Modifying the Surface of γ-Al2 O3 with Y2 Sn2 O7 Pyrochlore: Monolayer Dispersion Behaviour of Composite Oxides.

To investigate the dispersion behaviour of composite oxides on supports, and to obtain better supports for Pd for CO oxidation, a series of Y2 Sn2 O7 /Al2 O3 composite oxides with different Y2 Sn2 O7 loadings were prepared by a deposition-precipitation method. XRD and X-ray photoelectron spectroscopic extrapolation methods revealed that, similar to single-component metal oxides, composite oxides can also disperse spontaneously on support surfaces to form a monolayer with a certain capacity. The monolayer dispersion capacity/threshold for Y2 Sn2 O7 on the surface of γ-Al2 O3 is 0.109 mmol per 100 m2 γ-Al2 O3 , corresponding to 7.2 wt % Y2 Sn2 O7 loading. This is the first work to demonstrate monolayer dispersion of a composite oxide on a support. After combining Y2 Sn2 O7 with γ-Al2 O3 , active oxygen species can be introduced onto the catalyst surfaces. Thus, the interaction between Pd and the support is strengthened, the dispersion of Pd is improved in comparison with the single-component Y2 Sn2 O7 support, and a synergistic effect is induced between Pd and the composite support, which is beneficial to catalyst activity. By tuning the γ-Al2 O3 surface with different amounts of pyrochlore Y2 Sn2 O7 , CO oxidation activity on 1 % Pd/Y2 Sn2 O7 /Al2 O3 was improved. These findings may provide new insights into the design and preparation of effective supported noble metal catalysts with lower contents of noble metals.