The structure–activity relationships of Rh/CeO₂–ZrO₂ catalysts based on Rh metal size effect in the three-way catalytic reactions

With the continuous tightening of automotive emission regulations and the increasing promotion of energy-efficient hybrid vehicles, new challenges have arisen for the low-temperature performance of three-way catalysts (TWCs). To guide the design of next-generation TWCs, it is essential to further develop our understanding of the relationships between microstructure and catalytic performance. Here, Rh/CeO₂–ZrO₂ catalysts were synthesized with different Rh metal dispersion by using a combination of the wet impregnation method and reduction treatment. These catalysts included Rh single-atom catalysts, cluster catalysts, and nanoparticle catalysts. The results showed that the Rh nanoparticle catalyst, with an average size of 1.9 nm, exhibited superior three-way catalytic performance compared to the other catalysts. Based on the catalytic activity in a series of simple reaction atmospheres such as CO + O₂, NO + CO, and hydrocarbons (HCs) + O₂ and operando infrared spectroscopy, we found that metallic Rh sites on Rh nanoparticles are the key factor responsible for the low-temperature catalytic performance.