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

ÜNER D., Bayar I., Tabari T.

APPLIED SURFACE SCIENCE, vol.354, pp.260-266, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 354
  • Publication Date: 2015
  • Doi Number: 10.1016/j.apsusc.2015.07.045
  • Journal Name: APPLIED SURFACE SCIENCE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.260-266
  • Keywords: Nitric oxide, Photocatalytic oxidation, Immobilized TiO2, Hydroxyl groups, Relative humidity, Calorimetry, NITROGEN-OXIDES, WATER, PHOTODEGRADATION, DEGRADATION, ADSORPTION, SCIENCE
  • Middle East Technical University Affiliated: Yes

Abstract

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). (C) 2015 Elsevier B.V. All rights reserved.