Papers by Alexandr Simonov
This work describes the facile microwave synthesis of interlayer expanded, nanosized MoS 2 sheets... more This work describes the facile microwave synthesis of interlayer expanded, nanosized MoS 2 sheets that are vertically aligned on a well-conducting reduced graphene (rGO) support, as confirmed by X-ray diffraction, Raman and X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive X-ray analysis, and high-resolution transmission electron microscopy. Such structure has been predicted to be highly favorable for efficient electrocatalysis of hydrogen evolution by MoS 2 but could not be achieved until now. Films deposited from the microwave-synthesized MoS 2-rGO composites demonstrate outstanding and stable hydrogen evolution performance in acidic solution. These catalysts exhibit an exchange current density as high as 1.0 ± 0.2 A g −1 MoS2‑rGO , sustain a current density of 10 mA cm −2 (36 A g −1 MoS2‑rGO) at an overvoltage of 0.104 ± 0.002 V, and maintain steady performance for many hours. Importantly, our simple synthesis affords several advantages over more sophisticated methods used previously to prepare MoS 2 catalysts.
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Journal of Electroanalytical Chemistry, 2014
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The Journal of Physical Chemistry B, 2014
Detailed electrochemical studies have been undertaken on molecular aggregation of the organic sem... more Detailed electrochemical studies have been undertaken on molecular aggregation of the organic semiconductor 7,14-bis((triisopropylsilyl)-ethynyl)dibenzo[b,def]chrysene (TIPS-DBC), which is used as an electron donor material in organic solar cells. Intermolecular association of neutral TIPS-DBC molecules was established by using (1)H NMR spectroscopy as well as by the pronounced dependence of the color of TIPS-DBC solutions on concentration. Diffusion limited current data provided by near steady-state voltammetry also reveal aggregation. Furthermore, variation of concentration produces large changes in shapes of transient DC and Fourier transformed AC (FTAC) voltammograms for oxidation of TIPS-DBC in dichloromethane. Subtle effects of molecular aggregation on the reduction of TIPS-DBC are also revealed by the highly sensitive FTAC voltammetric method. Simulations of FTAC voltammetric data provide estimates of the kinetic and thermodynamic parameters associated with oxidation and reduction of TIPS-DBC. Significantly, aggregation of TIPS-DBC facilitates both one-electron oxidation and reduction by shifting the reversible potentials to less and more positive values, respectively. EPR spectroscopy is used to establish the identity of one-electron oxidized and reduced forms of TIPS-DBC. Implications of molecular aggregation on the HOMO energy level in solution are considered with respect to efficiency of organic photovoltaic devices utilizing TIPS-DBC as an electron donor material.
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Catalysis in Industry
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physica status solidi (b), 2010
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Journal of Electroanalytical Chemistry, 2015
ABSTRACT Abstract Unless the area of an inlaid disc electrode is sufficiently large, and/or the s... more ABSTRACT Abstract Unless the area of an inlaid disc electrode is sufficiently large, and/or the scan rate fast enough, the 'plateau' of a semiintegrated d.c. voltammogram or aperiodic component of an a.c. voltammogram has a slope. This phenomenon, which has its origin in non-planar diffusion at the edge of the disc, interferes with an otherwise efficient method of determining diffusion coefficients. Methods of circumventing this difficulty are presented and tested with simulated and experimental data. Crown
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Science Inspired by Martin Fleischmann, 2014
ABSTRACT This chapter overviews quantitative electrode kinetic study of fast reactions using the ... more ABSTRACT This chapter overviews quantitative electrode kinetic study of fast reactions using the ubiquitous macrodisk electrode under conditions of transient voltammetry. Thus, to adopt Fleischmann's philosophy the well-established approaches and consider the advantages of introducing sophisticated forms of data analysis, such as semi integration or applying Fourier transform methods of data analysis when a transient waveform is superimposed onto the ramp used in conventional DC cyclic voltammetry. According to the IUPAC convention as adopted in this chapter, oxidation gives rise to positive current, and reduction to negative current. Hence, all simulations and theoretical treatments discussed are based on the BV relationship. In this chapter, it is the quasi-reversible process that is of major interest, particularly when the reversible limit is approached – that is, the system has fast electrode kinetics. Apparently, k0 for the [Ru(NH3)6]3+/2+ process is also too fast to be measured by the FT AC voltammetric method.
