Studies of the oxygen reaction, including the oxygen ionization and evolution processes occurring at typical electrode materials in aqueous and nonaqueous electrolytes, are analyzed. A connection between the problematics of the oxygen electrode reaction in nonaqueous media and the developing of novel batteries, in the first place, Li–O2 batteries, is emphasized. Unlike aqueous solutions, the oxygen reduction in aprotic electrolytes was shown to occur without breaking of the O–O bond; it is accompanied by formation of poorly soluble product of two-electron reaction (Li2O2) in the pores of positive electrode. The effect of the solvent donor number and the anion composition on the oxygen reduction mechanism and the lithium peroxide deposit structure is described. A marked reduction of the Li2O2 oxidation overvoltage when passing from carbonaceous materials to platinum-containing catalysts in the positive electrode is elucidated; in the latter case, the effect of electrocatalyst type upon the Li2O2 formation reaction is somewhat reduced. The elucidation of the contribution of processes occurring at the free and lithium-peroxide-covered electrode surface during the oxygen reaction for wide variety of active materials is formulated as the main basic problem of the future research.

Nanostructured carbon materials (CMs), the structure can vary widely, are promising materials for the positive electrode of a lithium–oxygen battery (LOB). The electrochemical characteristics of CMs studied in model conditions and their porous structure, as well as testing them as an active material for the positive electrode in an LOB sample, show that nanotubes (CNTs) and Super P carbon black possess the highest charge–discharge characteristics in an aprotic solvent (DMSO). Mono- and bimetallic systems containing Pt, Pd, and Ru and synthesized on CNT and Super P allow one to reduce discharge and charge overvoltage. In the presence of catalytic systems, an improvement in the energy-conversion efficiency of up to 73–76.7% is achieved for the LOB positive electrode. The possibility of achieving a stable cycling process in an LOB with a positive electrode on the basis of developed catalysts and with a LiClO 4 /DMSO electrolyte is shown. For the first time, the positive influence of iodine (reducing the charge voltage to about 0.8–1.0 V as compared to the characteristics of an LOB using an electrolyte without additives) on the electrode characteristics of a Li–O 2 cell with the highly electron-donating solvent DMSO is demonstrated.

The characteristics of low-temperature hydrogen–oxygen (air) fuel cell (FC) with cathodes based on the 50 wt % PtCoCr/C and 40 wt % Pt/CNT catalysts synthesized on XC72 carbon black and carbon nanotubes (CNT) are compared with the characteristics of commercial monoplatinum systems 9100 60 wt % Pt/C and 13100 70% Pt/C HiSPEC. It is shown that the synthesized catalysts exhibit a high mass activity, which is not lower than that of commercial Pt/C catalysts, a high selectivity with respect to the oxygen reduction to water, and a significantly higher stability. The characteristics of PtCoCr/C and Pt/CNT were confirmed by testing in the hydrogen—oxygen FCs. However, when air was used at the cathode, especially in the absence of excessive pressure, a voltage of FC with the cathode based on PtCoCr/XC72 is lower as compared with the commercial systems. Probably, this is associated with the transport limitations in the structure of trimetallic catalyst synthesized on XC72 carbon black due to the absence of mesopores. This drawback was eliminated to a large extent by raising the volume of mesopores as a result of application of mixed support (XC72 + CNT) and the use of only CNT for the synthesis of the monoplatinum catalyst. However, this did not eliminate another drawback, namely, a low platinum utilization coefficient in the cathode active layer as compared with that measured under the model conditions in the 0.5 M Н 2 SO 4 solution. Therefore, further research is required to improve the structure of the catalytic systems, which are synthesized both on carbon black and nanotubes, while maintaining their high stability and selectivity.

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.

A possibility for application of the method of thin-layer rotating disk electrode (RDE) for investigation of kinetics of hydrogen electrooxidation on highly dispersed platinum catalysts formed on the carbon nanotubes (CNT) is studied. It is shown that the polarization curves of hydrogen oxidation on the studied catalysts approach the calculated curves for the diffusion overpotential of hydrogen reaction both in the acidic and alkaline electrolytes. This is the evidence, on the one hand, for a high activity of proposed catalysts in the hydrogen oxidation reaction and, on the other hand, for incorrect use of the Koutecky–Levich equation for calculating the kinetic currents in the case under consideration. The characteristics of hydrogen–oxygen fuel cell (FC) with anode based of synthesized 40Pt/CNT catalysts are highly comparative with the characteristics of FC containing commercial 60Pt catalyst (HiSPEC 9100) on the anode.

