Conjugated Polyelectrolyte/Bacteria Living Composites in Carbon Paper for Biocurrent Generation

Abstract

Successful practical implementation of bioelectrochemical systems (BES)requires developing affordable electrode structures that promote efficient electrical communication with microbes. Recent efforts have centered on immobilizing bacteria with organic semiconducting polymers on electrodes via electrochemical methods. This approach creates a fixed biocomposite that takes advantage of the increased electrode's electroactive surface area (EASA). Here, it is demonstrated that a biocomposite comprising the water-soluble conjugated polyelectrolyte CPE-K and electrogenic Shewanella oneidensis MR-1 can self-assemble with carbon paper electrodes, thereby increasing its biocurrent extraction by ≈6-fold over control biofilms. A ≈1.5-fold increment in biocurrent extraction is obtained for the biocomposite on carbon paper relative to the biocurrent extracted from gold-coated counterparts. Electrochemical characterization revealed that the biocomposite stabilized with the carbon paper more quickly than atop flat gold electrodes. Cross-sectional images show that the biocomposite infiltrates inhomogeneously into the porous carbon structure. Despite an incomplete penetration, the biocomposite can take advantage of the large EASA of the electrode via long-range electron transport. These results show that previous success on gold electrode platforms can be improved when using more commercially viable and easily manipulated electrode materials.

Increasing the molecular weight of conjugated polyelectrolytes improves the electrochemical stability of their pseudocapacitor gels

“…This particular feature unlocks a niche dual-mode function within the CPE hydrogels, making them capable of switching between biocurrent generation and electrochemical energy storage by utilizing an external stimulus, namely the addition or removal of Mg 2+ . 19,20 Consequently, these properties open up opportunities for devising the next generation of multi-functional pseudocapacitive devices that go beyond high energy density and power density. 11 Poly[2,6-(4,4-bis-potassium butanylsulfonate-4H-cyclopenta-[2,1-b;3,4-b ′ ]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (CPE-K, see Fig.…”

“…1) is a self p-doped CPE that forms a hydrogel through self-assembly via electrostatic and hydrophobic interactions once a critical concentration is reached. 14,17,[19][20][21] CPE-K hydrogels have reported specic capacitance values of up to 75 F g −1 , albeit with low cycling stabilities of 40% capacitance retention aer 1000 charge/discharge cycles. 15,19,20 Previous efforts to improve the cycling stability involve the incorporation of electrostatic interchain crosslinkers, such as multi-cationic 2D electrolytes and Mg 2+ ions.…”

“…14,17,[19][20][21] CPE-K hydrogels have reported specic capacitance values of up to 75 F g −1 , albeit with low cycling stabilities of 40% capacitance retention aer 1000 charge/discharge cycles. 15,19,20 Previous efforts to improve the cycling stability involve the incorporation of electrostatic interchain crosslinkers, such as multi-cationic 2D electrolytes and Mg 2+ ions. The resulting mechanically rigidied CPE-K hydrogels exhibit increased capacitance retention of $80% aer 1000 charge/discharge cycles.…”

Pseudocapacitive gels based on conjugated polyelectrolytes: thickness and ion diffusion limitations

“…1), a self-doped, p-type CPE that can self-assemble into a hydrogel with pseudocapacitive properties when dispersed in water. 2,9,[32][33][34][35] Of relevance is that the mechanical and electrochemical properties of CPE-K hydrogels can be tuned by the identity of the electrolyte solutions. 31,36,37 For example, improvements in capacitance and cycling stability were demonstrated by creating two-component CPE-K/2D-electrolyte gels with a thickness of 250 mm.…”

Enabling Electron Injection for Microbial Electrosynthesis with n‐Type Conjugated Polyelectrolytes

“…[18,19] Conjugated polyelectrolytes (CPEs) can be designed to be water-soluble and thereby offer opportunities for in situ integration with bacteria in aqueous media. [20][21][22] A p-type CPE capable of self-assembly into a 3D conductive matrix with S. oneidensis MR-1 was recently reported. [21] The π-conjugated backbone undergoes facile redox cycling-electrochemical doping (oxidation) by the electrode and de-doping by S. oneidensis MR-1.…”