Turing-type patterns on electrode surfaces

We report stationary, nonequilibrium potential and adsorbate patterns with an intrinsic wavelength that were observed in an electrochemical system wit h a specific type of current/electrode-potential (I-phi (DL)) characteristi c. The patterns emerge owing to the interplay of a self-enhancing step in t he reaction dynamics and a long-range inhibition by migration currents rath er than by diffusion. Theoretical analysis revealed that this self-structur ing of the electrode occurs in all electrochemical systems with an S-shaped I-phi (DL) characteristic in wide and well-accessible parameter ranges. Th is unusual pattern-forming instability in electrochemical systems has all t he characteristics of the mechanism proposed by Turing in 1952 in the frame work of an early theory of morphogenesis, Our finding might account for str ucture formation in certain biological systems that have gradients in the e lectric potential and may open new paths for fabricating patterned electrod es.