Largely Cu-doped LaCo1−xCuxO3 perovskites for TWC: Toward new PGM-free catalysts

Abstract Doping of LaCoO 3 with copper to add reduction functionality in addition to the known oxidation properties has been investigated, aiming at three-way catalysis (TWC) applications. Nanoscale perovskites with nominal composition LaCo 1− x Cu x O 3 , ( x  = 0, 0.1, 0.3, and 0.5) have been synthesized by means of the citrate method. A stable perovskitic phase with rhombohedral geometry up to an unprecedented x  = 0.5 has been obtained and characterized by BET, X-ray diffraction (XRD), Temperature Programmed Reduction (TPR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The crystallite size decreases with increasing the copper amount and also the morphology differs; moreover the surface reactivity with respect to atmospheric moisture and carbon dioxide is more evident in the sample with x  = 0.5. Reactivity has been measured in simple NO + CO and CO + O 2 model reactions, as well as with complex mixtures approaching automotive exhaust composition, at both stoichiometric and O 2 limiting conditions. The catalysts have been characterized after reaction as well. The perovskite with the highest Cu amount, LaCo 0.5 Cu 0.5 O 3 , exhibits an interesting compromise of oxidation and NO reduction functionality at interesting, low temperatures with very short contact time (GHSV = 1,000,000 h −1 ). Still, activity for NO reduction in real mixtures requires substoichiometric O 2 .