A. V. Kapustin

Nanocomposite material laccase/dispersed carbon carrier for oxygen electrode

The effect of carbon dispersion degree on the effectiveness of oxygen electroreduction by laccase at its immobilization at superdispersed colloid graphite (SCG) or acetylene carbon black (ACB) is studied. A method of synthesizing the highly active composite material based on SCG is suggested providing the optimum orientation of enzyme molecules for the direct bioelectrocatalysis due to the fact that the particles of the carrier (SCG) and laccase molecules are commensurable. The specific current of oxygen reduction per enzyme molecule for the composite of SCG + laccase is five times higher than that at the composite based on ACB. The effect of the specific activity increase is observed only at ultra-thin layers of the composite material at the electrode; for the creation of the gas-diffusion oxygen electrode the active layer structure should be optimized to remove the percolation effects.

VARIATIONS IN THE STRUCTURE AND ELECTROCHEMICAL CHARACTERISTICS OF MEMBRANE ELECTRODE ASSEMBLIES DURING THE ENDURANCE TESTING OF HYDROGEN-AIR FUEL CELLS

Variations in the characteristics of a membrane-electrode assembly (MEA) are studied during the endurance testing of a hydrogen-air fuel cell (FC) based on a Nafion 212 proton conducting membrane and platinum catalysts. It is shown that the voltage drop observed during MEA testing was mainly due to physicochemical transformations of the cathode catalyst, i.e., the oxidation of platinum and its subsequent recrystallization with nanoparticle coarsening. It is established that the rate of degradation increases along with temperature and loading, and with periodic FC depressurization. It is concluded that the enhancing effects of additional factors of degradation, e.g., platinum ion transport to the proton-conducting membrane and corrosion of the carbon carrier, were responsible for these processes.

Electroconductance and Penetrability of Polybenzimidazole Membranes in Alkaline Solutions

Effect of various factors on the conductance and penetrability of polybenzimidazole membranes is studied. The conductivity of alkali-doped membranes is no lower than 0.01 S cm–1. The membrane penetrability to methanol is close to that of Nafion.

Mediated Bioelectrocatalytic Oxidation of Glucose on a Glucose Oxidase-Containing Composite

A composite material, which includes glucose oxidase (GOD), finely divided colloidal graphite, ferrocene, and Nafion, is developed and investigated. Kinetic parameters of redox conversions of GOD and flavin adenine dinucleotide, which is present in the active center of GOD, indicate that GOD in the composite retains molecular integrity and enzymic activity. Ferrocene in the composite undergoes reversible oxidation and is reduced on the electrode. Bioelectrocatalytic oxidation of glucose on the composite occurs via a mediator path, and the half-wave potential of a polarization curve recorded on the electrode in the presence of glucose coincides with the redox potential of ferrocene, which is equal to 0.32 V (Ag/AgCl). Effect of the ferrocene amount in the composite and the glucose concentration in the bulk solution on the glucose oxidation is studied. The results are used to optimize the composites composition to ensure a stable operation of the enzyme electrode and effective glucose oxidation.