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Multinuclear Transition Metal Sandwich-Type Polytungstate Derivatives for Enhanced Electrochemical Energy Storage and Bifunctional Electrocatalysis Performances
67
Citations
63
References
2020
Year
Different transition metal (TM) units are introduced into a trivacant Keggin cluster to form three sandwich polytungstate derivatives, (H<sub>2</sub>en)[{K(H<sub>2</sub>O)<sub>0.5</sub>}<sub>2</sub>{K<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub>}{Ni(H<sub>2</sub>O)(en)<sub>2</sub>}<sub>2</sub>{Ni<sub>4</sub>(H<sub>2</sub>O)<sub>2</sub>(PW<sub>9</sub>O<sub>34</sub>)<sub>2</sub>}] (<b>1</b>), [Cu<sub>6</sub>(Himi)<sub>6</sub>{As<sup>III</sup>W<sub>9</sub>O<sub>33</sub>}<sub>2</sub>]·5H<sub>2</sub>O (<b>2</b>), and (H<sub>2</sub>btp)<sub>4</sub>[Fe<sup>III</sup><sub>2</sub>Fe<sup>II</sup><sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(AsW<sub>9</sub> O<sub>34</sub>)<sub>2</sub>]·4H<sub>2</sub>O (<b>3</b>) (en = ethanediamine; imi = imidazole; btp = 1,3-bis(1, 2, 4-triazol-1-yl) propane). Compound <b>1</b> is a 2,3,8-connected 3D network with {4<sup>3</sup>}<sub>2</sub>{4<sup>6</sup>·6<sup>6</sup>·8<sup>3</sup>·6<sup>12</sup>·8}{6}<sub>2</sub> topology based on bisupported tetra-Ni sandwich phosphotungstate and two kinds of potassium connection units. Compound <b>2</b> is a dense 12-connected 3D supramolecular network with {3<sup>24</sup>·4<sup>36</sup>·5<sup>6</sup>} topology based on hexa-Cu(imi) sandwiched arsenotungstate. Compound <b>3</b> represents the first mixed valence tetra-Fe substituted sandwich arsenotungstate assembly. Compounds <b>1</b>-<b>3</b> show enhanced supercapacitor performance (618.2, 603.4, and 504.6 F·g<sup>-1</sup> at a current density of 2.4 A·g<sup>-1</sup> with 91.5%, 89.3%, and 87.8% of cycle efficiency after 5000 cycles, respectively) compared to their maternal polyoxometalates (POMs) and most reported POM-based electrode materials, which suggests that the introduction of multinuclear TM into vacant POMs is an effective method to improve the energy storage performance of POMs. In addition, compounds <b>1</b> and <b>3</b> exhibit dual-functional electrocatalytic behaviors in the reduction of iodate and the oxidation of dopamine for introduction of {Ni<sub>4</sub>} and {Fe<sub>4</sub>} units.
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