| Summary: | Bimetallic AuPd nanoparticles supported on TiO<sub>2</sub> are known to catalyze the reduction of NO with CO. Here, we investigated the effects of the addition of lanthanum oxide to a AuPd/TiO<sub>2</sub> catalyst with a AuPd particle size of 2.1–2.2 nm. The addition of La<sub>2</sub>O<sub>3</sub> enhanced the catalytic activity; for example, at 250 °C, there was 40.9% NO conversion and 49.3% N<sub>2</sub>-selectivity for AuPd/TiO<sub>2</sub>, and 100% NO conversion and 100% N<sub>2</sub>-selectivity for AuPd-La (1:1)/TiO<sub>2</sub>. The temperature requiring 100% NO conversion dropped from 400 °C to 200 °C by the simple post-impregnation of La<sub>2</sub>O<sub>3</sub> onto AuPd/TiO<sub>2</sub>. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with modulation excitation spectroscopy (MES) demonstrated that CO adsorption occurs first on Au atoms and then, within 80 s, moves onto Pd atoms. This transformation between two adsorption sites was facilitated by the addition of La<sub>2</sub>O<sub>3</sub>.
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