Noncrystalline Titanium Oxide Catalysts for Electrochemical Oxygen Reduction Reactions
Noncrystalline Titanium Oxide Catalysts for Electrochemical Oxygen Reduction Reactions
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DOI：
10.1021/acsomega.7b00811
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发表时间：
2017-08
期刊：
影响因子：
4.1
通讯作者：
Satoshi Tominaka;A. Ishihara;T. Nagai;K. Ota
中科院分区：
文献类型：
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作者：
Satoshi Tominaka;A. Ishihara;T. Nagai;K. Ota
钛氧化物晶体广泛应用于各种领域，但其结构转变过程中形成的非晶中间体的官能团的研究很少。我们测量了不同热处理时间的氧化钛纳米颗粒的氧还原反应活性，发现在处理的某一时刻活性突然增加。利用高分辨率透射电子显微镜和x射线光电子能谱分析了它们的结构，并确定活性的突然增加对应于结构从还原的蛭石型层状钛酸盐转变为由brookite类TiO6八面体键域组成的无序结构。进一步的处理将这些类似brookite的区域转变为另一个阶段，具有更多的边缘共享位点，如钛型立方结构。这一发现将定位非晶，无序结构作为催化活性的可能起源，尽管纳米晶金红石颗粒也可能被认为是起源。
Titanium oxides crystals are widely used in a variety of fields, but little has been reported on the functionalities of noncrystalline intermediates formed in their structural transformation. We measured the oxygen reduction reaction activity of titanium oxide nanoparticles heat-treated for a different time and found that the activity abruptly increased at a certain time of the treatment. We analyzed their structures by using X-ray pair distribution functions with the help of high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy and ascertained that the abrupt increase in the activity corresponded to a structural transformation from a reduced lepidocrocite-type layered titanate to a disordered structure consisting of domains of brookite-like TiO6 octahedral linkages. The further treatment transformed these brookite-like domains into another phase having more edge-sharing sites like the TiO-type cubic structure. This finding would position noncrystalline, disordered structure as a possible origin of the catalytic activity, though nanocrystalline rutile particles might be also considered as the origin.