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Conjugated polymer hydrogels (CPHs) are emerging pseudocapacitive materials capable of forming redox-active hydrogels. Current efforts focus on increasing their areal capacitance (CAreal) and cycling stabilities by using binders tolerant to H2SO4-based electrolytes, while alternatives in more environmentally friendly electrolytes underperform due to low-capacity values. Herein, we demonstrate that it is possible to use conjugated polyelectrolyte (CPE), namely CPE-K, to create a single-component binder-free pseudocapacitive gel in environmentally friendly electrolytes (2 M: NaCl, MgCl2, and MgSO4), with CAreal 1.9 times larger than those reported for single-component binder-free CPHs. The resulting pseudocapacitive gel exhibited CAreal (523 mF cm−2 at 0.25 mA cm−2) scalable with its thickness in NaCl electrolytes, providing an attractive solution to improve the capacitance of devices while maintaining a minimal charge-collecting electrode surface footprint. In addition, the CPE-K gel demonstrates 86% capacitance retention after 100 000 cycles at 10 mA cm−2, which is higher than those reported for conventional state-of-the-art conjugated polymers. Electrochemical characterization revealed that CAreal at all cycling rates tested is proportional to dThk up to 750 μm, primarily due to facile ionic diffusion within the 3D conductive network of the gel. Thicker electrodes (dThk = 1250 μm) can be operated at a rate of 15 mA cm−2 with minimal capacity loss. These results demonstrate the potential applications of self-doped CPE gels in designing the next generation of multi-functional electrochemical energy storage and conversion technologies for targeting high energy and power density applications. [ABSTRACT FROM AUTHOR]

Interfacing bacteria as biocatalysts with an electrode provides the basis for emerging bioelectrochemical systems that enable sustainable energy interconversion between electrical and chemical energy. Electron transfer rates at the abiotic‐biotic interface are, however, often limited by poor electrical contacts and the intrinsically insulating cell membranes. Herein, we report the first example of an n‐type redox‐active conjugated oligoelectrolyte, namely COE‐NDI, which spontaneously intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. The incorporation of COE‐NDI into Shewanella oneidensis MR‐1 cells amplifies current uptake from the electrode by 4‐fold, resulting in the enhanced bio‐electroreduction of fumarate to succinate. Moreover, COE‐NDI can serve as a "protein prosthetic" to rescue current uptake in non‐electrogenic knockout mutants. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems hold the promise of enabling sustainable microbial‐mediated energy interconversion between electrical and chemical energy. Herein, it is demonstrated how a single conjugated polymer can be used to enhance bidirectional extracellular electron transfer through forming self‐assembled coatings on individual cells. Specifically, the n‐type conjugated polyelectrolyte p(cNDI‐gT2) exhibits a reduction potential window between −0.1 and −0.8 V (vs Ag/AgCl), thereby driving thermodynamically favored electron transfer in both directions across the abiotic‐biotic interface that involves the outer membrane cytochromes and flavins of Shewanella oneidensis MR‐1. Electrochemical tests show that injection from an external electrode into Shewanella oneidensis MR‐1 is enabled at negative potentials (−0.6 V), while electron extraction is possible at positive potentials (0.2 V). Relative to controls, the biohybrid shows a sixfold increase in biocurrent generation and a 35‐fold increase in current uptake for the bioelectrosynthesis of succinate from fumarate. This demonstrated abiotic‐biotic synergy provides new strategies for designing multifunctional biohybrids. [ABSTRACT FROM AUTHOR]

Conjugated polyelectrolyte (CPE) hydrogels synergize the electrical properties of redox-active polymers with the physical properties of hydrogels. Of particular relevance is their implementation as pseudocapacitors due to their high ionic conductivity, strong ionic–electronic coupling, and large electroactive surface area. To date, efforts to improve the cycling stability of such hydrogels are predominated by the use of additives – optimization of the CPE's intrinsic properties remains underexplored. Herein, the systematic increase in the molecular weight (MW) of a self-doped CPE, namely CPE-K, has been demonstrated as an effective strategy to enhance the cycling stability of the resulting hydrogel. At high MW, mechanically stronger hydrogels were obtained with a specific capacitance as high as 88 ± 4 F g−1 at 0.25 A g−1 and a cycling stability of 76% capacitance retention after 100 000 cycles at 2.5 A g−1. Furthermore, this strategy yields a wider working pseudocapacitive window, less internal resistance, and higher ionic conductivity within the 3D conductive network. We attribute the enhanced electrochemical performance to stronger inter-chain contacts for optimal morphological organization, as revealed by rheological measurements, resulting in stress-tolerant hydrogels with a higher degree of percolation within a 3D conductive network. These results position CPE-K hydrogels as a state-of-the-art organic material for long-term pseudocapacitive technologies and potentially for the next generation of multi-functional pseudocapacitive devices that go beyond high energy density and power density. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Power generation and charge storage devices are commonly uncoupled when it comes to the design of materials relevant for their fabrication. Here, it is demonstrated that the biotic–abiotic composite comprising the self‐doped conjugated polyelectrolyte CPE‐K and electrogenic bacteria Shewanella oneidensis MR‐1 can reversibly switch its function between electrical current generation in chronoamperometry mode (≈150 mA m−2) and electrochemical energy storage as a pseudocapacitor with a specific capacitance of up to 80 F g−1. Interconversion of desirable properties for the different functions is achieved by the simple addition and removal of Mg2+ in the bulk electrolyte. Potentiostatic, galvanostatic, and electrochemical impedance spectroscopy characterization, accompanied by imaging and cell viability tests, indicate that the modulation of properties is a result of reversible changes in CPE‐K macrostructures and in the number of living bacteria within the composite. The results show the possibility to realize an "on‐demand" switch between current generation and charge storage by one integrated "living" material. [ABSTRACT FROM AUTHOR]

