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Abstract

The steady and oscillatory regions of the CO oxidation reaction on the Pd(110) surface have been determined as a function of externally controlled parameters (flow rate, CO and oxygen partial pressures, temperature) over a wide range. At constant sample temperature and flow rate, the experiments yield a characteristic cross‐shaped phase diagram separating regions of monostability, bistability, and oscillatory behavior. The existence of a cross‐shaped phase diagram indicates the operation of a slow feedback process, which could be traced back to the (experimentally verified) formation and retarded removal of subsurface oxygen during the reaction. The diagram reflects one of the first well‐defined oscillatory systems in heterogeneous catalysis and may provide a general basis for mechanistic studies and models of oscillatory surface reactions.