3D Graphene-Based Macrostructures for Water Treatment

Laser Upcycling of Hemoglobin Protein Biowaste into Engineered Graphene Aerogel Architectures for 3D Supercapacitors

Graphene aerogels (GAs) with engineered architectures are a promising material for applications ranging from filtration to energy storage/conversion. However, current preparation approaches involve the combination of multiple intrinsically-different methodologies to achieve graphene-synthesis and architecture-engineering, complicating the entire procedure. Here, a novel approach to prepare GAs with engineered architectures based on the laser-upcycling of protein biowaste, hemoglobin, is introduced. Laser scanning achieves graphene-synthesis concurrently with architecture-engineering through the localized graphitization of hemoglobin along the laser-scan path, enabling the direct preparation of engineered GAs. The laser-upcycled GAs are uniquely decorated with fibrous graphitic structures, which significantly improves the surface area. Such structural formation is attributable to the inherent iron content of hemoglobin which leads to the formation of iron-based nanoparticles that catalyze the formation of nano-structured graphene. By leveraging the high electrical conductivity and unique structural morphology, the laser-upcycled GAs are applied as electrodes of symmetrical 3D supercapacitors. The fabricated supercapacitors exhibited a high specific capacitance (≈54.9 F g-1) and excellent cycle stability (≈94% retention), attributable to the laser-engineered architecture facilitating ion diffusion even for thick electrodes. Not only does this study provide a novel approach to prepare GAs with engineered architectures but showcases the potential of laser-upcycling in preparing advanced functional materials for future devices.

Comprehensive insights into the application of graphene-based aerogels for metals removal from aqueous media: Surface chemistry, mechanisms, and key features

Efficient removal of heavy metals and other toxic metal pollutants from wastewater is essential to protect human health and the surrounding vulnerable ecosystems. Therefore, significant efforts have been invested in developing practical and sustainable tools to address this issue, including high-performance adsorbents. In this respect, within the last few years, graphene-based aerogels/xerogels/cryogels (GBAs) have emerged and drawn significant attention as excellent materials for removing and recovering harmful and valuable metals from different aqueous media. Such an upward trend is mainly due to the features of the aerogel materials combined with the properties of the graphene derivatives within the aerogel's network, including the GBAs' unique three-dimensional (3D) porous structure, high porosity, low density, large specific surface area, exceptional electron mobility, adjustable and rich surface chemistry, remarkable mechanical features, and tremendous stability. This review offers a comprehensive analysis of the fundamental and practical aspects and phenomena related to the application of GBAs for metals removal. Herein, we cover all types of (bottom-up) synthesized GBAs, including true microporous graphene-based aerogels as well as other 3D graphene-based open-cell interconnected mesoporous and macroporous aerogels, foams, and sponges. Indeed, we provide insights into the fundamental understanding of the GBAs' suitability for such an important application by revealing the mechanisms involved in metals removal and the factors inducing and controlling the highly selective behavior of these distinctive adsorbents. Besides conventional adsorptive pathways, we critically analyzed the ability of GBAs to electrochemically capture metal pollutants (i.e., electrosorption) as well as their efficiency in metals detoxification through reductive mechanisms (i.e., adsorption-reduction-readsorption). We also covered the reusability aspect of graphene aerogels (GAs)-based adsorbents, which is strongly linked to the GBAs' outstanding stability and efficient desorption of captured metals. Furthermore, in view of their numerous practical and environmental benefits, the development and application of magnetically recoverable GAs for metals removal is also highlighted. Moreover, we shed light on the potential practical and scalable implementation of GBAs by evaluating their performance in continuous metals removal processes while highlighting the GBAs' versatility demonstrated by their ability to remove multiple contaminants along with metal pollutants from wastewater media. Finally, this review provides readers with an accessible overview and critical discussion of major recent achievements regarding the development and applications of GAs-based adsorbents for metal ions removal. Along with our recommendations and suggestions for potential future work and new research directions and opportunities, this review aims to serve as a valuable resource for researchers in the field of wastewater treatment and inspire further progress towards developing next-generation high-performance GBAs and expanding their application.

Upconversion nanoparticles incorporated with three-dimensional graphene composites for electrochemical sensing of baicalin from natural plants

Chinese medicine has been widely studied owing to its many advantages. Baicalin (Bn), extracted from natural plants, has been shown to have significant anti-inflammatory and anticancer activity. Therefore, it is of great significance to develop a suitable method to detect the content of Bn in traditional Chinese medicine. Herein, we report an electrochemical sensor for the sensitive detection of Bn in Scutellaria root samples through a synergistic effect between upconversion nanoparticles (UCNPs) and three-dimensional macroporous graphene (3DG). The prepared UCNP-3DG composite was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction spectroscopy (XRD). This proposed sensor exhibited a low detection limit of 3.8 × 10-8 M (S/N = 3). Importantly, the established method possesses good stability and selectivity and can successfully detect Bn in Scutellaria root samples. It provides a suitable strategy for the determination of Bn and has potential application prospects in the assay of traditional Chinese medicine.

Advanced nanoribbons in water purification: A comprehensive review

The increasing scarcity of clean water, coupled with the environmental repercussions of municipal and industrial wastewater, underscores the imperative for advancing novel technologies aimed at clean water production and effectively removing impurities and toxic contaminants. Research focusing on ribbon-based technologies has garnered substantial attention in recent years due to their promising applications in various fields. This article presents a comprehensive review of the diverse applications of ribbon in water and wastewater treatment. It delves into the various types of ribbon employed for water purification, elucidating their effectiveness in removing contaminants such as heavy metals, dyes, pesticides, medical waste, oil pollutants, and radioactive waste. We will also discuss methods such as adsorption, membrane separation, and advanced oxidation processes, which help to understand how ribbons remove pollutants from water. This review summarizes the recent progress in the field of water purification and discusses the current state-of-the-art research on the use of ribbons in wastewater treatment. The end of this article gives information about the regeneration and reusability of ribbons and about challenges and prospects.

The Simpler the Better: Ultrafast Air-Plasma Synthesis of 3D Crosslinked Graphene Nanoscroll-Nanosheet Aerogels at Room Temperature for Capacitive Deionization

Graphene nanoscroll (GNS) is an important 1D tubular form of graphene-derivative materials, which has garnered widely attention. However, conventional fabrication methods commonly suffer from complex processing and time-consuming. Herein, with graphene oxide (GO) as a precursor, the study puts forward a facile air-plasma synthesis strategy to fabricate 3D graphene nanoscroll-nanosheet aerogels (GSSA). It is demonstrated that without using any chemical additives, a highly efficient reduction-exfoliation-scrolling process can be achieved all-in-one at room temperature within 1 s. The GNSs "grew" from 2D graphene sheets and firmly cross-linked them together, and they not only provide a shortcut path for electron transport but also act as intrinsic spacers to prevent restacking of graphene sheets. When using as an electrode material for capacitive deionization (CDI), GSSA exhibits excellent merits of salt-removal performance. These findings open a new pathway to large-scale synthesis of high-quality and high-purity GNS-based materials with promising applications in CDI and beyond.

