The catalyst of the crystalline ceramics known as a perovskite-type oxide was designed and controlled at the atomic level in order to create a new function for self-regeneration of precious metals in a usage ambience without auxiliary treatment.
We have already reported that a catalyst with Pd supported on the perovskite-type oxide has higher activity than a catalyst with Pd supported on alumina. It was also found that Pd supported on the perovskite catalyst is finely dispersed [1, 2 and 3]
The object of this study was to investigate the mechanism of self-regeneration by using hyper-analytical facilities. XAFS analysis, at SPring-8 (8 GeV), revealed that Pd is in six-fold coordinations with oxygen in a perovskite crystal, which indicating that Pd occupies the B site of the unit formula of ABO3 in the perovskite crystal structure under oxidation atmosphere.
XPS analysis showed that metallic Pd at the surface of the perovskite crystal, which was segregated from the crystals in reduction atmosphere, formed a solid solution again in the perovskite crystals in oxidation atmosphere. This cycle, in which Pd segregated out from and shifted back into the perovskite crystal structure in accordance with the atmosphere, realized a precious metal regenerates itself and remains highly active without requiring any auxiliary treatment. We named such a catalyst “An Intelligent Catalyst”.