Fabrication of an asymmetric supercapacitor based on reduced graphene oxide/polyindole/ γ− Al2O3 ternary nanocomposite with high-performance capacitive behavior

Self-assembled monolayers of reduced graphene oxide for robust 3D-printed supercapacitors

Herein, additive manufacturing, which is extremely promising in different sectors, has been adopted in the electrical energy storage field to fabricate efficient materials for supercapacitor applications. In particular, Al2O3-, steel-, and Cu-based microparticles have been used for the realization of 3D self-assembling materials covered with reduced graphene oxide to be processed through additive manufacturing. Functionalization of the particles with amino groups and a subsequent "self-assembly" step with graphene oxide, which was contextually partially reduced to rGO, was carried out. To further improve the electrical conductivity and AM processability, the composites were coated with a polyaniline-dodecylbenzene sulfonic acid complex and further blended with PLA. Afterward, they were extruded in the form of filaments, printed through the fused deposition modeling technique, and assembled into symmetrical solid-state devices. Electrochemical tests showed a maximum mass capacitance of 163 F/g, a maximum energy density of 15 Wh/Kg at 10 A/g, as well as good durability (85% capacitance retention within 5000 cycles) proving the effectiveness of the preparation and the efficiency of the as-manufactured composites.

Supercritical CO2 mediated construction of aluminium waste recovered γ-Al2O3 impregnated Dracaena trifasciata biomass-derived carbon composite: A robust electrocatalyst for mutagenic pollutant detection

Inspired by the waste-to-wealth concept, we have recovered the gamma phase aluminium oxide nanoparticles (γ-Al2O3 NPs) from waste aluminium (Al) foils and fabricated a composite with Dracaena trifasciata biomass-derived activated carbon matrix (DT-AC) using supercritical carbon-di-oxide (SC-CO2) pathway. The prepared samples are characterized altogether by various micro- and spectroscopic analyses. Based on the results, the recovered γ-Al2O3 NPs are well impregnated in the DT-AC surface by the action of the microbubble effect from the SC-CO2. The higher D-band and ID/IG value of 1.07 in the Al2O3/DT-AC nanocomposite indicate increased defects and the amorphous nature of the carbon materials. The effect of scan rate (ν) demonstrated greater linearity in ν1/2 vs peak current in the electrochemical detection study of the mutagenic pollutant 4-(methylamino) phenol hemi sulfate, showing a quasi-reversible electron transfer process undergoing diffusion-controlled kinetics. Furthermore, the limit of detection is determined to be 3.2 nM L-1 with an extensive linear range, spanning from 0.05 to 618.25 µM/L. The incredible sensitivity of 2.117 μA μM-1 cm-2, along with excellent selectivity, repeatability, and stability, is observed. Further, the respectable recovery percentage of 98.61 % in the environmental water sample is perceived. The observed outcomes suggest that the prepared Al2O3/DT-AC composite performs as an excellent electrocatalyst material, and the processing techniques used are thought to be sustainable in nature.

Boosting the Capacity of Aqueous Li-Ion Capacitors via Pinpoint Surgery in Nanocoral-Like Covalent Organic Frameworks

Aqueous lithium storage devices are promising candidates for next-generation energy storage applications, featuring low-cost, safety, environmental benignness, and grid-scale merits. Developing reliable anode materials with fast Li⁺ diffusion is paramount to stimulate their development. Herein, the electrochemical performance and mechanism of a redox-active β-ketoenamine-linked covalent organic framework (COF) (2,6-diaminoanthraquinone and 2,4,6-triformylphloroglucinol COF, DAAQ-TFP-COF) for lithium storage in aqueous electrolyte are explored for the first time. Systematic studies demonstrate that, by the conversion of neutral COF into anionic COF via a pinpoint surgery on the β-ketoenamine linkage, the resultative COF shows doubled Li⁺ storage capacity (132 mAh g^-1 at 0.5 A g^-1 , 87% of theoretical specific capacity), good rate capability (108 mAh g^-1 at 10 A g^-1 ), and excellent cyclability in 1000 cycles. This pinpoint surgery can be promising in extending the electrochemical applications of β-ketoenamine-linked COFs. The Li⁺ storage mechanism is investigated by ex situ electron paramagnetic resonance, in situ/ex situ Fourier transform infrared investigations, and density functional theory calculations. As a proof of new concept, a novel aqueous lithium-ion capacitor assembled with DAAQ-TFP-COF anode delivers high specific capacitance of 224 F g^-1 (0.1 A g^-1 ), supercapacitor-level power density (≈4000 W kg^-1 ), and long cyclability.

