Pseudocapacitive Charge Storage Mechanism Research Articles

Assessment of electrochemical removal mechanisms of diverse transition metal dichalcogenides for caesium ion removal in wastewater treatment

Abstract Effective treatment of radioactive wastewater is crucial for broader nuclear energy adoption, with caesium radionuclides (most exist in the form of caesium chloride) presenting challenges due to their long half-life and biological hazards. Conventional adsorbents like zeolites and carbon-based materials, including graphene, face limitations in adsorption capacity due to the formation of electric double layers (EDL). This has led to the investigation of alternatives such as transition metal dichalcogenides (TMDs) e.g., MoS2, MoSe2, and WSe2, which offer promising galleries for caesium ion removal. Aside from extensively studied MoS2, there is limited research on the adsorption mechanisms and capacities of other TMDs like MoSe2 and WSe2. Here, we conduct a comparative study examining the removal mechanisms and capacities of exfoliated MoS2, MoSe2, and WSe2 nanosheets, alongside an evaluation of these properties in relation to graphene. Our investigation reveals distinct removal mechanisms and capacities among these three materials for capturing caesium ions in a variety of mechanisms. MoS2 nanosheets primarily utilise a pseudocapacitive charge storage mechanism via intercalation, as evidenced by a total charge storage of 0.78 C g1, with only 2.6% stored via EDL formation. In contrast, MoSe2 predominantly relies on EDL formation, with almost 60% of the total 0.54 C g1 charge storage attributed to this mechanism. Lastly, WSe2 exhibits a combination of both charge storage behaviours, with a total charge storage of 0.77 C g1, of which 14% is due to EDL formation. This research highlights the potential efficacy of TMDs as viable materials for caesium removal, offering an appealing alternative to conventional adsorbents and likely fostering advancements in water treatment technologies.

Controlling Structure and Morphology of MoS2 via Sulfur Precursor for Optimized Pseudocapacitive Lithium Intercalation Hosts

AbstractMolybdenum disulfide (MoS2)‐based electrode materials can exhibit a pseudocapacitive charge storage mechanism induced by nanosized dimension of the crystalline domains, which is why control over material structure via synthesis conditions is of significance. In this study, we investigate how the use of different sulfide precursors, specifically thiourea (TU), thioacetamide (TAA), and L‐cysteine (LC), during the hydrothermal synthesis of MoS2, affects its physicochemical, and consequently, electrochemical properties. The three materials obtained exhibit distinct morphologies, ranging from micron‐sized architectures (MoS2 TU), to nanosized flakes (MoS2 TAA and LC). While all three synthesized samples exhibit pseudocapacitive Li+ intercalation properties, the capacity retention of the latter two consisting of nanosized flakes is further improved at high cycling rates. The individual charge storage properties are analyzed by operando X‐ray diffraction, dilatometry, and 3D Bode analysis, revealing a correlation between the morphology, porosity, and the electrochemical intercalation behavior of the obtained electrode materials. The results demonstrate a facile strategy to control MoS2 structure and related functionality by choice of hydrothermal synthesis precursors.

Magnetic transition magnetocaloric and supercapacitor behavior in synthesized Sn0.6Mn0.1Ge0.3Te alloys

