Interfacial irreversible first-order reaction

Many different types of interfacial boundaries can be probed by SECM. The use of the SECM for studies of surface reactions and phase transfer processes is based on its abilities to perturb the local equilibrium and measure the resulting flux of species across the phase boundary. This may be a flux of electrons or ions across the liquid/liquid interface, a flux of species desorbing from the substrate surface, etc. Furthermore, as long as the mediator is regenerated by a first-order irreversible heterogeneous reaction at the substrate, the current-distance curves are described by the same Eqs. (34) regardless of the nature of the interfacial process. When the regeneration kinetics are more complicated, the theory has to be modified. A rather complete discussion of the theory of adsorption/desorption reactions, crystal dissolution by SECM, and a description of the liquid/liquid interface under SECM conditions can be found in other chapters of this book. In this section we consider only some basic ideas and list the key references. 

The reactor efficiency depends on the f/ -number and the specific interfacial area. For a first order irreversible reaction the following relationship is obtained ... 

Table 7 shows rate expressions for various regimes for fluid-fluid systems it is seen that the irreversible chemical reaction can dramatically alter the functional dependence of the specific rate of mass transfer of solute, R, on the physicochemical properties and hydrodynamical factors. Indeed, under certain conditions, R can be independent of the interfacial concentration of solute. A or the bulk concentration of reactive species, despite the intrinsic kinetic showing first order dependencies on the reactant concentrations (see Table 7). 

In the previous analyses of the combined effects of chemical reaction and diffusion, we have used first-order kinetics for the interfacial reaction. In this section we will examine the effect of reaction order with respect to the concentration of gaseous reactant ( , henceforth to be called simply, the reaction order ). We shall do this for the shrinking unreacted-core system without external-mass-transport resistance, and for irreversible reactions K oo). 

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