Electrode Materials For Supercapacitors Research Articles

Thiol-functionalized conductive Co-MOF and its derivatives S-doped Co(OH)2 nanoflowers for high-performance supercapacitors

The low conductivity of many traditional metal–organic-framework (MOF)-based electrode limits their developments in the field of electrochemical energy storage and still of great challenge. The controllable preparation of various kinds of nanomaterials using thiol-functionalized MOF shows great prospects. In this work, a thiol-functionalized metal–organic framework sheet structure (Co-MOF/NF) on nickel foam was successfully prepared by in situ interfacial growth synthesis, which was transformed into its derivatives S-doped β-Co(OH)2 nanoflowers Co-x/NF (x = 1, 2 and 6) in different concentrations of KOH solutions through ion etching/exchange reaction. The pristine thiol-functionalized Co-MOF/NF and its derivatives Co-x/NF (x = 1, 2 and 6) nanoflower-like arrays could be used as positive electrode materials for effective supercapacitors. Among them, the transformation of the nanoflower-like Co-1/NF electrode exhibits excellent electrochemical properties with high areal capacitance (1925 ± 23 mF/cm2 at 1 mA/cm2), good rate performance, excellent conductivity and decent cycling stability. The Co-1//AC ASC device provides a high energy density of 0.176 mWh/cm2 (92.6 Wh/kg) at a power density of 0.745 mW/cm2 (392.1 W/kg). And this Co-1//AC ASC device exhibits a good cycling stability and practical application in energy storage field. This study provides a new strategy for the pristine thiol-functionalized MOF and its conversion nanostructures for energy storage applications.

Enhancement of supercapacitor efficiency by Fe3+ doping in hydrothermally synthesized NiO nanoparticles

This study examines the physicochemical and electrochemical characteristics of hydrothermally produced, 800°C-annealed pure and Fe3+ doped (0.02, 0.04, and 0.06 M) NiO nanoparticles(NPs).The face-centred cubic structure of NiO NPs was verified by XRD analysis, and doping resulted in a decrease in crystallite size from 43.92 nm to 19.67 nm.FE-SEM revealed dense and irregularly arranged granular morphologies, while EDAX confirmed successful Fe3+ incorporation into NiO matrix. UV–Vis DRS showed an increase in bandgap energy from 3.15 eV to 3.71 eV. XPS confirmed the presence of Ni2+ and Fe3+ with their elemental compositions. According to BET analysis, Fe3+ doping increases pore size and specific surface area, which raises specific capacitance.VSM analysis of pure and Fe3+ doped NiO NPs demonstrated a transition from a weak ferromagnetic to a distinctive ferromagnetic behaviour, which is beneficial for energy storage as well as data storage applications.The electrochemical studies showed that 0.06 M Fe3+ doped NiO had the maximum specific capacitance of 360.96 F g−1 at the scan rate of 10 mV s−1and EIS Nyquist plots showed enhanced electrical conductivity. These results highlight the possibility of Fe3+ doped NiO NPs as excellent electrode materials for high-efficiency supercapacitors.

Capacitive behaviors for surface-sulfonated polyaniline nanofibers in different acidic electrolytes

Abstract Unique surface-sulfonated polyaniline nanofibers (PANI-S) were fabricated through one-pot polymerization to evaluate the feasibility of their applications as electrode materials for high-performance supercapacitors that can be operated in relatively weak acidic electrolytes. Benefiting from the self-doping effect and improved dispersion in aqueous solution for the nanofibers, as well as the effective buffering function of the electrolyte, the PANI-S exhibits excellent capacitive performance across a broad pH value range in acidic electrolytes. More clearly, the specific capacitance of the PANI-S remains remarkably stable, ranging from 752.4 to 754.4 F g−1 at a scan rate of 5 mV s−1 and from 575.4 to 536.8 F g−1 at a current density of 1 A g−1, as the pH value of the electrolyte varies from 0 to 6. However, the capacity retention rate of PANI-S gradually decreases from 79.2% to 37.2% as the current density increases from 1 A g−1 to 20 A g−1, with the pH of the buffered solution increasing from 0 to 6. The excellent electrochemical activity in low acidic electrolytes for PANI nanofibers can be attributed to the compensation effects of the self-doped local proton reservoir.

