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Summary: The LiNiO2 (LNO) positive electrode material is one of the most promising high‐voltage alternatives for the layered oxide materials such as LiCoO2 (LCO). However, the poor cyclability still limits widespread commercialization of LNO, whereas crack formation is one of the main issues leading to its premature aging. In this study, a series of Al‐doped LNO (LiNi1−xAlxO2, x = 0, 0.02, 0.04, 0.06) positive electrode materials are synthetized via a simple sol‐gel method. Overall, this study aims at providing new insights of the sol‐gel method and Al‐doped strategy for LNO positive electrode materials. The synthesis is found to readily yield in small nanosized crystals, which alleviate the cracking issue. Besides, the optimized Al‐doping amount (2 at%) in LNO decreases cation mixing and primary particle size resulting in improved layered structure stability attributed to more reversible H2‐H3 phase transitions. As a result, the assembled lithium ion batteries equipped with LiNi0.98Al0.02O2 can smoothly run for 400 cycles with a relatively high capacity retention of 81% at 100 mA g−1 charging‐discharging and a wide operating voltage window of 2.5‐4.5 V. [ABSTRACT FROM AUTHOR]

Summary: The Mn‐C‐O composites were synthesized by the electric‐arc discharge method. The composite materials were obtained by spraying of graphite electrode with the addition of MnO2. The morphology of Mn‐C‐O composites formed during electric‐arc spraying of metal‐carbon electrodes in various buffer gases (N2 and He) and the effect of their subsequent annealing in an oxygen‐containing atmosphere was studied. It was experimentally determined that MnOx (MnO, Mn3O4) nanoparticles are mainly formed in N2 atmosphere, and Mn7C3 carbide nanoparticles are formed in He atmosphere. This phenomenon is explained by different cooling rates of the formed composites. With further annealing of materials, partial oxidation of nanoparticles and graphitization of the carbon matrix occur due to the thermal effect of the oxidation reaction. According to the study of electrochemical activity of materials in the 1 M KOH aqueous electrolyte, the materials with a higher MnO content and a higher degree of soot graphitization have the highest electrochemical capacity of 135 Fg−1. [ABSTRACT FROM AUTHOR]

Thermally expanded graphite (TEG) is used as a template for precipitation of polyaniline from an aqueous solution of aniline hydrochloride and sodium persulfate used as an oxidant. In the first case, the TEG sample is used without treatment, in the second case the TEG sample is activated by ultrasonication before the polyaniline precipitation. Raman spectroscopy shows the formation of polymer layers on the surface of graphene layers. Near‐edge X‐ray absorption fine structure and X‐ray photoelectron spectroscopy reveal the influence of the TEG ultrasonication on the chemical state of polyaniline in the hybrid. This material shows a large specific capacitance in a 1 M H2SO4 electrolyte due to the Faradaic processes in the polyaniline and high stability during the cycling. [ABSTRACT FROM AUTHOR]

Electrochemically active hybrid electrodes have been obtained by non-covalent immobilization of homo-oligoribonucleotide probes on the surface of multi-walled carbon nanotubes (MWCNTs) grown vertically on a silicon substrate. Immobilization has been achieved by interaction of heterocyclic bases of oligonucleotide with MWCNT surface or through a pyrene anchor group pre-conjugated to oligonucleotide. The electrode capacitance signal measured in our model system allowed for the selective recognition of target RNA oligonucleotides. Pyrene-anchoring of oligonucleotide probes to the MWCNT surface was shown to provide the better selectivity and stability of electrochemical response of the hybrid electrode. [ABSTRACT FROM AUTHOR]

A novel nanostructured hybrid material PANI@MIL-101(Cr) (PANI = polyaniline, MIL-101(Cr) – trichromium oxo-1,4-benzenedicarboxylate) was obtained by the intra-pore oxidative polymerization of guest aniline molecules within MIL-101. The compound was fully characterized using PXRD, TGA, FT-IR spectroscopy, XPS and SEM techniques. An introduction of PANI has dramatically increased the material's selectivity towards carbon dioxide over nitrogen with a CO2 uptake value of 2.26 mmol g−1 at 273 K (1.2 bar). Furthermore, cyclic voltammetry measurements revealed that PANI@MIL-101(Cr) is a supercapacitor with a relatively high specific capacitance value of 135 F g−1. [ABSTRACT FROM AUTHOR]

