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Single-Crystal Model of Highly Efficient Water-Splitting Photocatalysts: A KTaO3 Wafer Doped with Calcium Cations
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-02-03 , DOI: 10.1021/acs.chemmater.9b04094
Tomoya Fujiwara 1 , Akira Sasahara 1 , Naohisa Happo 2 , Koji Kimura 3 , Kouichi Hayashi 3, 4 , Hiroshi Onishi 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-02-03 , DOI: 10.1021/acs.chemmater.9b04094
Tomoya Fujiwara 1 , Akira Sasahara 1 , Naohisa Happo 2 , Koji Kimura 3 , Kouichi Hayashi 3, 4 , Hiroshi Onishi 1
Affiliation
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Alkali tantalates, NaTaO3 and KTaO3, are known as highly efficient semiconductor photocatalysts for the overall water-splitting reaction when properly doped with foreign metal cations. Characterizing surface reaction sites is needed for further development. In this study, (001)-oriented KTaO3 wafers were doped with Ca cations thorough a solid-state reaction to provide platforms for surface science studies. X-ray diffraction showed a Ca-rich perovskite-structured surface layer that covers the Ca-poor or pristine KTaO3 substrate. The lattice of the surface layer was contracted and rotated relative to the substrate lattice. The heteroepitaxial junction of the surface layer on the substrate mimicked the core–shell structure that is found in real photocatalyst particles. Nanometer-scale islands spontaneously appeared on the surface to correct the lattice mismatch across the surface–substrate junction. X-ray fluorescence holography was applied to determine the local, atom-scale structure around Ca cations in the host lattice. Atom distributions reconstructed from Ca Kβ fluorescence holograms suggested that K and Ta cations were simultaneously exchanged with Ca cations. Local lattice deformation was quantitatively deduced around the Ca cations occupying the two different sites. The major features of real photocatalysts—heteroepitaxial surface–bulk junctions, surface restructuring to correct lattice mismatches, and simultaneous cation exchange—were reproduced in the doped wafers. The ability of X-ray fluorescence holography to determine a local structure around doping cations was also demonstrated.
中文翻译：
高效水分解光催化剂的单晶模型：掺杂钙阳离子的KTaO 3晶片
当适当地掺入外来金属阳离子时，碱金属钽酸盐NaTaO 3和KTaO 3被认为是用于整个水分解反应的高效半导体光催化剂。表征表面反应位点是进一步开发所必需的。在这项研究中，通过固态反应将（001）取向的KTaO 3晶片掺杂了Ca阳离子，从而为表面科学研究提供了平台。X射线衍射显示富含钙的钙钛矿结构表面层覆盖了贫钙或原始的KTaO 3基质。表面层的晶格收缩并相对于基板晶格旋转。基底表面层的异质外延结模仿了在真正的光催化剂颗粒中发现的核-壳结构。纳米尺度的岛会自发出现在表面上，以纠正整个表面-基底连接处的晶格失配。应用X射线荧光全息术确定基质晶格中Ca阳离子周围的局部原子尺度结构。从CaKβ荧光全息图重建的原子分布表明，K和Ta阳离子同时与Ca阳离子交换。定量推导了占据两个不同位置的Ca阳离子周围的局部晶格变形。真正的光催化剂的主要特征-外延表面-本体连接，在掺杂晶圆中复制了表面结构以纠正晶格失配，并同时进行阳离子交换。还证明了X射线荧光全息术确定掺杂阳离子周围的局部结构的能力。
更新日期：2020-02-04
中文翻译：
高效水分解光催化剂的单晶模型：掺杂钙阳离子的KTaO 3晶片
当适当地掺入外来金属阳离子时，碱金属钽酸盐NaTaO 3和KTaO 3被认为是用于整个水分解反应的高效半导体光催化剂。表征表面反应位点是进一步开发所必需的。在这项研究中，通过固态反应将（001）取向的KTaO 3晶片掺杂了Ca阳离子，从而为表面科学研究提供了平台。X射线衍射显示富含钙的钙钛矿结构表面层覆盖了贫钙或原始的KTaO 3基质。表面层的晶格收缩并相对于基板晶格旋转。基底表面层的异质外延结模仿了在真正的光催化剂颗粒中发现的核-壳结构。纳米尺度的岛会自发出现在表面上，以纠正整个表面-基底连接处的晶格失配。应用X射线荧光全息术确定基质晶格中Ca阳离子周围的局部原子尺度结构。从CaKβ荧光全息图重建的原子分布表明，K和Ta阳离子同时与Ca阳离子交换。定量推导了占据两个不同位置的Ca阳离子周围的局部晶格变形。真正的光催化剂的主要特征-外延表面-本体连接，在掺杂晶圆中复制了表面结构以纠正晶格失配，并同时进行阳离子交换。还证明了X射线荧光全息术确定掺杂阳离子周围的局部结构的能力。
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