Control of hydrogen release during borohydride electrooxidation with porous carbon materials.

Due to their highly tunable electrical and structural properties, carbon materials are widely used in fuel cells. This study reviews the latest modifications carried out in order to improve the electrochemical properties of carbon-based anodes in Direct Borohydride Fuel Cell (DBFC). However, in this type of fuel cell, various types of carbon (e.g. carbon black, activated carbons, carbon nanotubes, graphene and heteroatom-doped carbons and MOF-derived carbon materials) can provide not only catalyst support, but also hydrogen storage due to the extremely complex process of borohydride electrooxidation. Accurate control of porosity and carbon morphology is therefore necessary for high fuel cell efficiency. Finally, some prospects for the future development of carbon materials for DBFC design are presented. It should be emphasized, that the storage of hydrogen in solid form is a possible breakthrough for the future use of hydrogen as an ecological fuel, which is why scientific research in this topic is so important.

Long-Chain Ionic Liquids Based on Monoquaternary DABCO Cations and TFSI Anions: Towards Stable Electrolytes for Electrochemical Capacitors.

The desirable properties of ionic liquids (ILs) enable their use in various branches of chemistry, through a wide range of applications, e. g. as organic electrolytes. In the present study, an efficient two-step method was developed for the synthesis of long-chain ionic liquids with alkyl derivatives of DABCO as cations and bis(trifluoromethane)sulfonimide as anions. ILs obtained with high yields (≥91 %) were solids with melting points that increased with the rise in the number of carbon atoms of the alkyl substituent in the bicyclic cation. The structure of the compounds was confirmed by spectroscopic methods and elemental analysis. All compounds were soluble in the main solvents except water and hexane. The solubility in organic solvents such as acetonitrile allowed the use of synthesized ILs in electrochemical capacitors. Electrochemical tests revealed that the ILs enhanced the conductivity of organic electrolytes. This phenomenon improved the cyclability and reduced the internal resistance of the electrochemical capacitors.

Lignin-based dual component additives as effective electrode material for energy management systems.

A functional PbO-lignin electrode hydrid material composite was designed and manufactured. Moreover, its connection efficiency was confirmed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). We noted that the superficial layers of PbO combined with layers of the biopolymer and that oxygen atoms present in both materials had influence on the chemical environment of the neighboring compound. Hence, it can be said that the addition of PbO significantly contributes to the improvement of thermal stability of the final inorganic-organic system. In the framework of the study, the dispersive, morphological and structural characteristics were determined using scanning electron microscopy (SEM) and laser diffraction method. Electrochemical studies indicated that the PbO-lignin material exhibits better electrochemical properties compared to PbO without the addition of kraft lignin (increased capacitance, lower charge transfer resistance), as the specific capacitance after 5000 charge/discharge cycles was still at 95% of the initial value. Such promising operating parameters show that this material can be successfully used as an electrode material for energy management systems.

Boron-Doped Polygonal Carbon Nano-Onions: Synthesis and Applications in Electrochemical Energy Storage.

Doping of carbon nanostructures with heteroatoms, such as boron or nitrogen, is one of the most effective ways to change their properties to make them suitable for various applications. Carbon nano-onions (CNOs) doped with boron (B-CNOs) were prepared by annealing (1650 °C) nanodiamond particles (NDs) under an inert He atmosphere in the presence of B. Their physicochemical properties were measured using transmission (TEM) and scanning (SEM) electron microscopy, X-ray photoelectron spectroscopy (XPS), 10 B and 11 B solid-state magic-angle spinning (MAS) NMR spectroscopy, X-ray powder diffraction (XRD), Raman spectroscopy, porosimetry, and differential-thermogravimetric analyses (TGA-DTG). These properties were systematically discussed for the undoped and B-doped CNO samples. The amount of substitutional B in the CNO samples varied from 0.76 to 3.21 at. %. The TEM, XRD, and Raman analyses revealed that the increased amount of B doping resulted in decreased interlayer spacing and polygonization of the structures, which in turn led to their unusual physicochemical properties. All synthesized materials were tested as electrodes for electrochemical capacitors. The B-CNOs with low concentration of doping agent exhibited higher reversible capacitances, mainly owing to the formation of hydrophilic polygonal nanostructures and higher porosity.