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The influence of relative humidity on photocatalytic oxidation of nitric oxide (NO) over TiO2

Üner, Deniz
Bayar, Ibrahim
Tabari, Taymaz
The influence of relative humidity on NO oxidation over commercial TiO2 (47 m(2)/g catalyst) was investigated. The experimental methodology followed the protocols described in ISO-22197: 2007 (E) standard. The adsorption characteristics of oxygen and H2O were monitored by adsorption calorimetry. Oxygen adsorption was low; on the contrary water vapor exhibited the characteristics of multilayer adsorption. In the first monolayer, the heats of adsorption of water sharply decreased from 180 to 80 kj/mol till about 10 mu mol/g catalyst surface coverage. Constant adsorption heats of about 80 kJ/mol were measured for coverage of about 350 mu mol/g catalyst, corresponding to a monolayer. Adsorption further continued with a constant heat of about 40 kJ/mol corresponding to the condensation enthalpy of water at the measurement temperature of 50 degrees C. The photocatalytic NO oxidation rate expression was determined as No-r alpha cN(NO)(-00.12) c(H2O)(0.38).