Preparation and characterization of Bi-doped antimony selenide thin films by electrodeposition

Bi-doped antimony selenide (Sb_2−xBi_xSe₃) thin films have been prepared by potentiostatical electrodeposition and post annealing treatment. Cyclic voltammetry (CV) was used to investigate the electrochemical behaviors of electrodeposition. The suitable deposition potential for film preparation was determined to be about −0.40 V vs. SCE combining with CV, energy dispersive X-ray spectroscopy (EDS), environmental scanning electron microscope (ESEM) studies. After annealing, film shows improved crystallinity and a basic orthorhombic Sb₂Se₃ structure but having a larger d-spacing due to the substitution of Bi for Sb in Sb₂Se₃ lattice. The annealed film exhibits an absorption coefficient of larger than 10⁵ cm⁻¹ in the visible region, an direct optical band gap of 1.12 ± 0.01 eV, the n-type conductivity, an carrier concentration of 1.1 × 10¹⁹ cm⁻³ and an flat band potential of −0.40 ± 0.03 V vs. SCE.     

In situ UV–VIS spectroelectrochemical study of polyaniline degradation

The degradation of polyaniline at anodic potentials was studied with in situ UV–Vis spectroscopy of polymer‐coated ITO glass electrodes. Spectral changes at high potential values were observed and discussed. Degradation follows first‐order kinetics, with rate constants ranging from 8.40 × 10⁻⁶ to 2.93 × 10⁻³ s⁻¹ at electrode potentials of E_NHE = +0.85 to +1.20 V. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 287–294, 1999     

Electrocatalytic reduction of nitrate on copper electrode in alkaline solution

This work is devoted to the study of the kinetics and reaction mechanism of nitrate reduction on a copper electrode in 0.1 M NaOH, which acts as the supporting electrolyte. The experimental methods include cyclic voltammetry (CV), cronoamperometry (CA), controlled-potential electrolysis (CPE), and coulometry. In CV, there are three potential regions where charge transfer reactions take place, reactions which are associated with NO₃⁻ and/or intermediates reduction. Two isopotential points observed in CV indicate the existence of some competitive adsorption processes at the electrode surface.The three charge transfer steps were also made evident in the CA, CPE and coulometry studies. The correlation of the experimental results with the literature data led to the conclusion that NO₃⁻ reduction on a copper electrode in 0.1 M NaOH has an intermediate (N₂O₂²⁻) species, which reduces to N₂ at a potential of about −1.3 V and to NH₄OH at potential values lower than −1.4 V (both values are vs. SCE).     

Characterization of calcareous deposits in artificial seawater by impedance techniques: 3—Deposit of CaCO3 in the presence of Mg(II)

Calcareous deposits were formed on steel under cathodic protection conditions in artificial seawater at various potentials from −0.9 to −1.4 V/SCE. The deposition kinetics was analysed by chronoamperometry measurements and the calcareous layers were characterized by electrochemical and electrohydrodynamical impedance spectroscopies, scanning electron microscopy observations and X-ray diffraction analyses. At 20 °C, the deposits were composed of aragonite CaCO₃ when formed at potentials E comprised between −0.9 and −1.1 V/SCE, of brucite Mg(OH)₂ and aragonite when formed at −1.2 V/SCE, and only of brucite when formed at potentials E≤−1.3 V/SCE. However, the in situ impedance techniques demonstrated the presence of a Mg(II)-containing porous layer along with the aragonite deposit at E≥−1.1 V/SCE. In seawater enriched with Mg²⁺, the deposition of aragonite was almost totally inhibited, and the behavior of the film containing Mg(II) could be described.     

