Polyaniline Hydrogel Research Articles

Controllable synthesis of hierarchically porous polyaniline/MnO2 composite with wide potential window towards symmetric supercapacitor

MnO2 composites are appealing electrode materials for supercapacitors because of low cost, environmental friendliness, and high electrochemical activity. Herein, in an attempt to overcome the poor conductivity and limited potential window, the polyaniline (PANI) hydrogel is employed as the substrate to synthesize the PANI/MnO2 composite via the self-sacrifice reaction with KMnO4. The PANI/MnO2 composite prepared under heating condition (PM-H) shows hierarchically porous structure with large specific surface area/pore volume and facilitated electron/ion conduction. As a result, it delivers wide potential window of − 1.1–1.1 V and high specific capacitances of 314 F g−1 at 1 A g−1 and 263 F g−1 at 5 A g−1 (83.8% capacitance retention) in the three-electrode measurement. Moreover, the assembled symmetric supercapacitor delivers large operation window (0–1.8 V) and high energy/power density, e.g., a maximum energy density of 23.2 Wh kg–1 with power density of 720 W kg−1. Therefore, the present work paves a new way to construct PANI/MnO2 nanocomposite with ideal nanostructure and optimized electrochemical behavior for symmetric supercapacitor.

Antifouling Electrochemical Biosensor Based on Conductive Hydrogel of DNA Scaffold for Ultrasensitive Detection of ATP

As an energy supplier, ATP plays an important role in various life activities, and there is an urgent need to develop an effective means of detecting ATP. However, the traditional sensors face serious nonspecific adsorption. In this work, an antifouling electrochemical biosensor based on the interpenetrating network of Y-DNA scaffold and polyaniline hydrogel was designed for ATP detection. The polyaniline hydrogel was conducive to the transport of electrons and ions, the structure of Y-DNA cross-linked by ATP aptamers in the polyaniline hydrogel achieved the effect of signal amplification. Super hydrophilic cellulose nanocrystals (CNCs) and zwitterion polypeptide sequence (Pep) were doped to play a synergistic antifouling effect. The hydrogel sensor we have built has a wide linear range of 0.1 pM-1 μM for ATP detection and a low detection limit of 0.025 pM (S/N = 3). For ATP detection in actual serum samples, the recovery of this sensor was 99.5%-106%, and the relative standard deviation was 0.4%-2.88%. It is proven that the sensor has good ATP detection performance, and it will provide a certain reference value for the detection of other biological small molecules.

Artificial jelly channel inspired by the shark for sensing specific ions and environmental perturbation

The ampullae of Lorenzini (AoL) from sharks is an important tool to ensure their well-known six-sense function. Inspired by the jelly-like substance inside AoL, we design a polymer hydrogel to mimic it and achieve some of the functions of AoL. The polyvinyl alcohol (PVA)/polyaniline (PANI) hydrogel with an excellent ion conductivity of 10.8 mS cm−1 presents great selectivity toward Fe and Cu ions and high sensitivity for the environmental variation. By combining electrochemical analysis and molecular dynamics simulations, the inner mechanism for sensing specific ions can be explained by the large difference in ion conductivity between various cations related to the diversity in the diffusion barrier through the fabricated jelly system. The experimental results can further be well interpreted by finite element analysis (FEA) simulation, implying the function of this AoL-inspired jelly is to sense the ion variation and environmental perturbation nearby for collecting helpful information. These results will provide potential applications with similar function as the AoL for multifunctional undersea sensors.

Copolymerization of Aniline, Melamine and p‐Phenylenediamine for Enhanced Pseudocapacitance Hydrogel Supercapacitor Electrodes

AbstractA novel double‐crosslinked 3D network hydrogel, poly(aniline‐co‐p‐phenylenediamine‐co‐melamine) (PD2M4) is synthesized through the chemical oxidative copolymerization of aniline, melamine, and p‐phenylenediamine, and its properties are compared with those of polyaniline (PANI), poly(aniline‐co‐p‐phenylenediamine) (PPDA2), and poly(aniline‐co‐melamine) (PMA4) hydrogels. The morphologies, mechanical properties, and chemical compositions of the hydrogels are investigated by nitrogen physisorption, rheological test, microscopic measurements, and spectroscopic techniques, while electrochemical techniques are used to evaluate their electrochemical performances. In accordance with PANI, PPDA2, and PMA4 hydrogels, the PD2M4 hydrogel exhibited an interconnected long nanofiber structure that encouraged the diffusion of electrolyte ions. Its double‐crosslinked 3D network and high nitrogen‐doping content (6.3 at. %) offered synergistic effects that generated an impressive pseudocapacitance of 657 F g −1 at 0.2 A g−1, a superior rate capability of 72% retention at a high current density of 30 A g−1, and good cyclic stability of 62% after 2000 charge/discharge cycles. The present work, therefore, provides a novel copolymerization strategy for N‐doping and hierarchical network structure to enhance the electrochemical performances of PANI hydrogel electrodes in supercapacitor applications.

