Gold single-atoms confined at the CeO _x -TiO₂ interfaces with enhanced low-temperature activity toward CO oxidation

Abstract We use CeO _x -TiO₂ hetero-interfaces generated on the surface of CeO _x -TiO₂ hybrid oxide supporting powders to stabilize Au single-atoms (SAs) with excellent low-temperature activity toward CO oxidation. Based on intriguing density functional theory calculation results on the preferential formation of Au-SAs at the CeO _x -TiO₂ interfaces and the high activity of Au-SAs toward the Mars–van Krevelen type CO oxidation, we synthesized a Au/CeO _x -TiO₂ (ACT) catalyst with 0.05 wt.% of Au content. The Au-SAs stabilized at the CeO _x -TiO₂ interfaces by electronic coupling between Au and Ce showed improved low-temperature CO oxidation activity than the conventional Au/TiO₂ control group catalyst. However, the light-off profile of ACT showed that the early activated Au-SAs are not vigorously participating in CO oxidation. The large portion of the positive effect on the overall catalytic activity from the low activation energy barrier of ACT was retarded by the negative impact from the decreasing active site density at high temperatures. We anticipate that the low-temperature activity and high-temperature stability of Au-SAs that stand against each other can be optimized by controlling the electronic coupling strength between Au-SAs and oxide clusters at the Au-oxide-TiO₂ interfaces. Our results show that atomic-precision interface modulation could fine-tune the catalytic activity and stability of Au-SAs.