Eugene A. Streltsov

Electrochemical deposition of PbSe films

Abstract The mechanism of PbSe electrodeposition from aqueous solutions containing SeIV and PbII have been investigated. It has been found that PbSe formation is possible at potentials more positive than the Nernst potential EPb2+/Pb0. In this case the electrodeposition of PbSe is due to chemical interaction between overpotentially deposited selenium and underpotentially deposited lead adatoms.

Photoinduced and dark underpotential deposition of lead on selenium

Abstract The processes of the dark and photoinduced underpotential deposition (upd) of Pb ad-atoms on p-type Se electrodes have been studied. Under illumination with light absorbed by Se, the photoinduced upd of Pb ad-atoms (approximately a monolayer) onto the Se electrode occurs. The upd shift is about 800 mV. The Pb ad-atoms modify the Se surface and form electronic surface states in the Se bandgap, which promotes an efficient electron exchange between the valence band and redox species in solution. The surface states act as effective recombination centers for the photogenerated charge carriers and give rise to the subbandgap photocurrent enhancement. In the dark, the Pb upd occurs only on the electrode surface on which PbSe clusters were deposited. These clusters are formed both as a result of the chemical interaction of surface Se atoms with Pb bulk particles deposited at the cathodic polarization and due to the interaction of electrochemically generated H 2 Se with Pb 2+ cations. The Pb ad-atoms deposited on the Se surface are electrochemically oxidized at more positive potentials (by ca. 150 mV) than those deposited on the surface of PbSe clusters.

Effect of Cd(II) on electrodeposition of textured PbSe

Cathodic electrodeposition of PbSe from acidic aqueous electrolytes containing Se(IV), Pb(II) and Cd(II) has been investigated. It has been found that [100] oriented growth of PbSe crystallites takes place in some regions of Pb(II) and Cd(II) concentration. Electrosynthesis has been carried out under conditions of underpotential deposition of lead adatoms (Pbad) and overpotential deposition of Se. It has been established by cyclic voltammetry that at electrodeposition potential E = −0.30 V (versus Ag/AgCl) underpotential deposition of Cdad on Se atoms of the PbSe structure also takes place. Adsorption of Cdad and Pbad is irreversible due to the formation of the chemical bonds CdadSe and PbadSe. The presumption has been made that the mechanism of the Cd(II) effect consists in selective adsorption of Cdad on faces of PbSe crystals and inhibition of underpotential deposition of Pbad.

Electrochemical preparation of lead-doped amorphous Se films and underpotential deposition of lead onto these films

Abstract The process of the underpotential deposition (UPD) of Pb adatoms (Pb ad ) onto Se was used to produce nanocomposite films consisting of amorphous Se and nanosized PbSe clusters distributed throughout the film bulk. It was found that doping lead into Se films modifies their optical and photoelectrochemical properties and increases the efficiency of the charge transfer both in the film bulk and through the semiconductor | electrolyte interface. Introducing lead into the bulk of Se films significantly promotes the process of Pb ad UPD onto Se surface. The underpotentially deposited Pb ad interact chemically with Se surface atoms, resulting in the formation of a PbSe monolayer. The PbSe formed can be identified by the anodic peak corresponding to its electrochemical oxidation.

Bismuth underpotential deposition on tellurium

Abstract Electroless underpotential deposition (UPD) of Bi adatoms (Bi ad ) on Te by Bi III reduction with Ti III in aqua solution has been investigated. Comparison studies of electroless Bi UPD on Te and of a corresponding electrochemical process have been performed. Bi ad stability on Te under the open-circuit conditions has been investigated.

Magnetic Anisotropy in Bicomponent Self-Assembled Ni and Ni-Pd Nanowires Studied by Magnetic Resonance Spectroscopy

Self-ordered arrays of Ni, Ni(50)Pd(50), and Ni(78)Pd(22) nanowires were synthesized by simultaneous electrochemical deposition of Ni and Pd components into porous templates of anodic aluminum oxide using alternating current. This paper is focused on the interplay of structure and chemical composition of Ni and Ni-Pd bicomponent nanowires arrays and the peculiarities of its magnetic anisotropy.

Photoelectrochemical and Raman characterization of In2O3 mesoporous films sensitized by CdS nanoparticles.

Summary The method of successive ion layer adsorption and reaction was applied for the deposition of CdS nanoparticles onto a mesoporous In2O3 substrate. The filling of the nanopores in In2O3 films with CdS particles mainly occurs during the first 30 cycles of the SILAR deposition. The surface modification of In2O3 with CdS nanoparticles leads to the spectral sensitization of photoelectrochemical processes that manifests itself in a red shift of the long-wavelength edge in the photocurrent spectrum by 100–150 nm. Quantum-confinement effects lead to an increase of the bandgap from 2.49 to 2.68 eV when decreasing the number of SILAR cycles from 30 to 10. The spectral shift and the widening of the Raman line belonging to CdS evidences the lattice stress on the CdS/In2O3 interfaces and confirms the formation of a close contact between the nanoparticles.

Giant Incident Photon‐to‐Current Conversion with Photoconductivity Gain on Nanostructured Bismuth Oxysulfide Photoelectrodes under Visible‐Light Illumination

Nanostructured layered bismuth oxysulfide films synthesized by chemical bath deposition reveal a giant incident photon-to-current conversion efficiency (IPCE). This study shows that surprisingly for the cathodic photocurrent in the photoreduction process, the IPCE reaches ≈2500% in aqueous solutions containing [Fe(CN)6 ]3- . The giant IPCE is observed starting from a certain minimal oxidizer concentration (c > 10-3 m for [Fe(CN)6 ]3- ) and decreases nonlinearly with an increase of illumination intensity. Giant IPCE is determined by the decrease in resistivity of the bismuth oxysulfide film under illumination with photoconductivity gain, which provides the possibility of charge carriers from an external circuit to participate in the photoreduction process. Giant IPCE is observed not only in [Fe(CN)6 ]3- solutions, but also in electrolytes containing other photoelectron acceptors: Fe3+ , I3- , quinone, H2 O2 . In all, solution-processed layered bismuth oxysulfide films offer large-area coverage, nontoxicity, low cost, and compatibility with a wide range of substrates. Abnormally high photoelectrochemical activity, as well as a band gap energy value favorable for efficient conversion of solar light (1.38 eV, direct optical transitions), proves the potential of bismuth oxysulfide photoelectrodes for a new generation of high-performance photoconverters.

The formation and properties of heterostructures based on titanium dioxide films volume-doped with palladium particles

Abstract Photoelectrochemical and electrophysical properties of semiconductor heterostructures based on TiO2 films with Pd particles distributed thoughout the bulk of the oxide have been investigated. These heterostructures were prepared by pyrolysis of titanium resinate and PdCl2 mixture followed by reduction thermal treatment. The reduction process in the TiO2-Pd films takes place not only in the surface layer but in the entire volume as well and TiO2 films possess a high donor concentration (Nd ~ 1020 − 1021cm−3). Here, the TiO2 energy gap determined from quantum yield spectra increases due to the Burstein shift from 3.11 eV for TiO2 films to 3.21 eV for heterostructures.