Electrochemical performance of polyaniline-coated γ-MnO2 on carbon cloth as flexible electrode for supercapacitor

Versatile core-shell MnO2@PANI nanocomposites: Bridging photo-assisted zinc-ion batteries and wearable strain sensors for self-powered systems

With the continuous development of self-powered sensing systems, achieving efficient energy self-supply and high-performance signal acquisition simultaneously has emerged as a main trend for next-generation sensors. However, developing functional materials for such sensing systems is still facing crucial challenges. Herein, a multifunctional MnO2@PANI (MP) composite material was designed to realize a synchronized "integration" strategy. Specifically, the MP serves as a cathode in photo-assisted zinc-ion batteries (PA-ZIBs), enabling solar energy conversion and storage. The p-n heterojunction formed between MnO2 and PANI promotes effective separation of photogenerated electron-hole pairs and enhances Zn2+ kinetics. Therefore, the PA-ZIBs deliver a high self-charging voltage of 1.08 V and 33 % enhancement in specific capacity (reaching 249.5 mAh g-1 at 0.1 A g-1) under illumination. Meanwhile, it also functions as the active layer of a flexible strain sensor, achieving efficient mechanical signal detection. The core-shell structure and composite component improve both structural stability and conductivity. As a result, the sensor exhibits high sensitivity, a fast response time of 0.4 s, and excellent durability over 2000 cycles. Furthermore, proof-of-concept demonstrations validate the device's capability to simultaneously harvest solar energy and detect physiological signals. This work offers a new solution for designing self-powered sensing systems and intelligent healthcare applications by merging energy-autonomous operation with multifunctional sensing capabilities.

Electrochemical synthesis and supercapacitor performance of manganese and cerium oxide-doped polyaniline composites

In this study, polyaniline-based conductive polymers doped with manganese oxide and cerium oxide were electrochemically synthesized for the first time. Unlike previous studies, manganese oxide and cerium oxide doped polyaniline synthesis was carried out in perchloric acid. The resulting composite materials were characterized using spectroscopic and microscopic techniques. The doped polyaniline composites were employed as electrode components in supercapacitors and analyzed using cyclic voltammetry and electrochemical impedance spectroscopy. Changes in capacitive behavior over cycling were examined via galvanostatic charge-discharge measurements. The areal capacitance of the cerium oxide and manganese oxide doped polyaniline electrodes, synthesized under optimal conditions, were measured as 950 mF cm-2and 660 mF cm-2, respectively, at a charge-discharge current of 10 mA cm-2.

Organic-inorganic hybrid cathode enabled by in-situ interface polymerization engineering boosts Zn2+ desolvation in aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (RAZIBs) have attracted considerable attention for application in large-scale energy storage systems. However, the progress of RAZIBs has been hindered by the sluggish reaction kinetics and poor structural stability, which are closely associated with the desolvation process of hydrated Zn2+. To overcome these issues, an in situ interfacial polymerization strategy is proposed to uniformly germinate a polyaniline (PANI) layer on α-MnO2 and form an organic-inorganic hybrid cathode (MnO2@PANI). Theoretical calculations and experimental characterizations disclose that the polyaniline layer equipped with hydrophilic functional groups can effectively trap the active water molecules to break the strong attraction between H2O and Zn2+, thereby facilitating the desolvation process of hydrated Zn2+, and regulating the Zn2+ diffusion kinetics and electrode reaction kinetics on the cathode/electrolyte surface. Meanwhile, the irreversible phase evolution and dissolution of active species are largely suppressed due to the PANI shell protecting the α-MnO2 from the attack of active water molecules. As a consequence, the organic-inorganic hybrid cathode exhibits 401.9 mAh/g after 200 cycles at a current density of 0.5 A/g and long-term durability over 1000 cycles at a current density of 2.0 A/g without irreversible phase transformation. This work provides insight into the regulation of the desolvation process for high performance aqueous energy storage systems.

One-step depositing method of PAni/MnO2 composites for enhanced supercapacitor performance

Manganese dioxide (MnO2) is extensively used in supercapacitors, but its poor conductivity and low power density limit its applications. This study employed a one-step electrochemical deposition method to fabricate a polyaniline (PAni)/MnO2/carbon cloth (CC) composite electrode, which was assembled into flexible supercapacitors. Optimal process parameters were determined through exploring the effect of deposition durations on the electrochemical performance. With optimized synergistic effects between the components, the PAni/MnO2@CC composite electrode exhibits high specific capacitance of 1,694.25 mF cm-2 at 1 mA cm-2, which is remarkably better than that of PAni@CC, MnO2@CC, and other reported PAni-based electrodes. The assembled supercapacitor displays high energy density, superior bending performance, and good cycle stability. This easy-to-prepare composite electrode, with excellent energy storage capability, offers significant potential for flexible energy storage devices.

