Low-Temperature CO Oxidation over the Pt-TiN Interfacial Dual Sites

The metal-support interfacial synergistic catalysis allows the competitive reaction steps to occur in close proximity at different sites, thus decreasing the activation barrier and improving the catalytic efficiency. Combining the structural characterization, reactivity assessments and density functional theory (DFT) calculations, it is found that highly dispersed Pt clusters on TiN substrates favor the formation of Pt-TiN interfacial dual sites, which are highly reactive for the low-temperature CO oxidation with an apparent activation energy as low as 38.7 kJ mol(-1), much less than that on the traditional Pt/TiO2 or Pt/SiO2 catalysts. At low temperature, the surface sites of Pt are saturated with CO adsorption due to its high adsorption energy and the molecular O-2 dissociatively adsorbs on the Ti sites to form the titanium oxynitride (TiNxOy) skin with a low barrier of 0.1 eV. The O atoms binding on Ti sites readily react with the adjacent CO molecules adsorbed on the perimeter of Pt clusters to attain a catalytic cycle with a reaction barrier of 0.5 eV. The interfacial synergistic effect between Pt and TiN is the origin of the low temperature CO oxidation activity on the metal-nitride catalysts.