A scalable, aromaticity-preserved mechanochemical strategy for graphene edge functionalization is developed here, enabling an efficient, sustainable, and metal-free electrochemical platform based on high-quality graphene for environmental monitoring. Redox-functionalized graphene (Redox-G) is synthesized via ball milled exfoliation of graphite using anthraquinone as the milling agent. Successful graphite exfoliation and redox-active edge functionalization are verified via comprehensive analysis using XRD, FTIR spectroscopy, Raman spectroscopy, FESEM, HRTEM, and XPS. Electrochemical investigations confirm the intrinsic redox activity of the prepared graphene. Redox-G is further employed as a metal-free electrochemical sensor for the selective detection and electrocatalytic reduction of 4-nitrophenol (4-NP), a hazardous environmental pollutant. Cyclic voltammetric studies provide mechanistic insights into the electron-transfer processes, revealing distinct redox peaks originating from both 4-NP and Redox-G. Differential pulse voltammetry demonstrates three linear detection ranges (1–10, 10–90, and 90–1000 μM), along with a low detection limit of 0.1 μM and high sensing sensitivity (0.1907 μA/μM) toward 4-NP. Moreover, the sensing platform exhibits excellent selectivity, with minimal interference (∼1.44 %) from structurally related compounds and metal ions, as well as good repeatability, reproducibility, cycling stability, long term stability and reliable performance in 4-NP-spiked real water samples even on repeated measurements on consecutive days, thereby highlighting its practical applicability for environmental monitoring.

Being teratogenic, mutagenic, and carcinogenic, the removal of toxic Malachite Green (MG) dye from water is an intense area of research. Here, a hydrothermal technique is used for the facile preparation of magnetic nickel ferrite nanoparticles in the presence of Tween 20, which are used as adsorbents for the removal of MG dye from water. The structural, magnetic, and morphological investigations of the NiFe2O4 nanoparticles were studied using various characterization techniques, where the nanooctahedral morphology and magnetic nature of the cubic NiFe2O4 spinel structure are revealed using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM), and X-ray photoelectron spectroscopy (XPS). The effects of pH, time, initial dye concentration, and adsorbent dosage on MG adsorption are investigated to find out the most suitable conditions of adsorption. The adsorption isotherms and kinetics of MG adsorption have also been investigated, which helped to elucidate the mechanism of adsorption. The NiFe2O4 displayed a monolayer adsorption capacity of 20.46 mg/g and fits the Langmuir model, and a pseudo-second-order kinetic model is suggested for the adsorption, revealing a homogeneously adsorbed monolayer of MG onto the surface of the adsorbent. NiFe2O4 showed an incredible degree of selectivity in the adsorption of MG from a solution of MG and methyl orange. The prepared NiFe2O4 is distinguished by a great ease of separation from water, enabling repeated usage.

ABSTRACT Developing scalable and environmentally benign electrode materials with validated device‐level performance remains a key challenge in supercapacitor research. In this study, we report a solvent‐free reactive ball‐milling strategy followed by calcination to synthesize a mixed‐valence manganese oxide/g‐C 3 N 4 /N‐doped graphene nanocomposite (Mn x O y /g‐C 3 N 4 /NG). In this mechanochemical process, urea functions as a graphite‐exfoliating agent, nitrogen dopant, and precursor for graphitic carbon nitride, enabling the in situ formation of an integrated hybrid architecture. Structural and morphological analyses confirm the formation of exfoliated g‐C 3 N 4 and the uniform anchoring of mixed‐valence Mn 2 O 3 /Mn 3 O 4 nanoparticles on few‐layered, less‐defective N‐doped graphene. The synergistic combination of conductive graphene, redox‐active manganese oxides, and g‐C 3 N 4 enhances charge transport, provides abundant electroactive sites, and improves structural stability, resulting in excellent capacitive performance with no capacitance loss over 11,000 charge–discharge cycles. A flexible symmetric supercapacitor using a PVA‐KOH gel electrolyte delivers a specific capacitance of 119.8 F g −1 at 0.1 A g −1 , a maximum energy density of 16.6 Wh kg −1 , and a maximum power density of 1000 W kg −1 , while retaining 92.1% capacitance after 5000 cycles. The flexible device also powers a commercial digital timer, demonstrating the practical potential of this scalable mechanochemical strategy of graphene‐based electrode preparation for next‐generation wearable energy storage.