Flexible Hybrid Supercapacitor Achieving 2.2 V with NiCo2S4/Polyaniline/MnO2 and N, S-Co-Doped Carbon Nanofibers for Ultra-High Energy Density

Flexible all-solid-state asymmetric supercapacitors (FAASC) represent a highly promising power sources for wearable electronics. However, their energy density is relatively less as compared to the conventional batteries. Herein, a novel ultra-high energy density FAASC is developed using nickel-cobalt sulfide (NiCo2S4)/polyaniline (PANI)/manganese dioxide (MnO2) ternary composite on carbon fiber felt (CF) as positive and N, S-co-doped carbon nanofibers (CNF)/CF as negative electrode, respectively. Initially, porous δ-MnO2 nanoworm-like network is decorated on CF using potentiodynamic method. Subsequently, interconnected PANI nanostructures is grown on the MnO2 via a facile in situ chemical polymerization, followed by the electrodeposition of highly porous NiCo2S4 nanowalls. Benefiting from 3D porous structure of conductive CF and redox active properties of NiCo2S4, PANI and MnO2, FAASC achieved a superior energy storage capacity. Later, high-performance N, S-co-doped CNF/CF negative electrode is synthesized using electropolymerization of PANI nanofibers on CF, followed by the carbonization process. The assembled FAASC exhibits a wide voltage window of 2.2 V and remarkable specific capacitance of 143 F g-1 at a current density of 1 A g-1. The cell further delivers a superb energy density of 71.6 Wh kg-1 at a power density of 492.7 W kg-1, supreme cycle life and remarkable electrochemical stability under mechanical bending.

High-performance flexible asymmetric supercapacitor based on hierarchical MnO2/PPy nanocomposites covered MnOOH nanowire arrays cathode and 3D network-like Fe2O3/PPy hybrid nanosheets anode

The configuration of asymmetric supercapacitors (ASCs) has proven to be an effective approach to increase the energy storage properties due to the expanded working voltage resulting from the well-separated potential windows of the cathode and anode. However, carbonaceous anode materials generally suffer from relatively low capacitance, which restricts the enhancement of the energy storage performance of the full device in a traditional asymmetrical design. Herein, a rational design of all-pseudocapacitive ASCs (APASCs) using pseudocapacitive materials with a novel hierarchical nanostructure on both electrodes was developed to optimize the electrochemical properties for high-performance ASC devices. The assembled APASC employed the MnO2/PPy nanocomposites covered MnOOH nanowire arrays with core-shell hierarchical architecture as the cathode and Fe2O3/PPy hybrid nanosheets with 3D porous network-like structure as the anode. Owing to the coordinated pseudocapacitive properties and unique hierarchical nanostructures, this assembled APASC exhibited an exceptional volumetric capacitance of 4.92F cm-3 in a stable voltage window of 2 V, a maximum volumetric energy density of 2.66 mWh cm-3 at 19.72 mW cm-3, and excellent cyclic stability over 10,000 cycles (90.6 % capacitance retention), as well as remarkable flexibility and mechanical stability, providing insights for the design of flexible energy storage systems with enhanced performance.

Preparation of cyclodextrin polymer-functionalized polyaniline/MXene composites for high-performance supercapacitor

Controlled aggregation is of great significance in designing nanodevices with high electrochemical performance. In this study, an in situ aggregation strategy with cyclodextrin polymer (CDP) was employed to prepare polyaniline (PANI)/MXene (MX) composites. MXene served as a two-dimensional structure template. Due to supramolecular interactions, CDP could be controllably modified with PANI layers, effectively preventing the self-polymerization of PANI. As a result, this integration facilitated a more uniform growth of PANI on MXene and further improved the capacitance performance of CDP-MX/PA. In a three-electrode system, the specific capacitance of MX/PA at 1 A g-1 was 460.8 F g-1, which increased to 523.8 F g-1 after CDP-induced growth. CDP-MX/PA exhibited a high energy density of 27.7 W h kg-1 at a power density of 700 W kg-1. This suggests that the synthetic strategy employed in this study holds promise in providing robust support for the preparation of high-performance energy-storage device.