Back Cover: An n-Type Conjugated Oligoelectrolyte Mimics Transmembrane Electron Transport Proteins for Enhanced Microbial Electrosynthesis (Angew. Keywords: Biocatalysis; Biohybrid; Conjugated Oligoelectrolyte; Energy Conversion; Microbial Electrosynthesis EN Biocatalysis Biohybrid Conjugated Oligoelectrolyte Energy Conversion Microbial Electrosynthesis 1 1 1 08/10/23 20230814 NES 230814 B Microbial electrosynthesis b is a sustainable strategy for electricity-driven chemical production. Biocatalysis, Biohybrid, Conjugated Oligoelectrolyte, Energy Conversion, Microbial Electrosynthesis. [Extracted from the article]

In their Communication (e202305189), Guillermo C. Bazan et al. designed an n-type redox-active conjugated oligoelectrolyte (COE) that intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. Biocatalysis, Biohybrid, Conjugated Oligoelectrolyte, Energy Conversion, Microbial Electrosynthesis Keywords: Biocatalysis; Biohybrid; Conjugated Oligoelectrolyte; Energy Conversion; Microbial Electrosynthesis EN Biocatalysis Biohybrid Conjugated Oligoelectrolyte Energy Conversion Microbial Electrosynthesis 1 1 1 08/09/23 20230814 NES 230814 B Microbial electrosynthesis b is a sustainable strategy for electricity-driven chemical production. [Extracted from the article]

Abstract: Polymorphism, the ability for a given material to adopt multiple crystalline packing states, is a powerful approach for investigating how changes in molecular packing influence charge transport within organic semiconductors. In this study, a new “thin film” polymorph of the high‐performance, p‐type small molecule N‐octyldiisopropylsilyl acetylene bistetracene (BT) is isolated and characterized. Structural changes in the BT films are monitored using static and in situ grazing‐incidence X‐ray diffraction. The diffraction data, combined with simulation and crystallographic refinement calculations, show the molecular packing of the “thin film” polymorph transforms from a slipped 1D π‐stacking motif to a highly oriented and crystalline film upon solvent vapor annealing with a 2D brick‐layer π‐stacking arrangement, similar to the so‐called “bulk” structure observed in single crystals. Charge transport is characterized as a function of vapor annealing, grain orientation, and temperature. Demonstrating that mobility increases by three orders of magnitude upon solvent vapor annealing and displays a differing temperature‐dependent mobility behavior. [ABSTRACT FROM AUTHOR]

We probe anaerobic respiration of bacteria in the presence of conjugated polyelectrolytes (CPEs). Three different CPEs were used to probe how structural variations impact biocurrent generation from Shewanella oneidensis MR-1. For the self-doped anionic CPE only, absorption spectroscopy shows that the addition of S. oneidensis MR-1 leads to the disappearance of the polaron (radical cation) band at >900 nm and an increase in the band at 735 nm due to the neutral species, consistent with electron transfer from microbe to polymer. Microbial three-electrode electrochemical cells (M3Cs) show an increase in the current generated by S. oneidensis MR-1 with addition of the self-doped CPE relative to other CPEs and controls. These experiments combined with in situ cyclic voltammetry suggest that the doped CPE facilitates electron transport to electrodes and reveal structure-function relationships relevant to developing materials for biotic/abiotic interfaces. [ABSTRACT FROM AUTHOR]

