Interconnected NiS-nanosheets@porous carbon derived from Zeolitic-imidazolate frameworks (ZIFs) as electrode materials for high-performance hybrid supercapacitors

Nickel sulfide-based materials have shown great potential for electrode fabrication owing to their high theoretical specific capacitance but poor conductivity and morphological aggregation. A feasible strategy is to design hybrid structure by introducing highly-conductive porous carbon as the supporting matrix. Herein, we synthesized hybrid composites consisting of interconnected NiS-nanosheets and porous carbon (NiS@C) derived from Zeolitic-imidazolate frameworks (ZIFs) using a facile low-temperature water-bath method. When employed as electrode materials, the as-prepared NiS@C nanocomposites present remarkable electrochemical performance owing to the complex effect that is the combined advantages of double-layer capacitor-type porous carbon and pseudocapacitor-type interconnected-NiS nanosheets. Specifically, the NiS@C nanocomposites exhibit a high specific capacitance of 1827 F g⁻¹ at 1 A g⁻¹, and excellent cyclic stability with a capacity retention of 72% at a very high current density of 20 A g⁻¹ after 5000 cycles. Moreover, the fabricated hybrid supercapacitor delivers 21.6 Wh kg⁻¹ at 400 W kg⁻¹ with coulombic efficiency of 93.9%, and reaches 10.8 Wh kg⁻¹ at a high power density of 8000 W kg⁻¹, along with excellent cyclic stability of 84% at 5 A g⁻¹ after 5000 cycles. All results suggest that NiS@C nanocomposites are applicable to high-performance electrodes in hybrid supercapacitors and other energy-storage device applications.     

A bi-functional Co–Ni layered double hydroxide three-dimensional porous array electrode derived from ZIF-L(Co)@ZIF-L(Co,Ni) for oxygen evolution reaction and supercapacitors

Developing high-efficiency bifunctional materials for electro-catalysis and supercapacitors are urgently needed but challenging. Herein, we develop a self-supporting Co–Ni LDH electrode prepared by in-situ growing ZIF-L(Co)@ZIF-L(Co, Ni) on carbon paper followed by a pseudomorphic transformation. The optimized Co–Ni LDH/carbon paper electrodes (CN-2/CP) exhibit excellent electrochemical activity and stability in oxygen evolution reactions (OER) and supercapacitors. The CN-2/CP electrode displays a low overpotential of 230 mV at 10 mA cm^?2 and superior stability at 40-h chronopotentiometry for OER. For supercapacitor, the CN-2/CP electrode delivers a high specific capacitance of 1346 F g^?1 at 1 A g^?1 and maintains a capacitance of 88.5% after 7000 charge/discharge cycles at 20 A g^?1. Based on the physical and chemical characterization results, the high performance originates from the in-situ electrochemical conversion of metal hydroxide, improved conductivity, fast charge transfer at the interface and unique layered cross morphology providing more active sites.     

A comparative study of various polyelectrolyte/nanocomposite electrode combinations in symmetric supercapacitors

A more practical, nontoxic and cheaper electrolyte, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) was used to construct supercapacitors with different nanocomposite electrodes. The flexible devices were fabricated including active carbon (AC) electrode and nanocomposites electrodes of AC/nano-silica (nano-SiO₂) and AC/multiwalled carbon nanotubes (MWCNTs) at various weight percentages. The symmetrical cell made from AC electrodes generated a maximum specific capacitance (Cs) of 315 F g⁻¹ at 0.5 A g⁻¹. The energy density of this device was 55.5 Wh kg⁻¹ at a power density of 690 W kg⁻¹. Excellent performance was achieved after 5000 charge-discharge cycles where the supercapacitor maintains 92% of its activity. The energy storage capability of the supercapacitors was also investigated with the addition of nano-SiO₂ and MWCNTs. The Cs of the supercapacitors made with the electrodes AC/nano-SiO₂ (5%, 10%, 25% and 50%) were 172, 228, 247 and 55 F g⁻¹, respectively. Similarly, the capacity of the device including the electrodes of AC/MWCNTs (5%, 10%, 25% and 50%) varied as 191, 244, 93 and 20 F g⁻¹ at 0.5 A g⁻¹. The maximum energy density of the devices having nano-SiO₂ and MWCNT were 44.4 Wh kg⁻¹ and 43.8 Wh kg⁻¹, respectively at a power density of 520 W kg⁻¹. A supercapacitor with certain dimension successfully operated a light-emitting diode (LED).     

