(701g) Carbon Monoxide Oxidation on Nitrogen and Copper Doped TiO2

Titanium dioxide (TiO₂), is a well-known support for photocatalysis, where it shows its efficiency in the removal of unwanted impurities from water and air, as well as generating chemicals, particularly hydrogen from water splitting [1]. Meanwhile, various TiO₂-supported catalysts including Cu-TiO₂ have been previously developed for numerous industrial applications [2], such as the water gas shift (WGS) reaction, the selective catalytic reduction of NO_x, and carbon monoxide oxidation. Among those diverse catalytic processes, carbon monoxide oxidation is attractive especially for preventing the poisoning of Pt catalysts by CO in proton exchange membrane fuel cell.

We developed one efficient approach to improve the interaction between copper and titania support with the aid of nitrogen addition, and elucidated the important role that copper cluster plays in improved activity and stability in CO oxidation. The nitrogen concentration on the surface was optimized by tuning the initial weight ratio of urea and TiO₂ and calcination temperatures. The XPS analysis revealed the maximum nitrogen concentration on the surface was achieved once calcination temperature reached 450 ^oC. Compared with undoped TiO₂, the addition of nitrogen facilitated the copper bound on the surface as well as the increase of actual copper loading. TEM characterization also confirmed that copper formed small clusters on nitrogen modified TiO₂. Kinetic studies focused on the measurement of the reaction rate regarding the carbon monoxide oxidation reaction. Three-fold increases were observed over copper modified nitrogen-titania. Stability results from time-on-stream test and start-shutdown also favored the nitrogen modified Cu-TiO₂. The enhanced activity and stability could be attributed to nitrogen facilitating the formation of copper clusters on TiO₂ surface.

References:

1. Fujishima, A., Zhang, X.T., Tryk, D. A. Sur.Sci.Rep. 63, 515 (2008).
2. Bartholomew, C. H., Farrauto, R. J. in “Industrial Catalytic Process” p.67. Wiley-Interscience, New Jersey, 2006.