This study comprehensively investigates the structural, microstructural, vibrational, magnetic, and magnetocaloric properties of novelty Sn0.6Mn0.1Ge0.3Te alloys synthesized using the sealed tube solid-state reaction method. The observed magnetic behavior showcases a transition from paramagnetic (PM) to ferromagnetic (FM) phases at the Curie temperature TC = 29 K. Notably, magnetic entropy change (−ΔSM), relative cooling power (RCP), and refrigerant capacity (RC) are calculated as 1.5 J/kg-K, 42.05 J/kg, and 37.39 J/kg, respectively, under a magnetic field of 60 kOe. Arrott curve analysis further validates the magnetic phase transition, affirming a second-order transition between FM and PM phases. Critical exponents (β, γ, and δ) are derived from field-dependent magnetic entropy changes around the second-order transition and strongly agree with the mean field model. These critical exponents establish a clear correlation between critical behavior and magnetocaloric effects, reinforcing the potential of Sn0.6Mn0.1Ge0.3Te alloys for magnetocaloric applications. Investigations into the electrochemical properties of the alloy have indicated that it exhibits a specific capacitance of 152.9 F/g at a scan rate of 20 mV/s, demonstrating a predominantly pseudocapacitive charge storage mechanism. Additionally, the alloy has proven to be highly stable, retaining 94.2 % of its specific capacitance after 10,000 cycles.

Inducing and Understanding Pseudocapacitive Behavior in an Electrophoretically Deposited Lithium Iron Phosphate Li-Metal Battery as an Electrochemical Test Platform.

Our study has effectively employed electrophoretic deposition (EPD) using AC voltage to develop a lithium iron phosphate (LFP) Li-ion battery featuring pseudocapacitive properties and improved high C-rate performance. This method has significantly improved the battery's specific capacity, achieving an impressive 100 mAhg-1 at a 5 C discharge rate, which showcases its superior high-rate capability. Additionally, the battery displayed excellent reversibility during its performance cycles. These results confirm the EPD method's efficacy in improving LFP electrode performance, yielding notable improvements in cycling stability and high-rate capability. The enhanced capacity and high-rate performance of the electrophoretic-deposited LFP electrodes are largely due to the fast kinetics facilitated by pseudocapacitive behavior-induced charge storage and a high Li-ion diffusion constant measured in our EPD-deposited LFP electrodes. This underscores the practicality of our approach and the development of a fundamental test platform to investigate the pseudocapacitive charge storage mechanism in electrodes with typical battery-like behavior.

Synthesis, characterization, and synergistic effects of CuS/MnO2 nanocomposite electrodes for high-performance supercapacitors

Metal oxides, metal sulfides, and their derivatives exhibit impressive electrochemical capabilities, offering potential for the creation of novel electrodes with superior performance in supercapacitors. In this study, we introduce a novel binary composite consisting of copper sulfide and manganese oxide (CuS/MnO2). This composite is designed with specific CuS and MnO2 ratios (80 % and 20 %, respectively) to explore their electrochemical behavior and optimize the performance of these nanostructures. According to morphological and structural analysis, it was observed that the synthesis process yielded high-purity nanoparticles and nanorods of CuS and MnO2. Notably, no byproducts were detected, indicating a successful synthesis process. Through a rapid pseudocapacitive charge storage mechanism, the electrochemical investigations reveal that all electrodes in a three-electrode setup tested in 3 M KOH electrolyte solution and the novel CuS/MnO2 electrode exhibit typical capacitive behavior in the potential of 0.0–0.5 V, with good reversibility and charge storage properties (specific capacitance: 451 F g−1, low resistance: 1.21 Ω, cyclic stability: 98.33 % at 4 A g−1 continuously 2000 cycles). Surprisingly, the CuS/MnO2 nanocomposite (NC) exposed high power density is about 1997 W kg−1 and a maximum energy density of 28.19 W h kg−1exceptionally is achieved. The significance of additional transition metal oxide-based electrodes in achieving noticeably better performance is demonstrated by these results.

