Evgeniy N. Gribov

Sn₃O₄ are promising semiconductor materials due to their visible light absorption ability. In this work, a series of materials, such as SnO₂, Sn₃O₄ and Sn₃O₄/SnO₂ heterostructures, with different phase ratios were prepared using hydrothermal synthesis. The materials were characterized using X-ray diffraction (XRD), Raman and diffuse reflectance spectroscopy (DRS), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption (BET). Flat-band potentials (E_FB) of the samples were determined using the photocurrent onset potential (POP) method. It was shown that the potentials obtained with open circuit potential measurements versus illumination intensity (OCP) likely corresponded to the E_FB of SnO₂ nanoparticles in heterostructures due to interfacial electron transfer from the conducting band of Sn₃O₄ to that of SnO₂. The photo-electrooxidation processes of a series of organic substrates were studied in the potential range of 0.6–1.4 V vs. RHE under irradiation with ultraviolet (λ = 370 nm) and visible (λ = 450 nm) light. The Sn₃O₄ sample showed high activity in the photo-electrooxidation of acetone and formic acid in visible light. The Sn₃O₄/SnO₂ samples exhibited noticeable activity only in the oxidation of formic acid. The presence of the SnO₂ phase in the Sn₃O₄/SnO₂ samples increased the photocurrent values under ultraviolet illumination, but significantly reduced the oxidation efficiency in visible light.

A series of tin oxides were synthesized with polystyrene microspheres (250 nm) as the template. It was shown that an increase in the template content led to increasing specific pore volume and to the formation of bimodal pore structure with pores of 9 and 70 nm in diameter. Addition of cetyltrimethylammonium bromide (CTAB) during synthesis led to the formation of friable structures (SEM data), to an increase in the average pore diameter from 19 to 111 nm, and to the formation of macropores of 80–400 nm in size. All materials had similar surface properties and cassiterite structure with 5.9–10.8 nm coherent scattering region (XRD data). Flat-band potentials of the samples were determined and their photoelectrocatalytic properties to oxidation of water and methanol were studied in the potential range of 0.4–1.6 V RHE. It was shown that the sample obtained using CTAB was characterized by lower flat-band potential value, but appeared significantly higher photocurrent in methanol oxidation, which resulted from enhanced macro-meso-porous structure to facilitate methanol pore diffusion.

This paper describes the chemical engineering aspects for the preparation of highly active and stable nanocomposite photocatalysts based on N-doped TiO₂. The synthesis is performed using titanium oxysulfate as a low-cost inorganic precursor and ammonia as a precipitating agent, as well as a source of nitrogen. Mixing the reagents under a control of pH leads to an amorphous titanium oxide hydrate, which can be further successfully converted to nanocrystalline anatase TiO₂ through calcination in air at an increased temperature. The as-prepared N-doped TiO₂ provides the complete oxidation of volatile organic compounds both under UV and visible light, and the action spectrum of N-doped TiO₂ correlates to its absorption spectrum. The key role of paramagnetic nitrogen species in the absorption of visible light and in the visible-light-activity of N-doped TiO₂ is shown using the EPR technique. Surface modification of N-doped TiO₂ with copper species prevents its intense deactivation under highly powerful radiation and results in a nanocomposite photocatalyst with enhanced activity and stability. The photocatalysts prepared under different conditions are discussed regarding the effects of their characteristics on photocatalytic activity under UV and visible light.

New highly active electrocatalysts were obtained by depositing bimetallic Pt-Cu nanoparticles on the surface of an N-doped carbon support. The structural–morphological characteristics and electrochemical behavior of the catalysts were studied. Using current stress testing protocols, their resistance to degradation was assessed in comparison with that of a commercial Pt/C material. A combined approach to catalyst synthesis that consists in alloying platinum with copper and doping the support makes it possible to obtain catalysts with a uniform distribution of bimetallic nanoparticles on the carbon surface. The obtained catalysts exhibit high activity and durability.

The structural characteristics and electrochemical behavior of electrocatalysts obtained by liquid-phase synthesis of Pt and Pt-Cu nanoparticles on microparticles of an N-doped carbon support have been studied. A comparative assessment of the active surface area, catalytic activity in the oxygen reduction reaction and resistance to degradation of the obtained Pt/C-N and PtCu/C-N catalysts, as well as commercial Pt/C analogue, has been carried out.

The selective preparation, structural and spectroscopic study of two new rhenium cluster complexes trans-[Re₆S₈(bpy)₄(CN)₂] and trans-[Re₆S₈(bpy)₂(CN)₄]²⁻ (bpy = 4,4′-bipyridine) obtained by reactions of corresponding hexarhenium cyanohalides with molten bpy are reported. The complexes were crystallized as solvates, displaying supramolecular structures based on cluster units linked by numerous weak interactions with bpy molecules. The molecular compound trans-[Re₆S₈(bpy)₄(CN)₂] (1) is insoluble in water and common organic solvents, while the ionic compound trans-Cs_1.7K_0.3[Re₆S₈(bpy)₂(CN)₄] (2) is somewhat soluble in DMSO, DMF and N-methylpyrrolidone. The presence of the redox-active ligand bpy leads to the occurrence of multi-electron reduction transitions in a solution of 2 at moderate potential values. The ambidentate CN⁻ ligand is the secondary functional group, which has potential for the synthesis of coordination polymers based on the new cluster complexes. In addition, both new compounds show a weak red luminescence, which is characteristic of complexes with a {Re₆S₈}²⁺ cluster core.

The effect of electrochemical and gas-phase activation of high-surface-area carbon black Ketjen Black EC 600 DJ on its stability and electrochemical capacitance is studied. The electrochemical...