Hierarchical Nb@NbN core-shell-like nanocolumns for asymmetric supercapacitors

Transition metal nitrides (TMNs) are promising electrode materials for supercapacitors because of their high electrical conductivity and chemical stability. The rational design and facile synthesis of TMNs electrode materials with a unique nanostructure are the key to develop high-performance supercapacitors. Herein, we propose a two-step, binder-free, and eco-friendly approach utilizing magnetron sputtering at an oblique angle deposition configuration to fabricate hierarchical Nb@NbN core–shell-like nanocolumns for supercapacitors. This distinctive heterostructure not only creates lattice defects, increases active surface area, facilitates ion diffusion and charge transfer, but also optimizes the electronic structure and enhances the conductivity. As a result, the hierarchical Nb@NbN core–shell-like nanocolumn electrodes exhibit a high areal capacitance of 53.3 mF cm−2 at 1 mA cm−2 and an excellent capacitance retention of 93.5 % after 20,000 cycles, outperforming pristine NbN and the majority of previously reported TMNs electrodes. Moreover, the assembled Nb@NbN nanocolumns//VN thin films asymmetric supercapacitor device can deliver a maximum energy density of 49.8 mWh cm−3 and power density of 82 W cm−3. This work presents a facile and environmentally friendly strategy for the synthesis of TMNs core–shell-like nanocolumns, and further demonstrates their promising potential for use in supercapacitors.

Significantly enhanced electrochemical performance of Al-Ti3C2Tx MXene synthesized from Al-Ti3AlC2 MAX phase

MXenes, a type of two-dimensional nanomaterials consisting of transition metal carbides/nitrides, have emerged as promising electrode materials for supercapacitors. Especially, Ti3C2Tx MXene prepared from Ti3AlC2 MAX phase shows great application potential in flexible supercapacitors due to its facile synthesis, excellent conductivity and film-forming property. In contrast to conventional Ti3AlC2, excessive aluminum is incorporated in the synthesis process to produce Al-Ti3AlC2. In this study, Ti3AlC2 and Al-Ti3AlC2 MAX phases are used to synthesize Ti3C2Tx and Al-Ti3C2Tx MXenes, respectively, by the same method of HF:HCl etching and LiCl intercalation. The freestanding Ti3C2Tx and Al-Ti3C2Tx film electrode is separately prepared through simple vacuum filtration. The presence of excess aluminum during the Al-Ti3AlC2 synthesis facilitates to form more homogeneous grains structure with relatively larger particle sizes and an improved stoichiometric MAX phase with a Ti:C ratio closer to 3:2. The resulting Al-Ti3C2Tx nanosheets show improved oxidation resistance with relatively uniform and larger dimensions, which facilitate the higher conductivity with slightly increased interlayer spacing for the Al-Ti3C2Tx film. Therefore, the Al-Ti3C2Tx film electrode shows more efficient ions transport and charge transfer, and thus achieves significantly enhanced capacitance (399 F g−1 at 1 A g−1) and rate performance (63.6 % retention from 1 to 10 A g−1) compared to the Ti3C2Tx film electrode (342 F g−1 at 1 A g−1, 55.6 % retention from 1 to 10 A g−1). Moreover, the Al-Ti3C2Tx-based flexible sandwiched supercapacitor also exhibits superior energy storage performance. The impressive results indicate that Al-Ti3C2Tx MXene synthesized from Al-Ti3AlC2 MAX phase possesses the great application potential in flexible supercapacitors.