Modulating charge storage mechanism of cobalt-tungsten nitride electrodes using in situ formed metal-p-n heterojunction for ultrahigh energy density supercapattery

Supercapatteries combine both diffusion-controlled and capacitive charge storage mechanisms to simultaneously deliver exceptional power density and energy density. Though developing materials that combine both charge storage mechanisms for use as supercapattery electrodes is difficult, one solution has been to modify a material that inherently has one of these mechanisms so that it also exhibits the other form of charge storage. In the present study, we modulate the electrochemical reconstruction of a W5N4 electrode to modify its charge storage from pure battery-type to pseudocapacitive, thus enhancing its specific capacity and cyclic stability. This modulation was carried out by embedding Co in W5N4 (Co-W5N4), leading to the formation of W and N-doped Co(OH)2 as an active phase and producing a high specific capacity of 2211 C g−1 at 2 A g−1. The incorporation of a thin layer of TiO2 (Co-W5N4/TiO2) through atomic layer deposition minimized tungsten dissolution during reconstruction, thus generating in-situ a dynamic metal–p-n junction heterostructure (Co-W5N4||Co(OH)2||TiO2) that modulated the charge flow, achieving high-rate capability (retaining 53.1 % at 50 A g−1 compared to 2 A g−1) and cyclic stability (82.8 % after 100,000 cycles at a high current density of 40 A g−1). As illustrated by operando electrochemical impedance spectroscopy and physicochemical analysis, the dynamic response of metal–p-n junction sustains the pseudocapacitive charge storage mechanism at high current rate. This study thus demonstrates the formation of metal-p-n heterojunction and describes its dynamic response under actual charge/discharge operating conditions, providing useful information for the design of energy storage electrodes and energy conversion catalysts.

Unveiling π–π interactions in triptycene-phenazine/SWCNT redox chemistry using ESR spectroscopy

Trip-Phz/SWCNTs composites deliver a three-electron reaction, accompanied by a pseudo-capacitive charge storage mechanism. ESR spectroscopy confirms the strong π–π interactions between radical cations and SWCNTs, leading to a radical-free state.

Synthesis and characterization of zinc aluminate electrodes for supercapacitor applications

We report, for the first time, the thorough electrochemical characterization of zinc aluminate spinel. Four different stoichiometric composition of zinc aluminate (ZnAl1.5O3.25, ZnAl2O4, ZnAl2.87O5.30, and ZnAl4O7) were prepared by solution combustion method. The obtained powders after calcination at 1000 °C were characterized through scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction to analyze the morphology, elemental composition and structure, respectively, of the zinc aluminate compositions. The electrodes were prepared by coating slurry of zinc aluminate, carbon black and polyvinylidene fluoride on nickel foam in a ratio of 8:1:1. The electrochemical characterization was carried out by cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). ZnAl1.5O3.25 exhibited the highest specific capacity of 546 C/g at 1 mV/s and 336 C/g at 1 A/g, as appraised by CV and GCD analysis, respectively. EIS test revealed that ZnAl1.5O3.25 had the modest impedance value. The energy density value for ZnAl1.5O3.25 sample was 16.79 Wh/kg at 1 A/g with a power density of 179.9 W/kg. The as developed electrodes showed predominantly pseudo-capacitive charge storage mechanism.

Synthesis of Nickel Oxide Nanoarchitecture Crystals as an Advanced Electrode Material for Supercapacitors

A NiO nanoarchitecture with a chain-like structure material was synthesized using a CTAB-assisted sonochemical method and then applied as an electrode in supercapacitors. Spectral analysis like XRD, FTIR and SEM was used to characterize the crystalline nature, internal structure and morphological properties of NiO nanoarchitecture. At a scan rate of 5 mV s-1, the NiO material exhibits a pseudocapacitive charge storage mechanism and provides a specific capacitance of 562 with good rate capabilities. Moreover, the chain-like NiO material exhibits outstanding cycle stability, retaining 96% of the original capacitance after 3,000 cycles at a scan rate of 100 mV s-1. The high-performance, chain-like nanostructured NiO material is easy to make and is of great interest for improved energy storage devices.

