Preferential chemical vapor deposition for the synthesis of the catalysts for CO mediated NOx selective catalytic reduction

In previous studies IrRu/Al₂O₃ has exhibited good activity for NO_x reduction by CO at low temperature. The Ir-Ru alloy structure was revealed to be the origin of the outstanding activity of IrRu/Al₂O₃ in the CO-induced deNO_x reaction. In this work, preferential chemical vapor deposition (pCVD) was applied as an effective and selective Ir-Ru alloy catalyst synthesis method, which selectively deposits Ir precursor on the pre-existing Ru nanoparticles. The synthesized IrRu/Al₂O₃ catalysts were characterized by transmission electron microscopy, X-ray diffraction, X-ray absorption spectroscopy, temperature programmed reduction, X-ray photoelectron spectroscopy, and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTs) analyses. The results confirmed the formation of Ir-Ru alloy, and showed that Ir can be preferentially deposited on Ru surface via pCVD, rather than on the Al₂O₃ support. IrRu/Al₂O₃ synthesized by pCVD exhibited better performance in the NO_x reduction by CO than catalysts prepared by the conventional impregnation method. Its catalytic activity varied with Ir content, which was precisely controllable using pCVD. The investigation of catalyst surface by DRIFT revealed that the accelerated NO dissociation is the primary reason for its excellent low-temperature activity of the IrRu/Al₂O₃ catalyst prepared by pCVD.