Superior TWC Activity of Rh Supported on Pyrochlore-Phase Ceria Zirconia

Abstract Ceria-zirconia (CZO) materials remain as a crucial component of today’s three-way catalysts (TWC). To meet increasing stringent emission standards, pyrochlore-phase CZO (pyr-CZO) was examined as a superior oxygen storage capacity (OSC) material over traditional tetragonal-phase CZO (t-CZO) used in today’s automotive catalysts. By reducing t-CZO at 1200 °C in H2, 50% of the pyrochlore phase was formed in which an optimized balance of increased OSC / oxygen release rate (ORR) and adequate surface area was achieved. We further demonstrate that the addition of 0.1 wt% Rh onto pyr-CZO dramatically improves the TWC performance of Rh over traditional Rh/t-CZO catalysts, improving NO and alkane conversions while eliminating mass transfer limitations. In addition, increased OSC is observed for Rh/pyr-CZO-1200 °C catalysts without sacrificing ORR and water-gas shift (WGS) activity. The robustness of pyrochlore materials is demonstrated after redox aging at 910 °C, illustrating the implementation of pyrochlore as a support for Rh as viable.