Photoreduction of CO2 over reactive DC magnetron sputtered TiO2 thin films

CATL 32

Le Chen, Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Rd, Rm A236, Evanston, IL 60208, Michael E Graham, mgraham@northwestern.edu, Department of Material Science and Engineering, Northwestern University, Evanston, IL 60208, Gonghu Li, Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Rd, Rm A236, Evanston, IL 60208, and Kimberly A. Gray, k-gray@northwestern.edu, Department of Civil and Environmental Engineering, Institute for Catalysis in Energy Processes, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208.
A study of the role of solid-solid interfaces in the photocatalytic behavior of TiO2 has been undertaken utilizing reactive magnetron sputtering to create multilayer and mixed phase thin films consisting of the anatase and rutile phases. We show that sputter deposition provides excellent control of phase and interface formation and allow us to synthesize a variety of nanostructured materials. We have explored the range of phase synthesis that is controlled through the process parameters of pressure, oxygen partial pressure, target power, substrate bias (rf), deposition incidence angle, and post annealing treatment. We have successfully made multilayer coatings with different phase composition and added oxygen vacancies or nitrogen purposefully to some of the samples as well in order to create materials with visible photoresponse. These coatings have been characterized with SEM, TEM, and XRD to determine surface morphology, phase distribution and phase content. The ability of the sputtered films to photo-reduce CO2 was tested and compared (normalized for surface area) with other TiO2 films as Degussa P25 and sol-gel samples under UV/Vis illumination conditions. The sputtered mixed phase materials with oxygen vacancies were shown to be far superior to the rest of the films in the gas phase production of methane from CO2 and H2O. The mechanism of charge separation and transfer has been shown to depend strongly on the solid-solid interfaces with oxygen vacancies through EPR measurements in our laboratory.
 

Photocatalysis
1:30 PM-4:50 PM, Tuesday, August 21, 2007 BCEC -- 261, Oral

Catalysis & Surface Science Secretariat

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007