The problem of nonuniformity of pore filling in the template synthesis of nanowires is considered. The effect of the applied gradient of temperature on the instability of pore filling is analyzed. The model proposed takes into account the presence of outer thermal boundary layer and outer diffusion layer. The metal electrodeposition in porous template under the quasi-steady-state conditions is considered. The role of the temperature dependences of the exchange current density and the diffusion coefficient of metal cation is revealed. The deposition modes at which the initial dispersion of nanowire lengths can be reduced are determined.
The mass transfer during the nanowire formation by the metal electrodeposition into the pores with a high aspect ratio from a binary electrolyte is studied theoretically. The application of quasi-steady-state approximation is justified. The equations for the ion concentration and electric potential at the bottom and in the mouth of the pores, the reaction overpotential, and the variation of the current density with time are obtained. The problem of time dependence of unfilled pore part length is solved numerically. The distinctions between the results obtained under the potentiostatic and galvanostatic conditions are demonstrated.
In this work we analyze the applicability limits of the rotating ring-disk electrode (RRDE) technique for
quantifying the amount of oxygen produced during the oxygen evolution reaction (OER). We utilize a
state-of-the art IrO2 oxide as a carbon-free OER catalyst and La1xSrxMn0.5Co0.5O3d, x . 0.25 and 0.5
perovskites, which are studied in the presence of carbon. RRDE experiments are performed at different
IrO2 loadings under both potentiodynamic and potentiostatic modes. The experimental data allow us to
formulate the requirements to the experimental conditions necessary to avoid underestimation of the
A simple model of electrochemical growth of nanowires in the pores of anodic aluminum oxide (AAO) template is developed. The metal deposition is considered at various overpotentials. The model takes into consideration the ionic transfer both in the varying diffusion layer in the pores and in the diffusion layer above the template, which is determined by the external hydrodynamic conditions. The model takes into account the kinetics of electrochemical reaction by means of the Tafel equation and the diffusion transfer of metal cations both in the pores and in the outer diffusion layer. The analytical solution of the problem with several simplifications yields the equations for calculating the time dependence of current, the pore filling time, and other parameters of the process. An example of the application of the model for the analysis of nanowire growth in the template pores is compared with the experimental data showing good agreement.
A model of inhomogeneous pores filling during electrodeposition of ordered metal nanowire arrays isdeveloped. The model takes into consideration the ionic transfer both in the varying diffusion layer in thepores and in the diffusion layer above the template, which is determined by the external hydrodynamicconditions. The model takes into account the kinetics of electrochemical reaction (the Tafel equation)and the diffusion transfer of metal cations both in the pores and in the outer diffusion layer. In the quasi-steady-state approximation, two problems were considered. The problem for the case that the initiallength of one pore differs from that of all other pores is solved analytically. The problem for the case thatthe initial lengths of all pores are different is solved numerically. The time dependences of unfilled porelength are obtained for various overpotentials and various initial distributions of pore length. It is foundthat the pores filling inhomogeneity increases with increasing overpotential.
The six new bis(4-cyano-1-pyridino)alkanes derivatives with different alkyl chain length (n = 2-6) and cyanometallate anions ([Fe(CN)(6)](3) , [Co(CN)(6)](3) , [Fe(CN)(4)(CNH)(2)](2) and [Fe(CN)(6)](4) ) have been synthesized and characterized by 1H-NMR, single-crystal X-ray analysis and UV-vis spectroscopy. The electroreduction of the obtained compounds under potentiostatic conditions (E-1 = -0.75 V) and further electrode stabilization at E-2 = 0V resulted in the deposition of polyviologen films. The current efficiency of electropolymerization was found to increase with varying the counter anion in the row: [Fe(CN)(6)](3) < Br < [Co(CN)(6)](3) similar to [Fe(CN)(6)](4) . Analysis of cyclic voltammograms and EDX data demonstrated the simultaneous incorporation of [Fe(CN)(6)](4) and K+ ions into poly(pentyl-viologen) film during electropolymerization, and further expulsion of K+ ions during the film stabilization at E-2 = 0V. The electropolymerization efficiency was found to increase with increasing the alkyl chain length, resulting in the formation of polyviologen film with higher content of dimer form of viologen cation radical.
We propose and develop a classical density functional theory for the description of a minor amount of water dissolved in ionic liquid in the vicinity of an electrode. In addition to the electrostatic energy and lattice-gas mixing entropy terms, the utilised grand canonical potential contains several phenomenological terms/parameters that describe short-range interactions between ions of ionic liquid, water molecules and the electrode. Some of these have been earlier introduced in the theory of electrical double layer in pure ionic liquids. Based on this, we investigate the role of the remaining ’specific interaction’ parameters e those that characterize possible (i) specific interaction of ions and molecules with the electrode, which are responsible for their specific adsorption; and (ii) hydrophilicity/hydrophobicity of ions. As a result we obtain water electrosorption isotherms as a function of the potential drop across the electrical double layer, investigate its asymmetry with respect to the sign of electrode potential, and establish the relationship between the sign of this asymmetry and hydrophobicity/hydrophilicity of cations and anions. We also calculate the effect of water electrosorption on the double layer differential capacitance which brings clear new features to its voltage dependence, some of which have been already experimentally observed.