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...