Electrochemical polymerization of phenanthrene in mixed electrolytes of boron trifluoride diethyl etherate and concentrated sulfuric acid

A novel high‐quality polyphenanthrene (PPH) film with electrical conductivity of 10^?1 S cm^?1 was synthesized electrochemically by direct anodic oxidation of phenanthrene in boron trifluoride diethyl etherate containing 10% concentrated sulfuric acid (v/v). The oxidation onset potential of phenanthrene in this medium was measured to be only 0.91 V versus saturated calomel electrode (SCE), which was lower than that determined in acetonitrile + 0.1 mol L^?1 Bu₄NBF₄ (1.56 V versus SCE). As‐formed PPH films from this medium showed good electrochemical behavior and stability. De‐doped PPH films were thoroughly soluble in dimethylsulfoxide or CHCl₃. The structure and morphology of the polymer were investigated using UV‐visible and Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy. FTIR and ¹H NMR spectra showed that the PPH was grown via the coupling of the monomer mainly at the C₄, C₅, C₉ and C₁₀ positions. Fluorescence spectral studies indicated that PPH was a blue‐green light emitter. Copyright © 2007 Society of Chemical Industry     

Potentiodynamic and potentiostatic deposition of polyaniline on stainless steel: Electrochemical and structural studies for a potential application to corrosion control

Polyaniline (PAn) films were electrodeposited on stainless steel 304 (SS) from 0.5 M H₂SO₄ solution containing 0.1 M aniline (An) by using potentiodynamic and potentiostatic techniques. In particular, PAn films were prepared as follows: (i) by cyclic potential sweep (CPS) deposition upon varying the upper potential limit (E_l) of the polymerization potential region between 0.8 and 1.1 V, while the lower potential limit was equal to −0.2 V; (ii) by potentiostatic deposition upon varying the applied potential (E_appl) between 0.8 and 1.1 V. The potential sweep rate (dE/dt) was also varied for the An polymerization during the CPS deposition. Variation of the E_l, dE/dt and E_appl affects the PAn growth leading to films of different electrochemical and structural properties. The electrochemical properties of the PAn were examined by using cyclic voltammetry. Scanning electron microscopy was used to reveal the structure and morphology of the PAn films. Monitoring the open circuit potential (E_OC) of the PAn-coated SS electrode in 0.5 M H₂SO₄ shows that the SS remains in the passive state. PAn films can also provide protection to SS in chloride-containing 0.5 M H₂SO₄ for the studied period of time, although pits were detected during prolonged immersion. The protection efficiency seems to be related with the parameters E_l, dE/dt and E_appl varied during polymerization. The mechanism of the SS protection provided by the PAn coatings is discussed in terms of the active role of PAn in corrosive environments.     

Heterostructure interface effect on the ORR/OER kinetics of Ag–PrBa0.5Sr0.5Co2O5+δ for high-efficiency Li–O2 battery

Developing high-efficiency and cost-effective bifunctional electrocatalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is an urgent issue for the oxygen-based electrochemical devices. Herein, an interface engineering concept has been proposed to achieve high-performance Ag–PBSC (Ag–PrBa_0.5Sr_0.5Co₂O_5+δ) heterostructure nanofibers catalyst. Benefiting from the significant ligand action and interparticle cooperation of exsolved Ag NPs and PBSC double perovskite, ORR/OER catalytic kinetics have been successfully boosted. In details, the PBSC double perovskite possessing abundant oxygen vacancies can provide oxygen channels and facilitate the transfer of electrons and oxygen. The embedded Ag NPs can deliver superior catalytic durability for the heterostructure interface. As expected, the as-synthesized Ag-PBSC heterostructure catalyst performs a favorable electrochemical performance in the oxygen-based applications. In alkaline media, the catalyst exhibits an excellent activity for ORR (E_onset: 0.88 V vs. RHE and E_1/2: 0.72 V vs. RHE) and OER (1.67 V at 10 mA cm^–2). When adopting the Ag–PBSC heterostructure catalyst in LOBs, the corresponding battery provides an outperforming capacity performance (13 000 mAh g^–1), low discharge–charge polarization (1.37 V), and considerable cycling performance (128 cycles at the restricted capacity of 3 000 mAh g^–1 and 400 mA g^–1). Apparently, the work described here confirms that the interface engineering of perovskites can open up opportunities to develop highly active and durable heterostructure electrocatalysts for multitudinous oxygen-based electrochemical applications.     