Graphene aerogels as efficient adsorbers of water pollutants and their effect of drying methods

Environmental accidents highlight the need for the development of efficient materials that can be employed to eliminate pollutants including crude oil and its derivatives, as well as toxic organic solvents. In recent years, a wide variety of advanced materials has been investigated to assist in the purification process of environmentally compromised regions, with the principal contestants being graphene-based structures. This study describes the synthesis of graphene aerogels with two methods and determines their efficiency as adsorbents of several water pollutants. The main difference between the two synthesis routes is the use of freeze-drying in the first case, and ambient pressure drying in the latter. Raman spectroscopy, Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements are employed here for the characterisation of the samples. The as-prepared aerogels have been found to act as photocatalysts of aqueous dye solutions like methylene blue and Orange G, while they were also evaluated as adsorbents of organic solvents (acetone, ethanol and methanol), and, oils like pump oil, castor oil, silicone oil, as well. The results presented here show that the freeze-drying approach provides materials with better adsorption efficiency for the most of the examined pollutants, however, the energy and cost-saving advantages of ambient-pressure-drying could offset the adsorption advantages of the former case.

Electrothermal Transformations within Graphene-Based Aerogels through High-Temperature Flash Joule Heating

Flash Joule heating of highly porous graphene oxide (GO) aerogel monoliths to ultrahigh temperatures is exploited as a low carbon footprint technology to engineer functional aerogel materials. Aerogel Joule heating to up to 3000 K is demonstrated for the first time, with fast heating kinetics (∼300 K·min-1), enabling rapid and energy-efficient flash heating treatments. The wide applicability of ultrahigh-temperature flash Joule heating is exploited in a range of material fabrication challenges. Ultrahigh-temperature Joule heating is used for rapid graphitic annealing of hydrothermal GO aerogels at fast time scales (30-300 s) and substantially reduced energy costs. Flash aerogel heating to ultrahigh temperatures is exploited for the in situ synthesis of ultrafine nanoparticles (Pt, Cu, and MoO2) embedded within the hybrid aerogel structure. The shockwave heating approach enables high through-volume uniformity of the formed nanoparticles, while nanoparticle size can be readily tuned through controlling Joule-heating durations between 1 and 10 s. As such, the ultrahigh-temperature Joule-heating approach introduced here has important implications for a wide variety of applications for graphene-based aerogels, including 3D thermoelectric materials, extreme temperature sensors, and aerogel catalysts in flow (electro)chemistry.

Shape-Memory Three-Dimensional Evaporators with High Portability for Efficient Solar-Driven Freshwater Production

Solar-driven water evaporation can alleviate the severe water scarcity situation in a nonpolluting and sustainable manner. Although the design of integrated three-dimensional (3D) solar evaporators has been proven to be effective in achieving ultrahigh evaporation rates and energy efficiency, their scalable application is still hindered by complex manufacturing processes and poor portability. Herein, we report a highly portable shape-memory 3D solar evaporator by depositing MXene on low-cost lignin-cellulosic sponges for freshwater production. When not in use, the 3D evaporator can be compressed into a thin film with up to 89.3% volume reduction, ensuring minimal space occupation and high portability. When needed, due to the shape-memory effect, the 3D structure can be rapidly restored by swelling the compressed film in water, resulting in an efficient 3D solar evaporator. This 3D evaporator exhibits not only a high evaporation rate of 2.48 kg m-2 h-1 under 1 sun illumination but also excellent long-term stability and recyclability. In addition, the 3D evaporator itself can serve as a water reservoir without requiring a continuous water supply during evaporation, showing remarkable application flexibility. This work opens a new perspective for manufacturing highly portable and efficient 3D solar evaporators and may facilitate their progress from the laboratory to commercial applications.

Three-dimensional rGO/CNT/g-C3N4 macro discs as an efficient peroxymonosulfate activator for catalytic degradation of sulfamethoxazole

Over the past few years, advanced oxidation processes (AOPs) have shown promising efficiencies for wastewater remediation. Carbocatalysis, in particular, has been exploited widely thanks to its sustainable and economical properties but has an issue of recovery and reusability of the catalysts. To address this, three-dimensional (3D) binary and ternary graphene-based composites in the form of macro discs were created to activate peroxymonosulfate (PMS) for catalytic oxidation of sulfamethoxazole (SMX). Graphene oxide served as the base, while graphitic carbon nitride (g-C3N4) and/or single-walled carbon nanotubes (SWCNTs) were added. Among the various discs synthesized, rGNTCN discs (ternary composite) were proven to be the most efficient by completely degrading SMX in 60 min owing to their large surface area and nitrogen loading. The catalytic system was further optimized by varying the reaction parameters, and selective radical quenching and electron paramagnetic resonance tests were performed to identify the active radical, revealing the synergistic role of both radical and non-radical pathways. This led to the development of possible SMX degradation pathways. This research not only provides insights into ternary carbocatalysis but also gives a novel breakthrough in catalyst recovery and reusability by transforming nanocatalysts into macro catalysts.

The Use of Crystalline Carbon-Based Nanomaterials (CBNs) in Various Biomedical Applications

This review study aims to present, in a condensed manner, the significance of the use of crystalline carbon-based nanomaterials in biomedical applications. Crystalline carbon-based nanomaterials, encompassing graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and graphene quantum dots, have emerged as promising materials for the development of medical devices in various biomedical applications. These materials possess inorganic semiconducting attributes combined with organic π-π stacking features, allowing them to efficiently interact with biomolecules and present enhanced light responses. By harnessing these unique properties, carbon-based nanomaterials offer promising opportunities for future advancements in biomedicine. Recent studies have focused on the development of these nanomaterials for targeted drug delivery, cancer treatment, and biosensors. The conjugation and modification of carbon-based nanomaterials have led to significant advancements in a plethora of therapies and have addressed limitations in preclinical biomedical applications. Furthermore, the wide-ranging therapeutic advantages of carbon nanotubes have been thoroughly examined in the context of biomedical applications.

