Very Low Temperature CO Oxidation over Atomically Precise Au₂₅ Nanoclusters on MnO₂

Abstract

Atomically precise Au₂₅ nanoclusters have garnered significant interest in the field of heterogeneous catalysis due to their remarkable activity and selectivity. However, for the extensively studied reaction of low-temperature CO oxidation, their performance has not been competitive compared to other known gold nanocatalysts. To address this, we deposited Au₂₅(SR)₁₈ (R = CH₂CH₂Ph) nanoclusters onto a manganese oxide support (Au₂₅/MnO₂), resulting in a very stable and highly active catalyst. By optimizing the pretreatment temperature, we were able to significantly enhance the performance of the Au₂₅/MnO₂ catalyst, which outperformed most other gold catalysts. Impressively, 100% conversion of CO was achieved at temperatures as low as -50 °C, with 50% conversion being reached below -70 °C. Furthermore, the existence of ligands could also influence the negative apparent activation energy observed at intermediate temperatures. Analysis using X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), and X-ray diffraction (XRD) techniques indicated that the Au₂₅ nanoclusters remained stable on the catalyst surface even after pretreatment at high temperatures. In-situ modulation excitation spectroscopy (MES) spectra also confirmed that the Au cluster was the active site for CO oxidation, highlighting the potential of atomically precise Au₂₅ nanoclusters as primary active sites at very low temperatures.