Hierarchical three dimensional polyaniline/N‐doped graphene nanocomposite hydrogel for energy storage applications

AbstractWith the rapid development of portable, lightweight, and flexible electronics, the requirement for advanced energy storage systems has arisen that need to be flexible and cost‐effective with higher power/energy densities. In this context, a two‐step approach has been adopted to develop a binder‐free and flexible supercapacitor electrode on carbon cloth based on hierarchical three dimensional (3D) conducting polymer hydrogels. Firstly, nitrogen‐doped graphene (NGN) was synthesized using urea as a reducing as well as a doping agent. Subsequently, polyaniline (PAni) hydrogel has been grown on NGN nanosheets via insitu oxidative polymerization in the vicinity of carbon cloth and further utilized as an electrode for electrochemical measurements. Here, phytic acid was used as a gelatinizer and as a dopant resulting in the formation of a cross‐linked hydrogel structure. The direct deposition of PAni/NGN nanocomposite on carbon cloth strengthens the juncture involving the carbon cloth and electrode material, resulting in enhanced electron transmission. The 3D hydrogel architecture ascertains robust contact between electrolyte and electrode for an efficient charge storage system. For a two‐electrode symmetric arrangement, at 1 A/g, PAni/NGN nanocomposite hydrogel displayed a maximum specific capacitance of 808.7 F/g due to the pseudocapacitive reaction on/near the accessible surface area, as well as an outstanding rate capability and cyclic performance due to electric double layer capacitance (EDLC). The supercapacitor cell delivered maximum specific power and specific energy value of 0.44 kW/kg and 13.63 Wh/kg, respectively. Thus, the composite hydrogel has the benefit of being able to be utilized directly as binder‐free supercapacitor electrodes, leading to viable choice for high‐performance and cost‐effective energy storage devices.

A short review on the synthesis and advance applications of polyaniline hydrogels.

Conductive polymeric hydrogels (CPHs) exhibit remarkable properties such as high toughness, self-recoverability, electrical conductivity, transparency, freezing resistance, stimulus responsiveness, stretch ability, self-healing, and strain sensitivity. Due to their exceptional physicochemical and physio-mechanical properties, among the widely studied CPHs, polyaniline (PANI) has been the subject of immense interest due to its stability, tunable electrical conductivity, low cost, and good biocompatibility. The current state of research on PANI hydrogel is discussed in this short review, along with the properties, preparation methods, and common characterization techniques as well as their applications in a variety of fields such as sensor and actuator manufacturing, biomedicine, and soft electronics. Furthermore, the future development and applications of PANI hydrogels are also mentioned.

Double-cross-linked polyaniline hydrogel and its application in supercapacitors

Double-cross-linked polyaniline hydrogel and its application in supercapacitors

An amperometric nitrite sensing platform with enhanced sensitivity based on copper nanoparticle/nanostructured polyaniline hydrogel nanocomposite

An amperometric nitrite sensing platform with enhanced sensitivity based on copper nanoparticle/nanostructured polyaniline hydrogel nanocomposite

Fe-Ni Alloy Nanoclusters Anchored on Carbon Aerogels as High-Efficiency Oxygen Electrocatalysts in Rechargeable Zn-Air Batteries.

In this work, Fe-Ni alloy nanoclusters (Fe-Ni ANCs) anchored on N, S co-doped carbon aerogel (Fe-Ni ANC@NSCA catalysts) are successfully prepared by the optimal pyrolysis of polyaniline (PANI) aerogels derived from the freeze-drying of PANI hydrogel obtained by the polymerization of aniline monomers in the co-presence of tannic acid (TA), Fe3+ , and Ni2+ ions. In addition, the optimal molar ratio of the TA, Fe3+ , and Ni2+ ions for synthesis of Fe-Ni ANC@NSCA catalysts are 1:2:5, which can guarantee the formation of carbon aerogel composed of quasi-2D porous carbon sheets and the formation of high-density Fe-Ni ANCs with an ultrasmall size between 2 to 2.8nm. These Fe-Ni ANCs consisting of N4 -Fe-O-Ni-N4 moiety are proposed as a new type of active species for the first time, to the best of the authors' knowledge. Thanks to their unique features, the Fe-Ni ANC@NSCA catalysts show excellent performance in oxygen reduction reaction with a half-wave potential (E1/2 ) of 0.891 V and oxygen evolution reaction (260mV @ 10mA cm-2 ) in alkaline media as bifunctional catalysts, which are better than the state-of-the-art commercial Pt/C catalysts and RuO2 catalysts. Moreover, Zn-air battery assembled with the Fe-Ni ANC@NSCA catalysts also shows a remarkable performance and exceptionally high stability over 500 h at 5mA cm-2 .