Photocatalytic Performance of Nitrogen‐Doped and Cu2+ and Ag+ Co‐Doped Sodium Trititanate

Nano‐sized (i) N‐doped sodium trititanate and (ii) N and Cu²⁺ (Ag⁺) co‐doped sodium trititanates CuTi₃NO_6?x (Ag₂Ti₃NO_6?x) were prepared by a solid‐state and ion‐exchange methods, respectively. The materials were characterized by EDS, PXRD, XPS, FESEM, TEM, UV–visible DRS, and Raman spectroscopy. All the materials were crystallized in monoclinic lattice with P21/m space group. The bandgap energy of all the samples was deduced from their UV–visible DRS profiles. Visible‐light‐induced photocatalytic oxidation of the methylene blue (MB) and methyl orange (MO), cyclohexene and phenol, was examined. The Ag⁺ co‐doped trititanate exhibited the highest photocatalytic activity among the materials investigated.     

Electrochemical polymerization of 2‐phenylindole and characterization of its polymer

High‐quality poly(2‐phenylindole) (PPI) films were synthesized electrochemically by direct anodic oxidation of 2‐phenylindole (PI) in boron trifluoride diethyl etherate (BFEE). The onset oxidation potential of PI in this medium was measured to be only 0.83 V versus a saturated calomel electrode (SCE), which was much lower than that determined in acetonitrile (ACN) containing 0.1 mol L^–1 tetrabutylammonium tetrafluoroborate (1.05 V vs. SCE). PPI films obtained from BFEE showed good electrochemical behavior and thermal stability with an electrical conductivity of 10^–2 S cm^–1. Structural studies showed that the polymerization of PI mainly occurred at the 3,6‐positions. As‐formed PPI films could be partly dissolved in dimethyl sulfoxide. Fluorescence spectral studies indicated that PPI was a blue‐green light emitter. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of nitropyridine‐based π‐conjugated polymers and their chemical properties

π‐Conjugated poly(3‐nitropyridine‐2,5‐diyl) ( PPy‐3‐NO₂ ), poly(3,3′‐dinitro‐2,2′‐bipyridine‐5,5′‐diyl) ( PBpy‐3,3′‐diNO₂ ), and a poly(arylene ethynylene) type polymer consisting of a 3,3′‐dinitro‐2,2′‐bipyridine unit ( PAE‐1 ) were synthesized by Cu‐promoted Ullmann coupling reaction and Pd‐catalyzed coupling reaction. PPy‐3‐NO₂ and PAE‐1 were soluble in organic solvents such as DMSO, DMF, and chloroform, and gel permeation chromatography analysis showed a number average molecular weight (M_n) of 9,300 and 12,300, respectively. PPy‐3‐NO₂ gave intrinsic viscosity, [η], of 0.53 dL g^?1 in DMF. PBpy‐3,3′‐diNO₂ had somewhat lower solubility. The polymers exhibited a UV–vis peak at about 430 nm. PPy‐NO₂ received electrochemical reduction at ?1.5 V versus Ag⁺/Ag in acetonitrile, and gave an electrochemical redox cycle in a range from 0 to ?1.1 V versus Ag⁺/Ag in an aqueous solution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1763–1767, 2006     

Visible spectroelectrochemical characterization of Geobacter sulfurreducens biofilms on optically transparent indium tin oxide electrode

