Hierarchical porous carbon materials from nanosized metal-organic complex for high-performance symmetrical supercapacitor

Size-Dependent Effects of ZIF-8 Derived Cathode Materials on Performance of Zinc-Ion Capacitors

Zinc-ion capacitors (ZICs) have attracted great attention due to a series of advantages. However, the cathode materials are still the bottleneck for high-performance ZICs to be achieved. Therefore, ZIF-8-derived porous carbons are one of the most promising candidates but ZIF-8 nanoparticles with different sizes exhibited various electrochemical performances in ZICs. Herein, a series of monodispersed ZIF-8 nanoparticles are first prepared by a temperature-controlled process to fabricate the corresponding ZIF-8-based porous carbon nanoparticles with pre-designed sizes. The as-prepared materials have been tested as cathode materials in ZICs. Thus, their size effect allowed us to disclose its correlation with other factors such as ion transport/storage and capacitance. The results reveal that the optimal-sized porous carbon particles can effectively shorten the ion transport distance and accelerate the ion diffusion rate, resulting in lower electrical resistance, larger ion diffusion coefficients, and faster electron transport. The presented findings can facilitate the design of new advanced cathode materials paving the way for the development of high-performance cathode materials for ZICs in the future.

Al-MOF-derived spindle-like hierarchical porous activated carbon for advanced supercapacitors

Metal organic frameworks (MOFs) and their derivatives have been widely used in electrochemistry due to their adjustable pore size and high specific surface area (SSA). Herein, a spindle-like hierarchical porous activated carbon (SPC) was synthesized through carbonizing the Al-BTEC precursor and then alkaline washing with NaOH. The fabricated SPC has a uniform shuttle-shaped structure, showing a large BET surface area of 1895 m² g^-1 and an average pore size of 2.4 nm. The SPC product displays a high specific capacitance (SC) of 337 F g^-1 at 1 mV s^-1 and 334 F g^-1 at 1 A g^-1. The retention of SC is about 95% after 100 000 cycles when the current density is 50 A g^-1, indicating its excellent stability. Furthermore, the assembled symmetrical capacitor with a two-electrode system exhibits a high SC of 173 F g^-1 at 1 A g^-1 and an energy density of 15.3 W h kg^-1 at a power density of 336 W kg^-1. This work would provide a new pathway to design and synthesize carbon materials for supercapacitors with excellent properties in the future.

Controllable Carbonization of Plastic Waste into Three-Dimensional Porous Carbon Nanosheets by Combined Catalyst for High Performance Capacitor

Polyethylene terephthalate (PET) plastic has been extensively used in our social life, but its poor biodegradability has led to serious environmental pollution and aroused worldwide concern. Up to now, various strategies have been proposed to address the issue, yet such strategies remain seriously impeded by many obstacles. Herein, waste PET plastic was selectively carbonized into three-dimensional (3D) porous carbon nanosheets (PCS) with high yield of 36.4 wt%, to be further hybridized with MnO₂ nanoflakes to form PCS-MnO₂ composites. Due to the introduction of an appropriate amount of MnO₂ nanoflakes, the resulting PCS-MnO₂ composite exhibited a specific capacitance of 210.5 F g^-1 as well as a high areal capacitance of 0.33 F m^-2. Furthermore, the PCS-MnO₂ composite also showed excellent cycle stability (90.1% capacitance retention over 5000 cycles under a current density of 10 A g^-1). The present study paved an avenue for the highly efficient recycling of PET waste into high value-added products (PCSs) for electrochemical energy storage.

3D hierarchical graphene/CNT with interfacial polymerized polyaniline nano-fibers

In this work Polyaniline (PANI) fiber has been synthetized by the interfacial polymerization method. The thermal behavior of graphene - multiwall carbon nanotubes (MWCNs) composite material (C-Mix) blended with PANI fiber was investigated. Graphene was prepared by thermal reduction of the fabricated graphene oxide (GO) using modified Hummers' method. SEM measurement reveals that MWCNTs were well organized within 2D large surface area graphene nano-sheets to form 3D carbon-base hierarchical structure, and PANI was mixed as a binder polymer matrix. Structural measurements confirm the formation of wide area graphene sheets with crumples, wrinkles, and folds around the edges. Transmission electron microscopy (TEM) images agreed with the well distribution of CNTs within graphene nano-sheets. Also, the surface morphology of the synthesized composites has a spherical regular agglomeration of PANI granular structure on wide area graphene nano sheets with CNT embedded. The change in the existed phonon modes of the fabricated nano-composite was analyzed using Raman spectroscopy. Moreover, Seebeck coefficient changes from +132.4 μV/K to -10.3 μV/K after adding carbon-based materials which reflects the reverse of predominate carriers by doping PANI with carbon-based material. It has been noticed that there is an enhancement of thermal conductivity of the fabricated composite with respect to neat polymer. Hence, we propose that 3D carbon structure with PANI construct a stable N-Type thermoelectric material.