Pyrolysis of nitrogen-containing complexes of iron and cobalt on the surface of disperse carbon materials was used for synthesis of cathode catalysts for oxyhydrogen fuel cells (FC) with proton-conducting (acidic) and anion-conducting (alkaline) electrolytes. The catalysts were characterized by XPS and tested using a thin-film disc electrode and in oxyhydrogen FC under model conditions. Properties of the CoFe/C system prepared by pyrolysis of macroheterocyclic compounds of iron and cobalt on carbon materials (soot HS-72 and multilayer nanotubes (CNT)) were described for the first time. From XPS data, the surface of the catalytic CoFe/C systems is rich in carbon (95,5 at.%), contains nitrogen (2 at.%), oxygen (2 at.%) and metals (0,5 at.%). The data obtained by electrochemical measurements under model conditions revealed that the catalytic systems CoFe/CNT are close to the commercial platinum catalyst 60%Pt/C (HiSPEC9100) in their activity to oxygen reduction in an alkali medium (0,5 M KOH). Half-wave potentials are 0,85 and 0,88 V for catalysts CoFe/CNT and 60%Pt/C (HiSPEC9100), respectively. The maximal specific capacity of the oxyhydrogen FC with an anion-conducting electrolyte is 210 mW/cm2 (a 60%Pt/C (HiSPEC9100) based cathode) and 180 mW/cm2 (CoFe/CNT based cathode). In its characteristics, MEA with the non-platinum cathode compete well with the best analogues described in literature. The results obtained demonstrated the necessity of the further studies on scaling-up the technology for synthesis of the developed non-platinum cathode catalysts and on optimization of the MEA FC architecture based thereon.

The review is devoted to the analysis of the state-of-the-art in the development of highly dispersed non-platinum catalysts of О 2 electroreduction and their use in cathodes of alkaline fuel cell. Attention is focused on the development of catalysts for fuel cells with anion-exchange membrane. The range of catalytic materials under consideration includes complex oxides, unmodified carbon materials and also carbon materials doped with a transition metal and/or nitrogen. The main synthetic methods for nanodispersed catalysts are considered, particularly those used for synthesizing new types of N-doped carbon materials. A comparative description of peculiarities of О 2 reduction on different groups of catalysts is carried out. The possible nature of catalytically active centers is discussed. The problems of further studies on the development of nonplatinum catalysts for fuel-cells cathodes with anion-exchange membranes are formulated.

Рассмотрены современные задачи в области электрокатализа токогенерирующих реакций низкотемпературных водородо-воздушных топливных элементов (ТЭ). Эти задачи сформулированы в рамках основных закономерностей электрокатализа и его непосредственной связи с электрохимической кинетикой и адсорбционными процессами на межфазной границе. Анализ опубликованных данных и материалов, представленных на специализированных конференциях по ТЭ в США, Канаде и Англии, показывает, что целью мировой электрохимической науки является снижение расхода платины вплоть до ее полного устранения и решение вопроса об использовании дешевого водорода с примесями СО и СО 2 из различных альтернативных источников. На примере исследований в ИФХЭ РАН продемонстрированы результаты работ в этих направлениях.

Electrocatalytic characteristics of a series of carbon materials (carbon blacks XC-72 and Super P and also multiwall nanotubes) and binary metallic nanosystems formed on carbon black XC-72 (PtRu/C and PdRu/C) are studied in the cathodic and anodic reactions of the positive electrode of a lithium–oxygen cell with nonaqueous electrolyte in the first discharge/charging cycles. It is found that a significant decrease in the cell charging overpotential is observed at a transition from carbon supports to binary systems. Overvoltage of the cathodic process also decreases when DMSO-based electrolyte is used in the case of binary systems. The obtained results are due to acceleration of oxygen reduction (cell discharge stage) and facilitation of lithium peroxide oxidation (cell charging stage) on the PtRu/C and PdRu/C systems.

The rotating disk electrode technique was used to study in 0.5 M H2SO4 catalytic properties of products of pyrolysis of the metal-free polyacrylonitrile/carbon black composite, polyacrylonitrile/iron/carbon black composite, and also supported pyropolymers of Co(II) tetramethoxyphenyl porphyrine (CoTMPP) and Fe(III) tetramethoxyphenyl porphyrin chloride (FeTMPPCl). It is shown that the metal-free polyacrylonitrile/carbon black composite catalyzes the oxygen reduction reaction via the parallel path. Addition of up to 2% of Fe into the composite results in abrupt growth of the catalytic activity and share of the four-electron reaction, which provides the parallel–serial reaction path. The parallel reaction with no further catalytic conversion of H2O2 occurs on catalysts of the CoTMPP/Vulcan XC72 and FeTMPPCl/Vulcan XC72 series. The chemical composition is one of the key factors affecting activity and selectivity of CoTMPP/Vulcan XC72 catalysts. An increase in the precursor content from 5 to 30% is accompanied by an increase in selectivity k 1/k 2 from 0.14–0.30 to 0.5–1.7, where k 1 is the rate constant of the reaction of O2 reduction to H2O, k 2 is the rate constant of the reaction of O2 reduction to H2O2.

Results on the development of new cathodic catalysts (monoplatinum and cobalt-modified platinum) applied on carbon nanotubes are shown. By means of a complex of electrochemical and structural techniques, it is shown that as regards their activity under model conditions and within membrane-electrode assembles, the catalysts synthesized by the polyol method are close to commercial monoplatinum systems with the same mass content of platinum (20 wt %) and their corrosion stability is double that of commercial catalysts. Platinum modified with cobalt is characterized by still higher stability, which allows considering these catalytic systems as the candidates to be used in fuel cells after the corresponding optimization.

The optimal composition of membrane–electrode assemblies and operating conditions of hydrogen–air fuel cells, which provide a high efficiency and stability of catalytically active cathode layers and the fuel cell as a whole are determined for commercial monoplatinum electrocatalysts on the highly dispersed carbon support containing 60–70 wt % Pt. The degradation processes in the Pt/C catalysts are studied by a complex of electrochemical methods and the methods of structural analysis.