A novel approach to fabricate supercapacitors (SCs) via vapor printing, specifically oxidative chemical vapor deposition (oCVD), is demonstrated. Compared to stacking multiple layers into a SC, this method enables the monolithic integration of all components into a single-sheet substrate, minimizing the inactive materials and eliminating the possibility of multilayer delamination. Electrodes comprised of pseudocapacitive material, poly(3,4-ethylenedioxythiophene) (PEDOT), are deposited into both sides of a sheet of flexible porous substrate. The film deposition and patterning are achieved in a single step. The oCVD PEDOT penetrates partially into the porous substrate from both surfaces, while leaving the interior of the substrate serving as a separator. Near the surface, the PEDOT coating conforms to the substrate's structure without blocking the pores, resembling the substrate's intrinsic morphology with high surface area. The porously structured PEDOT coating, paired with in situ ion gel electrolyte synthesis, gives enhanced electrode-electrolyte interfaces. The monolithic device demonstrates high volumetric capacitance (11.3 F cm ), energy density (2.98 mWh cm ), and power density (0.42 W cm ). These outstanding performance metrics are attributed to the large loading of active materials, minimization of inactive materials, and good electrode-electrolyte interfaces. SC arrays can be printed on a single substrate without the use of wire interconnects.

Unconjugated redox polymers, such as polyvinylferrocene (PVF), have rarely been used for energy storage due to their low intrinsic conductivity. Conducting polymers with conjugated backbones, though conductive, may suffer from insuffi cient exposure to the electrolyte due to the often formed nonporous structures. The present work overcomes this limitation via simultaneous electropolymerization of pyrrole and electroprecipitation of PVF on electrode surfaces. This synthesis method relies on the π-π stacking interactions between the aromatic pyrrole monomers and the metallocene moieties of PVF. This fabrication process results in a highly porous polymer fi lm, which enhances the ion accessibility to polypyrrole (PPy). PPy serves as a "molecular wire," improving the electronic conductivity of the hybrid and the utilization effi ciency of ferrocene. The PVF/PPy hybrid exhibited a specifi c capacitance of 514.1 F g −1 , which signifi cantly exceeds those of PPy (27.3 F g −1 ) and PVF (79.0 F g −1 ), respectively. This approach offers an alternative to nanocarbon materials for improving the electronic conductivity of polymer hybrids, and suggests a new strategy for fabricating nanostructured polymer hybrids. This strategy can potentially be applied to various polymers with π-conjugated backbones and redox polymers with metallocene moieties for applications such as energy storage, sensing, and catalysis.

We describe a water treatment strategy, electrochemically tunable affinity separation (ETAS), which, unlike other previously developed electrochemical processes, targets uncharged organic pollutants in water. Key to achieving ETAS resides in the development of multicomponent polymeric nanostructures that simultaneously exhibit the following characteristics: an oxidation-state dependent affinity towards neutral organics, high porosity for sufficient adsorption capacity, and high conductivity to permit electrical manipulation. A prototype ETAS adsorbent composed of nanostructured binary polymeric surfaces that can undergo an electrically-induced hydrophilic-hydrophobic transition can provide programmable control of capture and release of neutral organics in a cyclic fashion. A quantitative energetic analysis of ETAS offers insights into the tradeoff between energy cost and separation extent through manipulation of electrical swing conditions. We also introduce a generalizable materials design approach to improve the separation degree and energetic efficiency simultaneously, and identify the critical factors responsible for such enhancement via redox electrode simulations and theoretical calculations of electron transfer kinetics. The effect of operation mode and multistage configuration on ETAS performance is examined, highlighting the practicality of ETAS and providing useful guidelines for its operation at large scale. The ETAS approach is energetically efficient, environmentally friendly, broadly applicable to a wide range of organic contaminants of various molecular structures, hydrophobicity and functionality, and opens up new avenues for addressing the urgent, global challenge of water purification and wastewater management. Broader contextSeparation processes are of paramount importance in the chemical and environmental industries, accounting for 10-25% of the world's energy consumption, and about a third of total capital and operation costs in industrial plants. The development of separation technologies for water treatment with high energy efficiency and low environmental impact has become a primary engineering challenge for the 21st century due to the worldwide occurrence of water contamination and its associated negative impacts on the environment and human health. Electrochemically controlled processes, such as capacitive deionization, have emerged as promising candidates for wastewater management and water desalination. However, since these previously developed electrochemical methods rely primarily on the electrostatic interaction between the electrode and the target pollutant, they only work for charged species (e.g., anions, cations), and are not applicable to uncharged organic pollutants, which constitute the majority of industrial and municipal water contaminants, including many dyes, pesticides, pharmaceuticals and carcinogenic aromatics. This study investigates a conceptually novel separation strategy that enables sensitive, programmable electrochemical control over the release and capture of u...

