Cu@LaNiO3 based nanocomposites in TWC applications

Several nanocomposites of the type CuO/LaNiO3 (Cu@LaNiO3) have been developed for application as noble metal free catalysts in TWC. The nanocomposites have been obtained by depositing copper oxide on lanthanum nickelate. The supporting perovskite has been prepared by means of the citrate route; copper, in contrast, was deposited by means of an innovative procedure: ammonia driven deposition precipitation method (ADP) optimized for deposition on perovskites. The nanocomposites have been developed based on the catalytic activity of LaNiO3 in oxidation and reforming reactions and of copper in reduction reactions. Nanocomposition is thus used to deposit a highly dispersed active specie (CuO) on an active support (LaNiO3) with the aim of building catalytic functionality. The obtained nanocomposites have been characterized by means of XRD, XPS, SEM, TPR, BET, EDX, and ICP and the obtained results are correlated to the amount of copper deposited and to the reactivity. The reactivity was studied first in two model reactions, CO oxidation and CO assisted NO reduction, in order to investigate the role played by the different species. Moreover, the reactivity under real conditions, i.e. with a complex mixture reflecting the actual automotive exhaust composition, was considered to evaluate the real applicability. Finally, high-temperature deactivation was investigated. XPS reveals that the deposition of copper oxide affects the surface composition of the nanocomposites; the XRD, SEM, and TPR results confirm that CuO is deposited on the LaNiO3 surface and no diffusion below surface is observed. CuO species are deposited both as highly dispersed phase and as bigger particles; the relative amount of these phases depends on the total amount of copper deposited. The reactivity in the CO oxidation reaction is not significantly affected by the copper deposition. In contrast the reactivity in NO reduction is strongly enhanced by the presence of highly dispersed copper species. Activity tests with mixture reflecting actual automotive exhaust, reveal an enhancement in CO oxidation, but no NO decomposition at stoichiometric conditions. Complete NO reduction is achieved at rich conditions; also, hydrocarbons reforming reactions typically occurring at substoichiometric O2, with CO and H2 production, are less supported, preserving the activity in NO reduction. Finally, the high-temperature aging test confirmed an interesting stability of catalytic activity.