Gravimetric Specific Capacitance Research Articles

Heteroatom-doped layered hierarchical porous carbon electrodes with high mass loadings for high-performance supercapacitors

Electrodes with high mass loadings are the impetus for improving the energy density of supercapacitors. However, such electrodes have poor charge and ion kinetics in most cases, and rationally designing them which have high electron and ion transport rates is a major challenge. In this work, a new heteroatom-doped hierarchical porous carbon material, called LPC-2, was developed with longan shell and KOH as its precursor and an activator, respectively, through heteroatom self-doping and architecture design integration, in which heteroatoms of nitrogen, oxygen and sulfur were found. Its frequency response was excellent at a scan rate up to 5 and 0.3 V s−1 when the mass loading was set to be 1.0 and 12 mg cm−2, respectively. At a high mass loading of 12 mg cm−2, LPC-2 had gravimetric and areal specific capacitances of 171 F g−1 and 2052 mF cm−2, respectively. The assembled LPC-2//LPC-2 symmetric supercapacitor can complete charge and discharge in 0.4 s, showing a high energy density of 10.8 Wh kg−1 at a high power density of 97.4 kW kg−1 in 6 M KOH. In addition, 99.5 % of the original capacitance was retained after 20,000 cycles at 10 A g−1, which embodies the application value of biomass-derived carbon in supercapacitors.

Carbon Dot/Ti3C2Tx MXene Hybrid on Carbon Cloth as a Flexible and Binder‐Free Supercapacitor Electrode with Commercial Scale Mass Loading

Flexible and binder‐free carbon dot/titanium carbide (CD/Ti3C2Tx) MXene electrode for supercapacitor is fabricated at commercial scale mass loading. The decline in specific gravimetric capacitance due to high mass loading is compensated by the synergistic enhancement in properties of the prepared CD/Ti3C2Tx hybrid. The optimized hybrid electrode gives a specific gravimetric capacitance of 373 F g−1 at a current density of 1 A g−1. The symmetric supercapacitor developed using the electrode has a specific gravimetric capacitance of 50 F g−1, energy density of 4.4 Wh kg−1, and power density of 66.6 W kg−1 at a current density of 1 A g−1. The device retains 90.8% capacitance after 5000 cycles when operated at a current density of 1 A g−1. Raman spectroscopy analysis provides an evaluation of the evolution of the electrochemical performance of the hybrid with the CD concentration. The work will open up new avenues in textile‐based supercapacitor technology for wearable electronics applications utilizing environment‐benign techniques.

Flexible and binder-free supercapacitor electrode with high mass loading using transition metal doped MoS2 nanostructures

Transition metal (TM) doping has been done on MoS2 to activate its inactive sites. The edge sites created on doping with nickel (Ni), cobalt (Co), and iron (Fe) provide a conductive, flexible, and binder-free electrode with high mass loading (>19 mg/cm2) over carbon cloth. The vertical flower-like morphology together with the presence of dangling bonds, imparts a high rate of adsorption and desorption process and outstanding super-capacitive properties. Due to the identical ionic radii, Ni atom will effectively replace the Mo atoms in MoS2 and also intercalate between the layers. The resultant lattice distortions, and the presence of Ni atom in the interstitial sites, provide faradaic and non-faradaic capacitance to the Ni-doped electrode, (Ni-MoS2/CC), giving it an excellent specific capacitance of 305.9 F/g compared to 170.2 F/g for the pure MoS2/CC electrode. The doping produced 180% increase in the specific capacitance of MoS2, which is the highest reported value for a high mass loading electrode. There is an enhancement in the properties of TM doped MoS2 electrodes prepared in the present study as binders and conductive additives are avoided. A symmetric supercapacitor developed using the Ni-MoS2/CC electrode gave a specific gravimetric capacitance of 50 F/g, energy density of 4.4 W h/kg, and power density of 79.1 W/kg at a current density of 0.5 A/g. The device retained 87.4% capacitance after 5000 cycles at a scan rate of 1 A/g.