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Many scientists consider autocatalytic sugars synthesis from formaldehyde in alkaline aqueous sol... more Many scientists consider autocatalytic sugars synthesis from formaldehyde in alkaline aqueous solutions via so-called formose reaction as a probable way of sugars formation at the prebiotic stage of the Earth evolution [1, 2]. However, the authors of paper [3] shown, that in the pure aqueous solution of formaldehyde, which does not contain even seeds of monosaccharides, the formose reaction of formaldehyde polymerisation does not occur. In this work we demonstrate that in the above mentioned solution the formose reaction can be initiated by ultraviolet radiation. A quartz cuvette (l = 10 mm) with an aqueous solution of formaldehyde (2 or 0.5 mol/l) and a magnetic stirrer was exposed to an ArF excimer laser radiation (wavelength 193 nm, 15 ns, 150 mJ, beam area 24 mm2). The location of the absorption maximum of carbonyl group of formaldehyde is 190 nm. In the course of the light-initiated reaction, in the UV spectra of solutions two absorption bands at 205 and 270 nm appear. Apparent...
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Origins of Life and Evolution of Biospheres
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5. Weber, A., Origins of Life and Evolution of the Biosphere. 28, 259-270, 1998 and refs therein.
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Electrochemistry Communications, 2015
ABSTRACT Interpretation of the current-potential-time (I-E-t) relationship ensuing from the half-... more ABSTRACT Interpretation of the current-potential-time (I-E-t) relationship ensuing from the half-cell reaction at the working electrode is of prime interest in voltammetry. It is now very common in chemistry papers to provide cyclic voltammograms showing the redox transformations of a wide range of inorganic, organic or biologically important materials. However, many of these reports only give a qualitative description of the electrode processes and even where quantitative data are provided, commonly simple forms of theory based on peak potentials as a function of a scan rate (e.g. [1,2]) are employed. In the d.c. form of cyclic voltammetry, a waveform of the kind shown in Fig. 1a is used. In a large amplitude a.c. voltammetric experiment which is the focus of this review, a sinusoidal (large amplitude in our case) or other time dependent periodic function is superimposed onto the d.c. ramp (Fig. 1b). Herein, we summarise the main advantages provided by combination of the a.c. and d.c. potential waveforms for voltammetric analysis and report on the progress in integration of a.c. voltammetry with contemporary computer assisted data analysis methods.
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ChemElectroChem, 2015
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Biosphere Origin and Evolution, 2008
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Electrochimica Acta, 2014
ABSTRACT Metal electrodeposition has recently attracted renewed interest in the context of the de... more ABSTRACT Metal electrodeposition has recently attracted renewed interest in the context of the design of tailored nanomaterials for various applications, such as, for example, fuel cells and sensors. This work is devoted to the investigation of the kinetics of potential-controlled deposition of Pt, at low (below 10 μg cm−2) metal loadings, on non-porous carbon supports (glassy carbon and highly oriented pyrolytic graphite), from Pt (II) and Pt (IV) precursor complexes, and the structure and the morphology of the ensuing deposits. Comparison of the data of this work with the results of our earlier study [L.M. Plyasova, I.Yu. Molina, A.N. Gavrilov, S.V. Cherepanova, O.V. Cherstiouk, N.A. Rudina, E.R. Savinova, G.A. Tsirlina, Electrochim. Acta 51 (2006) 4477], where much higher metal loadings were produced, confirms the scalability of the microstructure with the thickness of deposits, the electrode potential being the key factor defining the geometry, the mutual orientation and the degree of coalescence of Pt nano-crystals.
