Development of High Performance Three-Way-Catalyst Technology to Lower NOx Emission

One primary result of the reduction of platinum group metals (PGM) within a catalytic converter is the decline in NOx conversion efficiency. This paper hypothesizes that the primary factor of this decline to be hydrocarbon (HC) poisoning. To maintain high NOx conversion efficiency as the PGM reduces, Rh activation improvement becomes significant to overcome the HC poisoning. Analysis of the Rh deterioration mechanism found that it is effective to separately arrange Rh and CeO₂ on the converter, avoiding the Rh deactivation. By this improvement, we improved the catalyst activity at less than 25% of the original Rh loading.