High-efficient adsorption for versatile adsorbates by elastic reduced graphene oxide/Fe3O4 magnetic aerogels mediated by carbon nanotubes

Fabrication of highly elastic three-dimensional aerogel adsorbents with outstanding adsorption capacities is a long pursuit for the treatment of industrial contaminated water. In this work, a magnetic reduced graphene oxide (rGO)/Fe₃O₄/carbon nanotubes (CNTs) aerogel material was constructed by the electrostatic attraction between the negatively charged GO and positively charged CNTs following a one-pot water bath treatment. The as-synthesized aerogel demonstrated high compressive stress (28.4 kPa) and lower density (24.11 mg/cm³) with exceptional adsorption capacities for versatile adsorbates which are attributed to CNTs and magnetic Fe₃O₄ nanoparticles. The effect of pH, initial concentration of adsorbates (dyes, Cd (ІІ) ions, organic solvents, and pump oil), content of CNTs and cyclic times on the adsorption capacities of the aerogel were investigated in detail. Furthermore, from simulation, the adsorption kinetics, and thermodynamics of the aerogel for adsorbates were more satisfied by endothermic quasi-second-order kinetic model with characteristic physical adsorption. Thus, the optimized rGO/Fe₃O₄/CNTs-10 aerogel adsorbent can be used as a powerful and versatile tool to deal with contaminated industrial or domestic wastewater.

Three-Dimensional Mirror-Assisted and Concave Pyramid-Shaped Solar-Thermal Steam Generator for Highly Efficient and Stable Water Evaporation and Brine Desalination

Although significant advances have been achieved in developing solar-driven water evaporators for seawater desalination, there is still room for simultaneously enhancing water evaporation efficiency, salt resistance, and utilization of solar energy. Herein, for the first time, we demonstrate a highly efficient three-dimensional (3D) mirror-assisted and concave pyramid-shaped solar-thermal water evaporation system for high-yield and long-term desalination of seawater and brine water, which consists of a 3D concave pyramid-shaped solar-thermal architecture on the basis of polypyrrole-coated nonwoven fabrics (PCNFs), a 3D mirror array, a self-floating polystyrene foam layer, and a tail-like PCNF for upward transport of water. The 3D concave pyramid-shaped solar-thermal architecture enables multiple solar light reflections to absorb more solar energy, while the 3D mirror-assisted solar light enhancement design can activate the solar-thermal energy conversion of the back side of the concave pyramid-shaped PCNF architecture to improve the solar-thermal energy conversion efficiency. Crucially, selective accumulation of the precipitated salts on the back side of the concave pyramid-shaped architecture is realized, ensuring a favorable salt-resistant feature. The 3D mirror-assisted and concave pyramid-shaped solar-driven water evaporation system achieves a record high water evaporation rate of 4.75 kg m^-2 h^-1 under 1-sun irradiation only and exhibits long-term desalination stability even when evaporating high-salinity brine waters, demonstrating its great applicability and reliability for high-yield solar-driven desalination of seawater and high-salinity brine water.

A High-Temperature Accelerometer with Excellent Performance Based on the Improved Graphene Aerogel

A high-temperature accelerometer plays an important role for ensuring normal operation of equipment in aerospace, such as monitoring and identifying abnormal vibrations of aircraft engines. Phase transitions of piezoelectric crystals, mechanical failure and current leakage of piezoresistive/capacitive materials are the prominent inherent limitations of present high-temperature accelerometers working continuously above 973 K. With the rapid development of aerospace, it is a great challenge to develop a new type of vibration sensor to meet the crucial demands at high temperature. Here we report a high-temperature accelerometer working with a contact resistance mechanism. Based on the improved graphene aerogel (GA) prepared by a modulated treatment process, the accelerometer can operate continuously and stably at 1073 K and intermittently at 1273 K. The developed sensor is lightweight (sensitive element <5 mg) and has high sensitivity (an order of magnitude higher than MEMS accelerometers) and wide frequency response range (up to 5 kHz at 1073 K) with marked stability, repeatability and low nonlinearity error (<1%). These merits are attributed to the excellent and stable mechanical properties of the improved GA in the range of 299-1073 K. The accelerometer could be a promising candidate for high-temperature vibration sensing in space stations, planetary rovers and others.

Porous Flow Field for Next-Generation Proton Exchange Membrane Fuel Cells: Materials, Characterization, Design, and Challenges

Porous flow fields distribute fuel and oxygen for the electrochemical reactions of proton exchange membrane (PEM) fuel cells through their pore network instead of conventional flow channels. This type of flow fields has showed great promises in enhancing reactant supply, heat removal, and electrical conduction, reducing the concentration performance loss and improving operational stability for fuel cells. This review presents the research and development progress of porous flow fields with insights for next-generation PEM fuel cells of high power density (e.g., ∼9.0 kW L^-1). Materials, fabrication methods, fundamentals, and fuel cell performance associated with porous flow fields are discussed in depth. Major challenges are described and explained, along with several future directions, including separated gas/liquid flow configurations, integrated porous structure, full morphology modeling, data-driven methods, and artificial intelligence-assisted design/optimization.

pH-Responsive Carbon Foams with Switchable Wettability Made from Larch Sawdust for Oil Recovery

The global challenge of oil pollution calls for the efficient selective recovery of oil or organics from oil-water mixtures. A pH-responsive carbon foam (CF) made from liquefied larch sawdust (LLS) with switchable wettability was fabricated in this work. After grafted with poly 4-vinyl pyridine (P4vp), the CF obtained a switchable wettability surface, which allowed the CF to exhibit superhydrophilicity and superhydrophobicity at different pH levels, respectively. The results revealed that the pH-responsive CF possessed a three-dimensional (3D) spongy-like skeleton and porous structure with a diameter between 50 and 200 µm. Thus, the pH-responsive CF could absorb 15-35 g/g of oil/organics in a neutral aqueous solution at pH = 7 and desorb all the absorbate within 40 s after immersion in an aqueous solution at pH = 1. Moreover, only about 2.8% loss was observed for organic (chloroform) absorption and recovery after reusing up to 15 cycles, which indicated promising prospects in oil and organic recovery.

Ultrahigh Content Boron and Nitrogen Codoped Hierarchically Porous Carbon Obtained from Biomass Byproduct Okara for Capacitive Deionization

Capacitive deionization (CDI) is an environmentally friendly, energy efficient, and low cost water purification technique in comparison with other conventional techniques, and it has attracted considerable attention in recent years. Here, we use biomass byproduct okara as the starting material to fabricate a boron and nitrogen codoped hierarchically porous carbon (BNC) with ultrahigh heteroatom contents and abundant in-plane nanoholes for CDI application. With the interconnected hierarchical porous structure, the BNC not only exhibits a large surface area (647.0 m³ g^-1) for the adsorption of ions but also offers abundant ion transport channels to access the entire internal surface. Meanwhile, the ultrahigh dopants' content of B (11.9 at%) and N (14.8 at%) further gives rise to the increased surface polarity and enhanced capacitance for BNC. Owing to these favorable properties, BNC exhibits top-level salt adsorption capacity (21.5 mg g^-1) and charge efficiency (59.5%) at the initial NaCl concentration of ∼500 mg L^-1. Moreover, we performed first-principle simulations to explore the different effects between N-doping and N,B-codoping on the capacitive property, which indicate that the boron and nitrogen codoping of carbon can largely increase the quantum capacitance over the double layer capacitance. The results of this work suggest a promising prospect for the BNC material in practical CDI application.

