Supported metal nanoparticle catalysts play an essential role in most heterogeneous catalysis and industrial processes. Efficient use of precious metal atoms is both economically and commercially favorable for cost-effective catalytic processes, which could be realized by high dispersion. Singly atomic dispersion of noble metal atoms on a support offers the full use of precious metal atoms and bears potential of better catalytic performances due to different electronic structures of singly dispersed noble metal atoms.Here we report three catalysts, Rh1/Co3O4, Pt1/Co3O4, and Pd1/Co3O4, prepared by anchoring singly dispersed Rh, Pt, and Pd atoms on Co3O4 nanorods, which exhibit high activity and selectivity for the reduction of NO with H2 at a relatively low temperature. The single dispersion of precious metal atoms was confirmed by in situ EXAFS, evidenced by the lack of metal-metal bonds formed before and during catalysis. The single dispersion of Pt on Co3O4 was further supported by high-angle annular dark-field (HAADF)-STEM, showing separately anchored Pt atoms on Co3O4 nanorods. Ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) and in-situ EXAFS were used to track the surface chemistry and structure of catalysts under reaction conditions. In situ characterizations showed that the active sites are Rh1Con, PtCon and PdCon nanoclusters singly dispersed in the surface layer of Co3O4 nanorods restructured from Rh1/Co3O4, Pt1/Co3O4 and Pd1/Co3O4 in the mixture of reactant gases up to 300C during catalysis, respectively, which are responsible for the high activity and selectivity in the temperature range of 150-300C. This study shows that in situ studies significantly assist in understanding of catalytic performances and identification of new catalytic active sites, thus a direct correlation of catalytic performance and the corresponding surface chemistry and structure could be established.

Catalysis and in situ studies of singly anchored Rh, Pt, and Pd atoms on Co3O4 in reduction of NO with H2

248th National Meeting (2014)

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