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- Liang, Zuozhong, et al.
(author)
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Novel insight into the epitaxial growth mechanism of six-fold symmetrical beta-Co(OH)(2)/Co(OH)F hierarchical hexagrams and their water oxidation activity
- 2018
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In: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 271, s. 526-536
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Journal article (peer-reviewed)abstract
- The six-fold symmetry widely presents in both natural and artificial architectures. Understanding the growth mechanism of six-fold symmetrical materials is of fundamental interest and significance. Herein, we report the formation process of beta-Co(OH)(2)/Co(OH)F hierarchical hexagrams with a six-fold symmetrical arrangement. Our results demonstrate that hexagonal beta-Co(OH)(2) plates are first formed under the reaction condition. These hexagonal plates then act as templates for the growth of Co(OH)F nanorods. The intermediate material is therefore composed of plate-like beta-Co(OH)(2) hexagonal cores appended with six rod-like Co(OH)F branches, giving the beta-Co(OH)(2)/Co(OH)F hybrid. After prolonged reaction, the beta-Co(OH)(2) hexagons can be completely converted, leading to authentic six-branched Co(OH)F nanorods as the final product. Consequently, for both intermediate and final materials, the Co(OH)F nanorods are arranged with a six-fold symmetry. Importantly, these Co(OH)F nanorods grow along beta-Co(OH)(2) hexagon edges as lateral branches instead of perpendicular to hexagons. This uncommon epitaxial growth mechanism is considered to be a result of the matching between the b-axis of Co(OH)F crystals and the a-axis of beta-Co(OH)(2) crystals, which is beneficial for the electrocatalysis. The beta-Co(OH)(2)/Co(OH)F hierarchical hexagrams show enhanced water oxidation activity compared to the pure beta-Co(OH)(2) and Co(OH)F.
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