Effect of different electric field parameters on produced activated carbon for supercapacitor electrode materials

Effect of different electric field parameters on produced activated carbon for supercapacitor electrode materials

Hierarchical porous MXene film with diffusion path optimization for supercapacitor

MXenes have immense potential in electrochemical energy storage owing to their outstanding physicochemical properties such as their oxygen-containing groups that impart additional pseudocapacitance to acidic electrolytes. However, during electrode assembly, MXene nanosheets undergo restacking because of hydrogen bonding and van der Waals forces, which causes electrolyte ions to traverse long diffusion pathways between the long and narrow nanosheets. Exploiting the oxidative properties of Ti3C2Tx, a hierarchical porous MXene film with micro-, meso- and macroporous structures was successfully prepared using a simple hydrothermal oxidation and etching process to create micro- and mesoporous structures, followed by ice templating to prepare three-dimensional (3D) linked macroporous structures. Because these hierarchical pores have synergistic effects on electrochemical activity and electrolyte ion diffusion, the film attained a specific capacitance of 539F/g at a current density of 2 A/g when it was used as a supercapacitor electrode, which corresponds to one of the highest values reported for MXene-based electrodes. The film retained 83% of its specific capacitance when the current density was increased to 40 A/g, and exhibited excellent cycling stability. By using this multi-porous MXene design, synergistic improvement in ion diffusion was successfully realized and thus a new strategy to prepare high-performance supercapacitor electrode materials was developed.

Rice husk-derived nitrogen-doped graphitic carbon/graphene nanosheets self-assembly for high-performance supercapacitors with chemical blowing method

Carbon materials derived from waste biomass are increasingly popular in energy devices due to their renewability, environmental benefits, and rich heteroatom functionalization. Herein, a simple and low-cost method for synthesising rice husk-derived nitrogen-doped graphitic carbon/graphene nanosheets (RNGNs) by chemical blowing was developed. Carbon was derived from rice husk (RH), while nitrogen was sourced from ethylenediaminetetraacetic acid and iron sodium salt hydrate (EDTA-FE), serving multiple roles as a blowing agent, an activating agent and a graphitization catalyst in a closed system. This approach facilitates the formation of a unique 3D structure of 2D graphene self-assembly on the wrinkled surface of graphitic carbon. As an electrode material for supercapacitors, the obtained RNGN800–1:1 with high nitrogen content (5.02 %) shows good electrical conductivity and a large specific surface area (1130 m2 g−1). These characteristics bring about an impressive electrochemical performance (334.5 F g−1 at 0.5 A g−1, 75.6 % retention at 20 A g−1). Moreover, when assembled into symmetrical device, the RNGN800–1:1 demonstrates a high power density of 9.4 kW kg−1and an excellent energy density of 15.2 Wh kg−1 with outstanding long-term cyclability (remains 94.77 % after 25000 cycles). This study introduces a straightforward and environmentally friendly approach for synthesizing nitrogen-doped graphitic carbon/graphene nanosheets from sustainable biomass resources. The resulting material is expected to have broad applications across various areas, including adsorption, catalysis, and energy storage.

High-performance NF-loaded F-NiFe-LDH/rGO nanoflower/nanosheet composite electrode material achieving enhanced specific capacitance and energy density for supercapacitor

High-performance nanostructured F-NiFe-LDH/rGO composite electrode materials with F-NiFe-LDH nanoflowers and rGO nanosheets are synthesized in a controlled hydrothermal method by leveraging the strong synergistic effects between the components, enabling the construction of F-NiFe-LDH/rGO//AC asymmetric supercapacitors. The incorporation of rGO significantly enhances electron transport, resulting in an exceptional specific capacitance of 2860 F g−1 at a current density of 1 A g−1, with a remarkable capacity retention of 102 % after 1000 cycles. This represents a notable improvement in electrochemical energy storage, with surface-controlled capacitance contributing more in alkaline electrolytes for F-NiFe-LDH/rGO composite compared to F-NiFe-LDH alone. The asymmetric supercapacitor device exhibits a specific capacitance of 354 F g−1 at 1 A g−1, maintaining 92.31 % of its initial capacitance after 1000 charge/discharge cycles at 5 A g−1, and achieves an impressive energy density of 110 Wh kg−1 at 1 A g−1. The innovation of this work lies in the controllable preparation of nanostructured F-NiFe-LDH-rGO supercapacitor electrode material with enhanced specific capacitance and energy density by the synergistic effect between F-NiFe-LDH and rGO. This work offers a solid foundation for creating high-performance supercapacitor electrode materials and devices for energy storage applications.

