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.