A new mechanism of nano-catalyst generation based on the spinodal nano-decomposition in self-regenerating perovskite catalysts for automotive-emissions control is proposed. To demonstrate existence of the spinodal nano-decomposition in real perovskite catalysts, we performed first-principles calculations to evaluate the free energy of La(Fe 1−x Pd x )O 3 and La(Fe 1−x Rh x )O 3 . The result indicates appearance of a spinodal region in the phase diagram of each material. Formation of nano-catalyst particles in the perovskite host matrix is crucial for the self-regeneration of perovskite catalyst. Based on the spinodal nano-decomposition model, possible materials are designed for new three-way catalyst with no contents of precious metal.Self-regenerating Pd-, Rh-, and Pt-doped perovskite catalysts for automotive-emissions control are attracting much interest due to their unique functionalities. [1][2][3][4][5][6][7][8][9][10][11] In a conventional catalyst made of fine precious-metal particles supported on a solid like an almina, agglomeration of the metal particles is inevitable because of high temperature conditions in the redox environment. This is the very reason for deterioration of automotive three-way catalysts. In the self-regenerating perovskite catalysts, interestingly, the deterioration is strongly suppressed. Therefore, consumption of the precious metal is greatly reduced, providing a highly efficient solution for supply problems. The reason for non-deterioration is thought to be reformation of a precious-metal doped perovskite lattice in the NO x -reduction environment from segregated nano-particles of precious-metal created in the CO-and C x H-oxidation environment. In this regeneration model, precious-metal atoms are assumed to move into and out of the perovskite host matrixes. Growth of precious-metal grains is suppressed due to this repeated motion of precious metal atoms between a solid solution and metallic nano-particles during three-way catalytic reactions.In some doped perovskite structures, it is known that diffusion of oxygen happens rather frequently. At the same time, we may expect motion of metal atoms via a process exchanging metallic atoms. The process would be enhanced, if oxygen vacancies are created in the perovskite host crystal. This scenario might support the above model of self-regenerating perovskite catalysts. For realization of high efficiency in the three-way catalytic functions with * E-mail address: hkizaki@aquarius.mp.es.osaka-u.ac.jp 1/10Submitted to Applied Physics Express no deterioration, however, we should consider another model of the self-regenerating catalyst. The new model should explain some mysteries known experimentally in the perovskite catalyst. The self-regeneration can happen, only when the host perovskite lattice structure maintains its essential structure. We need to know why the redox reaction keeps its cycle in a redox environment changing in a frequency of about a few hertz (1 ∼ 4 Hz). Thus we need to understand motion of precious metal atoms in a rat...

To investigate chemical reactivity of Cu atomic-scale structures, we performed simulations based on the generalized gradient approximation in the density functional theory. An atomic layer of Cu forming a triangular lattice (TL) was found to give a stable structure. The nitrogen monoxide molecule (NO) was adsorbed on some atomic sites of TL or on an atomic step structure (ASS) of Cu. The molecular adsorption energy on TL was -0.83 eV. Our data suggested that dissociative adsorption of NO with a dissociation energy of -1.08 eV was possible with an energy barrier of order 1.4 eV. In this optimized structure, the nitrogen and oxygen atoms were embedded in the Cu layer. On the step, NO adsorbed at a bridge site and the formation energy of Cu-(NO)-Cu local bond connections was estimated to be around -1.32 eV. Molecular dissociation of NO with a dissociation energy of -0.37 eV was also possible around ASS.