Covalently linked 4-Aminopyridine on reduced graphene oxide for high performance electrochemical supercapacitor electrode material

The portability of electrical devices requires the demanding but essential task of improving supercapacitor energy density while preserving stability. Introducing an amine heterocyclic compound on a reduced graphene oxide (rGO) layer can enhance its capacity for energy storage. Here, we employed Catharanthus roseus flower extract as a green reducing agent to prepare rGO for the first time. A stable covalently linked 4-AP-rGO was produced through combining of 4-Aminopyridine on the rGO layer via nucleophilic substitution reaction process. The synthesized materials were systematically characterized by FT-IR, UV–visible, Raman, powder XRD, XPS, SEM, and TEM. Furthermore, the screen-printed carbon electrode (SPCE) was modified with 4AP-rGO (4AP-rGO/SPCE) to evaluate the electrochemical properties using CV, GCD, and EIS in 1 M H2SO4. The electrochemical performance of the 4AP-rGO/SPCE modified electrode was compared with unfunctionalized rGO. The pseudocapacitive efficacy of the 4AP-rGO was exceptional as evidenced by its high energy density (12.27 × 10−4 Wh kg−1), high power density (350.6 × 10−3 W kg−1), and high specific capacitance of (180.3 × 10−3 F g−1) at 1 A g-1. Over 10,000 cycles at 1 A g-1, it maintained 98.8 % capacitance, exhibiting exceptional cycling stability. The energy density of 4-AP-rGO is 2.1 times higher than that of rGO, indicating that it is a suitable candidate for energy storage applications.

NiMoO4@NiSe2 microspheres as electrode materials for high-performance supercapacitor

Supercapacitors as novel sustainable energy conversion systems have been a hot spot owing to their high specific capacitance and excellent cycle stabilities. However, the poor electron conductivity limits their further applications. Herein, we synthesize NiMoO4@NiSe2 samples by a controllable hydrothermal route. The heterogeneous structure consists of high conductive nanosheets and high capacitive particles. It can slow down the collapse of electrode materials and enhance the conductivity of material. It also facilitates ion diffusion and faradaic redox reaction, thereby improves the electrochemical performance. The as-synthesized electrode presents a specific capacity of 1193 C g-1 at 1 A g-1 and maintains 82.9 % of the initial capacitance after 10,000 times cycles. A hybrid capacitor is constructed using the composites as the electrode material. It possesses a capacitance of 101 C g-1 at 1 A g-1 and 85.8 % of the retention rate after 10,000 times charging-discharging. This impressive performance of composite could be attributed to their mesoporous surface with high specific surface area (48 m2g-1). Moreover, the supercapacitor shows excellent flexibility after folding, exhibiting a wide application prospect in the field of supercapacitors.

Rapid conversion of biomass to hierarchical porous carbons via one-step microwave carbonization/activation for long cycle-stable supercapacitor and zinc-ion capacitor

Biomass derived carbons as electrode materials for supercapacitors have drawn great attention owing to their low cost, high specific areas and abundant surface functional groups, but most of their preparation processes are time-consuming and power-wasting. In this work, we report a rapid and energy-saving strategy for preparing hierarchical porous carbons derived from loofah sponges for supercapacitors via one-step microwave carbonization/activation. Utilizing KOH as the microwave absorption medium and activator, the microwave carbonization/activation process can be completed within 6–10 min. The resulting loofah sponges derived porous carbons demonstrate a high specific capacitance of 294 F g−1 at 0.5 A g−1 and an outstanding retention rate of 74.8 % at 20 A g−1 in three-electrode setup for supercapacitor. The fabricated zinc-ion capacitor based on the as-prepared carbon materials displays a comparable energy density of 62.3 Wh∙kg−1 at the power density of 160 W kg−1. Notably, a remarkable long-term cyclic stability by retaining of 93.6 % of its initial capacitance is acquired after 30,000 cycles. Our research not only fabricates sustainable electrode materials for supercapacitors and zinc-ion capacitors but also provides a fast and energy efficient route for producing biomass derived carbon materials with high capacitive performances for commercial applications.

