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(A) Rate capability: current density vs. specific capacitance. (B) Cyclic voltammetry (CV) curve of three samples at 100 mv s⁻¹. (C) Nyquist plots of three samples; the inset is a magnification of the high-frequency range data and fitting equivalent circuit. (D) Galvanostatic charge–discharge (GCD) curve of APPy-850-SC at current densities of 1, 2, 4, 6, 8, and 10 A g⁻¹. (E) CV curve of APPy-850-SC at a scan rate of 20–200 mV s⁻¹. (F) Cycling stability and coulombic efficiency of APPy-850-SC at 6 A g ⁻¹ for 10,000 cycles. The inset shows photographs of two blue LEDs.
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Carbon-ionic liquid (C-IL) supercapacitors (SCs) promise to provide high capacitance and high operating voltage, and thus high specific energy. It is still highly demanding to enhance the capacitance in order to achieve high power and energy density. We synthesized a high-pore-volume and specific-surface-area activated carbon material with a slit m...
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Supercapacitors are one of the promising devices for the accumulation and storage of electrical energy. The purpose of this study is to develop a synthesis and modification method of carbon material to improve the electrochemical characteristics of a supercapacitor. In the proposed study, by varying the sequence and parameters of the processes of c...
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... In the last few decades, the demand for alternative high-performance energy storage devices has increased enormously due to the global energy crisis and environmental pollution. Due to this increasing demand, extensive research has been focused on portable and wearable electronic energy storage technologies, energy harvesting devices and hybrid electric vehicles [1][2][3][4]. In the field of portable electronics, lithium-ion batteries (LIBs) have been widely used as energy storage materials for several years due to their high energy density and long cyclic stability. ...
Supercapacitors (SCs) are considered as emerging energy storage devices that bridge the gap between electrolytic capacitors and rechargeable batteries. However, due to their low energy density, their real-time usage is restricted. Hence, to enhance the energy density of SCs, we prepared hetero-atom-doped carbon along with bimetallic oxides at different calcination temperatures, viz., HC/NiCo@600, HC/NiCo@700, HC/NiCo@800 and HC/NiCo@900. The material produced at 800 °C (HC/NiCo@800) exhibits a hierarchical 3D flower-like morphology. The electrochemical measurement of the prepared materials was performed in a three-electrode system showing an enhanced specific capacitance for HC/NiCo@600 (Cs = 1515 F g−1) in 1 M KOH, at a current density of 1 A g−1, among others. An asymmetric SC device was also fabricated using HC/NiCo@800 as anode and HC as cathode (HC/NiCo@600//HC). The fabricated device had the ability to operate at a high voltage window (~1.6 V), exhibiting a specific capacitance of 142 F g−1 at a current density of 1 A g−1; power density of 743.11 W kg−1 and energy density of 49.93 Wh kg−1. Altogether, a simple strategy of hetero-atom doping and bimetallic inclusion into the carbon framework enhances the energy density of SCs.
... The energy source crisis and effects of global climate change have promoted the rapid development of renewable energy technologies worldwide [1][2][3]. Lithium ion batteries (LIB) [4][5][6] and supercapacitors (SC) [7,8] are the two most popular energy storage systems and are widely used in portable electronic devices, electric vehicles and flexible wearable devices [9,10]. However, LIBs and SC still have some inevitable shortcomings, such as limited lithium storage, potential safety hazards, and energy density [11][12][13]. ...
... The oxygen content of PBC was 11.1%, whereas that of PBAC 4 increased to 24.6%, indicating that a large number of oxygen groups were connected to the carbon surface via KOH activation. As shown in Fig. 2(o), the high-resolution C1s spectrum of the samples can be divided into three peaks located at 284.8 eV, 285.6 eV, and 289.1 eV, mapping to C-C/C-H, C-N, and C--O/C--N, respectively [7,69,70]. Fig. 2(p) shows the high-resolution O spectrum. The divided peaks located at energies of 531.5 eV, 532.5 eV and 533.5 eV, were attributed to the contributions of C--O, C-OH/C-O-C and-OH, respectively [71][72][73][74]. ...
Rechargeable aqueous zinc-based hybrid supercapacitors (ZHSC) are widely used because of their safety, high capacity, cost-effectiveness, and environmental friendliness. However, the serious dendrite growth, low cycle life, and poor safety of zinc metal anodes greatly hinder their practical application. Additionally, the lack of excellent cathode materials also restricts further development of high-efficiency aqueous ZHSC. Herein, we report a novel persimmon-branch biomass carbon-based material with a naturally graded pore structure. Persimmon branch activated carbon (PBAC) was used as the cathode, and the anode was constructed using a zinc foil coated with one-step carbonized persimmon branch carbon (PBC). A new type of high-performance ZHSC was assembled using the porous structure of a carbon-based material and Cu²⁺-electrolyte additive. The hierarchical pore structure endowed the activated carbon with excellent electric double-layer capacitance characteristics as well as superb zinc ions storage ability. The artificial carbon-coated zinc metal anodes could homogenize the electric fields, and the Cu²⁺ from the electrolyte induced zinc metal deposition, which improved the cycle stability of the ZHSC. Therefore, the assembled ZHSC (PBAC4|ZnSO4+CuSO4|[email protected]) exhibited excellent electrochemical performance, high discharge capacity (182.8 mAh g⁻¹), good rate performance (51.4 mAh g⁻¹ at 10 A g⁻¹), high energy density (27.1 W h kg⁻¹ at 5 kW kg⁻¹ based on the weight of the active material) and demonstrated a long cycle life with 73.8% capacitance retention after 3000 cycles at 5 A g⁻¹ high current density.
