mF Cm-2 Research Articles

Stimuli-Triggered Diffusion Dynamics in Single-Junction Electrode for Enhanced Supercapacitor Performance: Insights into the Carrier Relaxation and Charge Transfer Kinetics.

Study of external triggers add new chemistry to energy storage research by virtue of controlling diffusion and charge transfer dynamics. Herein, we have chosen a model system, Ag2S-BiVO4 (Ag2S-BVO), for examining the diffusion dynamics upon light illumination using electrochemical and carrier relaxation studies. Favorable band alignments in the single-junction electrode lead to optimized carrier movement across the interfaces, developing a partial positive charge on the electrode, thereby enhancing the mass-transport of electrolyte ions toward the active electrode for efficient charge storage. Synergistic coupling across the heterojunction provides a high areal capacity of 338 mF cm-2 at 0.5 mA cm-2 under light illumination by facilitating the dominant diffusion characteristics within system. In addition, the Ag2S-BVO-based asymmetric supercapacitor exhibits an areal energy density of 32 mWh cm-2 @ 700 mW cm-2 under illumination. This study provides a strategy to tune the capacitive and diffusion contributions for high-performance light-sensitive supercapacitor devices.

A Dual Effect Additive Modified Electrolyte Strategy to Improve the Electrochemical Performance of Zinc-Based Prussian Blue Analogs Energy Storage Device.

Prussian blue analogs (PBA) exhibit excellent potential for energy storage due to their unique three-dimensional open framework and abundant redox active sites. However, the dissolution of transition metal ions in water can compromise the structural integrity of PBAs, leading to significant issues such as low cycle life and capacity decay. To address these challenges, we proposed a dual-effect additive-modified electrolyte method to alleviate such issues, introducing sodium ferrocyanide (Na4Fe(CN)6) into aqueous alkaline electrolytes. It could not only capture Zn2+ dissolved on the surface of Na1.86Zn1.46[Fe(CN)6]0.87 (ZnHCF) electrode material during the cycling process but also conduct redox reactions on the electrode surface to provide additional capacitance. Through experiments and molecular simulation calculations, it showed that Na4Fe(CN)6 can restrict the movement of Zn dissolution into the electrolyte on the electrode surface. Based on this, an asymmetric supercapacitor based on ZnHCF//activated carbon was assembled with a modified electrolyte. The assembled supercapacitor displayed a specific capacitance of 1,329.65 mF cm-2, a power density of 2,900 mW cm-2, and an energy density of 388.28 mW h cm-2. This study provides a new idea for the design and construction of stable and efficient PBA energy storage materials by inhibiting the leaching of transition metals in PBA.

Two-Dimensional Covalent Organic Frameworks with Carbazole-Embedded Frameworks Facilitate Photocatalytic and Electrocatalytic Processes.

Catalytic technologies are pivotal in enhancing energy efficiency, promoting clean energy production, and reducing energy consumption in the chemical industry. The pursuit of novel catalysts for renewable energy is a long-term goal for researchers. In this work, we synthesized three two-dimensional covalent organic frameworks (COFs) featuring electron-rich carbazole-based architectures and evaluated their catalytic performance in photocatalytic organic reactions and electrocatalytic oxygen reduction reactions (ORRs). Pyrene-functionalized COF, termed as FCTD-TAPy, demonstrated excellent photocatalytic performance for amino oxidation coupling and showed a remarkable preference for substrates with electron-withdrawing groups (up to >99% Conv. and >99% Sel). Furthermore, FCTD-TAPy favored a four-electron transfer pathway during the ORR and exhibited favorable reaction kinetics (51.07 mV/dec) and a high turnover frequency (0.011 s-1). In contrast, the ORR of benzothiadiazole-based FCTD-TABT favored a two-electron transfer pathway, which exhibited a maximum double-layer capacitance of 14.26 mF cm-2, a Tafel slope of 53.01 mV/dec, and a hydrogen peroxide generation rate of 70.3 mmol g-1 h-1. This work underscores the potential of carbazole-based COFs as advanced catalytic materials and offers new insights into the design of metal-free COFs for enhanced catalytic performance.