Harnessing dysprosium telluride/GPE as an effective electrode for energy storage and conversion

Hydrogen stands out as a clean alternative to fossil fuels, and its production via water electrolysis is promising, although the slow kinetics of the oxygen evolution reaction (OER) pose a significant challenge. Alongside energy conversion, the quest for effective energy storage remains critical. This study explores the potential of dysprosium telluride (Dy2Te3) as a highly efficient catalyst for OER and a supercapacitor electrode. The hydrothermally synthesized Dy2Te3 exhibits exceptional OER activity, characterized by an overpotential of 294 mV at 1.48 V vs. RHE, a low Tafel slope of 48 mV dec−1, and minimal interfacial resistance of 13 Ω. In a 1.0 M KOH solution, Dy2Te3 nanoparticles demonstrate outstanding supercapacitor performance, achieving a power density of 283.5 W kg−1, specific capacitance of 645.33 F g−1, and energy density of 22.8 Wh kg−1 at 1 A g−1. The high performance is attributed to enhanced electrical conductivity and a low impedance of 0.352 Ω in a three-electrode system. In a practical two-electrode configuration, Dy2Te3 nanoparticles deliver a specific capacitance of 479 F g−1, energy density of 94 Wh kg−1, and power density of 0.32 kW kg−1, with a reduced interfacial resistance of 1.03 Ω. These results underscore the potential of Dy2Te3 as a viable electrode material for both supercapacitors and water splitting, offering valuable insights into the application of lanthanide-based metal chalcogenides in energy technologies.

Unveiling the potential: Asymmetric supercapacitors with conductive polymers/Ti3C2Tx/Ni3S4 electrodes deliver high energy densities

Ti3C2Tx is considered a promising electrode material for supercapacitors due to its fast electronic properties, excellent hydrophilicity and mechanical properties. However, severe Ti3C2Tx nanosheet stacking reduces the exposed active sites and hinders the ion diffusion of Ti3C2Tx, leading to poor electrochemical performance. Here, we report a strategy for doping of Ti3C2Tx, in which the Ni3S4 and conducting polymer (CP) were selected as doping agent for Ti3C2Tx, and it is expected that metal sulfide and CP can overcome the defects of Ti3C2Tx. In this work, the conducting polymers were as polyaniline (PANI), polypyrrole (PPY) and poly(3,4-ethylenedioxythiophene) (PEDOT). As a result, the prepared composites exhibit superior multiplicative capacity with a capacitance of 2502 F g-1 (PANI/Ti3C2Tx/Ni3S4), 2440 F g-1 (PPY/Ti3C2Tx/Ni3S4), and 2620 F g-1 (PEDOT/Ti3C2Tx/Ni3S4), respectively. In addition, CP/Ti3C2Tx/Ni3S4// AC asymmetric supercapacitors were assembled with energy densities of 60.2 (PANI/Ti3C2Tx/Ni3S4), 86.7 (PPY/Ti3C2Tx/Ni3S4), and 53.4 (PEDOT/Ti3C2Tx//Ni3S4) Wh kg-1 at 1,500 W kg-1, respectively. This work develops a simple way to prepare the porous Ti3C2Tx film for supercapacitors with excellent electrochemical performance.

Vacancy Engineering of Selenium-Vacant NiCo2Se4 with Enhanced Electrochemical Performance for Supercapacitor.

Vacancy engineering effectively modulates the electronic properties of electrode materials, thereby improving their electrochemical performance. In this study, we prepared selenium-deficient NiCo2Se4 (Sev-NCS) using ethylene glycol as a reducing agent in NaOH alkaline environment, and investigated its potential as an electrode material for supercapacitors. Both theoretical and experimental results confirmed that the introduction of vacancies altered the morphology and electronic structure of NiCo2Se4, which in turn synergistically improved the conductivity and the diffusion capability of electrolyte ions. The optimized Sev-NCS electrode achieved an excellent specific capacitance of 2962.7 F g-1 at a current density of 1 A g-1 and superior cycling stability with a capacitance retention of 89.5% even after 10,000 cycles. Furthermore, an asymmetric device composed of the optimized Sev-NCS electrode as the positive electrode and activated carbon as the negative electrode achieved an energy density of 55.6 Wh kg-1 at a power density of 800 W kg-1. Therefore, this work offers novel insights into the role of vacancy engineering in improving the performance of transition metal compound-based electrode materials for supercapacitor.

