In this work, modification of nanocrystalline TiO2 photoanodes consisting of 20 nm diameter spheres for dyesensitized solar cells (DSSCs), by introducing silicon nanoparticles (Si-NPs) of different sizes, larger than TiO2 particles, obtained by two different pulsed laser technologies: mesoporous silicon ablation and micron-sized silicon powder fragmentation was studied. The distribution of various types of particles in the functional layer of the photoanode was obtained using scanning electron microscopy and energy-dispersive X-ray analysis. The effect of Si-NP size on photovoltaic properties was demonstrated. Dye-sensitized photoanodes modified with mezo Si-NPs demonstrated 17 % increase in short-circuit current (jsc) and increased energy conversion efficiency due to reduced electron recombination and improved charge collection compared to unmodified TiO2. Thus, the obtained results on modification of the surface of TiO2 photoanodes with Si-NPs have potential for improving the efficiency and stability of DSSCs.

TiO2 nanotube (TNT) electrodes were fabricated by electrochemical anodization of titanium in ethylene glycol electrolyte with added NH4F (0.5 wt.%) and water (2 % w/w). The (TNT)-cadmium oxide (CdO) composite was fabricated using potentiostatic cathodic deposition. Structural properties of the obtained coatings have been investigated by scanning electron microscopy and X-Ray photoelectron spectroscopy, Raman spectroscopy, X-Ray diffraction and transmission electron microscopy. The TNT-CdO electrode demonstrates high efficiency in photoelectrochemical degradation of methanol, ethylene glycol, glycerol and sorbitol in aqueous solutions of 0.1 M Na2SO4 upon irradiation by a simulated sunlight. The highest photooxidation currents were obtained for sorbitol. Intensity-modulated photocurrent spectroscopy shows that the photoelectrocatalysis efficiency is due to suppression of the electron-hole pairs' recombination and to increase in the rate of photo-induced charge transfer. Thus, the TNT-CdO composite is an effective photoanode for developing the technology of photoelectrochemical degradation of sorbitol and other alcohols by-products of biofuel production.

Nanoparticles (NPs) are defined as objects with dimensions ranging from 10−9 to 10−7 m [...]

Nanocrystalline TiO2 nanotube electrodes were fabricated by electrochemically anodizing the titanium in the electrolyte with an ethylene glycol with addition of 0.5

Thin-film nanocrystalline zinc oxide electrodes were fabricated by electrochemical deposition of ZnO on FTO-coated glass slides. ZnO electrodes were promoted by CdO coating on top of ZnO in amounts corresponding to 0.8, 0.1, and 0.05 C cm−2 in electric units. Modification of ZnO by a small amount of CdO, corresponding to 0.05 C cm−2, shifts the photoactivity of the composite photoanode into the visible part of the solar spectrum. It is shown that the ZnO/(0.05C)CdO/FTO electrode demonstrates high efficiency in photoelectrochemical degradation of methanol, ethylene glycol, and glycerol when irradiated by a simulated sunlight. According to intensity-modulated photocurrent spectroscopy (IMPS), the effect is due to suppression of the electron–hole pairs recombination and increase in the rate of photo-induced charge transfer. Therefore, thin-film photoanodes based on zinc oxide modified by CdO can be used for photoelectrochemical degradation of byproducts of biofuel production glycerol, and of other alcohols.

Thin-film nanocrystalline hematite electrodes were fabricated by electrochemical deposition and loaded with electrodeposited zinc oxide in various amounts. Under visible light illumination, these electrodes demonstrate high activity in the photoelectrochemical degradation of methanol, ethylene glycol and, in particular, glycerol. Results of intensity-modulated photocurrent spectroscopy show that the photoelectrocatalysis efficiency is explained by the suppression of the electron-hole pair recombination and an increase in the rate of photo-induced charge transfer. Thus, zinc oxide can be considered an effective modifying additive for hematite photoanodes.