Walnut shell-derived hierarchical porous carbon with high performances for electrocatalytic hydrogen evolution and symmetry supercapacitors

Walnut Shell-derived hierarchical porous carbon has been successfully synthesized by the efficient KOH activation process. The hierarchical porous carbon material activated at 600 °C, has the specific micropore area of 1037.31 m² g⁻¹ and micropore volume of 0.51 cm³ g⁻¹, which leads to have electrochemical performances of the hydrogen evolution reaction (HER) and supercapacitors. Specifically, as the hydrogen evolution reaction electrocatalyst, the walnut shell-derived carbon material activated at 600 °C exhibits a lower onset potential of 6.00 mV, a smaller Tafel slope of 69.76 mV dec⁻¹ and outstanding stability above long-term cycling. As a supercapacitor electrode material, the sample possesses specific capacitance of 262.74 F g⁻¹ at 0.5 A g⁻¹, the remarkable rate capability of 224.60 F g⁻¹ at even 10 A g⁻¹ and good long-term stability. A symmetric supercapacitor shows the highly energy density of 7.97 Wh kg⁻¹ at a power density of 180.80 W kg⁻¹. This novel and low-cost biomass material is very promising for the electrocatalytic water splitting and supercapacitors.     

Bio-enzymatic synthesis of nitrogen-doped porous carbon/SnO2/carbon microspheres as high-performance composite materials for lithium-ion and sodium-ion batteries

In this study, a nitrogen-doped 3D porous starch-derived carbon/SnO₂/carbon (PSC/SnO₂/C) composite is synthesized with porous starch as a carbon source by biological enzymatic hydrolysis. Compared with the traditional complex acid-base reagent method, the biological enzymatic method is more environmentally friendly and economical, and it can also naturally introduce nitrogen sources and dope the carbon layer. Many mesoporous nanostructures provide enough buffer space and promote the ions' and electrons’ transmission rate. The formation of the Sn–O–C bond between SnO₂ and carbon ensures the stability of the structure. As a result, the PSC/SnO₂/C composite exhibits a high initial discharge capacity (1802 mAhg⁻¹ at 0.2 A g⁻¹ for LIBs and 549 mAh g⁻¹ at 0.1 A g⁻¹ for SIBs) and good cycle stability (701 mAh g⁻¹ at 0.2 A g⁻¹ after 100 cycles for LIBs and 271 mAh g⁻¹ at 0.1 A g⁻¹ after 100 cycles for SIBs). This synthesis method can prepare other energy storage systems such as fuel cells, supercapacitors, and metal ion batteries.     

ZnMn2O4/milk-derived Carbon hybrids with enhanced Lithium storage capability

One of the effective ways to improve the conductivity and structural stability of binary metal oxide nanostructures is to tightly composite them with nano-carbon materials with excellent conductivity. However, the introduction of low density carbon materials also reduces the energy density of batteries. Therefore, we provides a new idea to enhance the lithium storage performance of carbon/binary transition metal oxide anode materials by multi-element co-doping carbon. ZnMn₂O₄ provides high lithium storage capacity; non-metallic heteroatoms in milk-derived carbon greatly improve the conductivity of carbon materials; metal heteroatoms in milk-derived carbon increase the density of carbon materials. Multicomponent co-doping carbon can build up the mass specific capacity, ratio performance, cyclic life and mechanical properties of binary metal oxides/porous carbon nanocomposites. As the anode materials of lithium-ion batteries, the ZnMn₂O₄/MC (milk-derived carbon) hybrids deliver a high reversible capacity of 1352 mAh g⁻¹ after 400 cycles at 0.1 A g⁻¹, and a remarkable long-term cyclability with 635 mAh g⁻¹ after 300 cycles at 1.0 A g⁻¹.     

