Effect of ceria surface facet on stability and reactivity of isolated platinum atoms
Effect of ceria surface facet on stability and reactivity of isolated platinum atoms
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DOI：
10.1007/s12274-022-4251-4
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发表时间：
2022-05
期刊：
影响因子：
9.9
通讯作者：
Bochuan Song;Shuxin Si;Asiye Soleymani;Y. Xin;Helena Hagelin-Weaver
中科院分区：
文献类型：
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作者：
Bochuan Song;Shuxin Si;Asiye Soleymani;Y. Xin;Helena Hagelin-Weaver
明确的表面结构和均匀性是探索多相催化剂结构-活性关系的关键因素。采用改进的原子层沉积法和三种定义明确的CeO 2纳米形状（八面体与（111）面，立方体暴露（100）面，棒与（100）和（110）面终端），用于合成超低负载Pt/CeO 2催化剂，并允许在还原条件下研究CeO 2表面小面对孤立Pt物种的影响。温和的还原温度（150 °C）还原了存在于二氧化铈载体表面上的初始铂离子，但保留了所有二氧化铈表面刻面上的孤立的Pt原子。相比之下，350 °C的还原温度揭示了初始单个Pt原子与各种二氧化铈表面刻面之间非常不同的相互作用，导致三种二氧化铈形状上不同且不均匀的Pt系综。为了分离面依赖的Pt-CeO 2相互作用并避免Pt物种之间的变化，在150 °C下还原后的Pt 1/CeO 2催化剂经受CO氧化条件。在CeO 2八面体和立方体上孤立的Pt原子在CO氧化反应中的活性较低，与CeO 2棒上的Pt相比。在CeO 2八面体上的Pt的情况下，这是由于强烈结合的CO阻断活性位点与稳定的CeO 2（111）表面一起限制了来自载体的氧供应。在CeO 2立方体上，一些Pt不能用于反应，并且CO强烈地结合在可用的Pt物种上。此外，负载在CeO 2立方体上的Pt催化剂不稳定，随着时间的推移。在这些条件下，CeO 2棒上孤立的Pt原子的活性要高得多，这是由于Pt-CO键强度较弱，并且由于氧空位形成的能量较低，从棒的富缺陷（110）表面更容易反向氧溢出。该CeO 2表面。负载在CeO 2棒上的Pt也随着时间的推移而非常稳定。这项工作表明了使用超低负载的活性金属和定义明确的氧化物支持物来隔离单个金属原子和氧化物支持物之间的相互作用，并确定氧化物支持物表面刻面在原子水平上对活性金属的影响的重要性。
Well-defined surface structures and uniformity are key factors in exploring structure-activity relationships in heterogeneous catalysts. A modified atomic layer deposition method and three well-defined CeO2nanoshapes, octahedra with (111) surfaces, cubes exposing (100) facets, and rods with (100) and (110) surface facet terminations, were utilized to synthesize ultra-low loading Pt/CeO2catalysts and allow investigations on the influence of ceria surface facet on isolated Pt species under reducing conditions. A mild reduction temperature (150 °C) reduces the initial platinum ions present on the surfaces of the ceria support but preserves the isolated Pt atoms on all ceria surface facets. In contrast, a reduction temperature of 350 °C, reveals very different interactions between the initial single Pt atoms and the various ceria surface facets, leading to dissimilar and nonuniform Pt ensembles on the three ceria shapes. To isolate facet dependent Pt-CeO2interactions and avoid variations between Pt species, the Pt1/CeO2catalysts after reduction at 150 °C were subjected to CO oxidation conditions. The isolated Pt atoms on the CeO2octahedra and cubes are less active in the CO oxidation reaction, compared with Pt on CeO2rods. In the case of Pt on the CeO2octahedra this is due to strongly bound CO blocking active sites together with a stable CeO2(111) surface limiting the oxygen supply from the support. On the CeO2cubes, some Pt is not available for reaction and CO is bound strongly on the available Pt species. In addition, the Pt catalysts supported on the CeO2cubes are not stable with time on stream. The isolated Pt atoms on the CeO2rods are considerably more active under these conditions and this is due to a weaker Pt-CO bond strength and more facile reverse oxygen spillover from the defect-rich (110) surfaces of the rods due to the lower energy of oxygen vacancy formation on this CeO2surface. The Pt supported on the CeO2rods is also remarkably stable with time on stream. This work demonstrates the importance of using ultra-low loadings of active metal and well-defined oxide supports to isolate interactions between single metal atoms and oxide supports and determine the effects of the oxide support surface facet on the active metal at the atomic level.