Tuning the interactions among Ce, Pd and Rh over Ce-modified Pd-Rh three-way catalyst for exhaust treatment of natural gas vehicles

Abstract Three Ce-modified Pd-Rh bimetallic catalysts for exhaust purification of natural gas vehicles (NGVs) under stoichiometric conditions were prepared by deposition-precipitation (DP), stepwise impregnation (SI) and co-impregnation (CI) methods, respectively. It demonstrated that before and after aging the catalyst prepared by DP technique displayed much higher activity for the conversions of CH4 and NO than the other two catalysts, especially at high temperatures (about 410~550 ℃). X-ray diffraction, CO-chemisorption, hydrogen temperature-programmed reduction and X-ray photoelectron spectroscopy analyses demonstrated that there were smaller CeO2 particles, higher metal dispersion, stronger reducibility and more surface metallic Pd species over the catalyst prepared by DP method. This might be due to the stronger Pd-Ce but weaker Pd-Rh interactions over the catalyst prepared by DP mean. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption analysis implied that the electronic structures of Pd in the three catalysts were different, which may be also induced by the different interactions among Rh, Ce and Pd in these catalysts. The results indicated that the performance of Pd-Rh three-way catalyst for NGVs exhaust purification can be enhanced by modulating the interactions of Pd-Rh and Pd-Ce. Our work may provide a new strategy for the preparation of three-way catalyst with high efficiency for NGVs.