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Energy storage in electrochemical hybrid capacitors involves fast faradaic reactions such as an intercalation, or redox process occurring at a solid electrode surface at an appropriate potential. Hybrid sodium‐ion electrochemical capacitors bring the advantages of both the high specific power of capacitors and the high specific energy of batteries, where activated carbon serves as a critical electrode material. The charge storage in activated carbon arises from an adsorption process rather than a redox reaction and is an electrical double‐layer capacitor. Advanced carbon materials with interconnecting porous structures possessing high surface area and high conductivity are the prerequisites 1128to qualify for efficient energy storage. Herein, we have demonstrated that a porous honeycomb structure activated carbon derived from Australian hemp hurd (Cannabis sativa L.) in aqueous Na2SO4 electrolyte showed a specific capacitance of 240 F/g at 1 A/g. The mass ratio of biochar to KOH during the chemical activation associated with the synthesis temperature influences the change in morphologies, and distribution of pore sizes on the adsorption of ions. At higher synthesis temperatures, the tubular form of the honeycomb starts to disintegrate. The hybrid sodium‐ion device employing hemp‐derived activated carbon (HAC) coupled with electrolytic manganese dioxide (EMD) in an aqueous Na2SO4 electrolyte showed a specific capacitance of 95 F/g at 1 A/g having a capacitance retention of 90 %. The hybrid device (HAC||EMD) can possess excellent electrochemical performance metrics, having a high energy density of 38 Wh/kg at a power density of 761 W/kg. Overall, this study provides insights into the influence of the activation temperature and the KOH impregnation ratio on morphology, porosity distribution, and the activated carbon's electrochemical properties with faster kinetics. The high cell voltage for the device is devoted to the EMD electrode. [ABSTRACT FROM AUTHOR]

Aqueous sodium (Na+) ion storage systems face challenges due to sluggish adsorption and diffusion of Na+ ions with larger size, hindering their potential for stationary applications. This issue is addressed by evolving the interfacial electronic coupling in atomically thin 2D WO3/WSe2 heterostructure for efficient Na+ ion storage. Density functional theory (DFT) analysis elucidates the superior charge storage capability for the WO3/WSe2 heterostructure facilitated by the charge transfer from the WO3 – WSe2 (002). The charge transfer from the W‐5d and O‐2p orbitals of WO3 to the valence W‐5d and Se‐4p orbitals of the WSe2 (002) surface boosts the electronic conductivity. As a result, the WO3/WSe2 electrode demonstrates exceptional Na+ ion storage, with a specific capacitance of 378.1 F g−1 at 1 A g−1, excellent rate capability, and long‐lasting cycling durability. The full cell comprising WO3/WSe2 as the negative and MnSe/MnSe2 as the positive electrode achieved a peak energy density of 82.1 Wh kg−1 at a power density of 1873.5 W kg−1, along with high rate capability and long‐cycle durability. Insights gained from this study pave the technique for the rational design and optimization of the interfacial electronic features in 2D heterostructures for next‐generation energy storage devices with enhanced performance and stability. [ABSTRACT FROM AUTHOR]

We report an efficient ORR electrocatalyst containing cobalt single atom and cobalt nanoparticle active sites embedded in a porous nitrogen-doped graphitic carbon network. The robust electrocatalyst exhibits superior electrochemical ORR activity with onset and half-wave potentials of 0.96 V and 0.87 V (vs. reversible hydrogen electrode), respectively, and has excellent durability and methanol tolerance further enhancing the potential of this system for practical applications. [ABSTRACT FROM AUTHOR]

The recognition of the importance of nanostructures is mainly due to the development of nanotechnology. For further developments in materials sciences, a concept that integrates nanotechnology with material chemistry to fabricate functional materials has to be proposed. Nanoarchitectonics will carry out this task. In nanoarchitectonics, we architect functional material systems from nano-units (atoms, molecules, nanomaterials). The methodology is not specific to any particular material or application. It covers a wide range. Therefore, nanoarchitectonics can be thought of as the method for everything in materials science. As typical demonstrations for usages of nanoarchitectonics, this review paper presents our work on nanoarchitectonics for supercapacitors. We divide it into two categories with different approaches. The first is the development of carbon materials as supercapacitor electrode materials from biomass. The second category is preparing carbon materials using structures created by supramolecular assembly of fullerenes such as C60 and C70. By presenting examples using opposite starting materials, a complex natural material, and an ultimately simple molecule, we will demonstrate the versatility and breadth of possibilities of this approach. [ABSTRACT FROM AUTHOR]

The energy storage performances of supercapacitors are expected to be enhanced by the use of nanostructured hierarchically micro/mesoporous hollow carbon materials based on their ultra-high specific surface areas and rapid diffusion of electrolyte ions through the interconnected channels of their mesoporous structures. In this work, we report the electrochemical supercapacitance properties of hollow carbon spheres prepared by high-temperature carbonization of self-assembled fullerene-ethylenediamine hollow spheres (FE-HS). FE-HS, having an average external diameter of 290 nm, an internal diameter of 65 nm, and a wall thickness of 225 nm, were prepared by using the dynamic liquid-liquid interfacial precipitation (DLLIP) method at ambient conditions of temperature and pressure. High temperature carbonization (at 700, 900, and 1100 °C) of the FE-HS yielded nanoporous (micro/mesoporous) hollow carbon spheres with large surface areas (612 to 1616 m2 g−1) and large pore volumes (0.925 to 1.346 cm3 g−1) dependent on the temperature applied. The sample obtained by carbonization of FE-HS at 900 °C (FE-HS_900) displayed optimum surface area and exhibited remarkable electrochemical electrical double-layer capacitance properties in aq. 1 M sulfuric acid due to its well-developed porosity, interconnected pore structure, and large surface area. For a three-electrode cell setup, a specific capacitance of 293 F g−1 at a 1 A g−1 current density, which is approximately 4 times greater than the specific capacitance of the starting material, FE-HS. The symmetric supercapacitor cell was assembled using FE-HS_900 and attained 164 F g−1 at 1 A g−1 with sustained 50% capacitance at 10 A g−1 accompanied by 96% cycle life and 98% coulombic efficiency after 10,000 consecutive charge/discharge cycles. The results demonstrate the excellent potential of these fullerene assemblies in the fabrication of nanoporous carbon materials with the extensive surface areas required for high-performance energy storage supercapacitor applications. [ABSTRACT FROM AUTHOR]