Two-step cathodic microwave electrodeposition for construction of Co9S3(OH)5@Ni(OH)2 hetero-structure as supercapacitor electrode materials

The preparation of two-phase electrode materials of Co9S8@Ni(OH)2 typically involves a laborious three-step process. In this study, a two-step cathode microwave electrochemical method was proposed for the fabrication of Co9S8@Ni(OH)2 electrode materials for supercapacitors, eliminating the need for precursor synthesis. This approach not only simplified the preparation process and saved time but also successfully produced a p-n heterostructure electrode material consisting of Co9S8@Ni(OH)2 phases, where the Co9S8 phase has a chemical formula of Co9S3(OH)5. This unique structure is capable of inducing an internal electrical field by facilitating the transfer of charge carriers from Co9S3(OH)5 to Ni(OH)2, thereby enhancing charge transfer kinetics. As a result, the electrode exhibited remarkable supercapacitive performance, achieving a high specific capacitance of 255.4 mAh g-1 (7.56 F cm-2) at 1 A g-1. Even at a 20-fold increase in charge/discharge current density, the specific capacitance remained high at 218.9 mAh g-1 (6.48 F cm-1), retaining 85.8 % of the initial capacity. Furthermore, the Co9S3(OH)6@Ni(OH)2 electrode materials demonstrated excellent durability, enduring 10000 cycles with a capacitance retention of 92.9 % of the initial value. An asymmetric supercapacitor constructed with Co9S3(OH)5@Ni(OH)2 as the anode and a commercial active carbon film as the cathode was able to power a red light diode continuously emitting light for up to 42 min.

Synthesis and investigation of charge storage characteristics in Ni-MOF/PANI composite as an active electrode material for supercapacitor

This study aimed to develop a more stable and efficient energy storage device, synthesis of nickel-based pristine metal organic framework (MOF) and combined it with the emeraldine base phase of polyaniline (PANI) which is confirmed with XRD, SEM and TEM. Both Ni-MOF and PANI exhibit faradaic (battery-like) behaviour. However, when these two materials are combined, the stability of the resulting material is enhanced. The initial materials, MOF and PANI, exhibit specific capacities of 42 C/g and 72 C/g, respectively. However, when these two materials are combined, their composite exhibits an enhanced specific capacity of 122 C/g. The cyclic voltammetry (CV) analysis shows oxidation and reduction peaks, indicating faradaic behaviour. This behaviour is further confirmed by electrochemical impedance spectroscopy (EIS). Upon comparing it with prior results, the specific capacity appears to be slightly lower. However, it is anticipated to exhibit stronger stability, which is contradictory. The composite material (Ni-MOF/PANI) exhibits remarkable capacitive retention of 99.25 % even after undergoing 5000 cycles, as anticipated. In order to validate the aforementioned findings and determine the extent of the current contribution from capacitive and diffusive control, Dunn's model was employed. The data demonstrates the prevalence of diffusive-controlled (faradaic) current over capacitive current. The highest proportion of current resulting from diffusion is 96 %, achieved at a scan rate of 5 mV/s. The highest proportion of current resulting from capacitance is 24 %, achieved at a scan rate of 300 mV/s. At lower scan rates, the material exhibits a greater faradaic behaviour, whereas at higher scan rates, there is a progressive increase in non-faradaic processes. The insufficient time for diffusive process at higher scan rates is the cause. The Dunn's model with quadratic correction is also performed and comparative results were shown. Overall, the material exhibits more stability and dominance in the faradaic process, which paves the path for improved performance.