Catalyst activity affects the reaction rate, and an increasing number of studies have shown that strain can significantly increase the electrocatalytic activity. Catalysts such as alloys and core-shell structures can modulate their properties through strain effects. Reasonable simulation techniques can be used to predict and design the catalytic performance based on understanding the strain action mechanism. Therefore, the methodological flow of theoretical simulations is summarised in this review. The mechanism underlying the strain-adsorption-reaction relationship is discussed using density functional theory (DFT) calculations. An introduction to DFT is given first, followed by a quick rundown of the strain classification and application. Typical electrocatalytic reactions, namely, the hydrogen and oxygen evolution reactions and oxygen reduction reaction, are taken as examples. After briefly explaining these reactions, the relevant studies on simulating the strain to tune the catalyst performance are covered. The simulation methods are summarised and analysed to observe the effects of strain on electrocatalytic properties. Finally, a summary of the issues with simulated strain-assisted design and a discussion on the perspectives and forecasts for the future design of effective catalysts are provided.
The massive exploitation and use of fossil resources have created many negative issues, such as energy shortage and environmental pollution. It prompts us to turn our attention to the development of new energy technologies. This review summarizes the recent research progress of non-precious transition metal single-atom catalysts (NPT-SACs) for the oxygen reduction reaction (ORR) in Zn-air batteries and fuel cells. Some commonly used preparation methods and their advantages/disadvantages have been summarized. The factors affecting the ORR performances of NPT-SACs have been focused upon, such as the substrate type, coordination environment and nanocluster effects. The loading mass of a metal atom has a direct effect on the ORR performances. Some general strategies for stabilizing metal atoms are included. This review points out some existing challenges of NPT-SACs, and also provides ideas for designing and synthesizing NPT-SACs with excellent ORR performances. The large-scale preparation and commercialization of NPT-SACs with excellent ORR properties are prospected.
Extensive research has been carried on the molecular adsorption in high surface area materials such as carbonaceous materials and MOFs as well as atomic bonded hydrogen in metals and alloys. Clathrates stand among the ones to be recently suggested for hydrogen storage. Although, the simulations predict lower capacity than the expected by the DOE norms, the additional benefits of clathrates such as low production and operational cost, fully reversible reaction, environmentally benign nature, low risk of flammability make them one of the most promising materials to be explored in the next decade. The inherent ability to tailor the properties of clathrates using techniques such as addition of promoter molecules, use of porous supports and formation of novel reverse micelles morphology provide immense scope customisation and growth. As rapidly evolving materials, clathrates promise to get as close as possible in the search of “holy grail” of hydrogen storage. This review aims to provide the audience with the background of the current developments in the solid-state hydrogen storage materials, with a special focus on the hydrogen clathrates. The in-depth analysis of the hydrogen clathrates will be provided beginning from their discovery, various additives utilised to enhance their thermodynamic and kinetic properties, challenges in the characterisation of hydrogen in clathrates, theoretical developments to justify the experimental findings and the upscaling opportunities presented by this system. The review will present state of the art in the field and also provide a global picture for the path forward.
Unevenly distributed magnesium (Mg) electrodeposits have emerged as a major obstacle for Mg-metal batteries. A comprehensive design matrix is reported for 3D magnesiophilic hosts, which regulate the uniform Mg electrodeposition through a synergistic coupling of homogenizing current distribution, geometric confinement, and chemisorptive interaction. Vertically aligned nitrogen- and oxygen-doped carbon nanofiber arrays on carbon cloth (denoted as “VNCA@C”) are developed as a proof of concept. The evenly arranged short nanoarray architecture helps to homogenize the surface current density and the microchannels built in this 3D host allow the preferential nucleation of Mg due to their geometrical confinement effect. Besides, the nitrogen-/oxygen-doped carbon species exhibit strong chemisorptive interaction toward Mg atoms, providing preferential nucleation sites as demonstrated by first-principle calculation results. Electrochemical analysis reveals a peculiar yet highly reversible microchannel-filling growth behavior of Mg metals, which empowers the delicately designed VNCA@C host with the ability to deliver a reduced nucleation overpotential of 429 mV at 10.0 mA cm⁻² and an elongated Mg plating/stripping cycle life (110 cycles) under high current density of 10.0 mA cm⁻². The proposed design matrix can be extended to other metal anodes (such as lithium and zinc) for high-energy-density batteries.
Herein, a novel activated hollow carbon nanospheres (AHCNSs) with enlarged specific surface area (SSA) of 1796 m ² ú g ⁻¹ and pore volume (Vp) of 1.33 cm ³ ú g ⁻¹ was synthesized from poly(aniline-co-pyrrole) hollow nanospheres via KOH activation method. The supercapacitor containing AHCNSs displayed high gravimetric capacitance ( C g ) of 290 F ú g ⁻¹ at 1 Aú g ⁻¹ and 79% capacitance retention even at 20 Aú g ⁻¹ in ionic liquid EMIMBF 4 , indicating its excellent rate capability. This study highlights the potential value of novel hollow structure activated carbon in the field of energy storage.
