Synthesis of Two New Polyoxometalate-Based Organic Complexes from 2D to 3D Structures for Improving Supercapacitor Performance†

Abstract

As an emerging energy-storage technology, research on supercapacitors is vital for advancing new energy applications, which rely on the development of electrode materials with superior properties. In this study, two novel polyoxometalate-based organic complexes (POMOCs), Ag4(imbta)4(PMoⅤMoⅥ11O40) (PMo12-Ag-imbta, 1) (imbta = 1-imidazole-1-methylene-1H-benzotriazole) and Ag4(pybta)4(PMoⅤMoⅥ11O40)(PMo12-Ag-pybta, 2) (pybta = 1-pyridine-3-methylene-1H-benzotriazole), were synthesized via a hydrothermal method utilizing Ag+, imbta/pybta and [PMo12O40]3−, respectively. In 1, Ag+, imbta, and [PMo12O40]3− form 2D layers via coordination bonds. At the same time, Ag+ forms a 1D chain with [PMo12O40]3−. In 2, Ag+ and pybta form four separate Ag-pybta spiral chains. In addition, the coordination interaction between Ag+ and [PMo12O40]3− not only induces the construction of the Ag-PMo12 2D network that promotes electron transport in 2, but also facilitates the development of the 3D structure characterized by the four-helix winding. Meanwhile, there are great many holes in 2, which are conducive to ion transport. Therefore, in a three-electrode system, 2-GCE exhibited higher capacitive performance (668 F·g−1 at 1 A·g−1) than 1-GCE (420 F·g−1 at 1 A·g−1), and displayed remarkable cycling stability (91.4% after 1000 cycles), moreover, its specific capacitance at 5 A·g−1 is four times of PMo12. This study contributes to the development and design of new crystalline electrode materials.