Polymeric adsorbents show great potential for the replacement of activated carbon for removing a wide range of toxic organic pollutants from wastewater streams since they do not suffer from costly regeneration needs and high attrition rates. Herein, an electrochemically regenerable polymeric adsorbent based on an intrinsically conducting polymer (CP), polypyrrole (PPy), doped with anionic surfactant dioctylsulfosuccinate (AOT), denoted PPy(AOT), for mitigating organic pollutants in wastewater is reported. A facile electropolymerization protocol to synthesize highly porous PPy(AOT) is developed, with an adsorption capacity of greater than 570 mg pollutant/g polymer in its superhydrophobic oxidized state. It is demonstrated that the hydrophobicity of PPy(AOT) and hence its affinity for organics can be modulated electrochemically through the re-orientation of AOT dopants, which can be exploited to regenerate the adsorbent and use it repeatedly for multiple adsorption/desorption cycles. It also explores the interactions between the adsorbed organic molecules and the surfactant-doped CP adsorbent using a combined density functional theory and molecular dynamics approach to elucidate the mechanism of electrochemical modulations of hydrophobicity and affinity of the material. The physicochemical insights are significant for developing broader applications of such material in drug delivery, sensing, self-cleaning surfaces, microfluidics, and artificial muscles.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201801466. negative effects on aquatic ecosystems and human health. [3][4][5] Adsorption is a common technology for removing organic pollutants from wastewater, and activated carbon (AC) is one of the most widespread adsorbents due to its high specific surface area and strong interactions with target compounds. [6][7][8] Methods for AC regeneration have drawbacks, however, thermal desorption is energy-intensive, while solvent regeneration may lead to substantial loss of AC and result in secondary pollution. [7][8][9][10] To overcome recyclability problems such as observed with AC, our group has previously developed a redox-responsive polymer gel with tunable hydrophobicity that reversibly adsorbs and releases organics in the presence of water. [11] However, in this case, the redox switching relied on the addition of chemicals, which introduced additional chemical agents to the remediation process, and the efficacy of the chemical stimuli was hampered by mass transfer limitations. [11,12] Therefore, it is desirable to design new adsorbent materials whose redox-responsive hydrophobicity can be tuned using mild electrical stimuli, thereby eliminating the use of chemicals in the regeneration process, and ultimately reducing the material waste and operating cost of adsorption technology for wastewater remediation. We have addressed this problem by developing two different methods for electrochemical control of the hydrophobic environment within the adsorb...

We report a method to control reaction kinetics using electrochemically responsive heterogeneous catalysis (ERHC). An ERHC system should possess a hybrid structure composed of an electron-conducting porous framework coated with redox-switchable catalysts. In contrast to other types of responsive catalysis, ERHC combines all the following desired characteristics for a catalysis control strategy: continuous variation of reaction rates as a function of the magnitude of external stimulus, easy integration into fixed-bed flow reactors, and precise spatial and temporal control of the catalyst activity. Herein we first demonstrate a facile approach to fabricating a model ERHC system that consists of carbon microfibers with conformal redox polymer coating. Second, using a Michael reaction whose kinetics depends on the redox state of the redox polymer catalyst, we show that use of different electrochemical potentials permits continuous adjustment of the reaction rates. The dependence of the reaction rate on the electrochemical potential generally agrees with the Nernstian prediction, with minor discrepancies due to the multilayer nature of the polymer film. Additionally, we show that the ERHC system can be employed to manipulate the shape of the reactant concentration-time profile in a batch reactor through applying customized potential-time programs. Furthermore, we perform COMSOL simulation for an ERHC-integrated flow reactor, demonstrating highly flexible manipulation of reactant concentrations as a function of both location and time.