PLA-ZnO/TiO2 Nanocomposite Obtained by Ultrasound-Assisted Melt-Extrusion for Adsorption of Methylene Blue

Access to fresh water is an increasing concern worldwide. The contamination of this vital liquid is largely caused by discharges of pollutants into rivers and seas from different types of industries. Waste dyes from different industries have been classified as harmful to health. In this study, polymeric nanomaterials based on polylactic acid (PLA) and nanoparticles of titanium dioxide (TiO₂) and zinc oxide (ZnO) modified by ultrasound-assisted extrusion were obtained. These materials were evaluated by FTIR, DRX, TGA, DSC, SEM and methylene blue adsorption. From the results of the physicochemical characterizations, it was possible to observe the presence of TiO₂ and ZnO nanoparticles dispersed in the polymeric matrix, increasing the crystallinity and thermal stability of the polymer. In addition, a good dispersion of the nanoparticles could be seen by means of SEM, due to the extrusion assisted by ultrasound. The methylene blue dye adsorption tests revealed that the best result was 98% dye adsorption in a time of 13 min for the 1.5% PZT sample. Additionally, this material could be used for 3 adsorption cycles without affecting its adsorbent properties.

Microfluidic electrospray generation of porous magnetic Janus reduced graphene oxide/carbon composite microspheres for versatile adsorption

HYPOTHESIS

Graphene-based microparticles materials are broadly utilized in all sorts of fields owing to their outstanding properties. Despite great progress, the present graphene microparticles still face challenges in the aspects of size uniformity, motion flexibility, and tailorable surface chemistry, which limit their application in some specific fields, such as versatile adsorption. Hence, the development of novel graphene microparticles with the aforementioned characteristics is urgently required.

EXPERIMENTS

We presented a simple microfluidic electrospray strategy to generate magnetic Janus reduced graphene oxide/carbon (rGO/C) composite microspheres with a variety of unique features. Specifically, the microfluidic electrospray method endowed the obtaiend microspheres with sufficient size uniformity as well as magnetic responsive motion ability. Additionally, magnetic-mediated surface assembly of phase transition lysozyme (PTL) nanofilm on the microspheres rendered the deposited area hydrophilic while non-deposited area hydrophobic.

FINDINGS

Such magnetic Janus rGO/C composite microspheres with regionalized wettability characteristics not only showed prominent performance in adsorbing organic liquids with high adsorption capacity and remarkable reusability but also displayed satisfying biocompatibility for the efficient uptake of bilirubin. More encouragingly, the microspheres could serve as adsorbents in a simulative hemoperfusion setup, which further demonstrated the clinical application potential of the magnetic Janus rGO/C microspheres. Thus, we anticipate that the obtained magnetic Janus rGO/C composite microspheres could show multifunctional properties toward water treatment and blood molecule cleaning.

Interfacial layering of hydrocarbons on pristine graphite surfaces immersed in water

Interfacial water participates in a wide range of phenomena involving graphite, graphite-like and 2D material interfaces. Recently, several high-spatial resolution experiments have questioned the existence of hydration layers on graphite, graphite-like and 2D material surfaces. Here, 3D AFM was applied to follow in real-time and with atomic-scale depth resolution the evolution of graphite-water interfaces. Pristine graphite surfaces upon immersion in water showed the presence of several hydration layers separated by a distance of 0.3 nm. Those layers were short-lived. After several minutes, the interlayer distance increased to 0.45 nm. At longer immersion times (∼50 min) we observed the formation of a third layer. An interlayer distance of 0.45 nm characterizes the layering of predominantly alkane-like hydrocarbons. Molecular dynamics calculations supported the experimental observations. The replacement of water molecules by hydrocarbons on graphite is spontaneous. It happens whenever the graphite-water volume is exposed to air.

Nanoclay- and TiO2 Nanoparticle-Modified Poly(N-vinyl pyrrolidone) Hydrogels: A Multifunctional Material for Application in Photocatalytic Degradation and Adsorption-Based Removal of Organic Contaminants

In recent times, access to clean water has become increasingly difficult and one of the most important problems for the sustainability of life due to environmental pollution. Based on this thought, in this study, a multifunctional hydrogel nanocomposite (nanoclay@TiO₂@PNVP) containing linear poly(N-vinyl pyrrolidone) (PNVP), nanoclay, and TiO₂ nanoparticles was synthesized and used as an adsorbent and photocatalyst for the adsorption-based and photocatalytic degradation-based removal of organic and pharmaceutical pollutants such as methylene blue (MB) and sildenafil citrate (SLD). The modification of the hydrogel with TiO₂ nanoparticles and nanoclay aimed to increase the adsorption capacity of the PNVP hydrogel as well as to gain photocatalytic properties for the effective removal of organic contaminants. This hybrid material, which can be cleaned in two different ways, can be reused and recycled at least 10 times. Characterization studies were carried out using Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, thermogravimetric analysis, differential thermogravimetry, and viscosimetry techniques. Optimization studies for the adsorption-based removal of organic contaminants were carried out on MB and SLD as model organic compounds. The optimum parameters for MB were found at pH 10 of the sample solution when 50 mg of the nanoclay@TiO₂@PNVP hydrogel nanocomposite was used for 420 min of contact time. It was observed that 99% of the MB was photocatalytically degraded within 150 min at pH 10. Our material had multifunctional applicability properties, showing high adsorption and photocatalytic performances over 99% for at least 10 times of use. For the removal of organic and pharmaceutical contaminants from wastewater, the synthesized material can be used in two treatment processes separately or in combination in one step, providing an important advantage for its usability in environmental applications.

Synthesis and characterization of a novel composite of rice husk-derived graphene oxide with titania microspheres (GO-RH/TiO2) for effective treatment of cationic dye methylene blue in aqueous solutions

Graphene oxide (GO) was synthesized utilizing rice husk (RH) as the starting raw material via a modified Hummers' method. Ground pencil leads were used as a control powder of the starting raw material to monitor the consistency of the synthesis method. TiO₂ microspheres were synthesized via a precipitated method using the pluronic F127 solution as the pore template. GO derived from RH (GO-RH) was composited with TiO₂ microspheres as GO-RH/TiO₂ composites by an impregnation method with weight ratios of 3:1, 2:2, and 1:3. Characterized results revealed GO-RH formed a ternary phase material of graphene oxide, graphite oxide, and silica. A typical microstructure of the calcined TiO₂ microspheres was found as the agglomerated anatase nanoparticles. Furthermore, the composites belong to large surface areas and numerous oxygen-containing functionalities on their surfaces. Removal efficiencies of cationic dye methylene blue (MB) from aqueous solutions by the composites, GO-RH and TiO₂, were studied under UV illumination for 180 min. Due to the effective combination of adsorption and photodegradation for the MB removal, the composites provided the higher efficiencies (99-100%) faster than those of GO-RH and TiO₂ and could be reused at least 4 times. Finally, a mechanism of the MB removal by the composites was proposed.