Contribution of electron localization and delocalization zones in the performance of electrochemically reduced graphene oxide based supercapacitors: An experimental and the first-principles study

Graphene oxide (GO) has been investigated as a promising electrode material for supercapacitors due to its intriguing physical and chemical properties. However, the interpretation of the pseudocapacitance and charge storage mechanism in GO and its derivatives is still debated and is yet to be understood. Here, we report a detailed and comprehensive analysis of the pseudocapacitive charge storage mechanism in GO and electrochemically reduced GO electrodes using cyclic voltammetry, electrochemical impedance spectroscopy combined with first principles calculations. Contrary to conventional believes, our results reveal that pseudocapacitive charge storage mechanism is due to conduction built by the electron delocalization region in GO during reduction rather than localized electron transfer. It is observed that the removal of oxygen functional groups from the surface of the GO leads to decrease in diffusion current and the reconstructed electron delocalization region contributes to increased specific capacitance. This work provides a clear and fundamental understanding of pseudocapacitive charge storage mechanisms in GO derivatives that will be also helpful in exploration of GO-based novel and hybrid electrode materials for high-performance supercapacitors.

Ultrafine Fe2VO4 nanoparticles anchored on Ti3C2Tx nanosheets (Fe2VO4@Ti3C2Tx) as high-energy anode for lithium-ion storage

Recently, as a new breakthrough for lithium-ion storage anode materials, transition metal vanadates, such as Fe2VO4, have attracted much attention, which, however, still suffer from slow electrochemical kinetics and substantial volume expansion. Hybrid with high conductivity materials is an effective route to deal with these issues. Herein, in situ synthesis of Fe2VO4@Ti3C2Tx composites with porous sandwich structure by co-precipitation-calcination process was reported. Ultrafine Fe2VO4 nanoparticles (10–15 nm) in situ grew and was anchored on Ti3C2Tx nanosheets, which effectively inhibits both the grain growth for Fe2VO4 and stacking for Ti3C2Tx, thus facilitating the electrochemical kinetics and alleviating the volume change of Fe2VO4 to maintain the integrated structure during the cycling process. As a result, Fe2VO4@Ti3C2Tx anode shows high Li+ diffusion coefficient (2.72 × 10−11 cm2 s−1) and pseudocapacitive charge storage mechanism (capacitive charge storage contribution 70.85–84.80 % at 0.2–1.0 mV s−1), which guarantee rapid charging and discharging capability. Consequently, outstanding rate performance (1012–595 mAh g−1 at 0.2–3.0 A g−1) and superior cycling capability (663 and 416 mAh g−1 at 1.0 A g−1 for 200 cycles and 2.0 A g−1 for 500 cycles, with the average capacity attrition rate of 0.059 % and 0.053 %, respectively), were achieved, which render Fe2VO4@Ti3C2Tx composites important potential for lithium-ion storage.

Redox Electrolytes-Assisting Aqueous Zn-Based Batteries by Pseudocapacitive Multiple Perovskite Fluorides Cathode and Charge Storage Mechanisms.

Aqueous Zn-based batteries (AZBs) have attracted intensive attention. However, to explore advanced cathode materials with in-depth elucidation of their charge storage mechanisms, improve energy storage capacity, and construct novel cell systems remain a great challenge. Herein, a new pseudocapacitive multiple perovskite fluorides (ABF3 ) cathode is designed, represented by KMF-(IV, V, and VI; M = NiCoMnZn/-Mg/-MgFe), and constructed Zn//KMF-(IV, V, and VI) AZBs and their flexible devices. Ex situ tests have revealed a typical bulk phase conversion mechanism of KMF-VI electrode for charge storage in alkaline media dominated by redox-active Ni/Co/Mn species, with transformation of ABF3 nanocrystals into amorphous metal oxide/(oxy)hydroxide nanosheets. By employing single or bipolar redox electrolyte strategies of 20mm [Fe(CN)6 ]3- or/and 10mm SO3 2- /Cu[(NH3 )4 ]2+ acting on KMF-(IV, V, and VI) cathode and Zn anode, the AZBs show an improved energy storage owing to additional capacity contribution of redox electrolytes. The as-designed Zn//polyvinyl alcohol (PVA)-KOH-K3 [Fe(CN)6 ]//KMF-(IV, V, and VI) redox gel electrolytes-assisting flexible AZBs (RGE-FAZBs) exhibit remarkable performance under different bending angles because of slight dissolution corrosion of zinc anode compared with liquid electrolytes. Overall, the work demonstrates the novel idea of conversion-type multiple ABF3 cathode for redox electrolytes-assisting AZBs(RE-AZBs) and their flexible systems, showing great significance on electrochemical energy storage.