Using a set of microscopic, spectroscopic, and electrochemical methods, a detailed study of the interrelation between the structural and electrochemical properties of the as-prepared nitrogen-containing multi-walled carbon nanotubes (N-MWCNTs) and their modified derivatives is carried out. It was found that after treatment of nanotubes with hydrochloric acid, their structure is improved by removing amorphous carbon from the outer layers of N-MWCNTs. On the contrary, ion bombardment leads to the formation of vacancy-type structural defects both on the surface and in the bulk of N-MWCNTs. It is shown that the treated nanotubes have an increased specific capacitance (up to 27 F·g−1) compared to the as-prepared nanotubes (13 F·g−1). This is due to an increase in the redox capacitance. It is associated with the reversible Faraday reactions with the participation of electrochemically active pyridinic and pyrrolic nitrogen inclusions and oxygen-containing functional groups (OCFG). Based on the comparison between cyclic voltammograms of N-MWCNTs treated in HCl and with an ion beam, the peaks on these curves were separated and assigned to specific nitrogen inclusions and OCFGs. It is shown that the rate of redox reactions with the participation of OCFGs is significantly higher than that of reactions with nitrogen inclusions in the pyridinic and pyrrolic forms. Moreover, it was established that treatment of N-MWCNTs in HCl is accompanied by a significant increase in the activity of nitrogen centers, which, in turn, leads to an increase in the rate of redox reactions involving OCFGs. Due to the significant contribution of redox capacitance, the obtained results can be used to develop supercapacitors with increased total specific capacitance. [ABSTRACT FROM AUTHOR]

Carbon nanostructures are promising electrode materials for energy storage devices because of their unique physical and chemical properties. Modification of the surface improves the electrochemical properties of those materials because of the changes in morphology, diffusion properties, and inclusion of additional contributions to redox processes. Oxygen-containing functional groups and nitrogen doped into the carbon matrix significantly contribute to the electrochemical behavior of reduced graphite oxide (RGO). In this work, RGO was synthesized during hydrothermal treatment of graphite oxide with a hydrazine sulfate aqueous solution. Different amounts of hydrazine sulfate were used to synthesize RGO with different nitrogen contents in the structure, and the same synthesis conditions made it possible to obtain a material with a similar composition of oxygen-containing functional groups. The materials with different nitrogen concentrations and similar amounts of oxygen were compared as electrode materials for a supercapacitor and as a negative electrode material for a Li-ion battery. It was shown that the presence of oxygen-containing functional groups has the greatest influence on the behavior and efficiency of supercapacitor electrode materials, while nitrogen atoms embedded in the graphene lattice play the largest role in lithium intercalation. [ABSTRACT FROM AUTHOR]

The reduction of graphite oxide makes it possible to obtain a graphene material with a developed surface, high conductivity and remarkable electrochemical behavior. The study of the electrochemical activity of oxygen‐containing functional groups on the graphene surface is important for the creation of electrochemical energy sources and sensors. In this work, the reduced graphite oxide is selectively decorated by carboxyl functional groups. The initial and carboxylated reduced graphite oxide are studied by SEM microscopy, FTIR, Raman, and X‐ray photoelectron spectroscopy. It is shown that a large number of carboxyl groups added to reduced graphite oxide surface change the sample morphology. Studying of reduced graphite oxide and carboxylated reduced graphite oxide by cyclic voltammetry shows reversible redox processes, which is associated with oxidation and reduction of the hydroxyl, carbonyl, and carboxyl groups. In addition, the dependence of peak potentials on the pH value is studied. [ABSTRACT FROM AUTHOR]

This work contributes to the understanding of single-walled carbon nanotube synthesis by an aerosol CVD method using ethylene and toluene as a hybrid carbon source. We evaluated an extensive set of synthesis conditions revealing the role of ferrocene, toluene, and ethylene. We found the fundamental role of ethylene promoting nanotube nucleation and catalyst activation degree at all the concentrations studied, and enhancing nanotube growth at low ethylene content. We observed the interplay effect of toluene and ethylene concentrations on the nanotube growth rate, accompanied by the detrimental effect of toluene on catalyst activation degree. Nevertheless, toluene apparently promotes nanotube crystallinity, increasing the film conductivity while used as an individual carbon source. Adjusting the ethylene and toluene concentrations, we produced carbon nanotube-based transparent and conductive films with an equivalent sheet resistance (at 90% transmittance at 550 nm wavelength) value of 57 Ω/□ at the synthesis yield of 0.24 cm2 L−1, which is at least two times higher than the results reported earlier. [Display omitted] • Ethylene boosts SWCNT nucleation and enhances catalyst activation degree. • Ethylene promotes growth rate but deactivates catalyst at high concentrations. • Toluene improves nanotube crystanillity and deteriorates catalyst activation degree. • Toluene and ethylene together yield in better performance unlike separate supply. • High-yield production of high-performance transparent conductive films demonstrated. [ABSTRACT FROM AUTHOR]