Alexander G. Krivenko

The search for new hydrogen evolution reaction (HER) electrocatalysts with lower cost and higher activity and stability than noble metal catalysts is essential. In this regard cobalt phosphide is considered one of the most promising nanomaterials. The present work proposes a simple and efficient method for the synthesis of a nanocomposite of graphene–phosphorene structures decorated with CoP nanoparticles 2–5 nm in size via the electrochemical exfoliation of black phosphorus carried out in the presence of nitrogen-doped few-layer graphene structures and followed by solvothermal synthesis in a Co²⁺-containing solution. The obtained CoP/EEBP/N-FLGS nanocomposite demonstrates high electrocatalytic activity and stability towards HER in an alkaline medium. The nanocomposite is characterized by an overpotential of 190 mV at a current density of 10 mA cm⁻² as well as a small Tafel slope (78 mV dec⁻¹). These characteristics make the CoP/EEBP/N-FLGS nanocomposite superior to most electrocatalysts based on cobalt phosphides. The results of this study could be in demand for the future design and improvement of HER electrocatalysts.

For the first time, graphene-phosphorene structures were synthesized using the plasma-assisted electrochemical method. The catalytic activity of the composite obtained in the electrolytic plasma mode and its mixtures with few-layer graphene structures toward the hydrogen evolution reaction was studied. A substantial increase in the catalytic activity of the phosphorene structures towards the hydrogen evolution reaction was realized by mixing them with few-layer graphene structures. The catalyst demonstrates excellent activity towards the hydrogen evolution reaction in alkaline media with a low overpotential of 940 mV at a current density of 10 mA·cm⁻² and a small Tafel slope of 130 mV dec⁻¹.

Diamond compacts were synthesized by thermobaric processing of graphite and amorphous boron mixtures under the conditions of the diamond thermodynamic stability (at a pressure of 8–9 GPa and temperature of ∼2500 K). The boron-doped diamond-compact electrode surface was modified by its subjecting to the action of cathodic, anodic, and cathodic–anodic electrolytic plasma formed under the applying of voltage pulses with amplitude up to 300 V in Na₂SO₄ aqueous solution. It was found by using rotating disc electrode that the applying of sole cathodic–anodic plasma provides negligible catalytic effect with respect to the oxygen reduction reaction. However, thus pre-processed electrode acquired significant electrocatalytical activity upon the cathodic treatment, with the consequence that the reaction of O₂ reduction to H₂O passed predominantly by the four-electron mechanism. At the same time, the cathodic polarization of the plasma-modified electrode produced no effect on the rate constant of the electron transfer in the [Ru(NH₃)₆]^2+/3+ redox couple; yet, the rate constant in the [Fe(CN)₆]^4–/3– one increased significantly. Hypothetically, the observed electrocatalytical effect in the oxygen reduction reaction is due to the formation, under the combined action of the cathodic–anodic plasma and cathodic polarization, of quinone groups at the boron-doped diamond surface; they play the role of active sites for the oxygen four-electron reduction.

A simple method for the mechanochemical synthesis of an effective metal-free electrocatalyst for the oxygen reduction reaction was demonstrated. A nitrogen-doped carbon material was obtained by grinding a mixture of graphene oxide and melamine in a planetary ball mill. The resulting material was characterized by XPS, EPR, and Raman and IR spectroscopy. The nitrogen concentration on the N-bmGO surface was 5.5 at.%. The nitrogen-enriched graphene material (NbmGO has half-wave potential of −0.175/−0.09 V and was shown to possess high activity as an electrocatalyst for oxygen reduction reaction. The electrocatalytic activity of NbmGO can be associated with a high concentration of active sites for the adsorption of oxygen molecules on its surface. The high current retention (93% for 12 h) after continuous polarization demonstrates the excellent long-term stability of NbmGO.

A graphene oxide aerogel (GOA) was formed inside a melamine sponge (MS) framework. After reduction with hydrazine at 60 °C, the electrical conductive nitrogen-enriched rGOA-MS composite material with a specific density of 20.1 mg/cm³ was used to fabricate an electrode, which proved to be a promising electrocatalyst for the oxygen reduction reaction. The rGOA-MS composite material was characterized by elemental analysis, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. It was found that nitrogen in the material is presented by different types with the maximum concentration of pyrrole-like nitrogen. By using Raman scattering it was established that the rGOA component of the material is graphene-like carbon with an average size of the sp²-domains of 5.7 nm. This explains a quite high conductivity of the composite obtained.

A new one-step method for the synthesis of an oxygen reduction electrocatalyst based on a nanocomposite of few-layer graphene structures and manganese oxides is proposed. It has been shown that by using the bipolar method of graphite exfoliation in the plasma electrolysis mode in solutions containing manganese salts, it is possible to obtain graphene nanostructures decorated with manganese oxides exhibiting high catalytic activity in the oxygen reduction reaction, which consists in a significant reduction in overpotential and an increase in the oxygen reduction current.

Few-layer graphene structures synthesized by the plasma electrochemical method are used as modifiers of epoxy binders. It is shown that the obtained structures have the maximum positive...

Isatin Schiff base ligands in combination with redox active metal ions have the potential to behave as non-innocent ligands facilitating industrially important chemical reactions. The ligand structure is easily modified by introducing substituents in three different positions, affecting the electron density distribution that was evaluated by Mulliken charge analysis and cyclic voltammetry for a range of isatin derivatives. It was noticed that coordination of these ligands to copper(II) bromide in alcohol resulted in copper reduction to Cu(I) species and alcohol oxidation. Compared to organic chemistry, the inorganic chemistry of these ligands remains poorly examined. Here, we present the structural study of sixteen novel copper complexes with mononuclear [Cu(L)₂]Hal_2/1 and halo-bridged binuclear [Cu₂(μ-Hal)₂(L)₂] structures (L = isatin Schiff base ligand; Hal = Cl, Br and I). Finally, application of the above complexes for alcohol oxidation was evaluated: the complexes selectively catalyse benzyl alcohol oxidation to the corresponding aldehyde with almost quantitative yields and high selectivity.

A comparative study of electrochemical characteristics of graphite electrodes and precipitates of suspensions produced by the graphite exfoliation is carried out. The graphite is exfoliated into...