Three-dimensional hierarchical nanosheets based spherical bismuth metal-organic frameworks: Controllable synthesis and high performance for supercapacitor

Metal-organic frameworks (MOFs) are considered as promising electrode materials in energy storage applications because of tunable chemical composition, large internal pore volume and high specific surface area. In this work, Bi-MOF materials with different molar ratios of Bi3+/benzene-1,3,5-tricarboxylic acid (H3BTC) are successfully prepared by solvothermal method. When the molar ratio of Bi3+/H3BTC is adjusted to 2:1, three-dimensional hierarchical Bi-MOF microspheres composed of many interconnected thin nanosheets are perfectly obtained. As-prepared Bi-MOF displays favorable specific surface area (69.5 m2 g−1) and pore size distribution (mean pore size of 6.43 nm), which provides abundant reactive electroactive centers, thereby exhibiting outstanding electrochemical performance. As-prepared Bi-MOF based electrode demonstrates a specific capacity of up to 896.1 C g−1 at 0.5 A g−1, and still possesses a capacity retention rate of 80.2 % from 0.5 A g−1 to 5.0 A g−1. At the same time, at 2.0 A g−1, it has a retention rate of 71.2 % even after 2000 cycles. The assembled BM-2//activated carbon device exhibits high energy density of 33.7 Wh kg−1 at power density of 1699.2 W kg−1. In addition, the device has capacity retention of 79.5 % after 1000 cycle at 5 A g−1. The results fully prove that as-prepared Bi-MOF based electrode possesses satisfactory electrochemical behavior, which provides a valuable reference for research and application of Bi-based materials in the field of supercapacitors.