An Energy-Adjustable, Deformable, and Packable Wireless Charging Fiber Supercapacitor.

Wireless charging energy storage devices eliminate bulky wires of wearable electronics. However, rigid shape and specific charging energy restrict their applications in space-limited portable electronics. Herein, an all-carbon fiber supercapacitor is presented that features shape-adjustable, packable, and energy-controllable wireless charging functions. With the unique on-dimensional circuit structure, the maximum energy transfer efficiency from the electrical energy received by the wireless charging unit to the output energy of the fiber supercapacitor can reach up to ≈60.8%, and meanwhile this integrated fiber device exhibits an outstanding area capacity of 803 mF cm-2 and energy density of 1004 µWh cm-2, superior to most of the fiber supercapacitors. Moreover, this unique device can endure significant deformation in shape of circles ranging from 2 to 20cm diameter, and can be packed into narrow spaces, such as smart bracelet and disk-shaped pet global positioning system (GPS). By altering the device shape, the wireless charging current, voltage, and power can be adjusted in the range of 0.5-20mA, 1.4-15.5V, and 0.003-313mW, accommodating the energy requirements for nearly all existing micro-electronics. This work offers unprecedented opportunities for packable, space-confined and energy harvesting controllable wearable electronics.

HaloTag-Modified, Ferrocene Labeled Self-Assembled Monolayers for Protein Sensing.

Ferrocene (Fc)-based disulfide molecules of various lengths with amino acid scaffolds and alkane or oligo(phenylene-ethynylene) (OPE) bridges are used in a mixed SAM with a di-(ethylene oxide) terminal mercaptoundecanol diluent (PEG2). The relative height of the Fc redox reporter in the SAM is compared to determine if there are protective effects like antifouling and specific detection. The HaloTag-binding motif is used as a proof-of-concept to investigate the electrochemical response to the HaloTag protein due to its known covalent and fast linkage. When the Fc-SAMs are exposed to the HaloTag protein, there are an antifouling nature and more specific detection for the engulfed Fc-based molecules (C6tBu/Halo). The further out the Fc is from the SAM layer, the more nonspecific adsorption is detected. The double layer capacitance (CDL) has the smallest change for the C6tBu control (ΔCDL = -0.1 μF cm-2) showing antifouling properties and produces a large change (ΔCDL = 0.9 μF cm-2) as well as a shift in oxidation potential when the active C6Halo is exposed to the HaloTag protein (ΔE1/2 = 50 ± 10 mV). The remaining Fc molecules are partially in or outside the PEG2 layer, allowing more ion penetration/mobility even when the HaloTag protein is bound. Generally, a more disordered environment was observed for the Fc-based molecules when adding the HaloTag ligand, which is evident from a larger Efwhm and higher CDL. Desorption of the SAMs with sodium iodide (NaI) showed retention of the HaloTag protein bound with the corresponding ligand, whereas negative controls did not. Self-assembled monolayers for MALDI mass spectrometry (SAMDI-MS) were used as an orthogonal detection technique to show the qualitative binding of the HaloTag protein to the electrode. Together, these results provide insight into the antifouling and detection methods of engulfing the redox molecules in the SAM diluent.

Significantly Enhanced Oxidation Resistance and Electrochemical Performance of Hydrothermal Ti3C2Tx MXene and Tannic Acid Composite for High-Performance Flexible Supercapacitors.

