Remarkable active-site dependent H 2 O promoting effect in CO oxidation

The interfacial sites of supported metal catalysts are often critical in determining their performance. Single-atom catalysts (SACs), with every atom contacted to the support, can maximize the number of interfacial sites. However, it is still an open question whether the single-atom sites possess similar catalytic properties to those of the interfacial sites of nanocatalysts. Herein, we report an active-site dependent catalytic performance on supported gold single atoms and nanoparticles (NPs), where CO oxidation on the single-atom sites is dramatically promoted by the presence of H2O whereas on NPs’ interfacial sites the promoting effect is much weaker. The remarkable H2O promoting effect makes the Au SAC two orders of magnitude more active than the commercial three-way catalyst. Theoretical studies reveal that the dramatic promoting effect of water on SACs originates from their unique local atomic structure and electronic properties that facilitate an efficient reaction channel of CO + OH. The issue that whether single-atom sites possess similar catalytic properties to the interfacial sites of nanocatalysts remains unresolved. Here, the authors demonstrate a large H2O promotional effect on CO oxidation over Au single-atom sites due to their unique local atomic structure and electronic properties.