We report visible spectroelectrochemical (SEC) characterization of cytochrome c₅₅₂ (cyt c₅₅₂) in viable Geobacter sulfurreducens biofilms on tin-doped indium oxide (ITO) electrodes poised at 0.24 V vs. SHE. G. sulfurreducens biofilms were grown in minimal medium with acetate as electron donor (turnover conditions), followed by 24 h incubation in electron donor-depleted medium (non-turnover conditions). The electronic absorption spectra of G. sulfurreducens biofilms showed the lowest energy absorption band in the reduced state at 552 nm, which indicated excess of cyt c₅₅₂ in the biofilm. The spectra under non-turnover conditions displayed gradual reduction of the cyt c₅₅₂, following the step-wise decrease of electrode potential from 0.0 V to −0.6 V vs. standard calomel electrode (SCE). The spectral changes were fully reversible in both positive and negative direction of the scan potential, with average midpoint potential value of −0.42 V vs. SCE. Confocal microscopy analysis revealed that the thickness of biofilms under turnover conditions and non-turnover conditions was approximately 35 and 3.5 μm, respectively. This is the first study to observe the reversible redox conversion of cyt c₅₅₂ in viable G. sulfurreducens biofilms.     

Electrolytic reduction of trichloroethylene and chloroform at a Pt- or Pd-coated ceramic cathode

Trichloroethylene (TCE) and chloroform (CF) were electrolytically dechlorinated in a two-compartment cell in which the working electrode (cathode) consisted of an Ebonex ceramic sheet plated with platinum (Pt) or palladium (Pd). The halogenated targets were not reduced using a cathode of untreated Ebonex. Under typical experimental conditions (e.g., cathode potentials E _C = –0.3 V to –1.4 V vs SHE, pH 7.0), transformations were first order in TCE and CF. Reaction kinetics were mass transport limited at E _C < –1.4 V. Transport-limited rate constants were 0.45 cm min^–1 for TCE reduction and 0.42 cm min^–1 for CF. The primary products of CF reduction were methane and hydrochloric acid. For TCE reduction, major products were ethane, ethylene and hydrochloric acid. Carbon and chlorine mass balances were within 5–10%. Current efficiencies ranged from nearly 100% at E _C = –0.5 V (both reactants) to 24.4% for TCE and 16.6% for CF at E _C = –1.4 V. Rate constants for TCE and CF transformations were inversely related to pH in the range 2 < pH < 11. Pt–Ebonex resisted sulfate and chloride poisoning. The Pd–Ebonex electrode quickly lost activity (50% loss in 5–10 min) in 0.1 M K₂SO₄ electrolyte (cathode potential, E _C = –1.15 to –1.4 V vs SHE).     

Organometallic and coordination chemistry on phosphazenes. III. Synthesis, characterization, and electrochemical behavior of transition metal-cinnamonitrile cyclophosphazene derivatives

Hexakist 4-formylphenoxy cyclophosphazene (1) reacts with six equivalents of cyanomethylenetriphenylphosphorane to give hexakist 4-cinnamonitrile cyclotriphosphazene bearing 12 functional groups tsix nitriles and six olefins' able to coordinate up to 12 metals. In this way a series of polynuclear phosphazene metal derivatives (8–12) was prepared with different transition metals and in different oxidation states. Pt(0), Pt(II) and Rh(I). The analogous cinnamonitrile derivatives (3–7) were prepared and used as models for the characterization of corresponding phosphazene compounds. The redox properties of the complexes3–5 and8–10 as well as of the free cinnamonitrile2 and the free substituted cyclophosphazene1 have been investigated by cyclic voltammetry (CV) and controlled potential electrolysis (CPE) in aprotic media (THF, CH₂Cl₂, or NCMe 0.2M [NBu₄][BF₄]), at Pt electrodes. Cathodic processes have been detected only when the unsaturated C=C bond of the cinnamonitrile group is uncoordinated: hence, for compounds1. 4. and9. they are irreversible occur at potentialsE _p ^red ca. –1.3 to ca. –1.9V vs SCE which are less cathodic than that exhibited by the free cinnamonitrile (2:E _p ^red ca. –2.0 V vs SCE), and are believed to be centered at the electron-acceptor empty ^* (C=C) orbital of each of the cinnamonitrile groups present in the molecule. Anodic processes are displayed only by complexes3. 5. 8. and10 with at least one Pt(0) site: they are irreversible, conceivably centered at such a metal center, and occur at potentials (E _p ^bv ca. 0.7 1.2 V vs SCE) which are dependent on the electronic effects of the ligands, in particular the strong electron-withdrawing ability of the cyclophosphazene group. Complex10 undergoes dissociation in NCMe to form9 and possibly solvated [Pt(PPh₃)₂] species which adsorb at the electrode surface. No evidence for any redox process centered at the phosphazene ring has been found.Presented at the 1st Italian Workshop on Cyclo- and Poly(phosphazene) Materials, February 15–16, 1996, at the CNR Research Area in Padova, Italy.     

