Improved palladium only three-way catalysts using phosphorus modified alumina support

Alumina with different amounts of phosphorus dopants was synthesized by sol–gel method, and has been used as the support for three-way catalysts (TWC). The P-doped samples display improved catalytic activity for CO/NOx/HC conversion. Moderate improvements of Pd dispersion are also noticed in the P-doped samples. It is confirmed that the active phosphorus species exist as P–O–Al units on the surface, which are mutually stabilized with Pd clusters. These dopants not only suppress the particles sintering and phase transformation during the ageing, but also decorate the Pd particles to be more active in TWC reactions.

► The surface area of γ-alumina increases as increasing the amount of P dopants.
► Phosphorus hinders the phase transition of γ-alumina at the high-temperatures.
► The aged P-doped catalysts exert the outstanding TWC activities.
► The P–O–Al sites strongly inhibit Pd sintering against the hydrothermal treatment.