FeSe2/TiO2 heterostructure as an efficient photocatalyst and their electrochemical energy storage applications

This paper reported the facile synthesis of FeSe2 and TiO2 and their different wt.% composites (75 and 50% of TiO2, here after FT-1 and FT-2) via solvothermal in/ex-situ sol-gel method for the first time efficient photocatalytic degradation of Rhodamine removal and supercapacitor applications. Small bandgap energy was obtained for FT-1 samples from the optical analysis, with a more negligible band edge absorption. The result shows that the composite of FeSe2 and TiO2 increases the absorption, which collectively enhances the separation of the charge carriers and redox activities. The photocatalytic activities analysis demonstrated that the FT-1 sample reveals the fastest removal of the RB dye in just 60 min (FT-2, FeSe2, and TiO2 = 90, 100, and 180 min) with good stability (98%) after several cycles. As supercapacitor electrode materials, all electrodes showed well-defined peaks in their CV loops and voltage plateaus in their charge/discharge profile, illustrating the pseudocapacitive charge storage mechanism. No voltage decay was observed during many discharge currents from the charge/discharge investigation, demonstrating the chosen potential frame is a suitable window for the FeSe2 and TiO2 nanomaterials. The higher capacity of 295 (FT-1) than other electrodes (FeSe2, TiO2, and FT-2 = 220, 115, and 240 C/g) at 1 A/g was obtained to reach 180 at 10 A/g, resulting in an enhanced rate capability of 82%. The high rate capability is the cause of its more minor charge transfer resistance, resulting in higher conductivity and supporting rapid charge transport kinetics. These outstanding properties open a new avenue for other FeSe2 and TiO2 nanomaterials for efficient energy storage technologies.

Electrochemical insights into the energy storage mechanism of birnessite in aqueous solutions

The birnessite structure of manganese dioxide makes this compound a promising electrode materials for energy storage devices including, in particular for supercapacitors, thanks to the high theoretical capacitance and pseudocapacitive response of MnO2. The effect of ionic species, in particular alkali cations, on the structure of birnessite has been intensively discussed, however their role on the charge storage mechanism is still controversial. Taking into consideration the solvation/desolvation process of different alkali cations (Li+, Na+, K+ and Cs+), this work unveils relevant new aspects of the pseudocapacitive charge storage mechanism of birnessite. The work also discusses the simultaneous contribution of non-faradaic (double-layer processes) and faradaic redox reactions to the charge storage mechanism based on electrochemical impedance spectroscopy (EIS) analysis. It was found that the relative extension of these processes was dependent on diffusional features related to the cation degree of solvation. Results revealed that the potassium birnessite exhibited an interesting specific capacitance value that reached 175.6 F g−1 at 0.5 A g−1 in a potential window of 0.8 V in 0.5 M Li2SO4. This capacitance value includes a contribution resulting from intercalation/deintercalation of cations in the interlayer region and a larger contribution from the double-layer processes (above 76%). This investigation provides new electrochemical insights on the charge storage of birnessite, highlighting the role of alkali ions intercalation in the interlayer structure of birnessite.

