Multinuclear Transition Metal Sandwich-Type Polytungstate Derivatives for Enhanced Electrochemical Energy Storage and Bifunctional Electrocatalysis Performances

• Published in: Inorganic chemistry 2020-04, Vol.59 (7), p.5149-5160
• Main Authors: Ma, Xinyue, Yu, Kai, Yuan, Jie, Cui, Liping, Lv, Jinghua, Dai, Wenting, Zhou, Baibin
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c00382

Different transition metal (TM) units are introduced into a trivacant Keggin cluster to form three sandwich polytungstate derivatives, (H2en)­[{K­(H2O)0.5}2­{K2(H2O)3}­{Ni­(H2O)­(en)2}2­{Ni4(H2O)2­(PW9O34)2}] (1), [Cu6(Himi)6­{AsIIIW9O33}2]·5H2O (2), and (H2btp)4­[FeIII 2FeII 2­(H2O)2­(AsW9 O34)2]·4H2O (3) (en = ethanediamine; imi = imidazole; btp = 1,3-bis­(1, 2, 4-triazol-1-yl) propane). Compound 1 is a 2,3,8-connected 3D network with {43}2{46·66·83·612·8}­{6}2 topology based on bisupported tetra-Ni sandwich phosphotungstate and two kinds of potassium connection units. Compound 2 is a dense 12-connected 3D supramolecular network with {324·436·56} topology based on hexa-Cu­(imi) sandwiched arsenotungstate. Compound 3 represents the first mixed valence tetra-Fe substituted sandwich arsenotungstate assembly. Compounds 1–3 show enhanced supercapacitor performance (618.2, 603.4, and 504.6 F·g–1 at a current density of 2.4 A·g–1 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 1 and 3 exhibit dual-functional electrocatalytic behaviors in the reduction of iodate and the oxidation of dopamine for introduction of {Ni4} and {Fe4} units.