Synthesis of rice husk derived porous carbon as low-cost and high-performance electrode material for supercapacitors

Porous carbon electrode materials derived from agricultural by-products of food processing have attracted widespread interest. Rice husk (RH) is a promising raw material owing to its abundance and low price. In this study, a supercapacitor electrode was prepared by using recycled RH and secondarily activated with ZnCl2 to enhance its electrochemical energy storage performance. RH carbonized at the optimum temperature (i.e., 800 °C) was activated to synthesize RH-800-X (X = 1, 2, 3, 4, or 5, representing the mass ratio of ZnCl2 to RH-800). Sample RH-800-3 exhibited the highest specific surface area (1348.29 m2 g−1) and mesoporous pore volume (0.8375 cm3 g−1) among the samples. In a three-electrode system, the prepared electrodes delivered a high specific capacitance (242 F g−1 at 0.3 A g−1 in 6 M KOH solution). Furthermore, the capacitance retention of RH-800-3 remained at 99.9 % after 17,000 charge/discharge cycles. The results demonstrate the excellent capacitive behavior and superior electrochemical performance of RH-800-3. In addition, symmetrical capacitors prepared using RH-800-3 have an energy density of up to 101 Wh kg−1 at a power density of 900 W kg−1. Therefore, this study presents a simple and effective method for preparing a high-performance electrode material from biomass-derived porous carbon (i.e., recycled RH) and offers a new perspective for the efficient utilization of waste biomass resources.

Potential difference-induced electrodeposition of defect-rich α-cobalt hydroxide on porous copper (PCu): High-voltage performance of supercapacitor

Designing electrode materials for aqueous battery-type supercapacitors to extend the operating voltage window remains a significant challenge to increase the energy density of aqueous supercapacitors. In this work, a directional electrodeposition method without any additives was employed to deposit α-Co(OH)2 onto a porous copper (PCu) current collector substrate, which involves the fabrication of a supercapacitor electrode material with a cross-linked network structure named α-Co(OH)2@PCu900. The potential difference between copper and cobalt facilitated the formation of a larger interlayer spacing for α-Co(OH)2. In addition, crystals of α-Co(OH)2 with different orientations exert stress on one another, leading to lattice distortion and vacancy formation. The morphology and microstructure of materials were analyzed through techniques such as SEM, HRTEM, XRD, and XPS, confirming the validity of the experimental design. This defect-rich, large interlayer spacing structure facilitates ion intercalation and deintercalation during the charge-discharge process, thereby expanding the operating voltage window. In a three-electrode system, α-Co(OH)2@PCu900 exhibited a potential range from −0.45 V to 0.55 V and demonstrated an areal capacitance of 2580 mF cm−2 and specific capacitance of 600 A g−1 at 2 mA cm−2. The α-Co(OH)2@PCu900 was used as the cathode material and commercial reduced graphene oxide (rGO) was used as the anode material in an asymmetric supercapacitor, and the ASC device exhibited an areal capacitance of 295.3 mF cm−2 and a specific capacitance of 87.89 F g−1. Notably, it retained a high energy density of 0.12 mW h cm−2 (35.27 Wh kg−1) at a power density of 1.7 mW cm−2 (505.95 W kg−1). This method established α-Co(OH)2@PCu900 as a promising supercapacitor electrode material, providing a viable strategy for designing and fabricating functional electrode materials.

Enhancing quantum capacitance in BNyne/Graphene heterostructures through transition-metal dopants for high-performance supercapacitors

Using Density functional theory (DFT), we investigated the charge storage capacity, quantum capacitance (CQ), geometry and electronic structures of BNyne/graphene heterostructures (BNyneGHs), as well as the impact of transition-metal dopants on their CQ. Our results showed that doping was more effective than vacancy defects in improving the CQ of BNyneGHs. Ti-doped BNyneGHs exhibited the highest CQ value of 360.08 μF/cm2, making them ideal positive electrode materials for supercapacitors (SCs). The presence of doping agents was found to enhance the density of states (DOS) around the Fermi level, resulting in improved CQ. Our calculations identified potential cathode or anode materials for high-energy-density SCs, providing theoretical support for the design of high-capacitance SCs.