Electropolymerization kinetics of o‐aminophenol and characterization of the obtained polymer films

Poly(ortho‐aminophenol) has been synthesized electrochemically from a previously deoxygenated acid medium. The initial rate of electropolymerization reaction on platinum electrode is small and the rate law is: Rate = k₂ [D]^0.50[HCl]^1.125[M]^1.29. The apparent activation energy (E_a) was found to be 68.63 kJ mol^?1. The polymer films obtained have been characterized by cyclic voltammetry, X‐ray diffraction, elemental analysis, TGA, scanning electron microscopy, ¹H NMR, UV–visible, and IR spectroscopy. The mechanism of the electrochemical polymerization reaction has been discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3093–3109, 2006     

Interaction of crosslinked ethylene–propylene–diene terpolymer blends with chlorinated organic penetrants

The sorption and diffusion of halogenated hydrocarbon penetrants through different ethylene–propylene–diene terpolymer (EPDM) blends, such as EPDM/natural rubber, EPDM/bromobutyl rubber, and EPDM/styrene butadiene rubber (50/50 w/w), were studied. The diffusion coefficient of halogenated penetrants fell in the range 1.5–14.52 × 10^?7 cm²/s in the temperature range of 25–60°C. Transport data were affected by the nature of the interacting solvent molecule rather than its size and also by the structural variations of the EPDM blends. 1,2‐Dichloroethane showed a lower mass uptake compared to other penetrants. The temperature dependence of the transport coefficient was used to estimate the activation parameters, such as the activation energy of diffusion (E_D) and the activation energy of permeation (E_p) from Arrhenius plots. The activation parameters for E_D of aliphatic chlorinated organic penetrants was in the range 7.27–15.58 kJ/mol. These values fell in the expected range for rubbery polymers, well above their glass‐transition temperature. Also, the thermodynamic parameters, such as enthalpy and entropy, were calculated and fell in the range 2–15 kJ/mol and 3–54 J/mol/K, respectively. Both first‐ and second‐order transport kinetics models were used to investigate the transport kinetics, and first‐order kinetics were followed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1366–1375, 2003     

Electrochemical polymerization of p‐terphenyl in mixed electrolyte of boron trifluoride diethyl etherate and CH2Cl2

High quality poly(p‐phenylene) (PPP) film with conductivity of 0.015 S cm^?1 was synthesized electrochemically by direct anodic oxidation of p‐terphenyl (PP) oligomers in boron trifluoride diethyl etherate (BFEE) containing 37.5% CH₂Cl₂ (v/v). The oxidation onset potential of PP in this medium was measured to be only 1.23 V vs. saturated calomel electrode (SCE), which was lower than that determined in CH₂Cl₂ + 0.1 mol L^?1 Bu₄NBF₄ (1.87 V vs. SCE). As‐formed PPP films showed good electrochemical behavior, good electrochromic property and good thermal stability. The structures and morphology of doped and dedoped PPP were investigated by UV‐vis, FTIR, and Scanning electron micrographs. The infrared spectroscopic measurements for the estimation of chain lengths revealed that PPP was composed of about 10 phenyl rings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrical response of polypyrrole films doped with dodecylbenzene sulfonic acid to acetone vapor

