Abstract
The development of three-way catalysts with improved low temperature activity is essential for automotive catalysis. Here, we show that solution atomic layer deposition (SALD) of titania or zirconia promoters on alumina supports lowers the light-off temperatures of rhodium-based catalysts by 50–150 °C compared to a commercial benchmark three-way catalyst. X-ray diffraction, scanning transmission electron microscopy–electron energy loss spectroscopy, diffuse reflectance UV–visible spectroscopy and X-ray absorption near edge structure results indicate that titania incorporated by SALD at one monolayer loading is present primarily as atomically disperse 5-coordinate Ti4+ species. These species persist after exposure to steam and corrosive gases at temperatures up to 960 °C. Zirconia incorporated onto alumina by SALD is present as few-nanometre oxide particles and supports a three-way catalyst activity that is superior to that of Rh on either alumina or zirconia. Our results show that molecularly precise synthesis can lead to robust promotion of precious metal activity and provide a promising path towards reducing emissions from gasoline vehicles.