The high electrical conductivity and low dimensionality of graphene is essential for the development of novel lightweight bioanodes for new-generation energy technologies. However, the integration of graphene in biointerfaces presents a formidable challenge, especially because the surface energy of graphene is not compatible with living matter. Here we propose a sustainable chemical control method to reach the demanded surface hydrophilicity and conductivity of graphene nanowalls to form a lightweight, graphene-based, sponge bioanode. The few-nanometer–thick conductive graphene nanowalls create biocompatible hydrophilic microconfinements to harvest the biomass density of electrogenic Shewanella Oneidensis MR-1. The graphene-based bioanode shows a stable and rapid response with a steady-state biocurrent density of 135.35 mA m−2 realized within a few hours. Our novel and sustainable graphene-based material provides a revolutionary energy opportunity for the establishment of new energy-related graphene industries as well as facilitates many startups. A facile and chemical-free method was leveraged to produce the graphene-based bioanode. Balancing the hydrophilicity and conductivity of the graphene nanowalls was achieved by simply tuning its reduction temperature and was the first time, revealed to play an important role in the performance of the microbial electrode. A steady-state bio-current density of 135.35 mA m−2 was realized within a few hours and with long-term duration. [Display omitted] [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems (BESs) are emerging as a platform technology with great application potentials such as wastewater remediation and power generation. Materials for electrode/microorganism modification are being examined in order to improve the current production in BESs. Herein, we report that the current production increased almost one fold in single-chamber BES reactors, by adding a conjugated polyelectrolyte (CPE-K) in the growth medium to co-form the anodic biofilm with Geobacter sulfurreducens cells. The CPE-K treated BESs had a maximum current density as high as 12.3 ± 0.5 A/m2, with that of the controls being 6.2 ± 0.7 A/m2. Improved current production was sustained even after CPE-K was no longer added to the medium. It was demonstrated that increased current resulted from improvement of certain biofilm properties. Analysis using electrochemical impedance spectroscopy (EIS) showed that CPE-K addition decreased the charge transfer resistance at the cell/electrode interface and the diffusion resistance through the biofilm. Protein quantification showed increased biomass growth on the electrode surface, and confocal scanning microscopy images revealed enhanced biofilm permeability. These results demonstrated for the first time that conjugated polyelectrolytes could be used for G. sulfurreducens biofilm augmentation to achieve high electricity production through tuning the anodic biofilm in BESs. • Adding CPE-K increased maximum current densities of G. sulfurreducens by one-fold. • The increased current sustained even with no further addition of CPE-K. • The improved performance resulted from increased biomass growth. • Adding CPE-K decreased charge transfer resistance at the cell/electrode interface. • Addition of CPE-K lead to more permeable G. sulfurreducens biofilm structure. [ABSTRACT FROM AUTHOR]

Nanocomposites: Recent Advances in n-Type Thermoelectric Nanocomposites (Adv. Recent advances in n-type organic-inorganic thermoelectric nanocomposites (TENCs) based on carbon nanotubes and inorganic nanocrystals are reviewed by Lidong Chen, Guillermo C. Bazan. An outlook on further improvement is given, along with methods to enhance their ambient stability, towards the fabrication of flexible TE devices. [Extracted from the article]

Organic/inorganic thermoelectric nanocomposites (TENCs) have seized great attention because they integrate the advantages of inorganic (i.e., high electrical conductivity) and organic (i.e., low thermal conductivity and mechanical flexibility) components. Major barriers that obstruct the development of this field are the lack of n‐type TE materials and their relatively low performance, leaving the construction of TE devices difficult to realize. This review article is therefore focused on recent advances on n‐type TENCs that primarily comprise carbon nanotube (CNT) and inorganic nanocrystal (NC)‐based hybrids. CNT‐based n‐type TENCs are fabricated mainly by transforming the p‐type CNT to n‐type with organic dopants or by blending CNTs with n‐type semiconducting polymers. NC‐based n‐type TENCs are typically obtained by blending semiconductor nanocrystals or metallic nanostructures with polymers. Additionally, the fabrication and thermoelectric performance of 2D layered superlattice structures are also reviewed. Finally, an outlook of n‐type TENCs is given with a perspective for their possible future improvements. [ABSTRACT FROM AUTHOR]

