NONLINEAR BEHAVIOR OF NITRIC-OXIDE REDUCTION REACTIONS OVER METAL-SURFACES

Chemical reactions carried out under strongly non-equilibrium conditio ns can result in a variety of interesting effects such as oscillations , chemical waves, kinetic phase transitions, bistability, instabilitie s and chaos-all of these effects being mathematically due to the stron g non-linearities in the kinetic rate equations describing these chemi cal processes. The present article reviews the various types of non-li near behaviour observed in several NO reduction reactions over Pt-grou p metals. A large part of this review deals with oscillations and spat iotemporal pattern formation in the NO-H-2 reaction over Rh surfaces: the reaction dynamics of this system has been realized on the microsco pic, mesoscopic and macroscopic scales using field emission microscopy , photoemission electron microscopy and macroscopic rate measurements respectively. The various mechanisms of this and the other reactions r eviewed in this article are also considered.