Anti-Shedding Nickel-Protection-Layer Boosting an Ultrahigh Loading Carbon Fiber@Co-NiSx Electrode to Deliver Superior Areal/Volumetric/Gravimetric Capacitance.

Challenges remain to show good capacitive performance while achieving high loadings of active materials for supercapacitors. Trying to realize this version, a nickel-protecting carbon fiber paper@Co-doped NiSx (Ni-CP@Co-NiSx) electrode with high specific gravimetric, areal, and volumetric capacitance is reported in this work. This free-standing electrode is prepared by an electroplating-hydrothermal-electroplating (EHE) three-step method to achieve a high loading of almost 26.7 mg cm-2. The cobalt-doping and nickel-protection strategies effectively decrease the impedance and inhibit the active material dropping from the electrode resulting from the expansion stress, which endows the Ni-CP@Co-NiSx electrode with a high rate and good cycling performance, especially with an ultrahigh specific areal/volumetric/gravimetric capacitance of 53.3 F cm-2/2807 F cm-3/1997 F g-1 at 5 mA cm-2, respectively. Employing activated carbon functionalized with riboflavin (AC/VB2) as a negative electrode, the asymmetric supercapacitor device delivers a very high energy density of up to 60.4 W h kg-1. This work demonstrates that electrodes with a high loading density and excellent performance can be obtained by the combination of the EHE method to adjust the internal conductivity and external structural stability.

Biological treatment as a green approach for enhancing electrochemical performance of wood derived carbon based supercapacitor electrodes

Wood-derived biochar is an eco-friendly and porous carbon material that can be used to prepare supercapacitor electrodes. For the purpose of addressing the deficiencies in the specific surface area and pore structure of wood-derived carbon as the raw material of electrodes, a biological pre-treatment method was developed to construct the desirable pore structure of wood by leveraging the lignin-degrading property of white-rot fungi. First, white-rot fungi with permeability and biodegradability on lignocellulosic substrates were used to regulate the pore structure of natural paulownia wood, which was then carbonized to produce a porous hyphae/wood-derived carbon conductive substrate. Afterward, manganese dioxide (MnO2) was deposited on the substrate to fabricate the MnO2/hyphae/wood-derived carbon (HWC-3M) electrode by the hydrothermal method. The degradation of lignin by white-rot fungi broke the original pore structure of wood, strengthened effective channels in the cell walls, and facilitated the loading of MnO2 into the channels to improve the ion transport rate. The HWC-3M had richer energy storage sites, more electrolyte ion transport channels, and better electrochemical performance than the control electrode made of untreated wood-derived carbon (HWC-0), showing an excellent areal specific capacitance (3395 mF/cm2 at a current density of 1.0 mA/cm2), moderate gravimetric specific capacitance (138.3 F/g), and good cycling stability (retention of 88.6% after 2000 cycles). The results indicate that pretreating wood-derived carbon composite electrode with white-rot fungi serves as a new green approach to develop high-performance electrochemical energy storage devices.

Walnut shell derived N, S co-doped activated carbon for solid-state symmetry supercapacitor device

The kernel of the walnut constitutes a nutrient-dense food source. However, the walnut shell is useless and was thrown away. Therefore, as a small initiative towards waste-to-wealth, herein we developed walnut shell-derived highly porous heteroatom (nitrogen and sulfur) doped activated carbon (NS-WAC) via KOH activation and post-processing treatment by thioacetamide (TAA). The NS-WAC exhibits a high specific surface area (SSA) and various particle size distribution (PSD) involving micropores, mesopores, and macropores, conferring substantial supercapacitor advantages. The NS-WAC possesses a significant proportion of mesopores, which can decrease the ion diffusion path length and improve ion transport efficiency. Hence, NS-WAC demonstrates promising electrochemical performance achieving a high gravimetric specific capacitance of 271.4 Fg−1 at 0.5 Ag−1 in 3 M KOH aqueous electrolyte. Furthermore, the solid-state symmetric supercapacitor (SSC) device exhibited a gravimetric specific capacitance of 52 Fg−1 and volumetric specific capacitance of 74.36F cm−3 at a current density of 0.5 Ag−1. This SSC device also exhibited a gravimetric energy density of 23.4 Wh Kg−1 at a power density of 250 W Kg−1 at a current density of 0.5 Ag−1. It showed superior cycle stability of 91.8% after 10,000 cycles at 5 Ag−1.

