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Seo, Hyun Ook,Park, Eun Ji,Kim, Il Hee,Han, Sang Wook,Cha, Byeong Jun,Woo, Tae Gyun,Kim, Young Dok Elsevier 2017 CATALYSIS TODAY - Vol.295 No.-
<P><B>Abstract</B></P> <P>We have studied the influence of water vapors on the activity of the photo-catalytic oxidation of acetaldehyde on the surface of TiO<SUB>2</SUB> film under UV light (365nm) irradiation. Photo-catalysis experiments were performed at atmospheric conditions under various humidity levels (0, 16.8, and 33.6 relative humidity%) using a high vacuum chamber equipped with online gas-chromatography as a batch-type reactor. Acetaldehyde and H<SUB>2</SUB>O molecules competitively adsorbed on the surface of TiO<SUB>2</SUB> film and the increase in the humidity decreased both the acetaldehyde removal and CO<SUB>2</SUB> evolution rates. The rate of CO<SUB>2</SUB> evolution was even more influenced by the humidity level of the gas mixture compared to the acetaldehyde removal rate, particularly over the certain level of relative humidity. We evidenced that the total oxidation of acetaldehyde was majorly mediated by oxygen molecules rather than H<SUB>2</SUB>O vapor under our experimental conditions. It is suggested that photo-catalytic total oxidation of acetaldehyde was promoted by the presence of large active sites ensemble near the adsorbed acetaldehyde, which were available to oxygen. Increase of humidity level disturbed this large ensemble, resulting in the reduction of photo-catalytic degradation rate of acetaldehyde under UV light irradiation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Higher humidity level decreased the photo-catalytic mineralization of acetaldehyde. </LI> <LI> The total mineralization of acetaldehyde was majorly mediated by O<SUB>2</SUB>. </LI> <LI> Water vapor was competitively adsorbed on TiO<SUB>2</SUB> surface with acetaldehyde and O<SUB>2</SUB>. </LI> <LI> Water molecules inhibited the adsorption of the acetaldehyde and O<SUB>2</SUB>. </LI> <LI> Active sites ensemble promoted the total mineralization of acetaldehyde. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
CO Oxidation of Catalytic Filters Consisting of Ni Nanoparticles on Carbon Fiber
Seo, Hyun-Ook,Nam, Jong-Won,Kim, Kwang-Dae,Kim, Young-Dok,Lim, Dong-Chan Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.4
Catalytic filters consisting of Ni nanoparticle and carbon fiber with different oxidation states of Ni (either metallic or oxidic) were prepared using a chemical vapor deposition process and various post-annealing steps. CO oxidation reactivity of each sample was evaluated using a batch type quartz reactor with a gas mixture of CO (500 mtorr) and $O_2$ (3 torr) at $300^{\circ}C$. Metallic and oxidic Ni showed almost the same CO oxidation reactivity. Moreover, the CO oxidation reactivity of metallic sample remained unchanged in the subsequently performed second reaction experiment. We suggested that metallic Ni transformed into oxidic state at the initial stage of the exposure to the reactant gas mixture, and Ni-oxide was catalytically active species. In addition, we found that CO oxidation reactivity of Ni-oxide surface was enhanced by increase in the $H_2O$ impurity in the reactor.
Interaction of TiO<sub>2</sub> Films on Carbon Fibers with Toluene
Seo, Hyun-Ook,Kim, Kwang-Dae,Luo, Yuan,Kim, Myoung-Joo,Dey, Nilay Kumar,Kim, Young-Dok Korean Chemical Society 2010 Bulletin of the Korean Chemical Society Vol.31 No.8
$TiO_2$ thin films were synthesized on carbon fibers using chemical vapor deposition. We show that these films can exhibit extraordinarily high absorption capacities of toluene vapor. Such an absorption phenomenon of toluene at room temperature was not found for other $TiO_2$ samples. Upon toluene absorption change in the color (darkening) of the film was found, indicating that these films can be used as an indicator of the existence of volatile organic compounds in the indoor environments. By X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM), a high concentration of OH species and a unique layered structure were found for the $TiO_2$ films and these could be related to their high absorption capacity of toluene.
Seo, Hyun Ook,Woo, Tae Gyun,Park, Eun Ji,Cha, Byeong Jun,Kim, Il Hee,Han, Sang Wook,Kim, Young Dok Elsevier 2017 APPLIED SURFACE SCIENCE - Vol.420 No.-
<P><B>Abstract</B></P> <P>We have studied the photo-catalytic degradation of acetaldehyde over the surface of TiO<SUB>2</SUB> films under UV light (365nm) irradiation both at dry and humid air conditions using a high vacuum chamber equipped with on-line gas-chromatography as a batch-type reactor. Changes of TiO<SUB>2</SUB> surfaces upon the photo-catalysis experiments were studied by X-ray photoelectron spectroscopy. The competitive adsorption of water and acetaldehyde resulted in the reduction of reaction rate of photo-catalytic degradation of acetaldehyde under the UV light irradiation. The photo-catalytic reaction rate of TiO<SUB>2</SUB> films towards acetaldehyde mineralization increased when the photo-catalysis experiments were performed repeatedly and it was much more pronounced under humid conditions. Our XPS analysis revealed that carbon impurities on the surface of TiO<SUB>2</SUB> films were removed by UV-light driven photo-catalytic mineralization under humid conditions. Water vapor facilitated the photo-catalytic removal of carbon impurities from TiO<SUB>2</SUB> surface generating additional active sites of TiO<SUB>2</SUB> which resulted in the enhanced photo-catalytic activity of TiO<SUB>2</SUB> films.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Changes of TiO<SUB>2</SUB> surfaces during photo-catalysis were studied by XPS. </LI> <LI> Role of humidity for photo-catalytic decomposition of acetaldehyde was studied. </LI> <LI> Competitive adsorption of water and acetaldehyde resulted in the reduction of reaction rate. </LI> <LI> Water vapor facilitated the photo-catalytic removal of carbon impurities from TiO<SUB>2</SUB>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>