“…It is well known that larger bulk CuO particles contribute very little or even negatively to the activity for CO oxidation owing to the coverage of active species on the catalyst surface. 7,11,58 Therefore, the lower activity of the 4-CCS and 5-CCS catalysts can be accounted for by the presence of more amounts of larger bulk CuO particles as evidenced by the XRD and Raman characterization results.…”