Surface-enhanced ozone dissociation in gas flow downstream of a dielectric barrier discharge ozonizer studied by using catalytic probes

A catalytic probe made of a nickel thin wire is introduced into the gas flow downstream of an atmospheric pressure dielectric barrier discharge ozonizer to examine the ozone dissociation process on a catalytic surface. The probe is placed downstream far from the discharge to avoid the influence of reactive species other than ozone. The measured voltage variation across the probe wire under a constant probe heating current is used as a measure of the temperature variation of the probe surface and the nearby gas temperature. The stainless steel and copper wire made probes are also used to examine the effect of catalytic activity. Experimental results show that, for a low probe heating current of 0.2 A, the temperature of the probe decreases with increasing ozone concentration almost independent of the probe materials due to catalytic dissociation of ozone, which removes heat of reaction from the probe. When the heating current is increased to 1.5 A, the temperature of the nickel probe increases with increasing ozone concentration due to thermal dissociation of ozone followed by surface catalytic recombination of oxygen radicals, which gives heat of reaction to the probe. On the other hand, the temperature of the stainless steel and copper made probes decreases with increasing ozone concentration despite the high heating current due mainly to the low catalytic activities.