Rational design of ultrahigh sensitive sunset yellow sensor based on 3D hierarchical porous graphitic carbon with sub-nanopores

The content of sunset yellow (SY) in food must be strictly controlled, because its excessive intake may cause many adverse health effects. Herein, we proposed an ultrasensitive SY sensor by using hierarchical porous graphitic (HPG) carbon derived from polyaniline hydrogel. After a first step of polymerization, the HPG carbon was prepared through carbonization and further chemical activation. In particular, the activation process endowed the HPG carbon with a high content of optimized porous architecture (sub-nanoporous surface area accounts for more than 90% of microporous surface area), and thus providing a structural basis for high efficiency of SY pre-concentration on HPG carbon surface. Therefore, the proposed sensor showed record-high sensitivity (5285.7 A M−1 cm−2) and ultra-low detection limit (0.15 nM), which represents a performance improvement in SY sensing. Furthermore, the sensor displays excellent selectivity, reproducibility and stability, exhibiting a great perspective in ultrasensitive monitoring of SY in commercial products.

A Hydrothermal Strategy to Fabricate Carbons‐Doped Polyaniline Hydrogels with Separation‐Free for Flexible All‐Solid‐State Supercapacitors

AbstractCarbon‐doped polyaniline (PANI) hydrogels (PFMH) are fabricated by a facile hydrothermal strategy that aniline monomers are in situ polymerized on mesoporous carbons (MC) and carbon fibers (CF) with phytic acids as both cross‐linkers and dopants. Likewise, MC and CF can provide heterogeneous active sites to initiate the polymerization, acting as the skeletons within multi‐dimensional interconnected channel structures. First‐principles density functional theory calculations show that the interactions between different bases of PANI and MC/CF are all adsorptive prone to possess the separation‐free structure, but the adsorptive interactions between different bases and MC are significantly stronger than those of CF. Therefore, MC would be tightly anchored by PANI chains to improve the mechanical strength, while CF can provide favorable conductivity interconnected network skeletons. As such, the electrical conductivity and fracture strength of PFMH are measured high up to 13.32 S m−1 and 233.4 kPa at the fracture deformation (54.7%), respectively. PFMH as supercapacitor (SC) electrodes can achieve the gravimetric specific capacitance of 637.9 F g−1 at 1 A g−1. In particular, the as‐fabricated flexible all‐solid‐state SCs can maintain normal operation under various deformation conditions, showing the great potential to become an advanced power device for wearable electronics.

Composites of Ni-MOF and polyaniline hydrogel for carbon monoxide resistant excellent catalysts of ethanol oxidation reaction

EOR is a semi-reaction of direct ethanol fuel cells (DEFCs), and determines the performance of the DEFCs. Therefore, it is very important for EOR to rationally design an electrocatalyst with excellent activity, stability and CO-resistance. Based on this, we report the synthesis of MOF based composite catalysts by a facile method, which is formed by combining polyaniline hydrogel (PANH) with MOF 1 and carbon cloth (CC). At the same time, the structures of the composites were characterized by XRD, SEM and XPS. Under the optimum conditions, the j value for EOR is 107 mA cm−2 under alkaline conditions at 0.6 V, which indicates that composite 2 has excellent catalytic activity for EOR, and is superior to that of the previously reported nickel-based catalysts for EOR. The Tafel slope and the exchange current density of composite 2 are 88.9 mV dec−1 and 1.95 × 10−5 A cm−2 respectively. In addition, the j value of composite 2 was 65% of the original value after 1000 CV cycles. However, when the electrolyte was changed into the original one (1 M KOH + 1 M EtOH), the j value returned to 74% of the original value. Based on the excellent electrocatalytic performance, good stability and anti-CO poisoning, composite 2 is expected to be an economic, efficient and CO poisoning resistant electrocatalyst for EOR.