MOF-Like 3D Graphene-Based Catalytic Membrane Fabricated by One-Step Laser Scribing for Robust Water Purification and Green Energy Production

Increasing both clean water and green energy demands for survival and development are the grand challenges of our age. Here, we successfully fabricate a novel multifunctional 3D graphene-based catalytic membrane (3D-GCM) with active metal nanoparticles (AMNs) loading for simultaneously obtaining the water purification and clean energy generation, via a "green" one-step laser scribing technology. The as-prepared 3D-GCM shows high porosity and uniform distribution with AMNs, which exhibits high permeated fluxes (over 100 L m^-2 h^-1) and versatile super-adsorption capacities for the removal of tricky organic pollutants from wastewater under ultra-low pressure-driving (0.1 bar). After adsorption saturating, the AMNs in 3D-GCM actuates the advanced oxidization process to self-clean the fouled membrane via the catalysis, and restores the adsorption capacity well for the next time membrane separation. Most importantly, the 3D-GCM with the welding of laser scribing overcomes the lateral shear force damaging during the long-term separation. Moreover, the 3D-GCM could emit plentiful of hot electrons from AMNs under light irradiation, realizing the membrane catalytic hydrolysis reactions for hydrogen energy generation. This "green" precision manufacturing with laser scribing technology provides a feasible technology to fabricate high-efficient and robust 3D-GCM microreactor in the tricky wastewater purification and sustainable clean energy production as well.

Fabrication of polyaniline/poly(vinyl alcohol)/montmorillonite hybrid aerogels toward efficient adsorption of organic dye pollutants

Fabrication of adsorbents with excellent adsorption capacity, outstanding stability, easy separation ability, excellent recyclability and widely generality for organic dyes removal from wastewater remains challenging. Herein, three-dimensional polyaniline/poly(vinyl alcohol)/montmorillonite (PANI/PVAL/MMT) hybrid aerogels with easy separation performance and highly effective reusable adsorption on both anionic and cationic dyes were fabricated by a simple in-situ polymerization method. As-prepared hybrid aerogels were characterized via infrared and Raman spectra, scanning electron microscopy, energy dispersive spectra mapping, small and wide-angle X-ray scattering, thermogravimetric analysis, mercury intrusion porosimetry and elemental analysis. The results showed that MMT particles were successfully incorporated into aerogel matrix. Well-defined hierarchical structure, where PANI nanofibers are coated on the skeleton wall, can be observed for PANI/PVAL/MMT when the incorporation amount of MMT was around 11.1 wt%. The adsorption performance of as-prepared hybrid aerogels on both anionic and cationic dyes was systemically carried out at different solution pH, adsorbent dosage and initial dye concentration. The data analysis showed that the adsorption process for PVAL/PANI/MMT aerogel for Reactive Black 5, methyl orange and safranin followed Freundlich isotherm and the maximum experimental adsorption capacities were found to be 199, 251 and 57.0 mg g^-1 at 25 °C, respectively. Mechanism studies indicated that the electrostatic interaction is the main driving force for the adsorption of dyes. The results demonstrated that the fabricated hybrid aerogel is an efficient adsorbent for the removal of both anionic and cationic organic dyes.

Highly efficient and rapid purification of organic dye wastewater using lignin-derived hierarchical porous carbon

Coating manufacturing, textile processing, and plastic industry have led to dramatical release levels of hazardous organic dye pollutants threatening public health and the environment. To solve this problem, porous carbon materials are being developed following with the United Nations initiative on water purification. However, conventional porous carbon materials face many challenges, such as limited removal rates, low adsorption capacity, and high chemicals consumption, hampering their large-scale utilization in dye wastewater treatment. Herein, we demonstrate a high-performance lignin-derived hierarchical porous carbon (LHPC) material directly prepared from renewable lignin through a low-cost activation procedure. The large specific surface area (1824 m²/g) enables the rapid and effective adsorption of organic dyes. Therefore, the LHPC exhibits an ultrahigh adsorption ability (1980.63 mg/g) and removal rate (99.03% in 10 min) for Azure B, superior to that of other adsorbents. Additionally, the LHPC adsorbent, organic dyes, eluting agent, and water all can be recycled and reused in a designed close-looped system. Its high removal ability and rate, strong retrievability, low-cost and scalable production combined with high dyes adsorption universality, positions our LHPC as a promising commercial adsorbent candidate for the purification of harmful organic dye wastewater, especially for heavily polluted area with an insistent demand for clear water.

Easy, Fast, Selective, and Simultaneous Separation of Hg(II) and Oil via Loofah-Sponge-Inspired Hierarchically Porous Membranes

In this work, Cu2Se/Cu membranes (CSMs) of hierarchical pores were fabricated via chemical dissolution of Cu and Se followed by redeposition of cuprous selenide (Cu2Se) on copper membranes (CMs), and applied for adsorption/removal/separation of Hg(II) among a variety of interfering metal ions. The CSM demonstrates the best comprehensive performance among previous Hg(II) adsorption membranes, having high selectivity (KHg/M = 2.9 × 104-3.0 × 105), high efficiency (>99%, 5 s to 3 min), high adsorption capacity (505 mg/g), and high flux (2.0 × 106 L m-2 h-1). Meanwhile, effects of Hg(II) concentration, flow rate, and the number of membrane layers and adsorption cycles were also investigated on the removal of Hg(II). Moreover, a Cu2Se/Cu membrane-plasma (CSM-p) with superhydrophilicity/underwater superoleophobicity was prepared on the basis of CSM, and simultaneous removal of Hg(II) and oil was realized by using CSM and CSM-p in combination. This work not only provides a new reference for design of highly selective, efficient metal ion adsorption/enrichment/separation materials but also presents a novel approach to the removal/enrichment/separation of multiple complex contaminants by the combination of different functional membranes.