Gas sorption and supercapacitive properties of hierarchical porous graphitic carbons prepared from the hard-templating of mesoporous ZnO/Zn(OH)2 composite spheres

Three-dimensional (3D) hierarchical porous carbon materials (PCMs) with graphitic carbon walls are facilely prepared through the hard-templating of acid-labile mesoporous ZnO/Zn(OH)₂ spheres. Furfuryl alcohol or phloroglucinol is employed as a carbon precursor for two hierarchical porous carbon materials (PCM-F and PCM-P). The basic surfaces of ZnO/Zn(OH)₂ are highly suited to the polymerization of the carbon precursors without extra catalysts. After carbonization followed by mild acid etching, hierarchical PCMs are obtained. These PCMs consist of interconnected turbostratic carbon wall structures. Gas sorption analysis indicates the surface areas of PCM-F and PCM-P are 1013 and 1075 m² g^-1, respectively. The corresponding pore volumes are very large, 3.39 and 3.01 cm³ g^-1, respectively. The uptake abilities for carbon dioxide and hydrogen are investigated at 196 and 77 K, respectively. The PCM-P reveals higher uptake of H₂ (1.19 wt%) and CO₂ (282.0 cm³ g^-1) than for PCM-F. In contrast, PCM-F shows a high gravimetric specific capacitance of 329.5 F g^-1 based on galvanostatic charge/discharge curves at a current density of 0.1 A g^-1. The PCM-F exhibits stable capacitance retention after 10,000 cycles at a current density of 5 A g^-1.

Evaluation of Nanoporous Carbon Synthesized from Direct Carbonization of a Metal⁻Organic Complex as a Highly Effective Dye Adsorbent and Supercapacitor

The synthesis of interconnected nanoporous carbon (NPC) material from direct annealing of ultra-small Al-based metal-organic complex (Al-MOC) has been demonstrated. NPC presents a large accessible area of 1,054 m²/g, through the Methylene Blue (MB) adsorption method, which is comparable to the high specific surface area (SSA) of 1,593 m²/g, through an N₂ adsorption/desorption analysis. The adsorption properties and mechanisms were tested by various dye concentrations, pH, and temperature conditions. The high MB accessible area and the good electrical conductivity of the interconnected NPC, led to a large specific capacitance of 205 F/g, with a potential window from 0 to 1.2 V, in a symmetric supercapacitor, and a large energy density of 10.25 Wh/kg, in an aqueous electrolyte, suggesting a large potential in supercapacitors.

Biomass waste-derived nitrogen-rich hierarchical porous carbon offering superior capacitive behavior in an environmentally friendly aqueous MgSO4 electrolyte

Nitrogen-doped porous carbons have been extensively investigated to improve the specific capacitance in aqueous electrolytes by increasing the specific surface area and nitrogen content and by optimizing the pore structure. However, research on the effect of electrolyte cations on the specific capacitance of these materials is rare, especially for neutral electrolytes. Herein, a nitrogen-rich hierarchically porous carbon (NRHPC) with a high nitrogen content of 12.3 atm% is successfully prepared by pyrolyzing a mixture of bagasse, K₂CO₃ and urea in a mass ratio of 2:1:4. It is found that NRHPC shows superior electrochemical performance in MgSO₄ than in Li₂SO₄ electrolyte, with specific capacitances of 315.0, 274.4, and 188.1 F g^-1 at 1.0, 10.0, and 100 A g^-1, respectively. Furthermore, it is found that the capacitance enhancement is closely related to the nitrogen content of the porous carbon materials. Theoretical calculation reveals that the Mg²⁺ ions have higher affinity towards the N atoms than Li⁺, producing higher charge storage capability via interaction between the Mg²⁺ and N atoms. When the 1.0 M MgSO₄ is used as electrolyte, a symmetric capacitor based on the nitrogen-rich hierarchically porous carbon shows a high energy density of 39.5 Wh kg^-1 at a power density of 0.9 kW kg^-1. Moreover, this as-assembled device displays superior long-term cycling stability, with a capacitance retention of >96.2% after 10,000 cycles at 10.0 A g^-1.

Multifunctional nitrogen-doped nanoporous carbons derived from metal–organic frameworks for efficient CO2 storage and high-performance lithium-ion batteries

Nitrogen-doped nanoporous carbons were prepared, capturing CO₂ of 10 mmol g⁻¹ at 45 bar and achieving a reversible capacity of 762 mA h g⁻¹.

Building metal-functionalized porous carbons from microporous organic polymers for CO2 capture and conversion under ambient conditions

Metal-functionalized porous carbons derived from microporous organic polymers remain highly desired for their intriguing physical and chemical properties.