High performance supercapacitor using N-doped graphene prepared via supercritical fluid processing with an oxime nitrogen source

Advances in the synthesis of heteroatom-doped graphene-based materials and their application in sensors, adsorbents and catalysis

In recent years, as a new type of carbon material, graphene has attracted much attention owing to its high conductivity, large specific surface area and excellent chemical stability. After introducing heteroatoms into graphene, the physical, chemical and biological properties of doped graphene are significantly enhanced. This review focuses on synthesis methods for N, B, P and S co-doped graphene and graphene-based composites and comprehensively discusses their recent applications in the fields of sensors, adsorbents and catalysis. The challenges and application prospects of heteroatom doped graphene materials are also proposed. This study provides a reference and guidance for the development and application of new doped graphene materials.

Bacterial cellulose-based film with self-floating hierarchical porous structure for efficient solar-driven interfacial evaporation

Interface solar water evaporation is a mean of rapidly evaporating water using solar energy. However, it is still a challenge to obtain solar evaporators with simple assembly, durability and high photothermal performance. Here, we demonstrated an effective post foaming strategy for treating nitrogen-doped reduced graphene oxide/bacterial cellulose film (F-NRGO@BC) prepared by a simple in situ culture method. The composite film contains hierarchical porous structure and bubbles on the film, achieving an integrated self-floating interface evaporator with excellent light absorption (96.5 %) and high toughness (200.18 kJ m-3). Porous structure and low enthalpy of F-NRGO@BC make a high evaporation rate of 1.68 kg m-2 h-1 and a low thermal conductivity of 0.644 W m-1 K-1 to ensure effective energy efficiency and heat insulation. This design of controlling surface morphology and internal structure provides a novel way for large-scale preparation and high-performance evaporator.

Recent Advances in Carbon-Based Electrodes for Energy Storage and Conversion

Carbon-based nanomaterials, including graphene, fullerenes, and carbon nanotubes, are attracting significant attention as promising materials for next-generation energy storage and conversion applications. They possess unique physicochemical properties, such as structural stability and flexibility, high porosity, and tunable physicochemical features, which render them well suited in these hot research fields. Technological advances at atomic and electronic levels are crucial for developing more efficient and durable devices. This comprehensive review provides a state-of-the-art overview of these advanced carbon-based nanomaterials for various energy storage and conversion applications, focusing on supercapacitors, lithium as well as sodium-ion batteries, and hydrogen evolution reactions. Particular emphasis is placed on the strategies employed to enhance performance through nonmetallic elemental doping of N, B, S, and P in either individual doping or codoping, as well as structural modifications such as the creation of defect sites, edge functionalization, and inter-layer distance manipulation, aiming to provide the general guidelines for designing these devices by the above approaches to achieve optimal performance. Furthermore, this review delves into the challenges and future prospects for the advancement of carbon-based electrodes in energy storage and conversion.

Porous Carbon Composite Generated from Silk Fibroins and Graphene for Supercapacitors

Hierarchical porous heteroatom-doped carbon composites were developed by carbonization followed by KOH activation process, with natural silkworm cocoon and chemical exfoliated graphene sheets as starting materials. The introduction of graphene sheets offers more hierarchical micro/meso porosities, a low charge-transfer resistance, and a large BET surface area of ∼1281.8 m² g^-1, which are responsible for the fast charge/discharge kinetics and the high rate capability compared with those of single silk fibroins-derived carbon materials. The silk fiber provides a high level of heteroatom functionalities (∼2.54% N and ∼21.3% O), which are desirable for high faradaic pseudocapacitance. The as-prepared carbon composite exhibited a high specific capacitance of 290 F g^-1 with good rate capability and cycling stability. The symmetric supercapacitors yielded a high value of energy density of 12.9 W h kg^-1 at a power density of 95 W kg^-1 with a 1.45 V voltage range in 1 M KOH aqueous electrolytes.

Synthesis and Electrochemical Study of Three-Dimensional Graphene-Based Nanomaterials for Energy Applications

Graphene is an attractive soft material for various applications due to its unique and exclusive properties. The processing and preservation of 2D graphene at large scales is challenging due to its inherent propensity for layer restacking. Three-dimensional graphene-based nanomaterials (3D-GNMs) preserve their structures while improving processability along with providing enhanced characteristics, which exhibit some notable advantages over 2D graphene. This feature article presents recent trends in the fabrication and characterization of 3D-GNMs toward the study of their morphologies, structures, functional groups, and chemical compositions using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. Owing to the attractive properties of 3D-GNMs, which include high surface areas, porous structures, improved electrical conductivity, high mechanical strength, and robust structures, they have generated tremendous interest for various applications such as energy storage, sensors, and energy conversion. This article summarizes the most recent advances in electrochemical applications of 3D-GNMs, pertaining to energy storage, where they can serve as supercapacitor electrode materials and energy conversion as oxygen reduction reaction catalysts, along with an outlook.