The electrochemical performances of Ti3C2Tx MXene are severely restricted by the easy oxidation and restacking. Herein, tannic acid (TA) is introduced into Ti3C2Tx dispersion, and the mixed dispersion is further subjected to a simple hydrothermal treatment to prepare the hydrothermal Ti3C2Tx and TA composite (h-Ti3C2Tx@h-TA). Due to the decomposition of TA into gallic acid (GA), hydrothermal TA (h-TA) is a mixture of TA and GA. The strong interaction between h-TA and MXene mainly involves chemical interaction between the hydroxyl groups in h-TA and the surface/edge Ti atoms, along with numerous hydrogen bonds. The h-TA intercalation weakens MXene restacking and increases interlayer spacing, thereby improving ion transport pathways and accessibility. The chemical interaction between the hydroxyl groups of GA and the Ti atoms significantly enhances oxidation resistance and pseudocapacitive active sites. Therefore, the h-Ti3C2Tx@h-TA film electrode shows significantly enhanced capacitance (848 F·g-1 at 1 A g-1) and cycling stability (100% retention after 20 000 cycles). Moreover, flexible sandwiched supercapacitors with symmetrical h-Ti3C2Tx@h-TA electrodes exhibit a high energy density of 30.1 Wh kg-1 at a high power density of 300 W kg-1, outperforming those of Ti3C2Tx-based film electrodes and sandwiched supercapacitors reported so far. The extrusion-printed microsupercapacitors with h-Ti3C2Tx@h-TA electrodes demonstrate high areal capacitance (135 mF cm-2 at 5 mV s-1) along with energy storage performance (6.74 μWh cm-2 at 506 μW cm-2) and cycling stability (98.8% retention after 41 460 cycles), all while maintaining excellent flexibility. These impressive results indicate the great application potential of the hydrothermal Ti3C2Tx MXene and tannic acid composite in flexible energy storage devices.

Highly Conductive Supramolecular Salt Gel Electrolyte for Flexible Supercapacitors.

Conductive gels have greatly facilitated the development of flexible energy storage devices, including supercapacitors, batteries, and triboelectric nanogenerators. However, it is challenging for gel electrolytes to tackle the trade-off issues between mechanical properties and conductivity. Herein, a strategy of all inorganic salt-driven supramolecular networks is presented to construct gel electrolytes with high conductivity and reliable mechanical performance for flexible supercapacitors. The salt gel is successfully fabricated by combining a salt supramolecular network constructed by NH4Mo7O24·4H2O and FeCl3·6H2O and a polymer network of poly(vinyl alcohol). The inorganic salt supramolecular network serves as a rigid self-supporting framework in the hydrogel system for improving the mechanical properties and providing abundant active sites for accelerating ion transport. Furthermore, the salt gel-enabled supercapacitors are equipped and exhibit a high specific capacitance (199.4 mF cm-2) and excellent energy density (27.69 μWh cm-2). Moreover, the flexible supercapacitors not only present remarkable cyclic stability after 3000 charging/discharging cycles but also exhibit good electrochemical stability even under severe deformation conditions. The strategy of salt-gel-driven flexible supercapacitors would provide fresh thinking for the development of advanced flexible energy storage fields.

MOF-on-MOF Derived Co2P/Ni2P Heterostructures for High-Performance Supercapacitors.

Metal-organic frameworks (MOFs) have been widely used as versatile precursors to fabricate functional nanomaterials with well-defined structures for various applications. Herein, the presynthesized Ni-MOF nanosheets were grown on a Ni foam (NF) substrate, which then guided the nucleation and further growth of Prussian blue analogues (PBA) nanocubes to form MOF-on-MOF of the PBA/Ni-MOF film. This film was subsequently converted into a Co2P/Ni2P heterostructure. The NF-supported Co2P/Ni2P composites exhibited excellent supercapacitor performance, delivering a high specific capacity of 5124.2 mF cm-2 at 1 mA cm-2 and a remarkable capacity retention of 80.69% after 3000 cycles at 10 mA cm-2. An asymmetric supercapacitor assembled using Co2P/Ni2P/NF as the cathode and activated carbon as the anode yielded a maximum energy density of 0.34 mWh cm-2 at a power density of 1.50 mW cm-2. The enhanced supercapacitor performance is attributed to the synergistic effects of the Ni2P and Co2P components with multiple valence states as well as the unique hierarchical structure, which provides efficient pathways for electron and ion transport while mitigating volume expansion during energy storage. This synthetic strategy demonstrates an effective approach to fabricate phosphide-based hybrid materials for high-performance supercapacitor applications.

