Evaluation of Rh Surface State and Catalyst Light-Off Performance by XPS Analysis

Abstract

Rh performance may not correlate with Rh particle size in automotive catalysts. Therefore, we studied the relation between Rh surface state and catalyst light-off performance by XPS analysis to find the cause. As a result, we found that there were metal Rh state, oxidized Rh state and highly oxidized Rh state in Rh surface state. In addition, we found that more metal Rh particles were produced by reduction treatment when the catalysts had both more oxidized Rh particles and less highly oxidized Rh particles. Furthermore, we found that Rh performance correlated with proportion of metal Rh particles.