The electrochemical noise of a hydrogen-air fuel cell was measured at different current loads. Frequency dependencies of power spectral densities of the noise were calculated for all load currents. For the first time, the phenomenological model describing the behavior of the noise was proposed for a fuel cell. The model is based on two sources of electrochemical noise. One of them is associated with a Faradic resistance of the cathodic reaction of oxygen electroreduction shunted by a parallel double layer capacitance. The values of impedance elements are obtained for each load from the data of electrochemical impedance method. Proposed model describes in detail and with a high accuracy the dependencies of noise power spectral densities obtained for all values of load currents. The usage of the model made it possible to calculate the amplitudes of the electrochemical noise current sources and to plot those dependencies on the fuel cell load current.

No abstract

No abstract

On the basis of precision X ray diffraction studies of glycinium trifluoroacetate, glycinium monohydrate with 1,5 naphthalenedisulfonic acid, and the α polymorph of glycine, topologi cal analysis of the electron density distribution function in the crystal was carried out. The sublimation energy of glycine was estimated and the role of hydrogen bonds in the charge transfer from the anion to the cation was studied. The role of cation-cation and anion-anion contacts in crystal stabilization was considered. Features of the specific interactions С...С, F...O, and F...N and sulfonic acid SO 3 -group were analyzed on the basis of the deformation electron density function and the electron localization function (ELF).Recently, a number of experimental and theoretical studies of inorganic and organic salts have shown that the crystal lattice is stabilized by not only cation-anion interactions but also by the formally repulsive interac tions between likely charged species (cation-cation or anion-anion). 1 These unusual types of interaction were also reported for a number of salt solutions. 2 Evidently, they are caused, to some extent, by the anion to cation charge transfer resulting from the cation-anion interac tions. 1a,c,e In the case of organic salts, the system of hydrogen bonds most frequently serves as the channel of charge transfer. 3 It is reasonable to suggest that the degree of charge transfer should be related to the strength of these interactions. 4 The degree of charge transfer and the strength of Н bonds can affect some physicochemical characteristics such as proton conduction 5 ; therefore, studies of charge transfer and hydrogen bond energies are of interest not only from the fundamental aspect but also for the design of materials with high ionic conductivity.The degree of charge transfer and the cation-anion interaction energy can formally be estimated from quan tum chemical calculations of isolated associates; however, this approach is poorly adjustable to real systems. Indeed, rather complex polyatomic associates are formed both in the crystal and in solutions, which makes inapplicable not only post Hartree-Fock methods but, in some cases, also the density functional theory. Moreover, complica * Dedicated to Academician A. I. Konovalov on his 75th birthday. tions arise related to the inclusion of basis set superposi tion errors (BSSE) and medium polarity, calculating of likely charged associates (which are generally unstable in the gas phase). Using IR spectroscopy and NMR spec troscopy, it is possible to prove the existence of hydrogen bonds and, in some cases, estimate their energy, 6 but it is impossible to determine the degree of charge transfer.Thus, precision X ray diffraction study of the electron density distribution function ρ(r) in the crystal is not just the best but actually the only suitable experimental method for simultaneous study of charge distribution and esti mation of the energy of intermolecular interactions in the crystal. The advantages of this approach for investi gating the natu...

No abstract