Measurements of current‐voltage curves at room temperature, in nitrogen and nitrogen‐acetone atmospheres have clearly demonstrated the rectifying behavior of the Al/PPy‐DBSA/Au structure. For this structure, the values of 0.82 eV and 2.31, for the barrier height and ideality factor, respectively, have been obtained in nitrogen atmosphere, while at concentration of 120 ppm of acetone, the corresponding values were 0.74 eV and 2.07. The barrier height value obtained from I–V characteristic is lower than the barrier height value obtained from C‐V measurements. The discrepancy can be due to the existence of an interfacial oxide layer between the semiconductor and Schottky contact metal. The density distribution curves of the interface states vary in the range (0.55–E_V) to (0.84–E_V) for pure nitrogen, and (0.45–E_V) to (0.60–E_V) in atmosphere with acetone. The interface state density has an exponential rise with bias from the midgap towards the top of the valence band of the PPy‐DBSA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and photocurrent generation of an electrostatically self‐assembled film of hemicyanine and poly(4‐styrenesulfonic acid‐co‐maleic acid)

In this article, we report on electrostatically self‐assembled thin films prepared by the alternative immersion of quartz‐coated and indium tin oxide coated glass substrates in aqueous solutions of a copolymer of poly(4‐styrenesulfonic acid‐co‐maleic acid) (PSSMA) and a hemicyanine of (E)?1,1′‐(propane‐1,3‐diyl)bis{4‐[4‐(dimethylamino)styryl]pyridinium} bromide (H³Br₂). The films were studied by means of ultraviolet–visible absorption and X‐ray photoelectron spectroscopies, scanning electron microscopy, and photoelectrochemical measurements. When irradiated with white light, the PSSMA/H³ monolayer film gave a stable cathodic photocurrent. The effects of the applied bias voltages, layer numbers of the (PSSMA/H³)_n films (where n stands for the number of bilayer films on both sides of the substrates), light intensities, pH value, and electron acceptor on the photocurrent generation of the (PSSMA/H³)_n film were examined. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39871.     

Electric Field Measurements inside Self-Assembled Multilayer Films at Electrode Surfaces by Electrochemically Modulated Surface Plasmon Resonance Experiments

The new in situ optical technique of electrochemically modulated surface plasmon resonance (EM-SPR) is described and applied to the measurement of the electrostatic fields inside noncentrosymmetric zirconium phosphonate (ZP) films formed from the asymmetric nonlinear optical material [1-[4-[4-[(N-(2-hydroxyethyl)-N-methyl)amino]phenyl]azo](5-phosphonopentyl)] pyridinium bromide (PY-AZO). In situ EM-SPR measurements on PY-AZO films yield a value for the change in electric field strength (ΔE) of 4 × 10³ V/cm for a change in electrode potential (Δϕ_m) at 0.0 V vs. SCE of ±25 mV (8 × 10⁴ V/cm for Δϕ_m = 1 V). This electric field strength value indicates that there is substantial ion penetration into the film in the electrochemical environment. Both the phase and magnitude of the surface optical response in the EM-SPR measurements are used to distinguish the molecular and metal electrode contributions to the overall optical signal. These two EM-SPR contributions are identified and separated in a quantitative fashion through a series of theoretical Fresnel calculations.     

Effect of process parameters on the electropolymerization potential and rate of formation of polypyrrole on stainless steel

Polypyrrole coatings were formed on stainless steel working electrodes in aqueous oxalic acid solution. The rate of formation of polypyrrole coatings on stainless steel increased proportionately with the current density but increased slightly with increased pyrrole concentration. Increasing oxalic acid concentration also had no significant change in the polymerization rate. The electropolymerization potential of pyrrole decreased significantly from 1.5 to 0.8 V versus SCE when the working electrode was polished. The polymerization potential, E_p, of pyrrole, increased however, with increased current density and decreased exponentially with the initial monomer and electrolyte concentration, respectively. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2433–2440, 1997