Carbon fiber coated by quinoa cellulose nanosheet with outstanding scaled salt self-cleaning performance and purification of organic and antibiotic contaminated water

To date, various solar driven evaporation technologies have been developed for treatment of seawater and wastewater but with the threat from salt polluted and single treatment of seawater. Herein, we develop a multifunctional evaporator constructed by carbon fiber coated by quinoa cellulose nanosheet (CFQC) with outstanding self-cleaning performance and good purification property for treatment of organic and antibiotic polluted water. The resulting Zn-CFQC exhibits good light to thermal performance which can absorb about 86.95% lights in the range of UV–Vis–NIR (200–2500 nm); therefore, the wet and dry surface temperatures of Zn-CFQC are held at 62.1 and 124.3 °C respectively, and keep a speed of 3.2 kg m⁻² h⁻¹ for water evaporating under 1000 W m⁻² illumination. Such good light-to-thermal capabilities can be mainly imputed to the unique surface microstructures of the carbon fiber which decorated by two-dimension cellulose and activated by ZnCl₂. Additionally, Zn-CFQC shows good salt automatic-cleaning capability at night and corresponding mechanism has been simply elucidated according to the chemical potential theory. The method of treatment of carbon fiber opens a new way for commercial carbon fiber utilization of solar assisted water purification.

3D Continuously Porous Graphene for Energy Applications

Constructing bulk graphene materials with well-reserved 2D properties is essential for device and engineering applications of atomically thick graphene. In this article, the recent progress in the fabrications and applications of sterically continuous porous graphene with designable microstructures, chemistries, and properties for energy storage and conversion are reviewed. Both template-based and template-free methods have been developed to synthesize the 3D continuously porous graphene, which typically has the microstructure reminiscent of pseudo-periodic minimal surfaces. The 3D graphene can well preserve the properties of 2D graphene of being highly conductive, surface abundant, and mechanically robust, together with unique 2D electronic behaviors. Additionally, the bicontinuous porosity and large curvature offer new functionalities, such as rapid mass transport, ample open space, mechanical flexibility, and tunable electric/thermal conductivity. Particularly, the 3D curvature provides a new degree of freedom for tailoring the catalysis and transport properties of graphene. The 3D graphene with those extraordinary properties has shown great promises for a wide range of applications, especially for energy conversion and storage. This article overviews the recent advances made in addressing the challenges of developing 3D continuously porous graphene, the benefits and opportunities of the new materials for energy-related applications, and the remaining challenges that warrant future study.

Graphene and graphene oxide with anticancer applications: Challenges and future perspectives

Graphene-based materials have shown immense pertinence for sensing/imaging, gene/drug delivery, cancer therapy/diagnosis, and tissue engineering/regenerative medicine. Indeed, the large surface area, ease of functionalization, high drug loading capacity, and reactive oxygen species induction potentials have rendered graphene- (G-) and graphene oxide (GO)-based (nano)structures promising candidates for cancer therapy applications. Various techniques namely liquid-phase exfoliation, Hummer's method, chemical vapor deposition, chemically reduced GO, mechanical cleavage of graphite, arc discharge of graphite, and thermal fusion have been deployed for the production of G-based materials. Additionally, important criteria such as biocompatibility, bio-toxicity, dispersibility, immunological compatibility, and inflammatory reactions of G-based structures need to be systematically assessed for additional clinical and biomedical appliances. Furthermore, surface properties (e.g., lateral dimension, charge, corona influence, surface structure, and oxygen content), concentration, detection strategies, and cell types are vital for anticancer activities of these structures. Notably, the efficient accumulation of anticancer drugs in tumor targets/tissues, controlled cellular uptake properties, tumor-targeted drug release behavior, and selective toxicity toward the cells are crucial criteria that need to be met for developing future anticancer G-based nanosystems. Herein, important challenges and future perspectives of cancer therapy using G- and GO-based nanosystems have been highlighted, and the recent advancements are deliberated.

Nickel sulfide nanorods decorated on graphene as advanced hydrogen evolution electrocatalysts in acidic and alkaline media

Nowadays, the fabrication of robust and earth-abundant hydrogen evolution electrocatalysts with noble-metal-like catalytic activities is still facing great challenges. In this report, nanorod (NR)-shaped nickel sulfide (NiS) is successfully decorated on graphene (Gr) by utilizing carbon cloth (CC) as a substrate (NiS-Gr-CC). Benefiting from the NR morphology and strong interfacial synergetic effect between NiS and Gr, the NiS-Gr-CC electrocatalyst shows good catalytic activity for hydrogen evolution reaction (HER). Specifically, the low Tafel slopes of 46 and 56 mV dec^-1 along with the small overpotentials of 66 and 71 mV at 10 mA cm^-2 are obtained in the acidic and alkaline electrolytes, respectively. Density functional theory results indicate that the combination of NiS and Gr can optimize the adsorption energy of H* during the HER process. The long-term durability measurement result reveals that our NiS-Gr-CC heterostructure has good electrocatalytic cycling stability (∼80 h) in both acidic and alkaline electrolytes. These results confirm that the NiS-Gr-CC heterostructure is a promising candidate for hydrogen evolution electrocatalyst with high catalytic activity.

Blow-spun nanofibrous composite Self-cleaning membrane for enhanced purification of oily wastewater

Membrane separation is one of the most effective strategies for water treatment. However, problems such as poor emulsion separation performance, single function and easy membrane fouling limit its application in dealing with complex wastewater. The synergistic treatment technology of adsorption and visible light catalysis is an efficient and environment-friendly method to degrade organic pollutants. Here, we report a simple method to fabricate Zeolitic Imidazolate Framework-8/Graphene oxide/Polyacrylonitrile (ZIF-8/GO/PAN) nanofibrous membranes and their multifunctional treatment capacity for complex wastewater. The construction of superhydrophilic and underwater superoleophobic surface structure has achieved excellent emulsion separation performance (with a maximum flux of 6779.66 L m^-2h^-1), visible light photocatalytic degradation (with an efficiency of 96.5% in 90 min) and antibacterial properties. Moreover, the fibrous membrane also shows good biosafety, and will not have toxic effects on aquatic organisms. These excellent performances endow this membrane with great potential in complex wastewater purification.

Fibrous Aerogels for Solar Vapor Generation

Solar-driven vapor generation is emerging as an eco-friendly and cost-effective water treatment technology for harvesting solar energy. Aerogels are solid materials with desirable high-performance properties, including low density, low thermal conductivity, and high porosity with a large internal surface, which exhibit outstanding performance in the area of solar vapor generation. Using fibers as building blocks in aerogels could achieve unexpected performance in solar vapor generation due to their entangled fibrous network and high surface area. In this review, based on the fusion of the one-dimensional fibers and three-dimensional porous aerogels, we discuss recent development in fibrous aerogels for solar vapor generation based on building blocks synthesis, photothermal materials selection, pore structures construction and device design. Thermal management and water management of fibrous aerogels are also evaluated to improve evaporation performance. Focusing on materials science and engineering, we overview the key challenges and future research opportunities of fibrous aerogels in both fundamental research and practical application of solar vapor generation technology.

