Characterization of uniform, nanodispersed NOx storage catalyst materials synthesized by successive ionic layer deposition

A dispersed phase of barium oxide (BaO) supported on alumina has been shown to be primarily responsible for NOx storage in practical lean NOx trap catalysts. Conventional impregnation based catalyst loading techniques generate a mixture of dispersed and less active bulk-like BaO phases on alumina, with the bulk-like phase increasing as weight loading increases. Samples of equivalent BaO weight loading on fused alumina were prepared by successive ionic layer deposition (SILD) and wet impregnation. NO2 temperature programmed desorption experiments demonstrate that SILD is uniquely capable of selectively synthesizing uniform, nanodispersed BaO rafts with high surface coverage. These nanodispersed SILD structures show remarkable thermal stability under high operating temperatures up to 650 °C.