In heterogeneous catalysis, the supported nanoparticles (NPs) should be one of the most popular conformations of catalysts. As for a fine NP with hundreds of atoms, only the outermost atomic layers directly interact with reactants, which means the major component core atoms at the bulk status are somehow indirectly involved in the catalytic process . In the past decades, downsizing the NPs has been widely applied to improve the performance of existing catalysts , and it has been well recognized that materials at the nano-scale can exhibit distinct physical and chemical properties from their bulk status. For example, in the late 1980s, Haruta et al. reported that the traditionally considered inert Au could exhibit outstanding CO oxidation reactivity when the catalyst is prepared as NPs with a size below 10 nm .