Design and synthesis of polyaniline/MWCNT composite hydrogel as a binder-free flexible supercapacitor electrode

The novel polyaniline/MWCNT composite hydrogel has been successfully synthesized on carbon cloth using in situ oxidative polymerization of aniline in the presence of MWCNT and phytic acid which can further be used as a binder-free electrode for supercapacitor. The use of electrode without binder is an effective approach to get better electrochemical behavior, which makes the ions move quicker. The supercapacitor cell has been built in a Teflon Swagelok assembly by sandwiching a separator impregnated with 1 M H2SO4 electrolyte between two symmetrical hydrogel electrodes and used further for electrochemical characterization. The electrochemical behavior of supercapacitor electrodes has been explored in a two-electrode cell configuration using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS) measurements. The electrochemical results reveal that in 1 M H2SO4 aqueous solution, polyaniline/MWCNT composite hydrogel possesses a high specific capacitance (Cs) value of 277.59 F/g as compared to Cs value of 142.24 F/g for polyaniline hydrogel at 0.25 A/g. The polyaniline/MWCNT electrode shows superior rate capability and outstanding cyclic stability up to 5000 consecutive cycles. The electrochemical performance of composite hydrogel may be attributed to its well-designed nanostructure and the collective effect of both components. It may be concluded that as prepared composite hydrogel serves as a favorable electrode material for highly capable flexible energy storage system.

Porous layered cobalt nanocrystal/nitrogen-doped carbon composites as efficient and CO-resistant electrocatalysts for methanol oxidation reaction

The development of active, stable and poison-resistant electrocatalysts for methanol oxidation reaction (MOR) has become a key challenge to improve the performance of direct methanol fuel cells (DMFCs). Herein, we report a simple strategy to prepare cobalt nanoscrystal/nitrogen-doped carbon (Co/N-C) composites as efficient and carbon monoxide (CO) resistant electrocatalysts for MOR. The Co/N-C composites are synthesized by the pyrolysis of porous CoCl2-polyaniline hydrogels. While CoCl2 is reduced to Co nanocrystals as active electrocatalyst for MOR, the polyaniline hydrogel is pyrolyzed to porous layered N-doped carbon that immobilize and protect Co nanocrystals, and also facilitate the mass and charge transfer through the electrolyte and electrode. After systematically exploring the preparation conditions of Co/N-C composites, we have found the optimal Co/N-C-1-500 (pyrolyzed at 500 °C) can achieve a high current density of 231 mA∙cm−2 at 0.8 V vs SCE for MOR in alkaline media. Meanwhile, the Co/N-C-1-500 catalyst presents a good durability and a high resistance to CO poisoning (93.5% retention of MOR activity), superior to the performance of Pt/C catalysts. With its high activity, good stability and superior resistance to CO poisoning, Co/N-C-1-500 is promising as a low-cost and efficient anode catalyst for DMFCs.

Hemin‐phytic Acid Functionalized Porous Conducting Polymer Hydrogel With Good Biocompatibility for Electrochemical Detection of H2O2 Released From Living Cells

AbstractA novel hemin/phytic acid doped polyaniline (PA‐PANI) hydrogel composite was prepared through a simple chemical and self‐assembly method, which was modified onto electrode for electrochemical detection of H2O2 released from living cells. It showed good analytical performance with high sensitivity, selectivity and a rapid response for the analysis of H2O2 in the range of 2 to 102 μM, with the detection limit of 1.2 μM. The favorable results mainly originated from both the high conductivity of PA‐PANI hydrogel and its network structure preventing hemin from self‐dimerization to provide active catalytic species. Furthermore, PA‐PANI with good biocompatibility allowed living cells to adhere and resulted in a short diffusion distance between H2O2 released from cells and electrode.

Long-term cell culture and electrically in situ monitoring of living cells based on a polyaniline hydrogel sensor.

