The intelligent catalyst having the self-regenerative function of Pd, Rh and Pt for automotive emissions control

Abstract

The self-regenerative function of precious metals in the intelligent catalyst is an epoch-making technology in the history of automotive catalysts after the 1970's. The mechanism of the self-regenerative function is studied by X-ray absorption fine-structure (XAFS) analyses. The function was realized through a cyclic movement of Pd between the outside (as Pd nanoparticles) and the inside (as Pd cations in the lattice) of the perovskite crystal in synchronization with the inherent fluctuations between reductive and oxidative (redox) atmospheres that occur in real automotive exhaust gases. As the result, the growth of Pd particles can be suppressed during the entire lifetime of the vehicle. Moreover, the speed of this function was measured at the time resolution of a 10 ms by in situ energy dispersive XAFS, and it is proved that the self-regenerative function occurs at an extremely high speed. Furthermore, the new perovskite catalysts which have the self-regenerative function of Rh and Pt, as well as Pd, are discussed here. This self-regenerative function provides a new and useful tool for designing the future catalyst technology.