Hydrothermal assisted synthesis of hierarchical SnO2 micro flowers with CdO nanoparticles based membrane for energy storage applications

Hierarchical nanostructures with appropriate morphology and surface functionalities are highly desired to achieve an optimized electrochemical property for active electrode materials. This work renders the facile hydrothermal synthesis of CdO, SnO2, and CdO–SnO2 nanocomposite, and their capacitive performance was tested. The formation of the pure samples and their composite was committed by low-temperature Raman spectroscopy and x-ray diffraction studies which revealed the tetragonal and cubic structures of CdO and SnO2 powder samples with good crystallinity and purity. The morphological postmortem reveals the formation of nanoparticles morphology of CdO with a highly smooth surface appearance. Besides, the SnO2 illustrates the morphology of the micro flowers composed of ultrathin nanosheets. More specifically, the electrochemical properties indicate the pseudocapacitive charge storage mechanism based on cyclic voltammetry and chronopotentiometry analysis. The CdO–SnO2 composite electrode displayed a higher capacitance due to additional pores/space offered for active sites and continuously allowed electrolyte ions to interact with the inner/outer surface of the electrode. These exciting findings led us to design and fabricate battery hybrid supercapacitors (BHSC) from CdO–SnO2, and activated carbon (AC), referred to as CdO–SnO2//AC BHSC, attains a high power delivery (5717 W/kg), and a maximum energy density of 42 Wh/kg at low discharge rate. Noteworthy, a stable cycling performance was obtained with only 91.3% retention after 8000 cycling at a large discharge current of 10 A/g, denoting the magnificent durability of the active electrode material.

Photocatalytic degradation and electrochemical energy storage properties of CuO/SnO2 nanocomposites via the wet-chemical method

Integrating semiconducting functional materials is a way to enlarge the photoexcitation, energy range, and charge separation, greatly elongating the photocatalytic efficiency to enhance the chemical and physical properties of the materials. This work depicts and investigates the impact of cuprous oxide (CuO) and tin dioxide (SnO2)-based catalysts with various CuO concentrations on photocatalytic and supercapacitor applications. Moreover, three distinct composites were made with varied ratios of CuO (5, 10, and 15% wt. Are designated as AT-1, AT-2, and AT-3) with SnO2 to get an optimized performance. The photocatalytic properties indicate that the CuO/SnO2 nanocomposite outperformed its bulk equivalents in photocatalysis using Methyl blue (MB) dye in a photoreactor. The results were monitored using a UV–visible spectrometer. The AT-1 ratio nanocomposite displayed 96% photocatalytic degradation compared to pure SnO2 and CuO. CV analysis reveals a pseudocapacitive charge storage mechanism from 0.0 to 0.7 V in a potential window in an aqueous medium. The capacitive performance was also investigated for all electrodes, and we observed that a high capacitance of 260/155 F/g at 1/10 A/g was attained for the AT-1 electrode compared to others, specifying good rate performance.

Crystallinity Tuning of Na3 V2 (PO4 )3 : Unlocking Sodium Storage Capacity and Inducing Pseudocapacitance Behavior.

As a promising cathode material of sodium-ion batteries, Na3 V2 (PO4 )3 (NVP) has attracted extensive attention in recent years due to its high stability and fast Na+ ion diffusion. However, the reversible capacity based on the two-electron reaction mechanism is not satisfactory limited by the inactive M1 lattice sites during the insertion/extraction process. Herein, self-supporting 3D porous NVP materials with different crystallinity are fabricated on carbon foam substrates by a facile electrostatic spray deposition method. The V5+ /V4+ redox couple is effectively activated and the three-electron reactions are realized in NVP for sodium storage by a proper crystallinity tuning. In a disordered NVP sample, an ultra-high specific capacity of 179.6 mAh g-1 at 0.2 C is achieved due to the coexistence of redox reactions of the V4+ /V3+ and V5+ /V4+ couples. Moreover, a pseudocapacitive charge storage mechanism induced by the disordered structure is first observed in the NVP electrode. An innovative model is given to understand the disorder-induced-pseudocapacitance phenomenon in this polyanion cathode material.