Accurate, in situ and long-term electrically monitoring of cell development plays an important role in cell study, which brings in challenges in terms of biocompatibility, processability, and sensing capability of electrochemical sensors. Based on biocompatible conductive polyaniline (PAni) hydrogels, we constructed a flexible sensor with flexible carbon cloth for electrical analysis of living cells. The carbon fiber substrate modified with conductive PAni hydrogels was selected as the electrode to promote the current collection of the sensor. The three dimensional nanostructured mesoporous matrix of PAni hydrogels is favorable for in situ generation of catalytic Pt nanoparticles and cell growth. With these hierarchically nanostructured features, the hydrogel electrochemical sensor was endowed with high sensitivity and selectivity in the detection of H2O2 (with a low detection limit of 1.6 μM in 0.01 M PBS and a wide linear range from 10 μM to 10 mM), and good biocompatibility for cell growth as long as 5 days. The accurate detection of H2O2 released from cells enabled us to differentiate the physiological states of cells and imitate the different stimuli-responsive behavior, which can provide real-time information on cell biological events. With outstanding biocompatibility, operability and repeatability, this strategy can be expanded to the fields of other biosensor fabrication and cell-related biomarker monitoring, which exhibits a broad application potential in bioanalysis catering to new generation sensors.

A ratiometric electrochemiluminescent cytosensor based on polyaniline hydrogel electrodes in spatially separated electrochemiluminescent systems.

Here, we proposed a ratiometric electrochemiluminescent (ECL) strategy in spatially multiplied ECL systems. By the specific recognition of hyaluronic acid with proteoglycan CD44 and epidermal growth factor with epidermal growth factor receptor on the cell surface, the cells were labelled with potential-resolved ECL probes, namely Ru(bpy)32+ and g-C3N4, respectively. The as-proposed cytosensor provides a multichannel ECL protocol to improve the throughput, which may push the application of ECL for the cellular immunoanalysis.

Robust copper nanocrystal/nitrogen-doped carbon monoliths as carbon monoxide-resistant electrodes for methanol oxidation reaction

Noble metal-based electrocatalysts present high activities for methanol oxidation reaction (MOR), but are limited by their high cost, low stability and poor resistance to carbon monoxide (CO) poisoning. The development of active and stable non-noble metal electrocatalysts for MOR is desired, but remains a challenge. Herein, we report a simple strategy to make copper nanocrystal/nitrogen-doped carbon (Cu/N-C) monoliths, which can serve as active and robust electrodes for MOR. Copper nanocrystals were electrochemically deposited onto a conductive polyaniline hydrogel and calcined to form Cu/N-C monolith, where the active copper nanocrystals are protected by nitrogen-doped carbon. Owing to their extremely high electrical conductivity (1.25 × 105 S cm−1) and mechanical robustness, these Cu/N-C monoliths can be directly used as electrodes for MOR, without using substrates or additives. The optimal Cu/N-C (FT) @500 monolith shows a high MOR activity of 189 mA cm−2 at 0.6 V vs. SCE in alkaline methanol solution, superior to most of reported Cu-based MOR catalysts. Cu/N-C (FT)@500 also presents a better stability than Pt/C catalyst in the long-term MOR test at high current densities. Upon carbon monoxide (CO) poisoning, Cu/N-C (FT)@500 retains 96% of its MOR activity, far exceeding the performance of Pt/C catalyst (61% retention). Owing to its facile synthesis, outstanding activity, high stability and mechanical robustness, Cu/N-C (FT)@500 monolith is promising as a low-cost, efficient and CO-resistant electrocatalyst for MOR.

A rod-on-tube CoMoO4@hydrogel composite as lithium-ion battery anode with high capacity and stable rate-performance

Hierarchical materials have been considered promising for secondary battery electrodes owing to their capability of accommodating volumetric change of active materials and providing short pathways for rapid transportation of ions and electrons. Herein, we present a rod-on-tube composite consisting of cobalt molybdate (CoMoO4) nanotubes coating with polyaniline (PANI) hydrogel nanorods, which exhibits a high electrochemical performance as Li-ion battery anode. The hierarchical CoMoO4@PANI is prepared through in-situ polymerizing PANI nanorods on the CoMoO4 nanotubes. The rod-on-tube structure could alleviate the volumetric change of CoMoO4 during lithiation-delithiation, and improve conductivity for electron transfer. When cycling at 0.5 A g-1, the presented CoMoO4@PANI anodes exhibit a large capacity of 805 mAh g-1 after 150 cycles along with a Coulombic efficiency of 99%, which are both exceeding those of the pristine CoMoO4. A well-recoverable rate-performance is achieved. Furthermore, the density of state (DOS) and band gap of the CoMoO4@PANI and pristine CoMoO4 are also investigated by using density functional theory (DFT) calculations.

Flexible Poly(vinyl alcohol)–Polyaniline Hydrogel Film with Vertically Aligned Channels for an Integrated and Self-Healable Supercapacitor

Although supercapacitors attract tremendous attention due to their high power density, long cycle life, and high efficiency, it is still a challenge to prepare flexible and wearable supercapacitors...