Enhanced interfacial charge transfer via in-situ construction of integrated NiO/NiCo2O4 heterojunction coupled with carbon layer for high-performance supercapacitor and photocatalysis

Constructing heterostructured composites presents a promising approach to enhance both electrochemical and photocatalytic performance. However, the low interfacial charge transfer efficiency caused by lattice mismatch severely hinders its potential application. Herein, integrated NiO/NiCo2O4 heterostructure with dodecahedral structure has been facilely prepared by a one-step in situ calcination method. In addition, to further promote the yield of photogenerated electrons and enhance electrochemical reaction kinetics, a carbon layer for charge transport is incorporated onto the outer shell of NiO/NiCo2O4 heterostructured. The elaborate designed and constructed integrated C1.0 @NiO/NiCo2O4 heterojunctions with efficient interfacial charge transfer channels exhibit an excellent gravimetric specific capacitance of 588 F g−1 at 1 Ag−1 for three electrode cell. Moreover, the C1.0 @NiO/NiCo2O4//AC supercapacitor has an excellent energy density of 68.13 Wh kg−1 at a high power density of 750 W kg−1, delivering a retention rate of capacitance exceeding 91.4% over 10000 cycles. The visible-light-induced degradation efficiency of rhodamine B (RhB) was determined to be 83.68% within a duration of 120 min. And a probable mechanism for its removal was proposed based on DFT calculations and experimental results of electrochemistry and photocatalysis. This work offers a novel perspective on the rational design of integrated heterostructured materials with enhanced interfacial charge transfer for high-performance supercapacitors and visible light-driven photocatalysis.

Enhancing gravimetric and volumetric capacitance in supercapacitors with nanostructured partially graphitic activated carbon

The volumetric and gravimetric capacitance of supercapacitors are primarily influenced by the specific surface area and porosity required for the formation of electric double layers in the electrode material, and these capacitance are known to have a trade-off relationship. To address this issue, additional capacitance enhancement mechanisms are needed not only at the electrode material surface but also within the limited mass and volume, which can be achieved through structural improvements of the material. In this study, we produce partially graphitic activated carbon with low specific surface area but nano-sized crystalline regions from petroleum pitch, a soft carbon precursor. This approach allows for improvements in gravimetric capacitance. The resulting activated carbon with a specific surface area of 1122 m2 g−1 exhibits volumetric specific capacitance of 27.9 F cc−1 and gravimetric specific capacitance of 38 F g−1 in an organic electrolyte, indicating a new direction for electrode materials in supercapacitors.

Acid substitutions for WO3 nanostructures synthesis by the hydrothermal route and its effect on physio-chemical and electrochemical properties for supercapacitors

In this study, we have developed a feasible and eco-friendly electrode material for supercapacitor (SCs) application by effectively synthesizing different morphological structures of tungsten oxide nanostructures (WO3-NSs). The concentrated acids play a crucial role in the synthesis of WO3-NSs and are employed to evaluate the electrochemical activity. The stable phase formation and the crystal structures of WO3-NSs were confirmed by thermogravimetric and X-ray analysis. From the field emission scanning electron microscope (FE-SEM), the hexagonal-shaped nanosheets, one-dimensional nanorods (1D NRs), and heterogeneous non-uniform agglomerated nanosheets were observed for the WO3-NSs. The presence of functional groups and the stretching-bending vibrations of WO bonds were detected by Fourier transform infrared, and Raman spectroscopy respectively. The transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) offers a more in-depth morphological, structural, and elemental composition and electronic states investigation of the optimized WO3-NRs. Additionally, the electrochemical properties of the WO3-NSs have been examined in 1 M KOH electrolyte using Nickel Foam (NF) as a current collector. Furthermore, the M-WO3-NF electrode reveals higher specific capacity (Csp) and gravimetric capacitance (Cg) of 72 mAh/g and 600 F/g with high energy density (Ed) of 17 Wh/kg, and power density (Pd) of 321 W/kg as well as the superior Columbic efficiency (96.9 %) at 5 mA/cm2. The M-WO3 electrode exhibits 91 % capacitive retention over 5000 cycles. The M-WO3-NF is used as the cathode and activated carbon (AC) as the anode in the design of an aqueous hybrid supercapacitor (AHSC) device. Notably, the M-WO3-NF//AC-NF device offers a Pd of 1060 W/kg at an Ed of 9 Wh/kg and remarkable electrochemical stability of 80 % over 3000 charge-discharge cycles. These results highlight the excellent electrochemical functionality and advantages of the M-WO3-NRs as a promising cathode for practical energy-storage systems.