Enhanced solar hydrogen evolution by laminated integration of n+p-SiIP/TiO2/Pt inverted pyramid black Si photocathode

The nano/microstructuring of silicon (Si) via chemical methods has garnered significant attention due to its excellent light-trapping capabilities across a wide spectral range. Current research has predominantly focused on the synthesis of pyramidal-shaped microtextures, which enable two reflections on the surface, while largely overlooking the superior light-trapping potential of inverted pyramid silicon (SiIP) microtextures, which theoretically allow for three reflections. Moreover, there has been limited investigation into the application of inverted pyramid black silicon for solar-driven hydrogen evolution. This study reports the synthesis of uniformly arranged inverted pyramid-textured black silicon using the copper-assisted chemical etching (Cu-ACE) method to enhance the efficiency of solar-driven water splitting for hydrogen production. The formation mechanism and the influence of copper-localized surface plasmon resonance (Cu-LSPR) from Cu nanoparticle (NP) byproducts on photoelectrochemical (PEC) activity were systematically analyzed. To reduce sidewall defects and minimize photogenerated carrier recombination, the surface of the SiIP was treated with tetramethylammonium hydroxide (TMAH). A vertical PN junction was developed through ion implantation to reduce the external bias of the SiIP. Additionally, a uniform TiO₂ antireflective layer was deposited via atomic layer deposition (ALD), reducing the average reflectance of the SiIP-T4 to 5.78 % over the 300–1100 nm wavelength range. MoSₓ and Pt NPs were electrodeposited to improve the fill factor and enhance HER kinetics. With optimized catalyst loading, the n+p-SiIP-T4/TiO₂/Pt 80 mC electrode achieved a photocurrent density of 8.0 mA cm−2 at 0 V vs. RHE, an applied bias photon-to-current efficiency (ABPE) of 0.93 % at 0.24 V vs. RHE, and a double-layer capacitance (Cdl) of 91 μF cm−2. The onset potential (Von) was positively shifted by ∼1.13 V to 0.49 V vs. RHE compared to a SiIP photocathode, and the photocathode operated continuously at 0 V vs. RHE for 27 h in an acidic electrolyte. These results demonstrate that SiIP has significant potential for PEC hydrogen evolution, with further performance optimization achievable through structural and surface engineering.

Flexible Fiber Shaped Self-Powered System Based on Conductive PANI for Signal Sensing and Energy Harvesting.

As science and technology advance, people are increasingly inclined to use sustainable and portable wearable electronic devices. The traditional supporting power source, batteries, suffers from issues of flexibility and lifespan, severely constraining the development of wearable devices. Alternatively, the self-powered system, serving as a power source, can effectively collect energy from the surrounding environment, achieving maintenance-free operation and high adaptability, which has attracted widespread research. The coaxial fiber-structured self-powering system proposed in this study is based on a supercapacitor (SC) and a triboelectric nanogenerator (TENG). The carbon fiber (CF) has polyaniline (PANI) and rGO connected to it, and a friction layer of silicone rubber is wrapped around the outside. The conductivity of the fiber was increased by multiple PANI graftings, and a coaxial fiber-type TENG with a 2 mm diameter was created. Following weaving, the TENG displays a high power density of 576 mW m-2 and an open-circuit voltage of 160 V and a short-circuit current of 9 μA. In addition, the flexible fiber-shaped supercapacitor uses NiAl-LDHs@CF as the negative electrode and AC@CF as the positive electrode, showing a specific capacitance of up to 281.4 mF cm-2. Furthermore, the SC and TENG are assembled into a coaxial self-power supply system, which has excellent performance and shows extensive potential applications in the field of wearable device power supply.