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Journal of Electroanalytical Chemistry, 2014
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Inorganic chemistry, Jan 21, 2015
A closo-type 11-vertex osmaborane [1-(η(6)-pcym)-1-OsB10H10] (pcym = para-cymene) has been synthe... more A closo-type 11-vertex osmaborane [1-(η(6)-pcym)-1-OsB10H10] (pcym = para-cymene) has been synthesized and characterized by single-crystal X-ray diffraction and elemental analysis, as well as by (11)B and (1)H NMR, UV-visible, and mass spectrometry. The redox chemistry has been probed by dc and Fourier transformed ac voltammetry and bulk reductive electrolysis in CH3CN (0.10 M (n-Bu)4NPF6) and by voltammetry in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (Pyrr1,4-NTf2), which allows the oxidative chemistry of the osmaborane to be studied. A single-crystal X-ray diffraction analysis has shown that [1-(η(6)-pcym)-1-OsB10H10] is isostructural with other metallaborane compounds of this type. In CH3CN (0.10 M (n-Bu)4NPF6), [1-(η(6)-pcym)-1-OsB10H10] undergoes two well-resolved one-electron reduction processes with reversible potentials separated by ca. 0.63-0.64 V. Analysis based on a comparison of experimental and simulated ac voltammetric data shows...
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ChemSusChem, 2014
The formose reaction (FR) has been long the focus of intensive investigations as a simple method ... more The formose reaction (FR) has been long the focus of intensive investigations as a simple method for synthesis of complex biologically important monosaccharides and other sugar-like molecules from the simplest organic substrate-formaldehyde. The fundamental importance of the FR is predominantly connected with the ascertainment of plausible scenarios of chemical evolution which could have occurred on the prebiotic Earth to produce the very first molecules of carbohydrates, amino- and nucleic acids, as well as other vitally important substances. The practical importance of studies on the FR is the elaboration of catalytic methods for the synthesis of rare and non-natural monosaccharides and polyols. This Minireview considers the FR from the point of view of chemists working in the field of catalysis with emphasis on the mechanisms of numerous parallel and consequent catalytic transformations that take place during the FR. Based on its kinetics, the FR may be considered as a non-radica...
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Analytical Chemistry, 2014
Many electrode processes that approach the &a... more Many electrode processes that approach the "reversible" (infinitely fast) limit under voltammetric conditions have been inappropriately analyzed by comparison of experimental data and theory derived from the "quasi-reversible" model. Simulations based on "reversible" and "quasi-reversible" models have been fitted to an extensive series of a.c. voltammetric experiments undertaken at macrodisk glassy carbon (GC) electrodes for oxidation of ferrocene (Fc(0/+)) in CH3CN (0.10 M (n-Bu)4NPF6) and reduction of [Ru(NH3)6](3+) and [Fe(CN)6](3-) in 1 M KCl aqueous electrolyte. The confidence with which parameters such as standard formal potential (E(0)), heterogeneous electron transfer rate constant at E(0) (k(0)), charge transfer coefficient (α), uncompensated resistance (Ru), and double layer capacitance (CDL) can be reported using the "quasi-reversible" model has been assessed using bootstrapping and parameter sweep (contour plot) techniques. Underparameterization, such as that which occurs when modeling CDL with a potential independent value, results in a less than optimal level of experiment-theory agreement. Overparameterization may improve the agreement but easily results in generation of physically meaningful but incorrect values of the recovered parameters, as is the case with the very fast Fc(0/+) and [Ru(NH3)6](3+/2+) processes. In summary, for fast electrode kinetics approaching the "reversible" limit, it is recommended that the "reversible" model be used for theory-experiment comparisons with only E(0), Ru, and CDL being quantified and a lower limit of k(0) being reported; e.g., k(0) ≥ 9 cm s(-1) for the Fc(0/+) process.
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Papers by Alexandr Simonov