Mechanoelectrochemistry of PPy(DBS) from correlated characterization of electrochemical response and extensional strain

Abstract

This paper investigates nanostructured morphology-dependent charge storage and coupled mechanical strain of polypyrrole membranes doped with dodecylbenzenesulfonate (PPy(DBS)). Nanoscale features introduced in PPy(DBS) using phospholipid vesicles as soft-templates create a uniform and long-range order to the polymer morphology, and lead to higher specific capacitance. It is widely stated that nanostructured architecture offer reduced mechanical loading at higher charge capacities, but metrics and methods to precisely quantify coupled localized strains do not exist. Towards this goal, we demonstrate the use of scanning electrochemical microscope with shear force imaging hardware (SECM-SF) to precisely measure charge storage function and volumetric strain simultaneously, and define two metrics--filling efficiency and chemomechanical coupling coefficient to compare nanostructured morphologies and thicknesses. For thin membranes (smaller charge densities), planar and vesicle-templated membranes have comparable mechanoelectrochemical response. For thick membranes (0.4 to 0.8 C cm(-2)), a 15% increase in charge storage is associated with 50% reduction in extensional strain. These results allow for the formulation of rules to design nanostructured PPy(DBS)-based actuators and energy storage devices.

Ionic redox transistor from pore-spanning PPy(DBS) membranes

“…29 For thickness (A E 4 0.15 C cm À2 ), it is observed from SEM images (see Fig. We demonstrate controlled ion transport across suspended PPy(DBS) for various thicknesses, cation concentrations, V m and V AC .…”

“…At smaller concentrations, below 200 mM, the amplification factor is relatively small, and it has a linear dependence between 200 mM and 1000 mM. 29,30 For thicker membranes (A E Z 0.4 C cm À2 ), amplification factor begins to decrease with increasing thickness for 100 mM Na + and V AC = AE100 mV. 3(C)) is due to asymmetric swelling of PPy(DBS) which minimizes ion transport.…”

Nanoscale polypyrrole sensors for near-field electrochemical measurements

“…The membrane appears as a small, three-dimensional, disk-like protrusion that is confined to the center of UME. Commonly observed characteristics of PPy(DBS), namely small "broccoli-floret" features are visible particularly along the periphery of the conducting polymer membrane [22]. The diameter of the PPy(DBS) film can be estimated from the SEM in Figure 4b to be almost 6 µm, which far exceeds the original diameter of the Pt-core (900 nm).…”

A structural model of ultra-microelectrodes for shear-force based scanning electrochemical microscopy

“…The quality of polishing and the diameter of the glass at the tip were characterized under an optical microscope (Omano OM36, USA). It must be noted that UMEs prepared through this process were devoid of any electroactive material (such as Pt/C) at the tip (as described in contemporary fabrication procedures (Mezour et al, 2011; Northcutt and Sundaresan, 2015; Venugopal et al, 2017)) to ensure a convergence criterion during finite element simulations and avoid electrochemical damage (such as recession and contamination of the Pt-core (Nioradze et al, 2013)) to the UME during z-approach to the substrate.…”

“…Following this, the UME was lowered in the z-direction to approach the base of an empty petri-dish at an arbitrary characteristic frequency which yielded a significant SF amplitude. The z-approach was automatically stopped when the SF amplitude dropped to 70% of the bulk SF value, thus indicating contact with the petri-dish (Northcutt and Sundaresan, 2015). Upon contact, the UME was excited at dither amplitude of 25 mV between 600 kHz - 700 kHz to produce a characteristic SF response different from that taken in bulk due to a change in boundary conditions from a fixed-free to a fixed-fixed cantilever (Northcutt et al, 2016).…”