TY - JOUR
T1 - Comparing and contrasting CO oxidation by Rh atoms and clusters on and under thin-film copper oxides
AU - Çınar, Volkan
AU - Adewale, Raphael
AU - Rickman, Maggie
AU - Miller, Grace
AU - Peurrung, Eva
AU - Guo, Dezhou
AU - Lim, Hojoon
AU - Hunt, Adrian
AU - Schilling, Alex C.
AU - Wang, Yicheng
AU - Hannagan, Ryan T.
AU - Waluyo, Iradwikanari
AU - Sykes, E. Charles H.
AU - McEwen, Jean Sabin
N1 - Publisher Copyright:
© 2026 The Author(s)
PY - 2026/9
Y1 - 2026/9
N2 - Single-atom catalysts, where isolated metal atoms are stabilized on oxide supports and excel in oxidation reactions, and single-atom alloys, where active atoms are dispersed in inert metal hosts and perform best under reducing conditions, have both gained significant attention in recent years. However, the catalytic behavior in the oxidation state space between these regimes remains poorly understood. Here, we compare CO oxidation with Rh under thin oxide films grown on RhCu(1 1 1) surface alloys and compare the results to the reactivity of Rh on thin oxide films grown on a Cu(1 1 1) surface. Temperature-programmed desorption shows two distinct CO2 peaks for Rh on the “29” oxide – arising from clusters (lower temperature) and single atoms (higher temperature), whereas Rh under the CuxO exhibits a single higher temperature CO2 peak that shifts to lower temperatures with increasing Rh coverage. The CO2 yield is markedly lower for Rh under the oxide due to oxygen encapsulation, but adsorbed CO at exposed Rh sites is fully converted with no intact CO desorption above 300 K, in contrast to Rh on the “29” oxide. Isotopic labelling confirms a Mars-van Krevelen mechanism in both systems, though C-O bond scission is suppressed when Rh is encapsulated. X-ray photoelectron spectroscopy confirms the enhanced CO oxidation activity for Rh on the “29” oxide as well as shows that the reaction occurred between CO and O adatoms. Density functional theory further show that Rh under the oxide enforces a Mars-van Krevelen pathway whose barrier strongly depends on Rh nuclearity, with clusters more active than isolated atoms. Moreover, while Rh under the oxide can follow Eley-Rideal/Mars-van-Krevelen pathways, Rh on the oxide follows a strict Langmuir-Hinshelwood/Mars-van-Krevelen mechanism. These findings provide new insight into how surface oxidation modulates the accessibility, structure, and reactivity of Rh atom and cluster sites in Cu-based catalysts.
AB - Single-atom catalysts, where isolated metal atoms are stabilized on oxide supports and excel in oxidation reactions, and single-atom alloys, where active atoms are dispersed in inert metal hosts and perform best under reducing conditions, have both gained significant attention in recent years. However, the catalytic behavior in the oxidation state space between these regimes remains poorly understood. Here, we compare CO oxidation with Rh under thin oxide films grown on RhCu(1 1 1) surface alloys and compare the results to the reactivity of Rh on thin oxide films grown on a Cu(1 1 1) surface. Temperature-programmed desorption shows two distinct CO2 peaks for Rh on the “29” oxide – arising from clusters (lower temperature) and single atoms (higher temperature), whereas Rh under the CuxO exhibits a single higher temperature CO2 peak that shifts to lower temperatures with increasing Rh coverage. The CO2 yield is markedly lower for Rh under the oxide due to oxygen encapsulation, but adsorbed CO at exposed Rh sites is fully converted with no intact CO desorption above 300 K, in contrast to Rh on the “29” oxide. Isotopic labelling confirms a Mars-van Krevelen mechanism in both systems, though C-O bond scission is suppressed when Rh is encapsulated. X-ray photoelectron spectroscopy confirms the enhanced CO oxidation activity for Rh on the “29” oxide as well as shows that the reaction occurred between CO and O adatoms. Density functional theory further show that Rh under the oxide enforces a Mars-van Krevelen pathway whose barrier strongly depends on Rh nuclearity, with clusters more active than isolated atoms. Moreover, while Rh under the oxide can follow Eley-Rideal/Mars-van-Krevelen pathways, Rh on the oxide follows a strict Langmuir-Hinshelwood/Mars-van-Krevelen mechanism. These findings provide new insight into how surface oxidation modulates the accessibility, structure, and reactivity of Rh atom and cluster sites in Cu-based catalysts.
UR - https://www.scopus.com/pages/publications/105041675788
U2 - 10.1016/j.jcat.2026.116910
DO - 10.1016/j.jcat.2026.116910
M3 - Article
AN - SCOPUS:105041675788
SN - 0021-9517
VL - 461
JO - Journal of Catalysis
JF - Journal of Catalysis
M1 - 116910
ER -