Flexible all-solid-state asymmetric supercapacitor based on three-dimensional MoS2/Ketjen black nanoflower arrays

High electrochemical properties of negative electrode materials are highly desirable for flexible asymmetric supercapacitors (ASCs). Although benefiting from the unique structure and broad operation potential, molybdenum disulfide (MoS₂) has caused concern as a negative electrode material because its low electrochemical stability and poor conductivity hinder the exploitation of its application in flexible ASCs. Here we investigated a facile two-step hydrothermal approach to fabricate MoS₂/Ketjen black (KB) composites on flexible carbon cloth. Following the construction of flower-like MoS₂ on carbon cloth, KB nanospheres were embedded in MoS₂ via a secondary hydrothermal route. The as-prepared MoS₂/KB electrode presents a high capacitance of 429 F g⁻¹ at a current specific of 1 A g¹. In addition, the hybrid ASC device of NiCo₂O₄//MoS₂/KB was built, which delivers a high energy density of 25.7 Wh kg⁻¹ and power density of 16 kW kg⁻¹. These results are ascribed to the favorable structure of MoS₂ and inherently superior conductivity of KB, which improves wettability, structural stability and electronic conductivity. In brief, the proposed all-solid-state ASC device offers potential application in future portable electronics and flexible energy storage devices.     

Self-assembled Mo doped Ni-MOF nanosheets based electrode material for high performance battery-supercapacitor hybrid device

The application of MOF materials in supercapacitors has been greatly restricted due to the poor conductivity and structural stability. Given that, this work improves the conductivity and stability of Ni-MOF by self-assembled strategy. We report here the Mo-doped Ni-MOF nanosheets (M-NMN), in which the Mo-based clusters are encapsulated in the holes of the Ni-MOF frame structure by self-assembly. The results show that the M-NMN-1 material with a Mi/Mo molar ratio of 1: 1 exhibits an excellent electrochemical performance. Furthermore, the nanosheet structure of the M-NMN-1 materials acts as a “superhigh way” for charge transport to accelerate charge transfer rate and enhance the conductivity of the electrode materials. As-prepared M-NMN-1 electrode material exhibits high specific capacity of 802 C g⁻¹ at 1 A g⁻¹. Furthermore, assembled battery-supercapacitor hybrid device exhibits an excellent energy density of 59 Wh kg⁻¹ at a power density of 802 W kg⁻¹, and superior cycle retention of 93% after 20,000 cycles.     

Hollow nickel-cobalt sulfide nanospheres cathode hybridized with carbon spheres anode for ultrahigh energy density asymmetric supercapacitors

There has been increasing attention to the transition metal sulfides because of their unique property such as high electrical conductivity. Moreover, hollow sphere structures can provide excellent performance in electrochemical energy conversion applications due to their rich holes volume and unique properties. In this study, nickel-cobalt sulfide （Ni-Co-S） hollow spheres are successfully synthesized by two step methods of hard template method and hydrothermal method. Benefiting from the hollow sphere structure with optimum size and mesoporous surface, the Ni-Co-S exhibits an excellent specific capacity of 819.9 C g^?1, and has good stability in the charge-discharge cycles. In addition, uniform size and monodisperse carbon sphere (CS) that synthesized by a simple self-assembly method also shows excellent electrochemical properties. Furthermore, the fabricated Ni-Co-S//CS asymmetric supercapacitor shows energy density of 65 Wh kg^?1 at a power density of 850 W kg^?1 and outstanding cycling stability with a capacity retention of 82.8% after 10,000 cycles, demonstrating that as-prepared Ni-Co-S hollow spheres and carbon spheres possess promising potential as electrode materials for high-performance asymmetric supercapacitors.     

A new Co-ZIF derived nanoporous cobalt-rich carbons with high-potential-window as high-performance electrodes for supercapacitors

In this work, a Co-ZIF material and the derived nanoporous cobalt-rich carbons by direct carbonization of this Co-ZIF material were synthesized and used as electrode materials for supercapacitors. This ZIF material exhibited a high specific capacitance of 160.3 F g⁻¹ at 0.5 A g⁻¹, an excellent rate capability (73.72 F g⁻¹ at 10 A g⁻¹), and a good cycling stability with 100% of its initials specific capacitance after 8000 cycles. In addition, the obtained derived nanoporous carbons displayed ideal capacitor behaviors and were promising electroactive materials for supercapacitors at low current density. The nanoporous carbon obtained at 650 °C possessed a highest specific capacitance of 393 F g⁻¹ at 0.5 A g⁻¹ and a wide potential application range of −1.0–0.33 V. In addition, a symmetric supercapacitor device consisting of Z-C-650 and activated carbon exhibited a maximum energy density of 61.23 Wh Kg⁻¹ at a power density of 700 W kg⁻¹ and predicted that Z-C-650 could be used as a potential energy storage material.     