Synthetic systems that facilitate electron transport across cellular membranes are of interest in bio‐electrochemical technologies such as bio‐electrosynthesis, waste water remediation, and microbial fuel cells. The design of second generation redox‐active conjugated oligoelectrolytes (COEs) bearing terminal cationic groups and a π‐delocalized core capped by two ferrocene units is reported. The two COEs, DVFBO and F4‐DVFBO, have similar membrane affinity, but fluorination of the core results in a higher oxidation potential (422 ± 5 mV compared to 365 ± 4 mV vs Ag/AgCl for the neutral precursors in chloroform). Concentration‐dependent aggregation is suggested by zeta potential measurements and confirmed by cryogenic transmission electron microscopy. When the working electrode potential (ECA) is poised below the oxidation potential of the COEs (ECA = 200 mV) in three‐electrode electrochemical cells containing Shewanella oneidensis MR‐1, addition of DVFBO and F4‐DVFBO produces negligible biocurrent enhancement over controls. At ECA = 365 mV, DVFBO increases steady‐state biocurrent by 67 ± 12% relative to controls, while the increase with F4‐DVFBO is 30 ± 5%. Cyclic voltammetry supports that DVFBO increases catalytic biocurrent and that F4‐DVFBO has less impact, consistent with their oxidation potentials. Overall, electron transfer from microbial species is modulated via tailoring of the COE redox properties. Insertion of synthetic constructs into the membrane of microorganisms can increase their ability to electronically communicate with abiotic components. Redox‐active membrane‐intercalating conjugated oligoelectrolytes are designed to mimic the function of native membrane proteins that move electrons through iron‐containing cytochromes. The oxidation potentials of redox‐active DVFBO and F4‐DVFBO modulate catalytic electron extraction from Shewanella oneidensis MR‐1. [ABSTRACT FROM AUTHOR]

In alignment with widespread interest in carbon neutralization and sustainable practices, we disclose that conjugated polyelectrolyte (CPE) hydrogels are a type of recyclable, electrochemically stable, and environmentally friendly pseudocapacitive material for energy storage applications. By leveraging ionic-electronic coupling in a relatively fluid medium, one finds that hydrogels prepared using a fresh batch of an anionic CPE, namely, Pris-CPE-K, exhibit a specific capacitance of 32.6 ± 6.6 F g -1 in 2 M NaCl and are capable of 80% (26.1 ± 6.5 F g -1 ) capacitance retention after 100,000 galvanostatic charge-discharge (GCD) cycles at a current density ( J ) of 10 A g -1 . We note that equilibration under a constant potential prior to GCD analysis leads to the K + counterions in the CPE exchanging with Na + and, thus, the relevant active material Pris-CPE-Na. It is possible to remove the CPE material from the electrochemical cell via extraction with water and to carry out a simple purification through dialysis to produce a recycled material, namely Re-CPE-Na. The recycling workup has no significant detrimental impact on the electrochemical performance. Specifically, Re-CPE-Na hydrogels display an initial specific capacitance of 26.3 ± 1.2 F g -1 (at 10 A g -1 ) and retain 77% of the capacitance after a subsequent 100,000 GCD cycles. Characterization by NMR, FTIR, and Raman spectroscopies, together with XPS and GPC measurements, revealed no change in the structure of the backbone or side chains. However, rheological measurements gave evidence of a slight loss in G ' and G ''. Overall, that CPE hydrogels display recyclability argues in favor of considering them as a novel materials platform for energy storage applications within an economically viable circular recycling strategy.

Interfacing bacteria as biocatalysts with an electrode provides the basis for emerging bioelectrochemical systems that enable sustainable energy interconversion between electrical and chemical energy. Electron transfer rates at the abiotic-biotic interface are, however, often limited by poor electrical contacts and the intrinsically insulating cell membranes. Herein, we report the first example of an n-type redox-active conjugated oligoelectrolyte, namely COE-NDI, which spontaneously intercalates into cell membranes and mimics the function of endogenous transmembrane electron transport proteins. The incorporation of COE-NDI into Shewanella oneidensis MR-1 cells amplifies current uptake from the electrode by 4-fold, resulting in the enhanced bio-electroreduction of fumarate to succinate. Moreover, COE-NDI can serve as a "protein prosthetic" to rescue current uptake in non-electrogenic knockout mutants., (© 2023 Wiley-VCH GmbH.)

Microbial bioelectronics require interfacing microorganisms with electrodes. The resulting abiotic/biotic platforms provide the basis of a range of technologies, including energy conversion and diagnostic assays. Organic semiconductors (OSCs) provide a unique strategy to modulate the interfaces between microbial systems and external electrodes, thereby improving the performance of these incipient technologies. In this review, we explore recent progress in the field on how OSCs, and related materials capable of charge transport, are being used within the context of microbial systems, and more specifically bacteria. We begin by examining the electrochemical communication modes in bacteria and the biological basis for charge transport. Different types of synthetic organic materials that have been designed and synthesized for interfacing and interrogating bacteria are discussed next, followed by the most commonly used characterization techniques for evaluating transport in microbial, synthetic, and hybrid systems. A range of applications is subsequently examined, including biological sensors and energy conversion systems. The review concludes by summarizing what has been accomplished so far and suggests future design approaches for OSC bioelectronics materials and technologies that hybridize characteristic properties of microbial and OSC systems.