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The effect of the introduction of Co to the Pd/TiO 2 catalyst for selective catalytic reduction of NO x by H 2 (H 2 -SCR) in the presence of oxygen has been systematically investigated in the present study. The additive Co can not only obviously improve NO x conversion but also enhance N 2 selectivity. The added Co induced the formation of Pd 0 over the bimetallic PdCo/TiO 2 catalyst, which is greatly conducive to the H 2 -SCR reaction. The spillover of H 2 was promoted due to the introduction of Co over PdCo/TiO 2 . In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that the addition of Co not only contributed to the adsorption and activation of NO x but also led to the generation of NH 3 species adsorbed on Lewis acid sites, making the reduction of NO x by the H 2 -SCR combined with NH 3 -SCR routes. All of these are responsible for the enhanced catalytic performance of the bimetallic PdCo/TiO 2 catalyst. The investigation would provide guidelines for the rational design of a highly active H 2 -SCR catalyst for the removal of NO x .

A Pd supported on a TiO2 nanowire (Pd/TiO2-NWs) catalyst was fabricated, and the catalytic performance for the selective catalytic reduction of NO x by H2 (H2-SCR) was investigated. It was found that the Pd/TiO2-NW catalyst exhibited higher H2-SCR activity and wider activity temperature window than Pd supported on the TiO2 nanoparticle (Pd/TiO2-P) catalyst. Based on a series of characterizations, Pd/TiO2-NWs with a nanowire structure possessed a large surface area, high Pd dispersion, high content of metallic Pd, and more surface adsorbed oxygen, all of which would contribute to the adsorption and activation of NO x and the spillover of hydrogen. Whereas for the Pd/TiO2-P catalyst, the favorable active Pd0 site is absent. In situ DRIFTS showed that more active intermediates (NO2, monodentate nitrate, and NH3 species) were formed over Pd/TiO2-NWs than the Pd/TiO2-P catalyst. All of these contributed to the enhanced H2-SCR activity of the Pd/TiO2-NW catalyst.