Copper oxide clusters modified by bismuth single atoms to catalyze CO oxidation

Abstract

Supported single atom and cluster catalysts have received an extensive attention in all kind of heterogeneous catalytic reactions due to their unique physical and chemical properties. In this work, we prepared silica-supported copper-bismuth oxide catalysts via incipient-wetness impregnation method. This Bi-doped catalyst exhibits an excellent performance in carbon monoxide oxidation with a reaction rate at 0.6 μmolCO·gcat−1·s −1 at 170 °C, which is about ten times of that for pure copper-silica catalyst. Furthermore, we found a unique active site structure: Bi single atom anchored on the surface of CuOx cluster via Bi−O−Cu structure with the help of comprehensive characterization method, especially aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and extend X-ray absorption fine structure (EXAFS) fitting result. On one hand, the Bi−O−Cu structure can significantly enhance the anti-sintering ability of copper species and provide more available Cu active site with similar apparent activation energy (~40 kJ·mol−1). On another hand, this structure not only increases surface active oxygen species confirmed by CO−temperature programmed reduction (CO−TPR), but also significantly strengthens the adsorption of CO molecule by CO−temperature programmed desorption (CO−TPD) and in-situ Diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) to promote the activity of CO oxidation. This work may provide a new guideline to synthesize high active atomic-scale catalysts for different redox reactions.