Copper catalysts, either un-supported or supported on an oxide, have been explored for carbon monoxide reactions for decades. Studies under high vacuum conditions suggested that low valent copper species, particularly Cu(I), has a comparable reaction rate as other precious metals. Meanwhile, the oxidation states and active sites of copper became complicated once copper species were supported on reducible metal oxides, including titanium dioxide. We investigated copper supported on nitrogen modified titanium dioxide (Cu-N-TiO2) for the carbon monoxide oxidation reaction. The interstitial nitrogen was identified as the dominant nitrogen species, which facilitate copper dispersion on the surface. Therefore, the reaction rate is improved compared with that of Cu-TiO2. Cu+ is beneficial to the carbon monoxide oxidation reaction. However, the value of ([Cu+]/[O]sur) is positively proportional to the reaction rates.