Metal phthalocyanine-linked conjugated microporous polymer hybridized with carbon nanotubes as a high-performance flexible electrode for supercapacitors

Metal phthalocyanine-linked conjugated microporous polymers (MPc-CMPs) have huge potential applications in energy conversion and storage systems. However, the inherent low conductivity limits their practical application. Herein, the MPc-CMPs are hybridized with highly conductive carbon nanotubes (CNTs) via the easy vacuum filtration method. Interestingly, the composite (denoted as CoPc-CMP/CNTs) shows the flexible feature, which can be served as the flexible binder-free electrode for supercapacitors (SCs). As expected, the flexible CoPc-CMP/CNTs exhibits a high specific capacitance of 289.1 F g⁻¹ at a current density of 1 A g⁻¹ and good capacity retention of 82.4% over 1350 cycles at a high current density of 10 A g⁻¹. Furthermore, First-principle calculations are used to elucidate the superiority of CoPc-CMP to other analogues. The good electrochemical performance could be attributed to the synergistic effect from the high pseudocapacitance and good conductivity of CoPc-CMP as well as the capacitive contribution and good conductivity of CNTs. Our strategy provides a new avenue to develop the high-performance SCs via rational integration of MPc-CMPs with highly conductive CNTs.     

Transforming waste sugar solution into N-doped hierarchical porous carbon for high performance supercapacitors in aqueous electrolytes and ionic liquid

Waste sugar solution is a by-product in the process of manufacturing vitamin C. Nowadays, the unused industrial waste residues are transformed into high efficient energy storage devices, such as supercapacitors electrodes, which are worth exploring because they are consistent with the concept of green and sustainable development. In this paper, a nitrogen-doped hierarchical porous carbon are obtained via pre-carbonization and KOH activation. The as-prepared material, possessed proper pore size distribution, large specific surface area and nitrogen-doping, exhibits good electrochemical performance, such as a high specific capacitance of 342 F g⁻¹ (0.1 A g⁻¹), good stability with 95% capacitance retention after 15,000 cycles in 6 M KOH. Moreover, the supercapacitors deliver a high energy density of 25.6 and 65.9 W h kg⁻¹ in the 1 M Na₂SO₄ and EMIMBF₄, respectively. The good electrochemical performance illustrates that the nitrogen-doped hierarchically porous carbon derived from the waste sugar solution is a potential candidate for energy storage.     

Rational design of hierarchical core-shell structured CoMoO4@CoS composites on reduced graphene oxide for supercapacitors with enhanced electrochemical performance

Engineering multicomponent active materials as an advanced electrode with the rational designed core-shell structure is an effective way to enhance the electrochemical performances for supercapacitors. Herein, three-dimensional self-supported hierarchical CoMoO₄@CoS core-shell heterostructures supported on reduced graphene oxide/Ni foam have been rationally designed and prepared via a facile approach. The unique structure and the synergistic effects between two different materials, as well as excellent electronic conductivity of the reduced graphene oxide, contribute to the increased electrochemically active site and enhanced capacitance. The core-shell CoMoO₄@CoS composite displays the superior specific capacitance of 3380.3 F g⁻¹ (1 A g⁻¹) in the three-electrode system and 81.1% retention of the initial capacitance even after 6000 cycles. Moreover, an asymmetric device was successfully prepared using CoMoO₄@CoS and activated carbon as positive/negative electrodes. It is worth mentioning that the device delivered the high energy density of 59.2 W h kg⁻¹ at the power density of 799.8 W kg⁻¹ and the excellent cycle performance (about 91.5% capacitance retention over 6000 cycles). These results indicate that the core-shell CoMoO₄@CoS composites offers the novelty strategy for preparation of electrodes for energy conversion and storage devices.     

Nickel-copper oxide nanoflowers for highly efficient glucose electrooxidation

The development of highly active and low-cost electrocatalysts with excellent durability is a major challenge for glucose catalysis. Here, we report a fast and low-cost electrodeposition method for preparing a new NiCuO flower-like nanostructure with non-noble metals. The new NiCuO catalyst shows significant efficiency for glucose electrooxidation, which reaches an oxidative peak mass activity of 376.80 A g⁻¹ and retains 66% of the original current over 10,000 s in a stability test by chronoamperometry. We credit the excellent glucose oxidation activity and outstanding stability to the combination of non-noble metal materials and the flower-like nanostructures of the NiCuO/ITO electrode, which results in large electrochemically active surface areas (ECSAs) of 85.9 m² g⁻¹ and fast charge transfer as measured by electrochemical impedance spectroscopy (EIS). This new NiCuO nanoflower catalyst provides a new functional material for the building of glucose fuel cells and other electrochemical devices.     

