Nanostructured Alkaline-Cation-Containing-MnO2 for Photocatalytic Water Oxidation
Nanostructured Alkaline-Cation-Containing-MnO2 for Photocatalytic Water Oxidation
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DOI：
10.1002/adfm.201202141
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发表时间：
2013-02-18
影响因子：
19
通讯作者：
Jiao, Feng
中科院分区：
文献类型：
--
作者：
Boppana, Venkata Bharat Ram;Yusuf, Seif;Jiao, Feng
从水中析出氧气是太阳能燃料生产的关键反应之一。在这里，合成了两种纳米结构的含 K-MnO2：K--MnO2 纳米片和 K--MnO2 纳米颗粒，两者在可见光驱动的水氧化中表现出高催化活性。首先通过质子离子交换用 H+ 离子取代 -MnO2 结构中的 K+ 离子来探索碱性阳离子在析氧中的作用。具有相似形态和晶体结构的H--MnO2催化剂表现出每个表面位点的活性比K--MnO2低大约一个数量级，尽管两种纳米结构H--MnO2催化剂具有大得多的BrunauerEmmettTeller (BET)表面积。每个表面 Mn 原子如此低的周转频率 (TOF) 可能是由于 Ru2+(bpy)3 敏化剂太大而无法进入质子交换过程中产生的额外表面积。此外，所制备的具有相同晶体结构的含Na-MnO2材料表现出与含K-MnO2相似的TOF，这表明碱性阳离子并不直接参与催化水氧化，而是稳定了-MnO2的层状结构。
Oxygen evolution from water is one of the key reactions for solar fuel production. Here, two nanostructured K-containing -MnO2 are synthesized: K--MnO2 nanosheets and K--MnO2 nanoparticles, both of which exhibit high catalytic activity in visible-light-driven water oxidation. The role of alkaline cations in oxygen evolution is first explored by replacing the K+ ions in the -MnO2 structure with H+ ions through proton ion exchange. H--MnO2 catalysts with a similar morphology and crystal structure exhibit activities per surface site approximately one order of magnitude lower than that of K--MnO2, although both nanostructured H--MnO2 catalysts have much larger BrunauerEmmettTeller (BET) surface areas. Such a low turnover frequency (TOF) per surface Mn atom might be due to the fact that the Ru2+(bpy)3 sensitizer is too large to access the additional surface area created during proton exchange. Also, a prepared Na-containing -MnO2 material with an identical crystal structure exhibits a TOF similar to that of the K-containing -MnO2, suggesting that the alkaline cations are not directly involved in catalytic water oxidation, but instead stabilize the layered structure of the -MnO2.