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Photocatalytic water oxidation by very small cobalt domains on a silica surface

机译：二氧化硅表面上非常小的钴结构域对光催化水的氧化

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摘要

Small domains of cobalt on silica (CoSBA) were prepared by the reaction of Co[N(SiMe_3)_2]_2 and SBA-15, resulting in a range of surface structures as the cobalt loading varied from 0.27 to 5.11 wt%. X-ray absorption spectroscopy (XAS) was employed to characterize these surface structures, which range from single-site cobalt atoms to small clusters of Co_3O_4. The CoSBA materials exhibit photochemical water oxidation catalysis, revealing distinct catalytic activities associated with characteristic types of surface structures that are dominant in particular concentration regimes. The catalytic turnover frequency for water oxidation of an isolated single-site cobalt atom (0.0143 s~(-1)) is much greater than that observed for a surface atom of a small cluster CO_3O_4 on silica (0.0006 s~(-1)). The CoSBA catalysts were recyclable for more than seven catalytic cycles (＞200 turnovers) with additional sacrificial oxidant, and no leaching of cobalt was observed. Post-catalytic analysis of CoSBA by XAS revealed that the cobalt atoms were partially oxidized to Co~(3+), without exhibiting significant surface migration and aggregation of cobalt atoms.
机译：通过Co [N（SiMe_3）_2] _2和SBA-15的反应制备了二氧化硅上的小畴（CoSBA），随着钴负载量从0.27到5.11 wt％的变化，形成了一系列表面结构。 X射线吸收光谱法（XAS）用于表征这些表面结构，其范围从单中心钴原子到Co_3O_4的小簇。 CoSBA材料表现出光化学水氧化催化作用，显示出与特定浓度范围内占主导地位的表面结构的特征类型相关的独特催化活性。分离出的单中心钴原子的水氧化催化周转频率（0.0143 s〜（-1））远大于二氧化硅上小簇CO_3O_4的表面原子的氧化周转频率（0.0006 s〜（-1））。 。 CoSBA催化剂与其他牺牲氧化剂一起可循环使用七个以上的催化循环（> 200次转换），并且未观察到钴的浸出。 XAS对CoSBA的后催化分析表明，钴原子被部分氧化为Co〜（3+），而没有明显的表面迁移和钴原子聚集现象。

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  • 来源
    《Energy & environmental science》 |2013年第10期|3080-3087|共8页
  • 作者

    Hyun S. Ahn; Junko Yano; T. Don Tilley;

  • 作者单位

    Departments of Chemistry and Chemical Engineering, University of California at Berkeley, Berkeley, California 94720, USA,Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA;

    Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA;

    Departments of Chemistry and Chemical Engineering, University of California at Berkeley, Berkeley, California 94720, USA,Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA;

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