ZnSe/CoSe/NCDPH composites as anode materials for lithium ion batteries with high capacity and long cycle

In this paper, dopamine hydrochloride (DPH) is introduced to synthesize ZIF-8@ZIF-67@DPH in the preparation of ZIF-8@ZIF-67. ZnSe/CoSe/NC_DPH (N-doped carbon) composites are calcined in a high-temperature inert atmosphere with ZIF-8@ZIF-67@DPH as the precursor, selenium powder as the selenium source. ZnSe/CoSe/NC_DPH has high discharge specific capacity, good cycle stability and outstanding rate performance. The first discharge capacity of ZnSe/CoSe/NC_DPH is 1616.6 mAh g⁻¹ at the current density of 0.1 A g⁻¹, and the reversible capacity remains at 1214.2 mAh g⁻¹ after 100 cycles, the reversible capacity is 416.7 mAh g⁻¹ after 1000 cycles at 1 A g⁻¹. Therefore, ZnSe/CoSe/NC_DPH composites provide a new step for the research and synthesis of new stable, high-capacity, and safe high-performance lithium ion batteries. The bimetallic selenide composites not only have bimetallic active sites, but also can form synergistic effect between different metal phases, which can effectively reduce the capacity attenuation caused by volume expansion and reactive stress enrichment during lithium storage of metal oxide anode materials. Meanwhile, N-doped carbon can improve the conductivity and provide more active sites to store lithium, thus improving its lithium storage capacity.     

Enhanced performance of carbon-based supercapacitors by constructing protonic and electric dual-channels in electrodes

Powdery carbonaceous materials have to use binder materials when they are integrated into electrodes for supercapacitors, which will results in high interfacial charge transfer resistances and reduced specific capacitance. To resolve the problem, protonic and electric dual-channels are constructed in electrodes by in situ synthesis of cesium hydrogen salt of phosphotungstic acid on the surface of carbonaceous materials. The cesium hydrogen salt particles are confirmed by a Fourier transform infrared spectroscopy, X-ray diffractometer and an energy dispersive X-ray spectroscopy. The electrochemical properties of as-fabricated electrodes are measured by cyclic voltammetry, galvanostatic charging-discharging, and impedance analysis with an electrochemical workstation. At a current density of 1 A g⁻¹, the electrode shows a specific capacitance of 152 F g⁻¹. Compared to the electrode without the cesium hydrogen salt, the value increases 25% at least. Furthermore, the specific capacitance retention of the electrode reaches 104% of its original capacitance after 5000 charge-discharge cycles, suggesting excellent cycling stability.     

One-step hydrothermal preparation of bi-functional NiS2/reduced graphene oxide composite electrode material for dye-sensitized solar cells and supercapacitors

To screen out suitable electrode materials and overcome the shortcomings of the existed electrode materials for the application in dye-sensitized solar cells and supercapacitors, NiS₂/reduced graphene oxide (NiS₂/rGO) composite material was prepared by a simple one-step hydrothermal method in this paper and applied in the field of both dye-sensitized solar cells and supercapacitors as electrode material. In an electrolyte of 6 M KOH, the NiS₂/rGO composite material with bilayer capacitance characteristics exhibited a high specific capacitance of 259.20 F g⁻¹ at the current density of 0.6 A g⁻¹, which was significantly higher than that of rGO (188.94 F g⁻¹). Moreover, at a current density of 2 A g⁻¹, the NiS₂/rGO composite material had 92.85% capacitance retention after 2000 cycles. When applied as counter electrode material for the dye-sensitized solar cells, the NiS₂/rGO composite material counter electrode exhibited a satisfactory photoelectric conversion efficiency (η) of 3.16% under standard simulated sunlight (AM 1.5 G), which was significantly higher than that of single rGO counter electrode (improved by 90.40%). The NiS₂/rGO composite electrode material prepared by a simple one-step hydrothermal method is a potential bi-functional composite electrode materials for both dye-sensitized solar cells and supercapacitors.     

