On the origin of oscillations in the electrocatalytic oxidation of HCOOH on a Pt electrode modified by Bi deposition

We report experimental observations on the temporal dynamics in the electro catalytic. oxidation of formic acid (HCOOH) on a polycrystalline Pt electro de modified by deposition of bismuth. Bismuth modification significantly en hanced the current density of HCOOH oxidation, since it suppressed the pois oning branch and increased the apparent direct oxidation rate. Impedance sp ectroscopy and the galvanostatic scan in HCOOH oxidation on Bi/Pt exhibited a hidden negative differential resistance and a Hopf bifurcation. The elec trocatalytic oxidation of HCOOH on Bi/Pt spontaneously underwent transition s from homogeneous catalytic activity to spatiotemporally inhomogeneous dis tributions of the interfacial electrode potential, in the form of traveling pulses of the interfacial potential. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.