Ammonium Ion-Pre-Intercalated MnO2 on Carbon Cloth for High-Energy Density Asymmetric Supercapacitors

With the continuous development of green energy, society is increasingly demanding advanced energy storage devices. Manganese-based asymmetric supercapacitors (ASCs) can deliver high energy density while possessing high power density. However, the structural instability hampers the wider application of manganese dioxide in ASCs. A novel MnO2-based electrode material was designed in this study. We synthesized a MnO2/carbon cloth electrode, CC@NMO, with NH4+ ion pre-intercalation through a one-step hydrothermal method. The pre-intercalation of NH4+ stabilizes the MnO2 interlayer structure, expanding the electrode stable working potential window to 0-1.1 V and achieving a remarkable mass specific capacitance of 181.4 F g-1. Furthermore, the ASC device fabricated using the CC@NMO electrode and activated carbon electrode exhibits excellent electrochemical properties. The CC@NMO//AC achieves a high energy density of 63.49 Wh kg-1 and a power density of 949.8 W kg-1. Even after cycling 10,000 times at 10 A g-1, the device retains 81.2% of its capacitance. This work sheds new light on manganese dioxide-based asymmetric supercapacitors and represents a significant contribution for future research on them.

A 3D stacked corrugated pore structure composed of CoNiO2 and polyaniline within the tracheids of wood-derived carbon for high-performance asymmetric supercapacitors

A novel 3D stacked corrugated pore structure of polyaniline (PANI)/CoNiO₂@activated wood-derived carbon (AWC) has been successfully constructed to prepare high-performance electrode materials for supercapacitors. AWC functions as a supporting framework that provides ample attachment sites for the loaded active materials. The CoNiO₂ nanowire substrate, consisting of 3D stacked pores, not only serves as a template for subsequent PANI loading, but also acts as an effective buffer to mitigate the volume expansion of the PANI during ionic intercalation. The distinctive corrugated pore structure of PANI/CoNiO₂@AWC facilitates electrolyte contact and significantly enhances the electrode material properties. The PANI/CoNiO₂@AWC composite materials exhibit excellent performance (14.31F cm^-2 at 5 mA cm^-2) and superior capacitance retention (80% from 5 to 30 mA cm^-2), owing to the synergistic effect among their components. Finally, PANI/CoNiO₂@ AWC//reduced graphene oxide (rGO)@AWC asymmetric supercapacitor is assembled, which has a wide operating voltage (0 ∼ 1.8 V), high energy density (4.95 mWh cm^-3 at 26.44 mW cm^-3) and cycling stability (90.96% after 7000 cycles).

Recent advances in polyaniline-based micro-supercapacitors

The rapid development of the Internet of Things (IoTs) and proliferation of wearable electronics have significantly stimulated the pursuit of distributed power supply systems that are small and light. Accordingly, micro-supercapacitors (MSCs) have recently attracted tremendous research interest due to their high power density, good energy density, long cycling life, and rapid charge/discharge rate delivered in a limited volume and area. As an emerging class of electrochemical energy storage devices, MSCs using polyaniline (PANI) electrodes are envisaged to bridge the gap between carbonaceous MSCs and micro-batteries, leading to a high power density together with improved energy density. However, despite the intensive development of PANI-based MSCs in the past few decades, a comprehensive review focusing on the chemical properties and synthesis of PANI, working mechanisms, design principles, and electrochemical performances of MSCs is lacking. Thus, herein, we summarize the recent advances in PANI-based MSCs using a wide range of electrode materials. Firstly, the fundamentals of MSCs are outlined including their working principle, device design, fabrication technology, and performance metrics. Then, the working principle and synthesis methods of PANI are discussed. Afterward, MSCs based on various PANI materials including pure PANI, PANI hydrogel, and PANI composites are discussed in detail. Lastly, concluding remarks and perspectives on their future development are presented. This review can present new ideas and give rise to new opportunities for the design of high-performance miniaturized PANI-based MSCs that underpin the sustainable prosperity of the approaching IoTs era.

Preparation of MnO2-Carbon Materials and Their Applications in Photocatalytic Water Treatment

Water pollution is one of the most important problems in the field of environmental protection in the whole world, and organic pollution is a critical one for wastewater pollution problems. How to solve the problem effectively has triggered a common concern in the area of environmental protection nowadays. Around this problem, scientists have carried out a lot of research; due to the advantages of high efficiency, a lack of secondary pollution, and low cost, photocatalytic technology has attracted more and more attention. In the past, MnO₂ was seldom used in the field of water pollution treatment due to its easy agglomeration and low catalytic activity at low temperatures. With the development of carbon materials, it was found that the composite of carbon materials and MnO₂ could overcome the above defects, and the composite had good photocatalytic performance, and the research on the photocatalytic performance of MnO₂-carbon materials has gradually become a research hotspot in recent years. This review covers recent progress on MnO₂-carbon materials for photocatalytic water treatment. We focus on the preparation methods of MnO₂ and different kinds of carbon material composites and the application of composite materials in the removal of phenolic compounds, antibiotics, organic dyes, and heavy metal ions in water. Finally, we present our perspective on the challenges and future research directions of MnO₂-carbon materials in the field of environmental applications.