Porous prussian blue analogs derived nickel-iron bimetallic phosphide nanocubes on conductive hollow mesoporous carbon nanospheres for stable and flexible high-performance supercapacitor electrode

Nickel-iron bimetallic phosphide (Ni-Fe-P) is the ideal battery-type materials for supercapacitor in virtue of high theoretical specific capacitance. Nevertheless, its actual adhibition is astricted on account of inferior rate capability and cyclic stability. Herein, we constructed hierarchical core–shell nanocomposites with hollow mesoporous carbon nanospheres (HMCS) packaged via prussian blue analogs derived Ni-Fe-P nanocubes (Ni-Fe-P@HMCS), as a positive electrode for hybrid supercapacitor (HSC). Profiting from the cooperative effects of Ni-Fe-P nanocubes with small size and good dispersibility, and HMCS with continuously conductive network, the Ni-Fe-P@HMCS composite electrode with abundantly porous architectures presents an ultrahigh gravimetric specific capacity for 739.8 C g−1 under 1 A g−1. Specially, the Ni-Fe-P@HMCS electrode presents outstanding rate capability of 78.4% (1 A g−1 to 20 A g−1) and cyclic constancy for 105% after 5000 cycles. Density functional theory implies that the composite electrode possesses higher electrical conductivity than bare Ni-Fe-P electrode by reason of the incremental charge density, and the electrons transferring from NiFe3P4 to HMCS layers. Additionally, the assembled Ni-Fe-P@HMCS//HMCS HSC facility delivers the high energy density for 64.1 Wh kg−1, remarkable flexibility and mechanical stability. Thus, this work proffers a viable and efficacious measure to construct ultra-stability electrode for high-performance portable electronic facilities.

In Situ S‐Doped Graphene Film using NaHSO3 as Sulfur Source for High‐Performance Flexible Supercapacitors

Herein, sulfur‐doped graphite film (SGF) is developed by a facile method. Graphene oxide (GO) film and low‐cost NaHSO3 are used for carbon and sulfur sources, respectively. A single‐step sulfur doping reaction is used to obtain SGF at 180 °C. The scanning electron microscopy (SEM) analysis of SGF reveals highly loose, highly crumpled characteristics. The SEM–energy‐dispersive spectroscopy shows that S is evenly distributed on the surface of SGF and doping amount of S is 4.6 wt%. SGF can attain high gravimetric and areal specific capacitance of 232.8 F g−1 and 672.5 mF cm−2 at 0.5 A g−1 and 1 mA cm−2 current density, respectively. The SGF shows excellent cycle stability (94.1% capacity retention after 10 000 cycles at 2.0 mA cm−2). Then, the assembled flexible SGF//SGF all‐solid‐state symmetric supercapacitor device can deliver a high energy density of 12.17 Wh kg−1 at a power density of 499.85 kW kg−1. The in situ doping method provides a simplistic and low‐cost synthesis process, which is suitable for large‐scale production of SGF. Furthermore, the well‐developed approach is applied to prepare arbitrary S‐doped matrix of carbon. Simultaneously, the fabricated SGF as the electrode material of flexible supercapacitor devices has great advantages in wearable electronics.