A Review on the Applications of Graphene in Mechanical Transduction

A pressing need to develop low-cost, environmentally friendly, and sensitive sensors has arisen with the advent of the always-connected paradigm of the internet-of-things (IoT). In particular, mechanical sensors have been widely studied in recent years for applications ranging from health monitoring, through mechanical biosignals, to structure integrity analysis. On the other hand, innovative ways to implement mechanical actuation have also been the focus of intense research in an attempt to close the circle of human-machine interaction, and move toward applications in flexible electronics. Due to its potential scalability, disposability, and outstanding properties, graphene has been thoroughly studied in the field of mechanical transduction. The applications of graphene in mechanical transduction are reviewed here. An overview of sensor and actuator applications is provided, covering different transduction mechanisms such as piezoresistivity, capacitive sensing, optically interrogated displacement, piezoelectricity, triboelectricity, electrostatic actuation, chemomechanical and thermomechanical actuation, as well as thermoacoustic emission. A critical review of the main approaches is presented within the scope of a wider discussion on the future of this so-called wonder material in the field of mechanical transduction.

Freestanding Ti3C2Tx MXene/Prussian Blue Analogues Films with Superior Ion Uptake for Efficient Capacitive Deionization by a Dual Pseudocapacitance Effect

Exploring and designing high-performance Faradaic electrode materials is of great significance to enhance the desalination performance of hybrid capacitive deionization (HCDI). Herein, open and freestanding films (MXene/Prussian blue analogues (PBAs), specifically, MXene/NiHCF and MXene/CuHCF) were prepared by vacuum filtration of a mixed solution of PBAs nanoparticles and a Ti₃C₂T_x MXene dispersion and directly used as HCDI electrodes. The conductive MXene nanosheets bridge the PBAs nanoparticles to form a three-dimensional (3D) conductive network structure, which can accelerate the salt ion and electron diffusion/transport kinetics for HCDI. Additionally, the PBAs nanoparticles can prevent the restacking of MXene nanosheets, expand their interlayer spacing, and facilitate the rapid diffusion and storage of ions. Benefiting from the dual pseudocapacitance and synergistic effect of PBAs and MXene, the obtained MXene/PBAs films show superior properties, with a high desalination capacity (85.1 mg g^-1 for the MXene/NiHCF film and 80.4 mg g^-1 for the MXene/CuHCF film) and an ultrafast salt-removal rate, much higher than those of other Faradaic electrodes. The synergistic effect, the adsorption of Na⁺ ions, and the enhanced conductivity of MXene/PBAs films were demonstrated through first-principles calculations. This paper offers a simple and convenient method for the design of freestanding HCDI electrodes and promotes the rapid development of HCDI technology.

Layered double hydroxide-modified membranes for water treatment: Recent advances and prospects

Layered double hydroxides (LDHs) represent an exciting class of two-dimensional inorganic materials with unique physicochemical properties. They have been widely employed in water treatment due to their high surface areas, excellent ion exchange capacities, and highly tunable structures. They have also been employed in the fabrication and development of membranes for water treatment. 2D nanostructures as well as tailorable "structure forming units", surface functionalization with desired moieties, and interlayer galleries with adjustable heights and internal compositions make them attractive materials for membrane separations. This paper critically overviews the recent advancements in the synthesis and applications of LDH based membranes in water purification. The synthesis techniques and the effect of LDH incorporation into different membrane compositions have been described. LDH-based membranes showed excellent antifouling capability and improved water flux due to enhanced hydrophilicity. Such membranes have been successfully used for the treatment of inorganics, organics from environmental water samples. This review will be useful for understanding the current state of the LDH-based membranes for water purification and defining future research dimensions. In the end, we highlight some challenges and future prospects for the efficient application of LDH-based membranes in water decontamination.

Bi-functional water-purification materials derived from natural wood modified TiO2 by photothermal effect and photocatalysis

As one of the sustainable and renewable materials, the carbonization of natural wood is generally considered as a low-cost, environmentally friendly method to fabricate carbon materials. Natural wood, by surficial carbonization, can possess an excellent photothermal effect, low heat loss, and easy water transportation in the solar water desalination process based on the unique structures, leading to high solar water desalination performance. Here, we design and construct a composite of commercial P25 nanocrystal-loaded semi-spherical wood with surficial carbonization at the semi-spherical end (P25/wC-s-s), which is beneficial for light harvesting and water evaporation due to the semi-spherical structure-induced large surface area. The composite displays bi-functions of high solar-to-vapour energy efficiency and an intriguing photo-degradation efficiency for organic pollutants in the solar water purification process. The research provides a novel approach to engineering an efficient, stable, and low-cost bi-functional device for the photothermal/photoelectronic conversion of water treatment.

A bifunctional water-purification material is designed by surficial carbonization of the semi-spherical end of a natural wood block and loading of P25 on the lateral surfaces of wood domains.

Carbon Materials for Solar Water Evaporation and Desalination

Seawater desalination is viewed as a promising solution to world freshwater scarcity. Solar assisted desalination is proposed to overcome the high energy consumption in current desalination technologies, as it uses abundant and sustainable solar energy as the only energy input. Interfacial solar vapor generation (SVG) has attracted considerable research interest due to its high energy conversion efficiency, simple implementation, and cost-effectiveness. Among all the candidate materials for solar evaporators, carbon-based materials stand out due to their intrinsic high solar absorption, highly tunable structure, easy preparation, low cost, and earth-abundancy. In this review, the recent progress on carbon-based materials for the development of interfacial SVG is summarized. First, a brief introduction to the basic design principles of the interfacial SVG system is presented. Then, recent efforts in carbon-based solar evaporators, from artificial structures to bioinspired configurations, focusing on their structure-function relationship are highlighted. Strategies for designing antisalt-fouling desalination systems are also summarized. Last, the challenges and opportunities of carbon-based materials for solar evaporation technology are elaborated.

Synthesis of 3D graphene-based materials and their applications for removing dyes and heavy metals

Contamination of water streams by dyes and heavy metals has become a major problem due to their persistence, accumulation, and toxicity. Therefore, it is essential to eliminate and/or reduce these contaminants before discharge into the natural environment. In recent years, 3D graphene has drawn intense research interests owing to its large surface area, superior charge conductivity, and thermal conductivity properties. Due to their unique surface and structural properties, 3D graphene-based materials (3D GBMs) are regarded as ideal adsorbents for decontamination and show great potential in wastewater or exhaust gas treatment. Here, this minireview summarizes the recent progress on 3D GBMs synthesis and their applications for adsorbing dyes and heavy metals from wastewater based on the structures and properties of 3D GBMs, which provides valuable insights into 3D GBMs' application in the environmental field.

