The factors determining pH effects on principal catalytic reactions in low-temperature fuel cells (oxygen reduction, hydrogen oxidation, and primary alcohols oxidation) are analyzed. The decreasing of hydrogen oxidation rate when passing from acidic electrolytes to basic ones was shown to be due to the electrode surface blocking by oxygen-containing species and changes in the adsorbed hydrogen energy state. In the case of oxygen reduction, the key factors determining the process’ kinetics and mechanism are: the O₂ adsorption energy, the adsorbed molecule protonation, and the oxygen reaction thermodynamics. The process’ high selectivity in acidic electrolytes at platinum electrodes is caused by rather high Pt-O₂ bond energy and its protonation. The passing from acidic electrolytes to basic ones involves a decrease in the oxygen adsorption energy, both at platinum and nonplatinum catalysts, hence, in the selectivity of the oxygen-to-water reduction reaction. The increase in the methanol and ethanol oxidation rate in basic media, as compared with acidic ones, is due to changes in the reacting species’ structure (because of the alcohol molecules dissociation) on the one hand, and active OH_ads species inflow to the reaction zone, on the other hand. In the case of ethanol, the above-listed factors determine the process’ increased selectivity with respect to CO₂ at higher pHs. Based on the survey and valuation, priority guidelines in the electrocatalysis of commercially important reactions are formulated, in particular, concepts of electrocatalysis at nonplatinum electrode materials that are stable in basic electrolytes, and approaches to the practical control of the rate and selectivity of oxygen reduction and primary alcohols oxidation over wide pH range.

The influence of the types and amounts of oxygen (O), nitrogen (N), and/or phosphorus (P) heteroatoms on the surface of carbon nanotubes (CNTs) on stability and catalytic activity in the oxygen reduction reaction (ORR) was investigated in alkaline media. It is shown that functionalization of CNTs leads to growth of the electrochemically active surface and to an increase in activity in the ORR. At the same time, a decrease in stability is observed after functionalization of CNTs under accelerated corrosion testing in alkaline media. These results are most significant on CNTs after functionalization in HNO₃, due to the formation of a large number of structural defects. However, subsequent doping with N and/or P atoms provides a further activity increase and enhances the corrosion stability of CNTs. Thus, as shown by the studies of characteristic parameters (electrochemical active surface values (S_EAS); E_1/2; corrosion stability), CNTs doped with N and NP are promising catalytic systems that can be recommended for use as fuel cell cathodes. An important condition for effective doping is the synthesis of carboxyl and carbonyl oxygen-containing groups on the surface of CNTs.

The degradation processes of HiSPEC 9100 (60% Pt/C) and 13100 (70% Pt/C) cathodic monoplatinum catalysts, which were tested under the model conditions and in the composition of membrane-electrode...

Functional bases of power sources of Li–O₂ type have been considered. Particular attention has been devoted to the Li–O₂ system with liquid aprotic electrolyte as the most promising version of a rechargeable Li–O₂ cell. The current status of research on the design of the principal components of Li–O₂ battery represented by catalytically active and patterned materials, as well as binders for the formation of positive electrode, solvents and electrolytes, and separation membranes has been characterized. Insights into the mechanisms of the reactions that occur during discharge and recharge have been challenged and the factors that restrict cycling and discharge capacity of Li–O₂ cell have been considered. Top-priority scientific and technological problems of the design of Li–O₂ battery, which is competitive with respect to lithium-ion batteries, have been stated.

Processes underlying the degrading of membrane-electrode assemblies of hydrogen-air fuel cells with Nafion 212 and MF-4SK membranes under the conditions of their accelerated stress testing and long-term life tests are analyzed. The cathode platinum catalyst corrosion was shown to be the main cause of the degrading of the fuel cell’s kinetically controlled current-voltage characteristics; the corrosion is accompanied by the platinum nanoparticles’ growth and the platinum ion partial transfer into the membrane. The overvoltage components of the membrane-electrode assembly and their changing during accelerated stress testing are determined. The voltage decrease at currents >0.5 A/cm² is shown to be mainly caused by the transport and ohmic resistance growth. The transport resistance components are calculated; the dependence of the cathode active layer resistance on the platinum catalyst surface area is revealed.