NaOH solution-assisted pyrolysis of waste polycarbonate for co-production of phenolic compounds and supercapacitor material

A green way for the sustainable utilization of waste polycarbonate (PC) was developed, i.e., NaOH solution-assisted pyrolysis to co-produce phenolic compounds and supercapacitor material. A lab-scale setup was employed for the pyrolysis of PC to explore the regulation effects of NaOH concentration and pyrolytic temperature on the production of phenol and 4-isopropenylphenol (IPP). The yields of phenol and IPP were up to 35.3 wt% and 29.9 wt% at 600 °C and NaOH concentration of 0.5 mol/L, which were much higher than those from pure PC pyrolysis (7.2 wt% and 3.6 wt%). Furthermore, the pyrolytic solid residue was directly subjected to the high-temperature activation to prepare activated carbon, which could be used as a supercapacitor material with an outstanding specific gravimetric capacitance of 182.1 F/g at 1 A/g.

AgBTC MOF-Mediated Approach to Synthesize Silver Nanoparticles Decorated on Reduced Graphene Oxide (rGO@Ag) for Energy Storage Applications

Nanowires of silver-based metal–organic framework (MOF) (AgBTC, BTC = 1,3,5-benzenetricarboxylate) were grown onto graphene oxide layers to generate GO-AgBTC nanocomposites. Thermal treatment of these composites in inert atmosphere produced reduced graphene oxide (rGO) decorated with well-dispersed and homogeneous silver nanoparticles (rGO@Ag). The easy and scalable synthesis of AgNPs via MOF-mediated synthesis was achieved by the thermal decomposition of the AgBTC directly onto the rGO surface. The structure, morphology, and electrochemical properties of this novel material were investigated by XRD, Raman, TGA, FE-SEM, TEM, cyclic voltammetry, and galvanostatic charge and discharge experimental techniques. The results showed improved capacitive features for rGO@Ag. Specific gravimetric capacitance measured by galvanostatic charge–discharge yielded a value of 151.97 F/g at the current density of 0.5 A/g, pointing out that MOF-mediated synthesis offers a facile method to generate rGO electrodes decorated by uniformly distributed nanoparticles for energy storage devices.

Symmetric and Asymmetric Supercapacitors of ITO Glass and Film Electrodes Consisting of Carbon Dot and Magnetite

To enhance the energy density, hybrid supercapacitors were fabricated, and their electrochemical features were investigated using a two-electrode configuration. By assembling nitrogen-doped graphene/magnetite (NG/Fe3O4) on indium tin oxide-coated (ITO) glass as a cathode and NG/carbon dots(Cdots)/Fe3O4 on ITO glass as an anode, a much higher gravimetric specific capacitance of 252.2 F/g, at a current density of 0.5 A/g, was obtained from this asymmetric supercapacitor compared with that (212.0 F/g) of a symmetric supercapacitor (NG/Cdots/Fe3O4)//(NG/Cdots/Fe3O4). A gravimetric energy density of 90.1 Wh/kg was obtained for an asymmetric ITO glass device at a specific power density of 400.0 W/kg. On the other hand, when an asymmetric two-electrode cell was fabricated with a Cdots/polypyrrole (PPy)/Fe3O4/TEMPO-oxidized cellulose nanofiber (TOCNF)-film electrode and a Cdots/PPy/TOCNF-film electrode, the specific capacitance (107.1 F/g) at a current density of 0.8 A/g was lower than that (456.4 F/g) of a symmetric (Cdots/PPy/Fe3O4/TOCNF)//(Cdots/PPy/Fe3O4/TOCNF)-film cell. Subsequently, a gravimetric energy density of 40.6 Wh/kg was achieved for a symmetric-film device at a specific power density of 320 W/kg. These results suggest that our method offers an efficient approach to developing symmetric and asymmetric devices consisting of hybrid materials for meeting the ever-increasing demands on energy-storage devices.