The scalable production of graphene with controlled chemical functionalities remains a central challenge in translating laboratory advances into practical technologies. Beyond conventional approaches that prioritize the surface area, functionalization or conductivity, increasing attention is being directed toward spatially selective defect engineering that preserves the aromatic π-conjugated carbon framework while enabling targeted interfacial reactivity, thereby providing high-quality graphene. In this context, shear-driven ball milling has emerged as a promising mechanochemical route for the synthesis of edge-functionalized graphene through preferential edge activation and controlled exfoliation. Unlike oxidation-intensive methods that often introduce extensive basal-plane damage, shear-assisted milling promotes layer delamination while largely preserving the intrinsic sp2 carbon network. Simultaneously, the mechanochemical environment activates newly generated edge sites, enabling direct reactions with selected milling agents and facilitating controlled incorporation of heteroatoms and functional groups. Such edge-focused functionalization provides an effective means of balancing electrical conductivity, wettability, ion accessibility, and electrochemical activity. This review critically examines the mechanistic principles governing graphite exfoliation during ball milling, the roles of milling agents and processing parameters in regulating structural evolution and surface chemistry, and the characterization strategies used to distinguish edge functionalization from basal-plane modification. Particular emphasis is placed on understanding the relationships between processing conditions, defect generation, functionalization pathways, and electrochemical performance. The influence of edge-engineered graphene on charge storage mechanisms in supercapacitors, lithium-ion batteries, sodium-ion batteries, zinc-ion systems, and hybrid energy-storage devices is comprehensively discussed. In addition, key considerations related to scalability, process economics, sustainability, contamination control, energy consumption, reproducibility, and industrial implementation are evaluated. Overall, this review establishes a process-structure-electrochemistry framework for shear-driven ball-milled graphene and highlights its potential as a scalable platform for the development of advanced graphene materials tailored for next-generation energy-storage technologies.

An eco-friendly, cost-effective strategy is demonstrated for developing efficient supercapacitor (SC) electrode by integrating graphene with oxygen-deficient sulfur-doped MoO3 (S-MoO3-x). Graphene is produced via mechanochemical exfoliation of graphite using sucrose as the milling agent, and is then composited with S-MoO3-x through hydrothermal treatment. Material characterization studies reveal that, during heat treatment, decomposition of sucrose-derived carbon spheres introduced holes in the graphene sheets, leading to the formation of a S-MoO3-x/holey graphene nanocomposite (S-MoO3-x/HG). Sulfur doping induces oxygen vacancies, enhancing conductivity and electrochemical performance by modifying the electronic structure of Mo active sites, as evident from material characterization studies. Electrochemical measurements in a three-electrode system are performed to evaluate the capacitance and durability of the S-MoO3-x/HG electrode. An asymmetric SC pouch cell device is fabricated using S-MoO3-x/HG as the anode and pure MoS2 as the cathode, operating at 1.4 V. The device exhibits a maximum energy density of 36.5 Wh Kg-1 and a power density of 700 W Kg-1, highlighting its outstanding performance. Notably, the device retains 100% of its capacitance after 15 000 cycles, highlighting its remarkable cycle life and long-term usability. Additionally, two such asymmetric devices are connected in series to power 15 red and yellow light-emitting diodes, further demonstrating their practical application in energy storage systems.