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.

Achieving Enhanced Capacitive Deionization by Interfacial Coupling in PEDOT Reinforced Cobalt Hexacyanoferrate Nanoflake Arrays

Capacitive deionization (CDI) as a novel energy and cost-efficient water treatment technology has attracted increasing attention. The recent development of various faradaic electrode materials has greatly enhanced the performance of CDI as compared with traditional carbon electrodes. Prussian blue (PB) has emerged as a promising CDI electrode material due to its open framework for the rapid intercalation/de-intercalation of sodium ions. However, the desalination efficiency, and durability of previously reported PB-based materials are still unsatisfactory. Herein, a self-template strategy is employed to prepare a Poly(3,4-ethylenedioxythiophene) (PEDOT) reinforced cobalt hexacyanoferrate nanoflakes anchored on carbon cloth (denoted as CoHCF@PEDOT). With the high conductivity and structural stability achieved by coupling with a thin PEDOT layer, the as-prepared CoHCF@PEDOT electrode exhibits a high capacity of 126.7 mAh g-1 at 125 mA g-1. The fabricated hybrid CDI cell delivers a high desalination capacity of 146.2 mg g-1 at 100 mA g-1, and good cycling stability. This strategy provides an efficient method for the design of high-performance faradaic electrode materials in CDI applications.

Porous carbon nanotube microspheres with tailorable surface wettability areas for oil adsorption

HYPOTHESIS

Oil adsorption is significant for water purification and environmental protection. However, the conventional bulk sorbents face the predicament of uncontrollable motion as well as hydrophobic nature the whole body, which largely restricts their uptake capacity underwater. Hence, novel adsorbent material for high-efficient oil uptake both at the surface and under the water is urgently required.

EXPERIMENTS

We presented a phase-transition lysozyme coating approach to fabricate porous carbon nanotube microspheres with tailorable surface wettability areas for versatile oil adsorption. Because of the existence of magnetic nanoparticle in one hemisphere, the multi-sites coating was easily achieved by constantly changing orientations of the magnetic field. Owing to the integration of various hydrophilic functional groups in lysozyme as well as remarkable adhesion to virtually arbitrary materials, the intrinsically hydrophobic surface of the microspheres was partially modified hydrophilic on multiple sites.

FINDINGS

It was demonstrated that the unique surface wettability feature and the porous structure enabled the microspheres to adsorb multiple contaminants both floating on the water and underwater. Besides, the magnetic-responsive ability allowed for controllable collection of oil contaminants. These features, along with the reusability, make the porous carbon nanotube microspheres excellent adsorbents for water purification.

Three-Dimensional Graphene-Based Macrostructures for Electrocatalysis

Electrochemical energy storage and conversion is an effective strategy to relieve the increasing energy and environment crisis. The sluggish reaction kinetics in the related devices is one of the major obstacles for them to realize practical applications. More efforts should be devoted to searching for high-efficiency electrocatalysts and enhancing the electrocatalytic performance. 3D graphene macrostructures (3D GMs) are one kind of porous crystalline materials with 3D structures at both micro- and macro-scale. The unique structure can achieve large accessible surface area, expose many active sites, promote fast mass/electron transport, and provide wide room for further functional modification. All these features make them promising candidates for electrocatalysis. In this review, the authors focus on the latest progress of 3D GMs for electrocatalysis. First, the preparation methods of 3D GMs are introduced followed by the strategies for functional modifications. Then, their electrocatalytic performances are discussed in detail including monofunctional and bifunctional electrocatalysis. The electrocatalytic processes involve oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, and carbon dioxide reduction reaction. Finally, the challenges and perspectives are presented to offer a guideline for the exploration of excellent 3D GM-based electrocatalysts.

Wastewater Remediation Technologies Using Macroscopic Graphene-Based Materials: A Perspective

Three-dimensional (3D) graphene-based macrostructures are being developed to combat the issues associated with two-dimensional (2D) graphene materials in practical applications. The 3D macrostructures (3DMs), for example, membranes, fibres, sponges, beads, and mats, can be formed by the self-assembly of 2D graphene-based precursors with exceptional surface area and unique chemistry. With rational design, the 3D macrostructures can then possess outstanding properties and exclusive structures. Thanks to various advantages, these macrostructures are competing in a variety of applications with promising performances unlike the traditional activated carbons, biochars and hydrochars, which have less flexibilities for modifications towards versatile applications. However, despite having such a wide range of applications, 3DMs remain applicable on laboratory scale due to the associated factors like cost and extensive research. This perspective provides an overview of available graphene-based macrostructures and their diverse synthesis protocols. In the synthesis, hydrothermal route, chemical vapor deposition (CVD), wet spinning, 3D printing, vacuum filtration, spray drying and emulsion methods are highlighted. In addition, the physio-chemical properties of these macrostructures are discussed with the relationship among the porosity, surface area and the bulk density. The perspective also highlights the versatile potentials of different 3DMs in wastewater remediation by adsorption, desalination, and catalytic oxidation, etc. Following the concluding remarks, future outlooks on commercial applications of 3DMs are also provided.

Controlling the structure and photocatalytic properties of three—dimensional aerogels obtained by simultaneous reduction and self-assembly of BiOI/GO aqueous colloidal dispersions

Water pollution affects all living habitats, since it is the most basic element that sustains all life forms and, as an exceptional solvent, it readily makes any compound available for living cells, either nutrients or noxious substances. Elimination of molecular contaminants from water quality is one of the most challenging technical problems that conventional treatments like flocculation and filtration fail short to defeat. Particulate photocatalysts, used to degrade contaminants, have the main drawback of their recovery from the water matrices. The inclusion of photocatalytic nanoparticles (NPs) into a large supporting framework, is presented as an innovative approach aiming to ensure a facile separation from water. To this end, three-dimensional (3D) aerogels with photocatalytic properties were prepared by a simple and scalable method based on the reduction—induced self-assembly of graphene oxide (GO) in the presence of BiOI nanoparticles. With the help of ascorbic acid, as a green reducing agent, partial reduction of GO into reduced graphene oxide (RGO) and self-assembly of both kinds of nanostructures into a porous monolith was achieved. BiOI doped RGO aerogels were further stabilized and morphologically controlled using poly (ethylene glycol) as stabilizer. The photocatalytic performance of these aerogels was evaluated by following the discoloration of methylene blue (MB) solution, under visible light irradiation, showing that structure and dispersion degree of NPs to be fundamental variables. Hence, this methodology is proposed to produce hybrid aerogels with controlled morphology and photocatalytic performance that has the potential to be used in water cleaning procedures.