Том 55, № 1 (2019)

The reactions of electrooxidation of methanol and formic acid pertain to the most important model electrocatalytic processes and are used in direct low-temperature fuel cells. The electrooxidation mechanisms of these substances were actively studied for many decades. Considerable progress in this field was achieved due to the combined use of electrochemical techniques, in situ IR spectroscopy, differential electrochemical mass spectrometry, isotope-kinetic method, ab initio calculations in terms of the density functional theory, and comparison with the results of gas-phase investigations. The fundamental role in understanding the mechanism of processes was played by measurements on single-crystal faces and surfaces with the known ratio of terraces, steps, and kinks. This allowed the information accumulated for catalysts formed by metal nanoparticles to be interpreted and the role of the structure and size factors in electrocatalysis to be revealed. Attention is focused on the nature of adsorbates and intermediates, the detailed reaction routes, the mechanism of possible slow stages, the pH effects, the roles of the nature of anions in acidic solutions and of the nature cations in alkaline solutions. The effect of the catalyst loading and the multistage character of electrooxidation processes on the efficiency of real fuel cells is noted. The mechanisms of Langmuir–Hinshelwood and Eley–Rideal are analyzed as applied to electrooxidation processes as well as certain peculiarities of CO adsorbate electrooxidation. The results on the mechanism of interaction between adsorbed oxygen and С1-compounds are discussed. The specific features of processes on bimetallic surfaces and the strategy for designing catalysts based on the views on the mechanism of processes, the control over the structure/ composition of the surface and its specific decoration with metal adatoms are considered. Certain topical research directions are formulated aimed at deeper understanding of the mechanisms of electrooxidation of C1-compounds.

The dissipation theorem does a respectable job of describing turbulent mass transfer in the rotating-cylinder system, although parameters still need to be obtained by fitting against experimental data. Unfortunately the available experimental data show discrepancies that hamper theoretical development. This is part of a long-range program to compare the predictions of the dissipation theorem to systems ranging from pipe flow and rotating cylinders to developing flows on a rotating disk and on a flat plate at zero incidence, where extensive experimental data exist. One learns that values of the eddy viscosity should superpose after dividing by the stress parameter R⁺ in order to obtain coherent behavior at very large Reynolds numbers. One innovation here is to use the mass-transfer data as a proxy for the absence of torque data. One finds that the data of Eisenberg and of Mohr do not constitute a single coherent data set even though they were obtained on the same apparatus and with the same chemical system. New experimental data are needed to resolve these discrepancies. The dissipation theorem is supposed to enhance our understanding of turbulence and permit prediction of the behavior of turbulence in a variety of systems. The next step is to apply it to developing flows on a flat plate and a rotating disk.