An innovative magnetic ternary catalyst, silver-doped nickel ferrite integrated into the nanoreactor mesoporous silica (Ag-NiFe2O4/meso-SiO2), has been synthesized, offering a promise in the catalytic transformation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). This design synergistically combines the exceptional catalytic activity of similar to 3 nm silver nanoparticles (AgNPs) with the structural advantages of ordered mesoporous silica (meso-SiO2), effectively stabilizing the nanoparticles and preventing agglomeration. The incorporation of a magnetic NiFe2O4 not only enhances reusability but also facilitates efficient magnetic recovery, addressing key challenges in catalyst reusability. Comprehensive characterization using XRD, FTIR spectroscopy, UV-vis DRS spectroscopy, XPS, FESEM, HRTEM, and VSM analyses confirms the material's structural integrity, mesoporosity, and robust magnetic properties. BET-BJH suface area-porosity analysis reveals a 262.2 m(2)/g surface area for meso-SiO2, with pore size in the range of 4.7-16.6 nm, which can accommodate both AgNPs (3 nm) and NiFe2O4 (similar to 15-18 nm) enabling reaction inside the channels and thereby meso-SiO2 acting as a nanoreactor for conversion of 4-NP. Employing a Box-Behnken design under response surface methodology, the catalyst achieved optimal reduction conditions; i.e., 0.2 mmol/L 4-NP, 5.3 mg catalyst, 49.1 mg NaBH4, and a reaction time of 12 min. The Ag-NiFe2O4/meso-SiO2 system demonstrated first order kinetics with exceptional catalytic efficiency, operational stability over five repeated cycles, and rapid magnetic separation, showcasing its potential as a model platform for sustainable nanocatalysis. This study pioneers the integration of noble-metal nanoparticles with magnetic materials inside the mesoporous nanoreactors, setting new dimensions of advanced catalytic systems in green and efficient chemical processes.

Flexible conducting wires are highly relevant nowadays due to their possible integration into various electronic gadgets, where energy storage devices are also needed. Here a material composed of N-doped holey graphene with aromatic primary amine groups at the edges (N-doped holey graphene amine) takes the dual role of conducting wire and electrode for supercapacitors. A facile ball-milling of graphite with the N-containing milling agent 1-naphthylamine followed by high-temperature treatment led to the formation of N-doped holey graphene as evident from the material characterization using transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, 13C NMR spectroscopy, atomic force microscopy and elemental analysis. In addition to pyridinic, pyrolytic, and graphitic N, the NMR spectrum and XPS confirm the presence of -NH2 attached to aromatic carbon. The graphene inks prepared at different temperatures including room temperature displayed variable conductivity suitable for the required applications; the sample treated at 250 degrees C was also used as an electrode material for supercapacitors. An areal capacitance of 12.33 mF/cm2 at a current density of 0.06 mA/cm2 is displayed by the graphene ink supercapacitor device together with an energy density of 1.71 mu Wh/cm2. A power density of 500 mu W/cm2 at a current density of 1 mA/cm2 is displayed, and at 0.5 mA/cm2, the device retained 100% of its capacitance after 5000 continuous charge-discharge cycles.

Herein, a green and facile approach is demonstrated for synthesizing less-defective graphene via ethyl cellulose (EC)-assisted mechanochemical treatment of graphite using ball milling. Structural analysis reveals that the produced graphene exhibits a few-layered turbostratic structure with minimal defects, making it highly conducting, suitable for various electronic and electrical applications. Functionalization at the edges of the graphene sheets restricts restacking and improves dispersibility in green solvents. The as produced graphene-based conducting wires, demonstrate reliable performance in electric circuits, effectively powering LEDs without any loss of efficiency, even in highly flexible configurations. Additionally, an interdigitated microsupercapacitor (MSC) constructed using the less-defective graphene exhibits an areal capacitance of 1151 mu F cm- 2 at 10 mu A cm- 2, coupled with excellent cycle life (95.5% capacitance retention after 3000 cycles). The MSC also shows an energy density of 28.5 mWh kg-1, a power density of 1108.28 mW kg-1, and a remarkable rate capability of 93%. These results highlight the potential of the less-defective, edge-functionalized graphene as a promising material for both flexible electronics and microenergy storage devices, offering sustainable, high-performance solutions for future energy storage systems and electronic applications.