Synthesis of Three-Dimensional Carbon Nanostructure/Copper Nanowire for Additive Interface Layer of Ionic Polymer Metal Composite

Additive interface materials for improved ionic polymer metal composite (IPMC) actuator performance are being investigated. In this study, three-dimensional carbon nanostructure/copper nanowire (3DC Cu-NW) with a novel structure was synthesized via low-pressure chemical vapor deposition. An IPMC actuator with a 3DC Cu-NW interface layer was fabricated, which exhibited improved actuation performance, long-term stability, and electrochemical properties. The proposed 3DC consists of carbon nanotubes (CNTs) and graphene, grown using an Fe catalyst and CH₄ gas, respectively. We optimized the growth conditions (Fe catalyst: 12.5 mg/L, CH₄: 20 sccm) to achieve a 3DC with an appropriate thickness and a large specific surface area. The 3DC Cu-NW benefited from a Cu oxidation prevention property and a large specific surface area. The electrochemical properties and actuation performance of the IPMC actuator improved with an increased 3DC Cu-NW concentration. An IPMC actuator with a 0.6 wt% 3DC Cu-NW interface layer exhibited 1.3- and 5.6-fold electrochemical property and actuation performance improvement, respectively, over an IPMC actuator with no 3DC Cu-NW interface layer. These results show that the proposed 3DC Cu-NW has potential as an IPMC actuator interface material, and that 3DC Cu-NW synthesis and application technology can be applied to future research on sensor, actuator, and flexible devices.

Supercritical Fluid-Facilitated Exfoliation and Processing of 2D Materials

Since the first intercalation of layered silicates by using supercritical CO2 as a processing medium, considerable efforts have been dedicated to intercalating and exfoliating layered two-dimensional (2D) materials in various supercritical fluids (SCFs) to yield single- and few-layer nanosheets. Here, recent work in this area is highlighted. Motivating factors for enhancing exfoliation efficiency and product quality in SCFs, mechanisms for exfoliation and dispersion in SCFs, as well as general metrics applied to assess quality and processability of exfoliated 2D materials are critically discussed. Further, advances in formation and application of 2D material-based composites with assistance from SCFs are presented. These discussions address chemical transformations accompanying SCF processing such as doping, covalent surface modification, and heterostructure formation. Promising features, challenges, and routes to expanding SCF processing techniques are described.

Electrochemical sandwich aptasensor for the carcinoembryonic antigen using graphene quantum dots, gold nanoparticles and nitrogen doped graphene modified electrode and exploiting the peroxidase-mimicking activity of a G-quadruplex DNAzyme

A sandwich-type electrochemical aptasensor has been constructed and applied for sensitive and selective detection of the carcinoembryonic antigen (CEA). The surface of a glassy carbon electrode (GCE) was first modified with nitrogen-doped graphene and then gold nanoparticles and graphene quantum dots electrodeposited on it to obtain an architecture of type GQD/AuNP/NG/GCE. In the next step, the CEA-binding aptamer was immobilized on the modified GCE. Hemin intercalates in the amino-modified hemin aptamer to form a hemin-G-quadruplex (hemin-G4) DNAzyme. The amino modified CEA aptamer II is connected to hemin-G4 by glutaraldehyde (GA) as a linker to produce CEAaptamerII/GA/hemin-G4 (=ApII/GA/DNAzyme). Through a sandwich mode, the ApII/GA/DNAzyme bioconjugates are captured on the modified GCE. Subsequently, the hemin-G4 acts as peroxidase-mimicking DNAzyme and rapidly catalyzes the electroreduction of hydrogen peroxide. The quantitative determination of CEA was achieved by differential pulse voltammetry, best at a working potential of around -0.27 V vs. Ag/AgCl. Under optimized conditions, the assay has a linear response in the 10.0 fg mL^-1 to 200.0 ng mL^-1 CEA concentration range and a lower detection limit of 3.2 fg mL^-1. Graphical abstract Schematic presentation of a sandwich-type electrochemical aptasensor based on nitrogen doped graphene (NG), gold nanoparticles (AuNPs) and graphene quantum dots (GQDs) modified glassy carbon electrode, and the hemin-G4 DNAzyme for femtomolar detection of the carcinoembryonic antigen.

Nickel skeleton three-dimensional nitrogen doped graphene nanosheets/nanoscrolls as promising supercapacitor electrodes

A novel nickel skeleton 3D nitrogen doped graphene (N-GR/NF) superstructure with interconnected graphene nanosheets and nanoscrolls was synthesized using a facile two-step method. By varying the precursor concentration, the assembly of a graphene aerogel can be easily regulated, yielding different micro-structures and morphologies which accelerate the fast electron/ion transportation. The N-GR/NF composites demonstrate enhanced capacitance of 250 F g^-1 at 5 A g^-1, good rate performance (237 F g^-1 at the current density of 12 A g^-1) and cycle stability (90.9% retention after 5000 cycles) in 1 M KOH electrolyte. This study provides a new strategy for the microporous engineering of graphene gel, promising for further exploitation in various other applications.

A three dimensional N-doped graphene/CNTs/AC hybrid material for high-performance supercapacitors

Single walled carbon nanotubes and activated carbon intercalated N-doped graphene hybrid material was successfully fabricated and exhibited high performance as a supercapacitor.

Facile synthesis of 3D nitrogen-doped graphene aerogel nanomeshes with hierarchical porous structures for applications in high-performance supercapacitors

3D N-GANMs with hierarchical pores are firstly synthesized using iron nitrate as the etching agent, which display excellent supercapacitive performances.