Preparation of two-dimensional sodium-boron phosphide nanosheets used for Na-ion hybrid supercapacitor devices

The development of high-performance sodium-ion hybrid supercapacitors (NISCs) are assembled using facile bulk preparations of sodium boron phosphide (Na-BP) nanosheets as the negative electrode (battery type) and mesocarbon microbeads (MCMB) as the positive electrode (capacitor type). The Na-BP is optimized through different annealing temperatures ranging from 700 to 900 °C under an inert atmosphere. The structural and morphological characterization of the as-prepared materials were investigated by XRD, micro-laser RAMAN, FE-SEM and FE-TEM. The hybrid NISCs were assembled with an Na-BP-700//MCMB, Na-BP-800//MCMB and Na-BP-900//MCMB device configuration with a wide potential of 1–4 V vs. (Na/Na+) and their revealed a gravimetric specific capacitance (Csp) of 48.66 F/g, 83.33 F/g and 125 F/g @ 0.1 A/g, respectively. Finally, Na-BP-900//MCMB device is exhibiting excellent capacity retention of 73.52% even after 10,000 cycles at 0.3 A/g. Moreover, sodium boron phosphide (Na-BP) facile preparations by annealing method and efficient scaleable process for preparing without pre-sodiations for future hybrid supercapacitor devices.

Insights into the Charge Storage Mechanism of Binder-Free Electrochemical Capacitors in Ionic Liquid Electrolytes

Electrochemical capacitors (synonymously supercapacitors) working under an electrochemical double-layer charge storage mechanism (EDLC) are widely investigated because of their excellent power density and cycle life; however, their energy density is lower than those of lithium-ion batteries. Ionic liquids (ILs) are of great interest as electrolytes for EDLCs due to their wide operational voltage window. Here, we provide a systematic investigation on the influence of anions of ILs on the charge storage mechanism and electrochemical stability of EDLC electrodes. Two IL electrolytes, viz., [1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI)], having similar cations but different anions and carbon nanotube (CNT) electrodes are chosen for this study. The CNT//BF4:TFSI//CNT-based device showed superior electrochemical performance (∼69 F·g–1 gravimetric specific capacitance, ∼949 W·kg–1 power density, and ∼139 Wh·kg–1 energy density at 0.5 A·g–1) to CNT//EMIMBF4//CNT and CNT//EMIMTFSI//CNT devices. The device using a mixture of BF4:TFSI (1:0.5) electrolytes has an operating voltage of 0–3.8 V and specific capacitance retention of ∼45% at 0.5 A·g–1 after 500 cycles. In the case of the IL mixture (BF4:TFSI), the combined anion structure and their properties play very crucial part in the improvement of the electrochemical performance of the CNT//BF4:TFSI//CNT device. The assembled Teflon Swagelok-type cell could light up green (3.3 V) and red (2.1 V) light-emitting diodes for more than 5 min.

CoNi bimetallic engineering on porous carbon for high energy density hybrid supercapacitors

Rationally designed, structurally stable, and high-capacity transition metal alloy decorated carbon composites have attracted considerable attention as electrode materials for high-performance hybrid supercapacitors (HSCs). A unique electrode material composed of mixed transition metals (Co and Ni) on fryums-derived porous carbon was synthesized using a facile one-step pyrolysis approach. The CoNi@C composite exhibited rich redox kinetics and good electrochemical performance in an aqueous alkaline electrolyte. In particular, the CoNi@C composite delivered a maximum specific capacity of 390 mA h g−1 at 1 A g−1 with good capacitance retention of 91 % over 5000 cycles. The gravimetric specific capacity of the CoNi@C composite was 1.3 times better than that of the single alloy composite. Moreover, the HSC fabricated with CoNi@C, and activated carbon electrodes exhibited a high energy density of 57.6 Wh kg−1 at a power density of 742 W kg−1 and good cycling stability with a low-capacity loss of 8 % after 5000 cycles. Utilizing high-voltage and energy density, the HSCs can power light-emitting diodes of different wavelengths, demonstrating its practical applicability in energy storage technologies. The structural verification of fryum-derived carbon revealed a good graphitization degree, ensuring its remarkable adaptability for device fabrication.