The inherent high conductivity and extensive surface area of holey graphene (HG) make it highly pertinent for energy storage applications. This study focuses on synthesizing a cathode material, NiO-incorporated Fe2O3 embedded holey graphene (NiO-Fe2O3/HG) under mild conditions. Material characterization using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), etc., confirm that the HG is few-layered and less-defective, with successful decoration by NiO and Fe2O3 nanoparticles. The XPS results demonstrate that the well-dispersion of NiO and Fe2O3 on the holey graphene sheets is facilitated by metal (M)-carbon interaction and M-O-C binding. Electrochemical studies highlight the suitability of NiO-Fe2O3/HG as a cathode material for supercapacitor applications, demonstrated by an areal capacitance of 75 mF/cm2 at a current density of 0.3 mA/cm2 in a three-electrode configuration, with cyclic stability 94.5% at 1 mA/cm2 over 5000 consecutive charge-discharge cycles, and coulombic efficiency 94.2%. Hall measurements confirm the high conductivity of the material (9.72 x 102 S/cm). An asymmetric super-capacitor device is fabricated using NiO-Fe2O3/HG coated on cotton cloth as the cathode and Fe2O3/graphene as the anode material, exhibiting an areal capacitance of 43 mF/cm2 (@ 4 mV/s) and 1.43 mF/cm2 (@ 0.2 mA/ cm2), along with a power density of 605.8 mu W/cm2 (@ 1 mA/cm2). Further, to get a theoretical insight into the supercapacitor application of the NiO-Fe2O3/HG, we have performed the density functional theory simulation, indicating better charge-transfer capabilities. The practical application of the supercapacitor is demonstrated by lighting up an LED.

Sodium oxide/porous carbon/graphene nanocomposite is prepared here via an eco-friendly method involving sodium carboxymethyl cellulose-assisted ball-mill exfoliation of graphite. Material characterization studies revealed the formation of a porous carbon network with sodium oxides well dispersed over the graphene, which is suitable for easy ion diffusion and accelerated electrochemical reactions. X-ray diffraction patterns, X-ray photoelectron spectral analysis, Raman spectra, and morphological analysis confirm the development of less- defective, well-exfoliated, edge-functionalized graphene. The well dispersed sodium oxide/nanoporous carbon over the graphene sheets leads to a high specific capacitance of 390.8 mF/cm2 in 2 M KOH and 120.0 mF/cm2 in 2 M Na2SO4 at a current density of 0.5 mA/cm2. The fabricated symmetric coin cell showed a maximum specific capacitance of 90 mF/cm2 and 91.5 % capacitance retention after 8000 cycles. An asymmetric device, featuring an extended voltage window of 1.5 V, was also fabricated; it demonstrated a specific capacitance of 13 mF/cm2, with energy density of 82.19 mWh/kg and power density of 7653.2 mW/kg. The in-built ions from the sodium oxide embedded in the electrode facilitated electric double-layer capacitance and Faradaic redox reactions leading to pseudocapacitance, and avoided the diffusion limitations of electrolyte ions, thus enhancing super- capacitor performance. The real-world applicability of this device is demonstrated by its ability to light an LED.