Electrochemical sensing is an efficient and inexpensive method for detection of a range of chemicals of biological, clinical, and environmental interest. Carbon materials-based electrodes are commonly employed for the development of electrochemical sensors because of their low cost, biocompatibility, and facile electron transfer kinetics. Electrospun carbon fibers (ECFs), prepared by electrospinning of a polymeric precursor and subsequent thermal treatment, have emerged as promising carbon systems for biosensing applications since the electrochemical properties of these carbon fibers can be easily modified by processing conditions and post-treatment. This review addresses recent progress in the use of ECFs for sensor fabrication and analyte detection. We focus on the modification strategies of ECFs and identification of the key components that impart the bioelectroanalytical activities, and point out the future challenges that must be addressed in order to advance the fundamental understanding of the ECF electrochemistry and to realize the practical applications of ECF-based sensing devices.

Performance stability of electrochemically active polymers (EAPs) remains one of the greatest and long-standing challenges with regard to EAP-based technologies for a myriad of energy, biomedical, and environmental applications. The performance instability of EAPs originates from their structural alteration under repeated charge-discharge cycling and/or flexing. In this work, a conceptually new "soft confinement" strategy to enhance EAP performance stability, including cyclic and mechanical, by using rationally designed, vapor-deposited organic networks is presented. These chemically cross-linked networks, when in contact with an electrolyte solution, turn into ultrathin, elastic hydrogel coatings that encapsulate conformally the EAP micro-/nanostructures. Such hydrogel coatings allow easy passage of ions that intercalate with EAPs, while simultaneously mitigating the structural pulverization of the EAPs and/or their detachment from substrates. Fundamentally distinct from extensively studied "scaffolding" or "synthetic" approaches to stabilizing EAPs, this soft confinement strategy relies on a postmodification step completely decoupled from the EAP synthesis/fabrication, and enjoys the unique advantage of substrate-independency. Hence, this strategy is broadly applicable to various types of EAPs. The proposed stability enhancement strategy is demonstrated to be effective for a range of EAP systems with differing chemical and morphological characteristics under various testing conditions (repeated charging/discharging, bending, and twisting). electronic devices. [14][15][16] Possible mecha nisms causing the cycling instability of EAPs include structural pulverization due to repeated swelling and shrinkage of polymer backbones, and collapse of initially present ion channels resulting in difficulty of subsequent redoping. [14,[17][18][19][20] A widely adopted approach to enhancing EAP stability is integration of the EAPs with conductive scaffolds, such as porous graphite foams, [21] carbon nanotube sponges, [22] nickel foams, [23] and partially exfoliated graphite. [18] These scaffolds are usually porous and dimensionally stable, and thus act as robust supports for EAP films to reduce their structural alteration. Such a "scaffolding" approach relies on effective hybridization of the EAP with the underlying conductive substrate, a non trivial task. The integration process often requires judicious surface modification of the scaffold materials to create specific interactions (e.g., covalent bonding, π-π stacking) with the EAP, and a lengthy screening process to determine the reac tion conditions for the growth of a certain EAP on the scaffold. A few less common methods based on deliberate synthetic strategies for improving EAP stability have also been dem onstrated, such as creation of supramolecular structures, [24] synthesis of hyperbranched EAPs, [25] and dopant/EAP engi neering. [26,27] These scaffolding and synthetic approaches have shown great promise when applied to certain types of EAP sys tems, but are highly...

We report the systematic structural manipulation of turbostratic electrospun carbon nanofibers (ECNFs) using a microwave-assisted oxidation process, which is extremely rapid, highly controllable, and affords controlled variation of the capacitive energy storage capabilities of ECNFs. We find a non-monotonic relationship between the oxidation degree of ECNFs and their electrocapacitive performance, and present a detailed study on the electronic and crystalline structures of ECNFs to elucidate the origin of this non-monotonic relation. The ECNFs with an optimized oxidation level show ultrahigh capacitances at high operation rates, exceptional cycling performance and an excellent energy-power combination. We have identified three key factors required for optimal energy storage performance for turbostratic carbon systems: (i) an abundance of surface oxides, (ii) microstructural integrity and (iii) an appropriate interlayer spacing.