Enhanced Catalytic Activity of Pd Supported on TiO2 Nanowire for the H2-SCR of NOx in the Presence of Oxygen

A Pd supported on a TiO2 nanowire (Pd/TiO2-NWs) catalyst was fabricated, and the catalytic performance for the selective catalytic reduction of NOx 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 NOx 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.