Here, the modification of semiconductor thin film hematite photoanode by doping with Sn ions is reported. Undoped and Sn-doped hematite films are fabricated by the electrochemical deposition of FeOOH from aqueous alkaline electrolyte, followed by calcination in air. The photoanodes were tested in photoelectrocatalytic oxidation of water, methanol, ethylene glycol, and glycerol. It is shown that modification by tin dramatically increased the activity of hematite in the photoelectrochemical oxidation of alcohols upon visible light irradiation. The photoelectrocatalytic activity of Sn-modified hematite increased in the sequence of: H2O < MeOH < C2H2(OH)2 < C3H5(OH)3. The quantum yield of photocurrent in the oxidation of alcohols reached 10%. The relatively low photocurrent yield was ascribed to the recombination of photoexcited holes within the hematite layer and on surface states located at the hematite/electrolyte interface. Intensity-modulated photocurrent spectroscopy (IMPS) was used to quantify the recombination losses of holes via surface states. The IMPS results suggested that the hole acceptor in the electrolyte (alcohol) influences photocurrent both by changing the charge transfer rate in the photoelectrooxidation process and by the efficient suppression of the surface recombination of generated holes. Thin-film Sn-modified hematite photoanodes are promising instruments for the photoelectrochemical degradation of organic pollutants.

Photoelectrocatalytic oxidation of methanol was studied on thin-film nanocrystalline hematite electrodes prepared by the sol–gel method and doped by TiO2, Bi, and Co. The modification of hematite is shown to lead to its transformation into a material demonstrating high activity in the photoelectrochemical process of methanol oxidation under illumination in the visible range of the spectrum. According to the data of photocurrent modulation spectroscopy, this is due to a decrease in the rate of recombination of electron–hole pairs generated by light. Therefore, thin-film photoanodes based on modified hematite have good prospects for practical application in the photoelectrochemical degradation of organic pollutants.

Photoelectrocatalytic oxidation of methanol, ethylene glycol, glycerol, and 5,6,7,8-tetrahydro-2-naphthol on thin-film nanocrystalline hematite electrodes fabricated by electrochemical deposition and promoted with spin-coated titanium has been studied. It is shown that the modification of hematite transforms it into material exhibiting high activity in the photoelectrochemical process of substrate oxidation upon illumination with light in the visible region of the spectrum. The highest activity is observed in the reaction of photoelectrocatalytic oxidation of glycerol. Results of intensity-modulated photocurrent spectroscopy (IMPS) suggest that the effect is due to an increased rate of charge transfer in the process of photoelectro-oxidation and efficient suppression of the recombination of generated electron-hole pairs. Therefore, thin-film photoanodes based on modified hematite are promising for practical application in the photooxidation of glycerol, a by-product of biofuel production, as well as in the photoelectrochemical degradation of other organic pollutants, including those formed during the production of pharmaceuticals.

Nanoscale catalysts based on cluster compounds of cobalt with tellurium and selenium Co3(PhTe)5(CO)4 and [(C5HMe4)]2Co3(PhSe)6, as well as iron-containing C5HMe4CoSe2Fe2(CO)7 and C5HMe4CoTe2Fe2(CO)7, deposited onto a Vulcan XC-72 highly dispersed carbon substrate from organic solutions and subjected to subsequent thermal destruction are developed. The obtained catalysts are characterized by X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The activity of the obtained catalysts in the electrochemical reaction of oxygen reduction in 0.1 M KOH is studied. It is shown that the reduction of oxygen at the obtained catalysts predominantly proceeds according to a four-electron mechanism, while the metal chalcogenide catalysts are tolerant to the presence of methanol in the electrolyte as opposed to a Pt(20%)/C standard platinum catalyst (E-TEK).

Nanosized bimetallic PtMo, PtFe and trimetallic PtMoSn catalysts deposited on highly dispersed carbon black Vulcan XC-72 were synthesized from the cluster complex compounds PtCl(P(C6H5)3)(C3H2N2(CH3)2)Mo(C5H4CH3)(CO)3, Pt(P(C6H5)3)(C3N2H2(CH3)2)Fe(CO)3(COC6H5C2C6H5), and PtCl(P(C6H5)3)(C3N2H2(CH3)2)C5H4CH3Mo(CO)3SnCl2, respectively. Structural characteristics of these catalysts were studied using X-ray diffraction (XRD), microprobe energy dispersive spectroscopy (EDX), and transmission electron microscopy (TEM). The synthesized catalysts were tested in aqueous 0.5 M H2SO4 in a three-electrode electrochemical cells and in single fuel cells. Electrocatalytic activity of PtMo/C and PtFe/C in the oxygen reduction reaction (ORR) and the activity of PtMoSn/C in electrochemical oxidation of ethanol were evaluated. It was shown that specific characteristics of the synthesized catalysts are 1.5–2 times higher than those of a commercial Pt(20%)/C catalyst. The results of experiments indicate that PtFe/C, PtMo/C, and PtMoSn/C catalysts prepared from the corresponding complex precursors can be regarded as promising candidates for application in fuel cells due to their high specific activity.