A dual synthetic strategy is introduced here for the preparation of a hybrid g-C3N4/graphene nanocomposite using a cost-effective ball milling method followed by thermal treatment for supercapacitor applications. Graphite is exfoliated to graphene via a top-down route, where melamine serves as both the milling agent and the precursor for the bottom-up synthesis of g-C3N4. This approach integrates both materials efficiently, yielding synergistic properties. The hybrid material delivers an ultrahigh specific capacitance of 1415.7 F g-1 at 3 A g-1, with negligible internal resistance, confirming its excellent energy storage performance. Cyclic voltammetry and Dunn's method analysis reveal significant pseudocapacitive contributions to energy storage. A coin cell supercapacitor with the g-C3N4/graphene electrodes exhibits an areal capacitance of 222.3 mF cm-2 (168.3 F g-1) at 0.1 mA cm-2 with an energy density of 13.54 mu Wh cm-2 (23.3 Wh kg-1) and a power density of 5.13 mW cm-2 (3885.3 W kg-1). The device, after 10,000 galvanostatic charge-discharge cycles, shows an increase in its activity to 109.9% as a result of the improved diffusion of electrolyte ions over time. A series-connected arrangement of three symmetric supercapacitors is utilized to power a mini fan and illuminate five green LEDs, highlighting the real-world applicability.

Electrodes that exhibit both high energy and power densities are highly desirable for the development of supercapacitors competitive with rechargeable batteries. In this study, a novel mesoporous phosphorus-doped graphitic carbon nitride (P-g-C₃N₄) anchored with magnetic Fe₃O₄ was synthesized via a facile (NH₄)₂HPO₄-assisted solvothermal method and confirmed through material characterization. X-ray photoelectron spectroscopic (XPS) analysis revealed a strong interaction between carbon in the P-g-C₃N₄ and iron, while vibrating sample magnetometry (VSM) confirmed the superparamagnetic behaviour imparted by Fe₃O₄. The energy storage performance of the Fe₃O₄/P-g-C₃N₄ nanocomposite as a supercapacitor electrode material was evaluated using a modified carbon paste electrode. It demonstrated a remarkable specific capacitance of 3470 mF/cm2 at a current density of 3 mA/cm2, significantly higher than that of the individual components. This enhancement is attributed to several factors, including high surface area, mesoporosity, improved electron transport due to P-doping, and the pseudocapacitive contribution from the Fe₃O₄. The Fe₃O₄/P-g-C₃N₄ nanocomposite showed good cycling stability, retaining 74.1

Herein, a novel method is employed for the facile, and low-cost preparation of three-dimensional holey graphene (3DHG) starting from graphite for supercapacitor applications. 3D nanopatterning of the holey graphene (HG), prepared via a jaggery-assisted ball mill exfoliation of graphite, is achieved here via heat treatment with urea, where the decomposition of urea causes more nanoholes on the graphene sheets. The structural and morphological analyses reveal the edge functionalization, less-defective nature, and extensive nanopores on 3D aligned graphene. Use of 3DHG as a supercapacitor electrode material is investigated and a high specific capacitance of 423 F/g (@3 A/g) is observed. The symmetric coin cell supercapacitor fabricated using the 3DHG delivers high energy density (7.5 Wh/kg), power density (106 W/kg), and long durability (100 % capacitance retention after 8000 cycles). Furthermore, the asymmetric assembly with 3DHG as the anode material with HG cathode exhibits a higher cell voltage of 1.6 V, which diminishes the voltage limitation of aqueous electrolyte-based super- capacitors. The present study demonstrates exceptional supercapacitor performance of 3DHG architecture adequate for commercial energy storage applications.