Graphene Film with a Controllable Microstructure for Efficient Electrochemical Energy Storage.

The agglomeration of graphene sheets and undesired pore size distribution usually lead to unsatisfactory electrochemical properties of reduced graphene oxide (RGO) film electrodes. Herein, crumpled exfoliated graphene (EG) sheets are adopted as the microstructure-regulating agent to tune the morphology and micro-/mesopore amounts with the aim of increasing active surface sites and ion transportation paths in electrodes. With the optimum ratio between EG and GO, the resulting 75%-EG/RGO shows significantly improved specific gravimetric capacitance (Cs) and rate capability when compared with pure RGO electrodes in a symmetrical supercapacitor system. Moreover, when coupling the 75%-EG/RGO cathode with a Zn anode to form a Zn ion hybrid supercapacitor (ZHS), the 75%-EG/RGO exhibits a much higher Cs of 327.39 F g-1 at 0.1 A g-1 and can maintain 91.7% capacitance after 8000 cycles. Systematic ex situ X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS) measurements reveal that the charge storage mechanism is based on both reversible physical adsorption and dual ion uptake. Furthermore, the quasi-solid-state flexible ZHS also presents high capacitive performance and can maintain ∼100% capacitance under various bending states, demonstrating potential application in wearable electronics. This strategy opens up a new path for constructing high-performance graphene film electrodes.

One-Dimensional π-d Conjugated Coordination Polymer Intercalated MXene Compound for High-Performance Supercapacitor Electrode.

MXenes possess the characteristics required for high-performance supercapacitors, such as high metallic conductivity and electrochemical activity, but their full potential remains unrealized owing to their tendency to self-restack when fabricated into an electrode. Designing an MXene interlayer with an effective intercalant has, therefore, become an important criterion to alleviate the restacking issue while also synergistically interact with MXene to further improve its electrochemical activity. This study reports the intercalation of 1D π-d conjugated coordination polymer (Ni-BTA) within the Ti3 C2 Tx nanosheet for the fabrication of a highly efficient supercapacitor electrode. Ni-BTA, which consists of a nickel center and 1,2,4,5-benzenetetramine (BTA) organic chain, is uniformly intercalated by direct synthesis on the abundant oxygen terminals on the Ti3 C2 Tx nanosheet surface. The intercalated Ni-BTA acts as an effective charge carrier transportation pathway through its 1D stretched delocalized π-d electrons while participating in pseudocapacitive activity with the Ni centers. As a result, the Ni-BTA/MXene film exhibits excellent rate performance and a gravimetric specific capacitance of 264.4Fg-1 at 5mVs-1 . This magnitude is retained up to 94.6% after 10000 cycles. The present study provides insights into the design of MXene interlayers for the fabrication of highly robust and stable supercapacitors.

Highly Porous Carbon Aerogels for High-Performance Supercapacitor Electrodes

In recent years, porous carbon materials with high specific surface area and porosity have been developed to meet the commercial demands of supercapacitor applications. Carbon aerogels (CAs) with three-dimensional porous networks are promising materials for electrochemical energy storage applications. Physical activation using gaseous reagents provides controllable and eco-friendly processes due to homogeneous gas phase reaction and removal of unnecessary residue, whereas chemical activation produced wastes. In this work, we have prepared porous CAs activated by gaseous carbon dioxide, with efficient collisions between the carbon surface and the activating agent. Prepared CAs display botryoidal shapes resulting from aggregation of spherical carbon particles, whereas activated CAs (ACAs) display hollow space and irregular particles from activation reactions. ACAs have high specific surface areas (2503 m2 g-1) and large total pore volumes (1.604 cm3 g-1), which are key factors for achieving a high electrical double-layer capacitance. The present ACAs achieved a specific gravimetric capacitance of up to 89.1 F g-1 at a current density of 1 A g-1, along with a high capacitance retention of 93.2% after 3000 cycles.