Keggin-Type Vanadotungstate Nanocluster-Anchored Polypyrrole Nanotubes for Enhanced Capacitance Performances

Polypyrrole nanotubes (PNTs) have excellent electrical conductivity, a high specific surface area (SSA), and certain mechanical strength and are good substrate materials for composite polyoxometalates. In this work, Keggin-type vanadotungstate (AgVW 12 ) was uniformly dispersed on PNTs to yield a binary composite AgVW 12 @PNTs by the solvothermal method. This composite demonstrated a higher specific capacitance ( C s of 1115.7 F g –1 at 2 A g –1 ), a better rate performance ( C s of 719.7 F g –1 at 15 A g –1 ), smaller electrochemical impedance, and longer cycle life than PNTs and AgVW 12 . The eminent electrochemical performance can be ascribed to the reversible multielectron transfer capability of AgVW 12, the excellent electrical conductivity of PNTs, and the structural features of hollow PNTs and the porous AgVW 12 . Kinetic calculations suggest that the pseudocapacitance contribution accounts for half of the charge storage process at 80 mV s –1, and this contribution increases with higher sweep rates. The AgVW 12 @PNTs-CC//AC-CC device displays a higher energy density of 43.28 W h kg –1 at a power density of 3250 W kg –1 and a long cycle life (91.45% capacitance retention after 10,000 cycles). These results surpass most reported ASC devices. The findings indicate that the anchoring of POMs on conductive polymers with structural advantages can overcome their own shortcomings and maximize their superior redox properties.