Uniformly accessible working electrode

Unlike transient methods, the theory for steady-state techniqnes is relatively simple. Equation (15.14) describes the shape of a steady-state voltammogram at any uniformly accessible working electrode (i.e., when the surface concentrations and diffusion fluxes of redox species are uniform over the entire electrode surface) ... 

More recent works have demonstrated the application of numerical simulation to exploring non-uniformly accessible 3D nanoelectrode geometries. For example, Streeter and Compton employed the finite difference approach to examine diffusion limited currents at isolated spheroidal and hemispheroidal nanoparticle electrodes immobilized on inert substrates. Building on this. Ward et al. used numerical methods to simulate isolated spherical nanoparticle voltammetry in the limit of irreversible electron transfer kinetics and derived a simple expression describing the voltammetric wave-shape ... 

That is to say, no additional approximations are involved. Thus, the Singh and Dutt approximation is expected to work best for both time-dependent and steady-state behaviour with or without the presence of first-order kinetics, when the concentrations near the electrode are not too different from the concentration gradient averaged over the length of the electrode. Whilst this requirement might be considered to be contradictory to the essential non-uniformity of accessibility to the electrode, we shall see in Sect. 4.1 that this is not the case for steady-state problems. 

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