Here, the superior structural features of graphitic carbon nitride (g-C3N4) in combination with integrated mesoporous channels have been explored for its use as a supercapacitor electrode material. A facile template-free strategy is adopted for the preparation of ZnO-incorporated modified g-C3N4 nanocomposite, where material characterization via x-ray difraction, Fourier transfrom infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy and x-ray photoelectron spectroscopy analysis revealed the presence of structurally modified g-C3N4 having uniform circular mesoporous channels with well-dispersed ZnO with strong Zn-C and Zn-N interactions. The electrical double-layer capacitance together with the pseudocapacitance of the ZnO/g-C3N4 electrode material resulted in improved performance, leading to a specific capacitance of 146.3 F g(-1) at a current density of 0.5 A g(-1); an increased capacitance is observed in 5000 repeated charge-discharge cycles. A symmetric coin cell supercapacitor fabricated from the material displayed an energy density of 38.8 mWh kg(-1) at a power density of 4259 mW kg(-1). Additionally, the long life of 6000 cycles (retaining 100% specific capacitance) exhibited by the coin cell supercapacitor further indicates the promising energy storage nature of the ZnO-incorporated modified g-C3N4 mesoporous nanoarchitecture. Real life application of the ZnO/g-C3N4-derived supercapacitor is illustrated by lighting up a green LED with a series connection of four coin cells.

In the present work, a green high-yielding method for the preparation of graphene is introduced via ultrasonic-assisted liquid phase exfoliation (LPE) of graphite in a green solvent medium, since the common preparation method of graphene via graphite oxide is hazardous. A high concentration of 3.2 mg/ml graphene is achieved here in a comparatively short duration of 3 h ultrasonication. By using a mixed solvents strategy (acetophenone and isopropyl alcohol, 1:19 V/V), surface energy requirements needed for the exfoliation of graphite are satisfied here with acetophenone, where isopropyl alcohol further facilitated the exfoliation via non-conventional CH-π and OH-π interactions. Turbostratic graphene in high-yield (16 %) in a simple means of ultrasonic assisted LPE is the added attraction of the present procedure. The less-defective structure of graphene, its few-layered turbostratic nature, and edge functionalization of the sheets are evident from the material characterization via Raman spectroscopy, XRD, TEM-SAED, and XPS analyses. Here, we report a combination of the attractive conducting polymer polyaniline (PANI) with the as-prepared graphene for supercapacitor applications, where the PANI/graphene nanocomposites with different aniline concentrations (PANI1.125/G, PANI4.5/G, and PANI9/G) have been prepared via in-situ polymerization of aniline in the graphene dispersion. The structure and morphology of the nanocomposites are investigated using different characterization techniques which revealed that the molecular structure of the PANI is retained in the nanocomposites even with a strong interaction with graphene. FESEM and TEM images revealed the good coverage of graphene sheets with PANI that limit the volume change of PANI during the repeated charge-discharge processes. Electrochemical studies showed that PANI4.5/G has the highest specific capacitance of 126.16 mF/cm2 at a current density of 1 mA/cm2, resulting from the perfect combination of the pseudocapacitance behavior of the PANI along with the electrical double layer capacitance of graphene. A symmetric supercapacitor device is also fabricated with PANI4.5/G, which showed the highest areal capacitance of 116.38 mF/cm2 similar to that with three-electrode studies and also good cycling stability with 87 % capacitance retention in the specific capacitance after 6000 cycles. It also exhibited an energy density of 16 µWh/cm2 (0.29 Wh/kg) and a power density of 3.99 mW/cm2 (72.72 W/kg).

This study reports the development of high-performance supercapacitor electrodes using Fe3O4 nanotubes synthesized via a graphene-assisted nanopatterning strategy. The Fe3O4 nanotubes, formed through a simple precipitation method, exhibit diameters between 6 and 16 nm and a mesoporous structure that enables rapid ion transport and excellent resistance to volumetric stress during cycling. Decorating these nanotubes with alpha-Fe2O3 nanoparticles enhances the pseudocapacitive response. Graphene sheets serve as a conductive scaffold, reducing nanotube diameter and improving charge transport. Comprehensive characterization using FESEM, HRTEM, Raman spectroscopy, XRD, and XPS confirmed the formation of the Fe2O3@Fe3O4/graphene nanocomposite with a well-integrated structure. Electrochemical testing of coin cell supercapacitors revealed a high areal capacitance of 300 mF/cm2, energy density of 41.6 mWh/cm2, and power density of 5 W/cm2. The device retained 84.2 % of its capacitance after 10,000 charge-discharge cycles, demonstrating excellent long-term stability. The practical potential of the Fe2O3@Fe3O4/graphene electrodes was validated by powering 15 green LEDs using a 4 x 4 cm2 pouch cell. These results underscore the effectiveness of metal oxide nanotubes supported on graphene for scalable, efficient, and durable energy storage, offering a promising approach for next-generation supercapacitor technologies.