This review focuses on pressing issues of photoelectrocatalytic degradation of organic pollutants of wastewaters on semiconductor materials upon their irradiation with both UV and visible light of the solar spectrum. Various photoactive semiconductor materials were considered, including titanium dioxide ( n -TiO 2 ), zinc oxide, tungsten oxide, hematite, and composites based on n -TiO 2 doped with metals, nonmetals, carbon, and polymer materials. The effect of structural factors and the electrolyte selection on the photoelectrochemical generation and the efficiency of active reagents for the oxidation of the main components of organic pollutants, as well as the effect of the electrolyte components adsorption on the photoelectrocatalytic characteristics of the electrodes have been demonstrated. Suggestions have been made on the prospects of the method of photoelectrocatalytic wastewater decontamination from organic pollutants.

Film photoanodes were made from nanocrystalline TiO2 doped with Bi3+ ions at a concentration of 0.13-3.09 at. %, and their activity towards photoelectrocatalytic oxidation of methanol was studied. It was shown that with a decrease in the Bi content, the photoelectrocatalytic activity of film electrodes gradually increases both when illuminated with monochromatic light (lambda = 461 nm, power of 10 mW cm(-2); lambda = 369 nm, power of 7.5 mW cm(-2)) and when illuminated by a solar simulator with a power of 1 sun (100 mW cm(-2)). It was shown that a decrease in the Bi content leads to a decrease in the recombination losses and to an increase in the efficiency of the transfer of holes involved in the photoelectrocatalytic oxidation of methanol. As a result, doping of TiO2 with an optimal amount of Bi (0.13 at. %) provides selective electrocatalytic oxidation of methanol at the photoanode.

A new approach to functionalize porphyrinoids was developed based on the Vilsmeier formylation followed by the azine formation and a new class of the compounds namely azines of porphyrinoids was obtained. Variously substituted azine porphyrins, chlorins and their dyads were synthesized, and their structural and electronic parameters were studied with X-ray diffraction analysis, electronic absorption and emission spectra, electrochemistry and DFT calculations. Azine represents a very peculiar bridge with an unclear conjugation ability affecting optical properties of chromophores. This work was aimed to reveal azine properties and the influence of the azine bridge on the chromophores linked. The results of investigation allowed to conclude that azine bridge can partly be regarded as a conjugation switch with a high threshold level of switching, where limited conjugation in the ground state can be greatly increased at higher energy states of the azine molecule.

A nanoscale bimetallic alloy catalyst PtFe/C is prepared by pyrolysis of the heterometallic platinum-iron carboxylate complex [PtFe(OAc)(4)](2)O center dot 4CH(2)Cl(2) on Vulcan XC-72 carbon black. It is characterized by X-ray powder diffraction analysis, X-ray fluorescence spectroscopy, transmission electron microscopy, and electro-chemical methods. Its activity in the oxygen reduction reaction (ORR) is tested in an aqueous H2SO4 electrolyte in model conditions, using a rotating disc electrode (RDE) technique, and in the membrane electrode assembly of the hydrogen-air single fuel cell. The synthesized catalyst is a tetragonal PtFe intermetallic compound with Pt:Fe = 1:1 atomic ratio. It is uniformly distributed over the carbon support with a predominant metal particle size between 3 and 6 nm. The ORR specific activity of the prepared alloy catalyst is superior to that of a commercial Pt/C E-Tek catalyst and, thus, the PtFe/C catalyst may be a promising cathode material for hydrogen-air fuel cells.

New cobalt-iron chalcogenide clusters C5HMe4Co(CO)E2Fe2(CO)(6) (E = Se, Te) were prepared and characterized by IR and NMR spectroscopy; their structures were determined by single-crystal XRD. Catalysts consisting of nanoparticles of bimetallic chalcogenides of cobalt and iron deposited on highly dispersed carbon black Vulcan XC-72 were made from the synthesized clusters. Structural characteristics of these catalysts were assessed using X-ray phase analysis (XRD), microprobe analysis (EDX), and transmission electron microscopy (TEM). It was shown that on the obtained catalysts oxygen electroreduction reaction in alkaline medium proceeds according to a four-electron mechanism, and the catalysts are tolerant to methanol presence.