Construction of Moiré-like TiO2/polypyrrole electrodes for high performance photo-assisted supercapacitors

There is currently a need for research into using external energy to increase the performance of the supercapacitor in energy storage systems because of their poor energy density. This paper reports the effective creation of photo-assisted supercapacitors with moiré-like morphology using polypyrrole (PPy) and titanium dioxide nano powder to replicate the surface of inexpensive and widely available CD discs. The composite material combines the moiré-like superstructure's strong light trapping property with titanium dioxide's high photo-sensitivity, achieving the aims of boosting light absorption, extending the optical route, and improving capacitor performance under light. By combining morphology construction and external energy interventions to improve capacitor performance, the specific capacitance under light is 509.0 F g−1 at 1 A g−1, 13.1 % higher than the same material without moiré-like morphology (449.9 F g−1). When assemble into a sandwich-structured symmetric supercapacitor, it has an area specific capacitance of 99.42 mF cm−2 and an energy density of 7.28 Wh kg−1 at a power density of 217.4 W kg−1, outperforming typical photo-assisted supercapacitors. The current work suggests a practical and straightforward method for increasing the light absorption efficiency and performance of photo-assisted supercapacitors.

Novel electrochromic-supercapacitor device based on P(TPACz)/WO3-PDA nanocomposite film

Organic–inorganic composites of (E)-3,5-di(9 H-carbazol-9-yl)-N-(4-(diphenylamino)benzylidene)aniline/dopamine-modified WO3 (P(TPACz)/WO3-PDA) were prepared by electrochemical polymerisation. The as-prepared P(TPACz)/WO3-PDA composites showed good electrochromic and electrochemical performance. The prominent electrochemical performance of P(TPACz)/WO3-PDA represents a high areal capacitance (32.15 mF cm−2 at 0.1 mA cm−2) and wide range of potential windows (-2.0−1.6 V). Additionally, symmetric supercapacitor devices based on P(TPACz)/WO3-PDA composite films were successfully constructed, which exhibited a high specific capacitance (13.88 mF cm−2 at 0.02 mA cm−2) and an energy density of 7.71 × 10−3 mWh cm−2 in n-doped station. The remarkable electrochromic and electrochemical performances are due to the synergy between the organic polymer and WO3-PDA. A complete large-area composite film structure with high conductivity promises fast electronic transport. This study provides a method for preparing multifunctional composite electrode materials, offering technical support for intelligent displays and energy storage technologies.

Electrochemical Performance of Niobium MXenes with Lanthanum.

MXenes are the newest class of two-dimensional nanomaterials characterized by large surface area, high conductivity, and hydrophilicity. To further improve their performance for use in energy storage devices, heteroatoms or functional groups can be inserted into the Mxenes' structure increasing their stability. This work proposes insertion of lanthanum atoms into niobium-MXene (Nb-MX/La) that was characterized in terms of morphogy, structure, and electrochemical behavior. The addition of La to the Nb-MXene structure was essential to increase the spacing between the layers, improving the interaction with the electrolyte and enabling charge/discharge cycling in a higher potential window and at higher current densities. Nb-MX/La achieved a specific capacitance of up to 157 mF cm-2, a specific capacity of 42 mAh cm-2 at 250 mV s-1, a specific power of 37.5 mW cm-2, and a specific energy of 14.1 mWh cm-2 after 1000 charge/discharge cycles at 50 mA cm-2.

Hierarchical crystalline/defective NiO nanoarrays with (111) crystal orientation for effective electrochromic energy storage

Developing high performance electrochromic materials with energy storage function is essential for next generation smart display devices. Here, a double-layer NiO film (NiO-dl) was prepared by compositing the defective NiO (d-NiO) with the crystalline NiO (c-NiO), with a unique prismatic nanosheet array structure. The synergistic effect as well as the large active area with defect sites and valence modulation brought about by the (111) crystal plane-oriented growth of the sputtering process can promote the intercalation and extraction of OH− and Li+, which greatly enhances the electrochemical properties. Specifically, the NiO-dl film achieves a prominent optical modulation covering visible region (89.5 % in KOH and 64.8 % in Li+ electrolyte at 550 nm) and near-infrared region (54.5 % in KOH and 37.2 % in Li+ electrolyte at 1000 nm), a high transparent bleached state (92.7 %), a superior coloring efficiency (44.7 cm2 C−1) and robust stability (95.1 % retention after 1000 cycles). A high area capacitance of 99.5 mF cm−2 at 0.14 mA cm−2 with the promising cycling performance exhibits the supercapacitor characteristics. The comprehensive evaluation of the NiO-dl film demonstrated its exploitative potential application in electrochromic energy storage fields.