Scalable Preparation of Nanostructured Hybrids of Transition Metal Sulfide/Oxide With Carbon Materials for High-Performance Supercapacitors

The ever-growing demands and rapid development of energy storage devices and systems pressed the need for low-cost yet highly performing electrode materials. The transition metal oxide and sulfide-based hybrids holds great promise as the active electrode materials in supercapacitors, due to their large surface area and variable oxidation states. These properties enable significantly high energy storage via electrical double layer and pseudocapacitive charge storage mechanisms. Herein, we discuss a facile, scalable, and environment-friendly preparation process to produce transition metal sulfide and oxides based on resource rich metals such as Mn, Fe, V etc. and their hybrids with carbonaceous materials, such as carbon nanotubes and graphene. This strategy encompasses solvent-less mixing of a metal salt, surfeit yet non-toxic abundant elemental sulfur and carbon precursor under continuous ball milling and thermo-annealing. The resulting nanohybrids were thoroughly investigated by means of several techniques. XRD, HRTEM, SEM, Raman and BET could gather insights on the morphology and the fine material structure, as well as on the spectroscopic properties. Finally, the electrochemical properties as supercapacitor components were investigated in regards with varyingly increasing carbon content. The nanohybrids were tested in both aqueous and organic electrolytes for bettering energy and power performances. Charge storage performances and components stability in both symmetric and asymmetric devices were assessed via CV, GCD, EIS.

Synthesis of carbon-modified cobalt disphosphide as anode for sodium-ion storage

Phosphorus-rich metal phosphides have a high theoretical sodium-ion storage capacity. For example, cobalt disphosphide (CoP2) possesses a theoretical sodium-ion storage capacity of about 1330 mAh g−1, while the theoretical capacity of cobalt phosphide (CoP) is about 893 mAh g−1. However, it is currently challenging to synthesise phosphorus-rich metal phosphides. Herein, we report the synthesis of phosphorus-rich rod-like cobalt disphosphide with a carbon shell (CoP2@C) by thermal decomposition of polydopamine-coated cobalt oxalate in the presence of sodium hypophosphite. The as-obtained CoP2@C anode delivered a high sodium-ion storage capacity of ∼550 mAh g−1 at 500 mA g−1 due to its multi pseudocapacitive and intercalation charge storage mechanisms. These preliminary results show that CoP2@C hold a great promise for developing high-performance electrochemical energy storage devices based on sodium-ion as the charge carrier.

Vapor-phase polymerization of fibrous PEDOT on carbon fibers film for fast pseudocapacitive energy storage

Poly(3,4-ethylenedioxythiophene) (PEDOT) has emerged as one of promising conductive polymers in energy storage devices. However, the conventional solution oxidative polymerization usually produces PEDOT with low conductivity and limited surface area. This work reports the preparation of highly conductive fibrous PEDOT by a vapor-phase polymerization initialized with Fe2O3 nanosheets that are uniformly electrochemically deposited on the N-doped carbon nanofibers (CNFs) film. The incorporation of highly conductive PEDOT nanofibers expands the film and simultaneously increase the film conductivity by 80 times (103 S cm−1). Accordingly, an areal capacitance of 1926 mF cm−2 at 5 mA cm−2 with a PEDOT mass loading of 8.68 mg cm−2 has been achieved. Importantly, the fast pseudocapacitive charge storage mechanism afford the CNF-PEDOT a high-rate capability which retains 68% capacitance in 5–50 mA cm−2. Especially, the CNF-PEDOT film electrode exhibits an outstanding stability with 87% capacitance retention after 10,000 consecutive charging and discharging cycles at 50 mA cm−2. A CNF-PEDOT-based supercapacitor delivers an energy density of 97 μWh cm−2 at power density of 0.45 mW cm−2, surpassing state-of-the-art PEDOT-based devices. This work will open a new avenue for preparing highly conductive PEDOT hybrid electrodes towards high-performance supercapacitors.