Architectural configurations of Pt-based bimetallic catalysts for CO oxidation

Bimetallic catalysts are widely used in many heterogeneous catalytic processes. With rational design of the surface structure of the bimetallic catalysts, improved catalytic performance can be achieved in comparison to their parent metals. In the bimetallic catalytic systems, three typical surface architectures can be constructed, including alloy, core-shell, and mixture of monometallic particles.[1] Furthermore, the chemical state of one of the two metals could be in either metallic or oxidized, which depends on the reaction atmosphere.[2-3] It has been demonstrated that the architectural configuration of the bimetallic catalysts is critical to their catalytic performance. Here, Pt-based bimetallic catalysts were applied for CO oxidation. In Pt-Fe systems, we demonstrate that the nanostructured ferrous oxides (FeO) grown on Pt present the best reactivity to the CO oxidation among various Fe-Pt(111) surface structures. Using surface science measurements and density functional calculations, we show that the interface confinement effect can be attributed to the stabilization of the monolayer-dispersed ferrous oxide nanoislands and coordinatively unsaturated ferrous (CUF) sites at the edges of the FeO nanoislands by taking advantage of strong adhesion between the nanostructured oxides and the metal substrates. The CUF sites together with the metal supports are active for O2 activation, and the structural ensemble was highly efficient for CO oxidation using both model systems and practical supported catalysts.[4] The interface confinement effect could be extended to other oxide-metal systems as well. In Pt-Ni systems, we observe the formation of monolayer-dispersed NiO nanoislands on Pt(111) and the interface-confined coordinatively unsaturated Ni atoms. The NiO/Pt(111) is highly active for CO oxidation.[5] References: [1] Yunxi Yao, Qiang Fu, Zhen Zhang, Hui Zhang, Teng Ma, Dali Tan, Xinhe Bao, “Structure control of Pt-Sn bimetallic catalysts supported on highly orientated pyrolytic graphite (HOPG)”, Applied Surface Science 254 (2008) 3808-3812. [2] Teng Ma, Qiang Fu, Haiyan Su, Hongyang Liu, Yi Cui, Zhen Wang, Rentao Mu, Weixue Li, Xinhe Bao, “Reversible structural modulation of Fe-Pt bimetallic surface and its effect on reactivity”, ChemPhysChem 10 (2009) 1013-1016. [3] Rentao Mu, Qiang Fu, Hongyang Liu, Dali Tan, Runsheng Zhai, and Xinhe Bao, “Reversible surface structural changes in Pt-based bimetallic nanoparticles during oxidation and reduction cycles”, Applied Surface Science, 255 (2009) 7296-7301. [4] Qiang Fu, Weixue Li, Yunxi Yao, Hongyang Liu, Haiyan Su, Ding Ma, Xiangkui Gu, Limin Chen, Zhen Wang, Hui Zhang, Bing Wang, Xinhe Bao, “Interface confined ferrous sites for catalytic oxidation”, Science 328 (2010) 1141-1144. [5] Rentao Mu, Qiang Fu, Hong Xu, Hui Zhang, Dali Tan, Xinhe Bao, “Architecture of Pt-Ni bimetallic catalysts for CO oxidation: from model systems to real catalysts”, To be submitted.Bimetallic catalysts are widely used in many heterogeneous catalytic processes. With rational design of the surface structure of the bimetallic catalysts, improved catalytic performance can be achieved in comparison to their parent metals. In the bimetallic catalytic systems, three typical surface architectures can be constructed, including alloy, core-shell, and mixture of monometallic particles.[1] Furthermore, the chemical state of one of the two metals could be in either metallic or oxidized, which depends on the reaction atmosphere.[2-3] It has been demonstrated that the architectural configuration of the bimetallic catalysts is critical to their catalytic performance. Here, Pt-based bimetallic catalysts were applied for CO oxidation. In Pt-Fe systems, we demonstrate that the nanostructured ferrous oxides (FeO) grown on Pt present the best reactivity to the CO oxidation among various Fe-Pt(111) surface structures. Using surface science measurements and density functional calculations, we show that the interface confinement effect can be attributed to the stabilization of the monolayer-dispersed ferrous oxide nanoislands and coordinatively unsaturated ferrous (CUF) sites at the edges of the FeO nanoislands by taking advantage of strong adhesion between the nanostructured oxides and the metal substrates. The CUF sites together with the metal supports are active for O2 activation, and the structural ensemble was highly efficient for CO oxidation using both model systems and practical supported catalysts.[4] The interface confinement effect could be extended to other oxide-metal systems as well. In Pt-Ni systems, we observe the formation of monolayer-dispersed NiO nanoislands on Pt(111) and the interface-confined coordinatively unsaturated Ni atoms. The NiO/Pt(111) is highly active for CO oxidation.[5] References: [1] Yunxi Yao, Qiang Fu, Zhen Zhang, Hui Zhang, Teng Ma, Dali Tan, Xinhe Bao, “Structure control of Pt-Sn bimetallic catalysts supported on highly orientated pyrolytic graphite (HOPG)”, Applied Surface Science 254 (2008) 3808-3812. [2] Teng Ma, Qiang Fu, Haiyan Su, Hongyang Liu, Yi Cui, Zhen Wang, Rentao Mu, Weixue Li, Xinhe Bao, “Reversible structural modulation of Fe-Pt bimetallic surface and its effect on reactivity”, ChemPhysChem 10 (2009) 1013-1016. [3] Rentao Mu, Qiang Fu, Hongyang Liu, Dali Tan, Runsheng Zhai, and Xinhe Bao, “Reversible surface structural changes in Pt-based bimetallic nanoparticles during oxidation and reduction cycles”, Applied Surface Science, 255 (2009) 7296-7301. [4] Qiang Fu, Weixue Li, Yunxi Yao, Hongyang Liu, Haiyan Su, Ding Ma, Xiangkui Gu, Limin Chen, Zhen Wang, Hui Zhang, Bing Wang, Xinhe Bao, “Interface confined ferrous sites for catalytic oxidation”, Science 328 (2010) 1141-1144. [5] Rentao Mu, Qiang Fu, Hong Xu, Hui Zhang, Dali Tan, Xinhe Bao, “Architecture of Pt-Ni bimetallic catalysts for CO oxidation: from model systems to real catalysts”, To be submitted