Hydrogen bond crosslinking hydrogel for high-performance ultra-low temperature MXene-based solid state supercapacitors

The electrochemical performance of aqueous electrolytes at low temperatures is frequently suboptimal due to their low freezing point (0 °C). In this study, we constructed MXene-based ultra-low temperature polyvinyl alcohol/nanocellulose-H2SO4 (PVA/CNF-H2SO4) hydrogel electrolytes utilising hydrogen bonding between water molecules and nanocellulose. The process results in a reduction in the amount of free water present in the hydrogel electrolyte, lowering its freezing point to -77.35 °C. PVA/CNF-H2SO4-based solid-state supercapacitors (C7-SSC) demonstrate a capacitance of up to 813 mF cm-2 at -50 °C, exhibiting high-rate performance at low temperatures. The capacitance remains at 45 F g-¹ at a current density of 20 A g-¹. The maximum areal energy and power densities of our C7-SSC achieve 113 μWh cm-² and 0.4 μW cm-² at -50 °C, respectively, surpassing the majority of state-of-the-art devices. This work provides new insights into MXene-based hydrogel manufacturing and expands the range of potential applications for such materials.

Pt nanoparticles loaded on three-dimensional porous carbon as electrocatalysts for hydrogen evolution reaction

The electrochemical catalytic hydrogen evolution reaction (HER) holds significant potential for the sustainable production of environmentally friendly hydrogen energy. Currently, the precious metal Pt is widely acknowledged as the most superior electrocatalyst. However, its limited availability and exorbitant cost impede its extensive application. In this study, low Pt-loaded three-dimensional (3D) porous carbon composites were successfully synthesized as catalysts using a template-free method and a high-temperature pyrolysis method. By evaluating the HER performance of different Pt concentrations of the catalysts Pt/C-X (X=0, 0.05, 0.1, 0.2, 0.4, 0.7 mmol) in acid solution, it was observed that the overpotential of Pt/C-0.2 reached as low as 17 mV with a significantly low Tafel slope value of 48 mV cm−2. Meanwhile, the Bilayer capacitance (Cdl) reached an impressively high value of 247.5 mF cm−2. Consequently, this also provides a promising way to enhance the catalytic performance of the loaded catalysts.

High Areal Capacitance and Rate Capability of 3D-Printed Thick Electrodes with Optimized Conductive Networks from the Core-Sheath Structure.

Material extrusion 3D printing has received enormous attention to potentially overcome its limits by tailoring and designing thick electrodes. In this work, we prepared a thick reduced graphene oxide/carbon nanotube-reduced graphene oxide/carbon nanotubes/manganese oxide@carbon nanotubes (rGC-rGCMC) electrode with controlled lattice architectures, core-sheath structure, and hierarchical porosity by material coaxial extrusion 3D printing, freeze-drying, and thermal treatment. The volume ratios of core to sheath, including 100%-0%, 0%-100%, 20%-80%, 30%-70%, 40%-60%, and 50%-50%, were designed to investigate the influences of the core-sheath structure on thick electrodes. The electrodes with a core-sheath volume ratio of 30%-70% electrodes exhibited an enhanced areal specific capacitance of 588.27 mF cm-2 (39.48 F g-1) at a scan rate of 0.5 mA cm-2. All capacitance decays from core-sheath electrodes (20%-80%, 30%-70%, 40%-60%, and 50%-50%) were smaller than those from rGCMC (0%-100%) electrodes, indicating the improved rate capability from the core-sheath structure. On comparison of 30%-70% core-sheath electrodes with electrodes made of a homogeneous 30% rGC and 70% rGCMC mixture (30%+70%), lower capacitance (382.27 mF cm-2 and 25.66 F g-1 at 0.5 mA cm-2) of the 30%+70% mixture electrode without a core-sheath structure suggested less efficiency to harvest electrons from the redox reactions. Electrochemical impedance spectroscopy (EIS) data further supported and explained the resistances of thick electrodes with different volume ratios.

