Splitting, platinum particles

Particle splitting is not merely of academic interest. Recently, it has been demonstrated that three-way automotive exhaust catalysts can be made from supported palladium alone, rather than from rhodium and platinum. The opportunity results in part from improvements in technology that permit palladium to be redispersed by a particle-splitting process during lean-bum periods. Possibly this redispersion results from palladium particle splitting. 

These data are corroborated by results obtained from continuous photolysis experiments. Cabowax-20M protected Pt catalyst when coupled to Ru02 fails to split water under illumination of a cyclic system containing Ru(bipy)3+ as a sensitizer and methylvio-logen as an electron relay. By contrast, if the Pt microspheres are protected by PVP-Ci6 simultaneous H2 and 02 productions are observed. The lack of specificity of the Carbo-wax 20 M protected particles is attributed to the strongly hydrophylic nature of this protective polymer providing facile access of the Ru(bipy)3+ cation to the platinum surface. Uncharged hydrophylic polymers appear thus unsuitable for Pt protection in this cyclic water decomposition system. 

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