Ternary 3D reduced graphene oxide/Ni0.5Zn0.5Fe2O4/polyindole nanocomposite for supercapacitor electrode application

A facile two-step strategy has been reported for the preparation of a ternary 3D reduced graphene oxide/Ni_0.5Zn_0.5Fe₂O₄/polyindole nanocomposite (GNP) and this composite is applied as an electrode material for supercapacitor applications. Remarkably, Ni_0.5Zn_0.5Fe₂O₄ nanoparticles (NZF) decorated on reduced graphene oxide (GN2) are achieved by a facile hydrothermal method followed by coating with polyindole (PIN) through an in situ emulsion polymerization process. The structure, porosity, morphology, and thermal stability of the resulting ternary GNP hybrid material were characterized via X-ray diffraction (XRD), Raman spectroscopy, Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). This combination of hybrid material has a favorable mesoporous structure that enables high exposure of active sites for fast electron transport for supercapacitor applications. We demonstrate here that the ternary GNP hybrid electrode material is capable of delivering a favorable specific capacitance of ∼320 F g⁻¹ at 0.3 A g⁻¹ within the potential range from −0.1 to 1 V, with desirable rate stability and excellent cycling stability in the three-electrode system. Furthermore, an asymmetric supercapacitor (ASC) of a two-electrode configuration was fabricated using 3D RGO and GNP as the negative and positive electrodes, respectively. Such a device manifests a favourable C_sp of 48.9 F g⁻¹ at 0.5 A g⁻¹ and retains stability of 84% even after 2000 cycles. This ASC device exhibits a significant energy density of 16.38 W h kg⁻¹ at a power density of 1784 W kg⁻¹. The synergistic effects of pseudo and double layer capacitive contributions from PIN and GN2 make this ternary GNP hybrid electrode material of great promise in supercapacitor applications.

A facile two-step strategy has been reported for the preparation of a ternary 3D reduced graphene oxide/Ni_0.5Zn_0.5Fe₂O₄/polyindole nanocomposite (GNP) and this composite is applied as an electrode material for supercapacitor applications.

Recent Advances in Graphene and Conductive Polymer Composites for Supercapacitor Electrodes: A Review

Supercapacitors (SCs) have generated a great deal of interest regarding their prospects for application in energy storage due to their advantages such as long life cycles and high-power density. Graphene is an excellent electrode material for SCs due to its high electric conductivity and highly specific surface area. Conductive polymers (CPs) could potentially become the next-generation SC electrodes because of their low cost, facile synthesis methods, and high pseudocapacitance. Graphene/CP composites show conspicuous electrochemical performance when used as electrode materials for SCs. In this article, we present and summarize the synthesis and electrochemical performance of graphene/CP composites for SCs. Additionally, the method for synthesizing electrode materials for better electrochemical performance is discussed.

Structure-designed synthesis of hollow/porous cobalt sulfide/phosphide based materials for optimizing supercapacitor storage properties and hydrogen evolution reaction

Cobalt-based transition metal phosphides/sulfides have been viewed as promising candidates for supercapacitor (SCs) and hydrogen evolution reaction (HER) featured with their intrinsic merits. Nevertheless, the sluggish reaction kinetics and drastic volume expansion upon electrochemical process hinder their commercial application. In this work, the hollow/porous cobalt sulfide/phosphide based nanocuboids (C-CoP₄ and CoS₂ HNs) with superior specific surface area are achieved by employing a novel chemical etching-phosphatization/sulfuration strategy. The hollow/porous structure could offer rich active sites and shorten electrons/ions diffusion length. In virtue of their structural advantage, the obtained C-CoP₄ and CoS₂ HNs perform superior specific capacitance, fast charge/discharge rate and beneficial cycling stability. The advanced asymmetrical supercapacitors assembled by C-CoP₄ and CoS₂ HNs deliver exceptional energy density, respectively. Furthermore, when employed as hydrogen evolution reaction electrocatalysts, C-CoP₄ and CoS₂ HNs yield favorable electrocatalytic activity. These findings shed fundamental insight on the design of dual-functional transition metal phosphide/sulfide based materials for optimizing hydrogen evolution reaction and supercapacitor storage properties.