Eco-friendly and low-cost methods for the scalable production of high-quality graphene are highly recommended for its use in electric or electronic applications, as the commonly employed graphene oxide (GO) route is associated with drastic oxidizing conditions and toxic reducing agents, where the resultant reduced graphene oxide (rGO) fails to display the electrical properties of pristine graphene. Herein, we present a new green and facile in-situ approach for the high-yielding synthesis of a carbon sphere/graphene nanocomposite through graphite exfoliation via a simple sucrose-mediated mechanical peel-off via ball-milling followed by hydrothermal treatment. The anchoring of carbon spheres on the graphene sheets and oxygen-containing functional groups on the carbon atoms have been revealed using FESEM imaging and XPS analysis respectively. The electrical double layer capacitance together with the pseudocapacitance make the carbon sphere/graphene electrodes promising for energy storage applications, with a high specific capacitance (511 F/g @2 A/g current density) and long-term stability (86.2% capacitance retention @10000 cycles). The high performance of the carbon sphere/graphene nanocomposite is achieved through improved hybridization of the two materials and the consequent synergistic effect as an outcome of the unique in-situ fabrication approach; in addition, insertion of the carbon spheres prevents the restacking of the graphene layers. A symmetric coin cell supercapacitor was constructed from the carbon sphere/graphene nanocomposite and the device displayed a high specific capacitance of 1344 mF/g at 8 mA/g and a good energy density of 186 mWh/kg at a high specific power of 4000 mW/kg. The practical applicability of the fabricated supercapacitor as an energy storage device has also been investigated.

Herein, Cu2O–CuO incorporated oxygen-doped g-C3N4 has been utilized for the colorimetric sensing of H2O2 by the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). The material characterization studies via XPS, XRD, FTIR spectroscopy etc. proved the presence of both Cu2O and CuO as well as the doping of oxygen on g-C3N4. The use of citric acid in the preparation led to a mesoporous architecture together with oxygen doping to g-C3N4. The high peroxidase-like activity of the present Cu-incorporated exfoliated g-C3N4 nanoenzyme aroused from the improved features such as smaller band gap, porous nature, oxygen doping to g-C3N4, and thus resulted fast electron mobility and transfer. Michaelis–Menten mechanism is used to study the kinetics, where the obtained Km and Vmax values are found to be relevant in comparison with the reported studies. From the mechanistic investigation, the reactive oxygen species involved in the TMB oxidation is ascertained as oxygen superoxide radical anion (•O2−). The linear range in sensing is 2.5–250 µM with a limit of detection (LOD) of 1 µM H2O2. The nanoenzyme showed the least amount of interference and a promising reusability in H2O2 sensing.

Supercapacitors are high-efficiency green energy storage devices featuring long cycle and shelf life. The attainment of high- power density in combination with promising energy density is one of the main targets of developing hybrid supercapacitor electrode materials. Among the different electrical double-layer capacitance materials, graphene has an outstanding role due to its high surface area and conductivity. In addition, it can act as an excellent matrix for the dispersion of a variety of nanomaterials. Among the various pseudocapacitor metal oxides, α-Fe2O3 has the auspicious features of cost-effectiveness, environment friendliness, and natural abundance together with its high theoretical capacitance. This review target to explore the preparation methods and the features of α-Fe2O3/graphene. A glance at the greener methods of graphene and its nanocomposite preparation is given in the review. The future of these materials and the directions for further studies are also briefly mentioned at the end