Fingering instabilities in propagating fronts of the CO oxidation reaction on Pt(100)

Introduction Interfacial patterning is a common feature of many non-linear systems ranging from isothermal chemical reactions [1] to viscous flow systems [2]. Underlying this behavior is the spatial decoupling of chemical species due to differences in convective or diffusive transport. The oxidation of CO on Pt(100) represents a non-linear system where adsorbed CO and O are significantly decoupled due to differences in binding energy on the Pt surface. However, patterns on reaction-diffusion fronts are not typically observed in this system as diffusive transport naturally adds curvature and therefore stability to propagating fronts. We have offset this natural tendency towards curvature by locally forcing the surface reaction to generate planar reaction fronts on an otherwise stable surface. Under these unique reaction conditions, reaction fronts were observed to undergo fingering bifurcations and subsequent finger tip-splitting [3].