posted on 2022-12-09, 13:42authored byJun Cai, Yunjian Ling, Hui Zhang, Bo Yang, Fan Yang, Zhi Liu
CO
oxidation on Rh has received considerable attention because
of its importance in commercial three-way catalyst applications. Although
many studies have been conducted on this process, detailed analysis
of the formation of Rh–O species has not yet been carried out,
particularly with respect to their activity for CO oxidation. In this
work, we reported the in situ study of Rh–O species and their
activity for CO oxidation over the Rh(110) surface using advanced
surface science techniques, including ambient-pressure X-ray photoelectron
spectroscopy, ambient-pressure mapping of resonant Auger electron
spectroscopy, and ambient-pressure scanning tunneling microscopy.
The Rh–O species, (2 × 1)–O, (10 × 2)–O,
trilayer O–Rh–O, and Rh2O3, were
demonstrated to be formed in sequence as the O2 chemical
potential increases. CO titration experiments demonstrated that the
reactivity of the Rh–O species followed the sequence (2 ×
1)–O > (10 × 2)–O > trilayer O–Rh–O
≫ Rh2O3. The titration reaction on the
trilayer oxide was a two-step process, which started with an intrinsic
reaction of O–Rh–O, followed by a relatively higher
reaction rate. The change of reaction rate was a result of the restructuring
from O–Rh–O to (10 × 2)–O. Our results provided
the correlation of the surface Rh–O species and reactivity
of the CO oxidation on Rh-based catalysts.