Green and facile synthesis of porous carbon spheres from waste solution for high performance all-solid-state symmetric supercapacitors

Porous carbon spheres materials display huge potential for energy storage, but their general synthesis need chemical activation agent with highly corrosive to create pores. In this work, a simple, environment-friendly and less time-demanding method is used to prepared porous carbon spheres using K₂FeO₄ as activation agent and waste solution as the precursor. The K₂FeO₄ employ in this work acts both as an activating agent and a catalyst. In addition, replacing KOH with K₂FeO₄ does not only reduce the corrosion of equipment but also increases the content of oxygen. The optimized porous carbon spheres with high specific surface area, hierarchical pore structure and surface heteroatom can deliver a high specific capacitance of 260 F g⁻¹ at 0.1 A g⁻¹ and good cycling stability (90% retention after 15000 cycles at 5 A g⁻¹). Furthermore, the all-solid-state symmetric supercapacitors fabricated based on as-prepared samples exhibit good electrochemical performance in the PVA/KOH electrolyte. This work offers a green route to convert waste solution into porous carbon spheres, which are promising candidate material for supercapacitors to energy storage.     

Nickel–cobalt layered double hydroxide/NiCo2S4/g-C3N4 nanohybrid for high performance asymmetric supercapacitor

Graphitic carbon nitride (g-C₃N₄) with semiconducting nature can be considered for energy storage system by modifying its electrical conductivity and structural properties through formation of hybrid with materials such as bimetallic metal sulfide and nickel-cobalt layered double hydroxide (LDH). g-C₃N₄ as a N-rich compound with basic surface sites can change the surface properties of nanohybrid and impress the charge transfer. In this study, a nanohybrid based on nickel-cobalt LDH and sulfide and graphitic carbon nitride (NiCo LDH/NiCo₂S₄/g-C₃N₄) was synthesized through a three-step method. At first, Ni doped ZIF-67 was formed at the surface of g-C₃N₄ nanosheets and then the product was calcined in a furnace to form NiCo₂O₄/g-C₃N₄. At next step, the sample was hydrothermally converted to NiCo₂S₄/g-C₃N₄ using thioacetamide and finally modified with NiCo LDH nanoplates to form porous structure with high surface area. The NiCo LDH/NiCo₂S₄/g-C₃N₄ nanohybrid showed high specific capacitance of 1610 F g^?1 at current density of 1 A g^?1 and also excellent stability of 108.8% after 5000 cycles at potential scan rate of 50 mV s^?1, which makes it promising candidate for energy storage. An asymmetric system was prepared using nickel foams modified with NiCo LDH/NiCo₂S₄/g-C₃N₄ and g-C₃N₄ as positive and negative electrodes, respectively. The specific capacitance of 246.0 F g^?1 was obtained at 1 A g^?1 in 6 M KOH solution and system maintained 90.8% cyclic stability after 5000 cycles at potential scan rate of 50 mV s^?1. The maximum energy density and power density of the system were calculated as 82.0 Wh kg^?1 and 12,000 W kg^?1, respectively, which demonstrate its capability for energy storage.     

3D carboxyl and hydroxyl co-enriched graphene hydrogels as binder-free electrodes for symmetric supercapacitors

At present, amino acids are often used as the source of heteroatom functional groups for the preparation of doped graphene materials. However, a large amount of amino acids will be used as reaction precursors in the preparation process, which will lead to increased cost, reduced efficiency and waste of resources. Herein, a very small amount of neutral l-alanine is employed to synthesize 3D carboxyl and hydroxyl co-enriched graphene hydrogels (CHGHs) by a one-pot hydrothermal method. The CHGHs contain copious carboxyl and hydroxyl groups, and a small amount of nitrogen-containing functional groups. In addition, the CHGHs also present large specific surface areas and 3D porous structures. Therefore, the CHGH-20 binder-free electrode displays a high specific capacitance of 262.8 F g⁻¹ at 0.3 A g⁻¹, and this value still maintains 84.3% (221.6 F g⁻¹) at 10 A g⁻¹ in a two-electrode system in 6 M KOH. Furthermore, the CHGH-20 electrode also displays outstanding cycle stability with 103.6% of its initial capacitance after 10,000 cycles at 10 Ag⁻¹. Therefore, the CHGHs samples prepared by a very small amount of neutral l-alanine have great significance for the practical application of supercapacitors.