetic seawater solutions. Under ultrasonic conditions, the converted CO₂ products were found to be mainly CH₄, C₂H₄ and C₂H₆ including large amount of CO which was subsequently converted into CH₄. We have found that introducing molecular H₂ plays a crucial role in the CO₂ conversion process and that increasing hydrogen concentration increased the yields of hydrocarbons. However, it was observed that at higher hydrogen concentrations, the overall conversion decreased since hydrogen, a diatomic gas, is known to decrease cavitational activity in liquids. It was also found that 1.0 M NaCl solutions saturated with 2% CO₂ + 98% H₂ led to maximum hydrocarbon yields (close to 5%) and increasing the salt concentrations further decreased the yield of hydrocarbons due to the combined physical and chemical effects of ultrasound. It was shown that CO₂ present in a synthetic industrial flue gas (86.74% N₂, 13% CO₂, 0.2% O₂ and 600 ppm of CO) could be converted into hydrocarbons through this method by diluting the flue gas with hydrogen. Moreover, it was observed that in addition to pure water, synthetic seawater can also be used as an ultrasonicating media for the sonochemical process where the presence of NaCl improves the yields of hydrocarbons by ca. 40%. We have also shown that by using low frequency high-power ultrasound in the absence of catalysts, it is possible to carry out the conversion process at ambient conditions i.e., at room temperature and pressure. We are postulating that each cavitation bubble formed during ultrasonication act as a “micro-reactor” where the so-called Sabatier reaction -$C{O}_2+4H_2\stackrel{\mathit{Ultrasonication}}{\to }C{H}_4+2H_{2}O$ - takes place upon collapse of the bubble. We are naming this novel approach as the “Islam-Pollet-Hihn process”.     

In situ confinement of iron-based active sites within high porosity carbon frameworks with enhanced activity for rechargeable Zn–air battery

Non-noble bifunctional electrocatalysts with robust activity and stability toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are greatly significant but challenging for Zn-air batteries. Here, in situ confinement of FeN_x active sites in high porosity carbon framework (FeN_x/CMCC) derived from chelate of carboxymethylcellulose (CMC) and iron ions were synthesized. Particularly, construction of FeN_x within porous carbon framework accelerates the electron transfer and the sufficient utilization of active centers, and then expedites the reaction kinetics of ORR and OER. As expected, the optimized FeN_x/CMCC exhibits superior ORR activity with a larger half-wave potential of 0.869 V. The rechargeable Zn-air battery delivers a higher power density of 99.6 mW/cm² and a special capacity of 781.9 mA h/g_Zn at 10 mA/cm², together with excellent durability of over 335 h. Remarkably, the as-assembled solid-state battery exhibits a higher open circuit voltage (OCV) of 1.5 V, a special capacity of 709.7 mA h/g_Zn, as well as prolonged cycling stability (90 h). Moreover, the flexible solid-state battery displays negligible loss of electrochemical performance under various bending angles, illustrating its potential application in flexible electronic devices.     

Relationship of nanostructure and thermo-chemical response/thermal ablation of carbon aerogels

In this work, the interfacial mass balance relations combined with the non-parametric kinetic (NPK) analysis results were used for evaluating the thermo-chemical ablation process and oxidation mechanism of carbon aerogels with various porous structure. It was found that the two-parameter model of Nomen–Sempereis was able to describe the kinetics of the oxidation reaction and to reveal the structure-dependent contribution of two main processes with chemical and physical nature. The porosity of the carbon aerogel, rather than the other microstructural features, was realized more effective on the rate of ablation.     

Design of Functional Carbon Composite Materials for Energy Conversion and Storage

The carbon composite materials have been a research hotspot in the fields of catalysis, energy conversion and so on, because of their features of large structure and morphology variety, good chemical and electrochemical stability, and high electronic conductivity, large specific surface area and rich active sites. This paper summarizes some research progress of carbon composite materials, including assembly methodologies, their structure regulation, properties, and related applications. Moreover, the current challenges and the prospects of these materials are also discussed.     

Methylthiouracil‐modified Carbon Paste Electrode as a New Voltammetric Sensor Based on a 1,4‐Michael Addition Reaction for Detection of Dopamine

A sensitive dopamine sensor was constructed based on the modified carbon paste electrode with methylthiouracil as a nucleophile in the 1,4‐Michael addition reaction. An ECE mechanism was suggested for dopamine oxidation at the modified electrode. Design of experiments was used in the optimization of variables. Under the optimum conditions, calibration graph was linear in the range of 0.20–15.0 µM with a detection limit of 73 nM. The relative standard deviations (n=5) for 0.50 µM of dopamine was 3.83 %. The selectivity of the sensor was also studied. The developed sensor was applied for analysis of pharmaceutical and biological samples.     

Simple and Precise Quantification of Iron Catalyst Content in Carbon Nanotubes Using UV/Visible Spectroscopy

Iron catalysts have been used widely for the mass production of carbon nanotubes (CNTs) with high yield. In this study, UV/visible spectroscopy was used to determine the Fe catalyst content in CNTs using a colorimetric technique. Fe ions in solution form red–orange complexes with 1,10-phenanthroline, producing an absorption peak at λ=510 nm, the intensity of which is proportional to the solution Fe concentration. A series of standard Fe solutions were formulated to establish the relationship between optical absorbance and Fe concentration. Many Fe catalysts were microscopically observed to be encased by graphitic layers, thus preventing their extraction. Fe catalyst dissolution from CNTs was investigated with various single and mixed acids, and Fe concentration was found to be highest with CNTs being held at reflux in HClO₄/HNO₃ and H₂SO₄/HNO₃ mixtures. This novel colorimetric method to measure Fe concentrations by UV/Vis spectroscopy was validated by inductively coupled plasma optical emission spectroscopy, indicating its reliability and applicability to asses Fe content in CNTs.