The central problem in porous electrodes with an immobilized enzyme and nanosized particles of the support is the creation of an active layer, which is a composite comprising the support particles and enzyme molecules. For a composite to function efficiently, a connected macroscopic-size structure comprising support particles must be formed in the composite i.e. there must emerge a percolation cluster [1], which is labeled here an electron cluster [2]. This connected macroscopic-size structure connects the front and the rear surfaces of the porous electrode. The task of this structure is to conduct current and supply electrons to the enzyme molecules. It is obvious that only with the emergence of an electron cluster upon reaching a certain minimum concentration (percolation threshold) of the support particles in the composite the electrochemical activity of a porous electrode with an immobilized enzyme becomes other than zero. And now all the enzyme molecules that enter the composition of the composite happen to be divided into two classes. One class comprises molecules that are intimately linked to an electron cluster, having been supplied with electrons, these molecules are capable of realizing bioelectrocatalysis. We had labeled such enzyme molecules "active" [2]. The other class consists of the rest of the enzyme molecules; these are not intimately linked to an electron cluster, not supplied with electrons, and exhibit no electrochemical activity.In porous electrodes of fuel cells the setting of a function of electrocatalysis (bioelectrocatalysis-special case) apart from a function of transport of electrons required for performing an electrochemical process occurred not right away. In the first generation of hydrogen-oxygen fuel cells [3] (in what follows we will bear in mind only hydrogen-oxygen systems) a porous metallic matrix (it was prepared from skeleton catalysts) performed two functions simultaneously: it was both an electrocatalyst and a carrier of electrons. In so doing, any locus of such a matrix could have taken part in electrocatalysis. The porous electrodes for the second generation of fuel cells were prepared by mixing and subsequent caking of agglomerates of particles of a catalyst (usually it was platinum black) and agglomerates of particles of a hydrophobizing agent (polytetrafluoroethylene). The mechanism of the action of hydrophobized porous electrodes was dismantled for example in [4]. In contradistinction to porous electrodes functioning in fuel cells of the first generation, now the entire amount of platinum black could not have been provided for with electrons, only its connected portion that formed an electron cluster could. However, just as before, functions of electrocatalyst and conducAbstract -The efficiency of the operation of a porous electrode with an immobilized enzyme is defined, in particular, by a lucky structure of its active layer, which can contain nanosized particles of the support. The composites of such a kind are prepared with the aid of methods of colloidal chemistr...
