Superior performance hybrid (electrostatic double-layer and faradaic capacitor) polymer actuators incorporating noble metal oxides and carbon black

Abstract

The electrochemical and electromechanical properties of polymeric actuators prepared using iridium oxide (IrO2) or ruthenium oxide (RuO2)/carbon black (CB)/ionic liquid (IL) electrodes and formed without ultrasonication were compared with actuators prepared using solely CB or single-walled carbon nanotubes (SWCNTs) with an IL.The IrO2/CB/IL actuators surpassed the strain performance of the CB and SWCNT-only actuators. The electrode in these actuator systems appears to represent an electrochemical capacitor (EC) composed of an electrostatic double-layer (EDLC) and a faradaic capacitor (FC), the latter of which primarily determines the capacitance. The CB functions largely by increasing the electroconductivity of the actuator. The functioning mechanisms of these actuators are different from those of CB and SWCNT-only actuators, which act solely as EDLC units. Both metal oxide (MO2) and CB are required to produce high strain values that surpass the performance of SWCNT polymer actuators and are suitable for practical applications.The actuator displacement response frequency dependence could not be simulated using an electrochemical kinetic model derived for CB/VGCF/IL and SWCNT-based actuators. This model appears to apply only to EDLC-based actuator systems and thus does not pertain to the present EDLC/FC system, in which the capacitance of the electrode comes primarily from the FC effect.