Polyoxometalate-Based Metal-Organic Framework/Polypyrrole Composites toward Enhanced Supercapacitor Performance

Supercapacitors are energy storage equipment that have attracted particular attention owing to its wide operating temperature range, high-power density, and small size, whereas the limited energy density has always been a main obstacle in many applications. Composite materials have a forward-looking application value in the manufacture of innovative supercapacitors due to the synergistic effect between various components. We propose a plain oxidative polymerization method to prepare the polyoxometalate-based metal-organic framework/polypyrrole composites (PW12@MIL-101/PPy-n, n represents the volumes of pyrrole) toward supercapacitor electrodes for the first time. PW12@MIL-101 possesses rich and fully accessible active sites as well as regular porosity provided by PW12 and MIL-101(Fe), respectively. PPy can effectively meliorate the conductivity of PW12@MIL-101 by accelerating the Faradaic process at the surface, and then facilitate electron/ion transfer between PW12@MIL-101 nanocrystallines. As a result, PW12@MIL-101/PPy-0.15 composite has a noticeably higher specific capacitance (1217 mF . cm(-2)), which is better than PW12@MIL-101 (158 mF . cm(-2)) and MIL-101 (117 mF . cm(-2)). Meanwhile, the relevant symmetric supercapacitor assembled with PW12@MIL-101/PPy-0.15 displays a sizable energy density of 20.7 Wh/kg at a power density of 277.6 W/kg. About 83.7 % of the pristine capacitance is still reserved after 2000 consecutive charges and discharges.