Construction of Sb-capped Dawson-type POM derivatives for high-performance asymmetric supercapacitors
Chuanwei Zhou, Xi-Yue Wang, Zhan-Peng Duan, Tong-Ze Hu, Hao-Tong Wang, Si-Qin Gong, Shu-Yun Shi, Xianyu Chu
Abstract
Modified polyoxometalate (POM) derivatives are promising pseudocapacitive active materials due to their abundant active sites and high redox capacity. Here, we constructed four antimony-capped Dawson-type molybdate clusters with high specific capacitance properties for the first time through the traditional hydrothermal method, formulated as [Cu(im) 2 ] 4 {[C u 2 ( im ) 2 ] 1/2 (im)}[H 3/2 (S b 1 S b 1/3 S b 2/3 )P 2 M o 7 V M o 11 VI O 62 ]·H 2 O (1); [Cu(bzim) 2 ][H 4 S b 1 S b 1/2 × 2 P 2 M o 7 V M o 11 VI O 62 ]·(bzim) 4 ·2H 3 O (2); [(bzim) 4 (NO 3 ) 1/2 ][H 5/2 S b 2 P 2 M o 3 V M o 15 VI O 62 ]·H 3 O (3); [(bzim) 4 (bzim) 1/3 ][HS b 2 P 2 M o 2 V M o 16 VI O 62 ]·H 3 O (4) (im= imidazole, bzim= benzimidazole). The compounds 1–4 all contain Sb-capped Dawson type {P 2 Mo 18 } anions with 3D supramolecular channel structures. Especially, compound 1 expresses a porous 2D metal-organic layer formed by Cu-ims transition metal complexes (TMCs) through the Cu-O interaction, and Sb capped-polyanions are exactly filled in the holes. Importantly, compound 1 exhibits a higher specific capacitance (C s ) value of 1401.75 F g −1 than the other three compounds (1141 F g −1 , 1027.3 F g −1 , and 978.25 F g −1 ) at a current density of 1.4 A g −1 . In addition, the asymmetric supercapacitor Sb-P 2 Mo 18 //AC assembled with compound 1 and active carbon exhibits good cycling stability (89.14 %), and possesses an excellent energy density of 17.78 W h Kg −1 , which could be attributed to the high redox capacity and excellent electronic conductivity. The experimental results demonstrate the feasibility of the synthesis strategy and pave the way for exploring novel high-performance polyoxometalate-based pseudocapacitive materials.