Electrochemical Analysis Comparison of Nitrogen Undoped and Doped Ti3C2Tx/Co3O4 Hybrid Composites on Carbon Cloth for Application as Electrode in Supercapacitor

Supercapacitor provides great potential for good energy storage devices application, compared with other energy storage such as rechargeable batteries, fuel cell, dielectric capacitors and so on. Freestanding and flexible electrodes are vital for the development of flexible and wearable devices that store energy. But the significant trade-off between mechanical flexibility and electrode electrochemical performance limits the fabrication of efficient energy storage systems. In this research, we report the synthesis of a 2D material Ti3C2Tx and Co NPs on carbon cloth (CC) substrate. Co NPs was synthesized by microplasma reactors which eliminate harmful reducing agents and are efficient and cost-effective. And the Co NPs/Ti3C2Tx were synthesized by hydrothermal method for supercapacitor. These materials were characterized by scanning electron microscopy (SEM) Energy Dispersive Spectroscopy and X-Ray Diffraction for morphology and phases analysis. Besides these Transmission electron microscopies (TEM) and X-ray Photoelectron spectroscopy (XPS) were also done. For electrochemical analysis these materials were applied on the 2.25 cm2 carbon cloth as active material (working electrode) by various electrochemical techniques in 1 M H2SO4 electrolyte. The Co NPs/Ti3C2Tx electrode had a maximum gravimetric capacity of 52 mAh g-1, specific capacitance of 580 mF cm-2 and 240 F g-1 at the current density of 1 mA cm-2. Figure 1

Copper Vanadium Oxide Yolk-Shell Microspheres with Excellent Capacitance and Cycling Performance for Electrochromic Supercapacitor.

Vanadium pentoxide (V2O5) is considered a promising material for electrochromic supercapacitors due to its rich color transitions and excellent electrochemical capacity. However, V2O5 exhibits low electrical conductivity, and its volume changes dramatically during charge-discharge cycles, leading to structural collapse and poor long-term cyclability. These issues have hindered the development and application of V2O5. In this study, copper vanadium oxide yolk-shell microspheres (CVO) were synthesized through a one-step solvent heat treatment with an annealing process. With the doping of copper element, the capacitance, conductivity, and cyclic stability of CVO microspheres were significantly enhanced. Subsequently, the sphere-wire network structure was formed by blending Na2V6O16·3H2O nanowires (NVO), resulting in the formation of CVO/NVO composites. The three-dimensional sphere-wire network efficiently facilitates the acquisition of additional redox sites and strengthens the material-to-substrate bonding. Under the combined influence of these favorable factors, CVO/NVO achieved a high specific capacitance of 39.2 mF cm-2, with a capacitance retention of 84% after 7500 cycles at a current density of 0.7 mA cm-2. The fully inorganic solid-state electrochromic supercapacitor (ECSC), assembled on the basis of CVO/NVO, demonstrates a vivid and clearly distinguishable color change (ΔE* = 37). Even more impressive is the energy storage capacity (18.4 mF·cm-2) and the cycling stability (up to 89% retention after 10,000 cycles) exhibited by the devices. These key performances are superior to those of most of the previously reported V2O5-based ECSCs, opening a promising avenue for the development of V2O5-based electrochromic energy storage devices.

Prussian Blue Anchored on Reduced Graphene Oxide Substrate Achieving High Voltage in Symmetric Supercapacitor.

In this work, iron hexacyanoferrate (FeHCF-Prussian blue) particles have been grown onto a reduced graphene oxide substrate through a pulsed electrodeposition process. Thus, the prepared FeHCF electrode exhibits a specific volumetric capacitance of 88 F cm-3 (specific areal capacitance of 26.6 mF cm-2) and high cycling stability with a capacitance retention of 93.7% over 10,000 galvanostatic charge-discharge cycles in a 1 M KCl electrolyte. Furthermore, two identical FeHCF electrodes were paired up in order to construct a symmetrical supercapacitor, which delivers a wide potential window of 2 V in a 1 M KCl electrolyte and demonstrates a large energy density of 27.5 mWh cm-3 at a high power density of 330 W cm-3.