Sergey V. Morozov

Hydrogen fuel electrode based on bioelectrocatalysis by the enzyme hydrogenase

Abstract Our aim is to show, that the enzymes as electrocatalysts are able to improve the performance characteristics of the fuel cells. The hydrogen fuel electrode based on hydrogenase from Thiocapsa roseopersicina immobilized directly on carbon filament material has been made. The enzyme electrode has operated according to electron tunneling between the enzyme active site and the electrode support; this mechanism is called direct bioelectrocatalysis. Under pure hydrogen the efficiencies in energy conversion of the enzyme electrode and the noble metal based commercial fuel electrode are similar concerning both the hydrogen equilibrium potential achieved and the current densities in H2 oxidation. However, the use of the enzyme electrodes completely avoids the problem of poisoning the anode by the impurities of carbon monoxide present in reforming gas, which limits the use of cheap hydrogen containing fuel. The stability of the biological catalysts can be drastically improved by their immobilization on electrode supports, which provide the development of commercially competitive biofuel cells.

Hydrogenase electrodes for fuel cells

Considering crucial problems that limit use of platinum-based fuel cells, i.e. cost and availability, poisoning by fuel impurities and low selectivity, we propose electrocatalysis by enzymes as a valuable alternative to noble metals. Hydrogenase electrodes in neutral media achieve hydrogen equilibrium potential (providing 100% energy conversion), and display high activity in H(2) electrooxidation, which is similar to that of Pt-based electrodes in sulphuric acid. In contrast with platinum, enzyme electrodes are highly selective for their substrates, and are not poisoned by fuel impurities. Hydrogenase electrodes are capable of consuming hydrogen directly from microbial media, which ensures their use as fuel electrodes in treatment of organic wastes.

Bioelectrocatalytic hydrogen production by hydrogenase electrodes

Production of molecular hydrogen by enzyme electrodes based on direct bioelectrocatalysis by [NiFe] hydrogenases from different sources (Thiocapsa roseopersicina and Desulfovibrio fructosovorans) was investigated. Hydrogen evolution was independently controlled by means of mass spectrometry. A strong correlation between the cathodic current generated by the hydrogenase electrodes and the rate of hydrogen evolution was demonstrated.

Bioelectrocatalysis by Hydrogenase Th. Roseopersicina Immobilized on Carbon Materials

Application of various carbon materials as substrates for immobilizing hydrogenase and creating a hydrogen enzyme electrode is studied. A stable, highly-active electrocatalyst for mediatorless oxidation–evolution of hydrogen is obtained. The electrocatalyst uses hydrogenase from Th. roseopersicina immobilized on an inactive carbon material (based on carbon cloth TVSh-300M) and retains more than 50% of its initial activity after a half year in storage. An equilibrium hydrogen potential is established on enzyme electrodes made of a graphitized cloth and graphite rods with hydrogenase immobilized on them.

Indexing of Hierarchically Organized Spatial-Temporal Data Using Dynamic Regular Octrees

The paper is devoted to theoretical and experimental study of indexing methods as applied to spatial-temporal datasets appearing in different science and industry domains. For this purpose a general spatial-temporal data model is presented as a scene that admits hierarchically organized, heterogeneous spatial objects with individual temporal behaviors. For the model presented we argue the relevance of dynamic event-driven regular octrees as an underlying spatial-temporal indexing structure to a wide class of applications and prove its effectiveness for queries such as scene reconstruction, region search, and collision detection.