Promoting Effect of Ni in Pt/TiO<sub>2</sub> Activity for Nitrogen Oxide to Ammonia Reaction Using CO–H<sub>2</sub>O Reductant

TiO2 supported bimetallic (Ni1Pt1, Ni1.6Pt1 or Ni2.6Pt1) and monometallic (Pt or Ni) catalysts were prepared by incipient wetness method. The catalytic activity of these catalyst was examined for nitrogen oxide to ammonia reaction using low temperature (<200 °C). Among tested monometallic and bimetallic catalysts, Ni1.6Pt1/TiO2 catalyst exhibited high NO conversion and ammonia formation. Ni1.6Pt1/TiO2 was highly stable up to 60 h for nitrogen oxide to ammonia reaction. Whereas, the stability of Pt/TiO2 catalyst was decreased after 40 h. Addition of Ni to Pt catalyst might be resist sintering and provide thermal stability in bimetallic catalyst. XRD analysis showed no diffraction peak of Ni and Pt, indicating Ni and Pt metal were well-dispersed in Ni1.6Pt1/TiO2 catalyst. Furthermore, the activation energy over Ni1.6Pt1/TiO2 (34.3 kJ mol−1) catalyst was 1.7 times lower activation energy than that of Pt/TiO2 (50.4 kJ mol−1). In controlled experiments, DRIFT analysis showed ammonia was formed via isocyanate (NCO) intermediate formation. The peak intensity of NCO peak over Ni1.6Pt1/TiO2 catalyst comparatively was high which indicated that ammonia formation was highly favorable.