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 NOx 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 deNOx 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 NOx 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.