La
3+
cross-linking produces robust membranes from small-flake graphene oxide, which induces fast organic solvent permeances.
Membranes for organic solvent nanofiltration (OSN) or solvent-resistant ...nanofiltration (SRNF) offer unprecedented opportunities for highly efficient and cost-competitive solvent recovery in the pharmaceutical industry. Here, we describe small-flake graphene oxide (SFGO) membranes for high-performance OSN applications. Our strategy exploits lateral dimension control to engineer shorter and less tortuous transport pathways for solvent molecules. By using La
3+
as a cross-linker and spacer for intercalation, the SFGO membrane selective layer was stabilized, and size-dependent ultrafast selective molecular transport was achieved. The methanol permeance was up to 2.9-fold higher than its large-flake GO (LFGO) counterpart, with high selectivity toward three organic dyes. More importantly, the SFGO-La
3+
membrane demonstrated robust stability for at least 24 hours under hydrodynamic stresses that are representative of realistic OSN operating conditions. These desirable attributes stem from the La
3+
cross-linking, which forms uniquely strong coordination bonds with oxygen-containing functional groups of SFGO. Other cations were found to be ineffective.
Metal oxides of earth‐abundant elements are promising electrocatalysts to overcome the sluggish oxygen evolution and oxygen reduction reaction (OER/ORR) in many electrochemical energy‐conversion ...devices. However, it is difficult to control their catalytic activity precisely. Here, a general three‐stage synthesis strategy is described to produce a family of hybrid materials comprising amorphous bimetallic oxide nanoparticles anchored on N‐doped reduced graphene oxide with simultaneous control of nanoparticle elemental composition, size, and crystallinity. Amorphous Fe0.5Co0.5Ox is obtained from Prussian blue analog nanocrystals, showing excellent OER activity with a Tafel slope of 30.1 mV dec−1 and an overpotential of 257 mV for 10 mA cm−2 and superior ORR activity with a large limiting current density of −5.25 mA cm−2 at 0.6 V. A fabricated Zn–air battery delivers a specific capacity of 756 mA h gZn−1 (corresponding to an energy density of 904 W h kgZn−1), a peak power density of 86 mW cm−2 and can be cycled over 120 h at 10 mA cm−2. Other two amorphous bimetallic, Ni0.4Fe0.6Ox and Ni0.33Co0.67Ox, are also produced to demonstrate the general applicability of this method for synthesizing binary metal oxides with controllable structures as electrocatalysts for energy conversion.
Simultaneous control of bimetallic oxide nanoparticle elemental composition, size, and crystallinity yields a high‐performance bifunctional oxygen evolution and reduction electrocatalyst for rechargeable Zn–air batteries. This method has general applicability toward various binary, tertiary, or even quadruple metal systems.
1D supercapacitors (SCs) have emerged as promising candidates to power emerging electronics in recent years because of their unique advantages in energy storage and mechanical flexibility. There are ...four main research fronts in the development of 1D SCs: 1) enhancing mechanical characteristics, 2) achieving superior electrochemical performance, 3) enabling multiple device integration, and 4) demonstrating multifunctionality. Here, a brief history of 1D SCs is presented and significant research achievements regarding the four fronts identified as the main pillars of the development of 1D SCs are highlighted. The current challenges of the fabrication and utilization of 1D SCs are critically examined and potential solutions are analyzed. Plus, the performance inconsistencies arising from the improper use and extreme diversity of performance evaluation and reporting methods are highlighted. Beyond, perspectives on future efforts are provided and goals regarding the four research fronts are set, to further push 1D SCs toward practical applications. The development of 1D SCs is summarized here, with existing obstacles diagnosed, corresponding solutions proposed, and future directions indicated accordingly.
1D supercapacitors have emerged as promising candidates to power emerging electronics. There are four research fronts, including: 1) enhancing mechanical characteristics, 2) achieving superior electrochemical performance, 3) enabling multiple device integration, and 4) demonstrating multifunctionality. Recent research achievements are summarized, existing obstacles are diagnosed, corresponding solutions are proposed, and future directions are indicated.
Biogas is an increasingly attractive renewable resource, envisioned to secure future energy demands and help curb global climate change. To capitalize on this resource, membrane processes and ...state-of-the-art membranes must efficiently recover methane (CH4) from biogas by separating carbon dioxide (CO2). Composite (a.k.a. mixed-matrix) membranes, prepared from common polymers and rationally selected/engineered fillers, are highly promising for this application. This review comprehensively examines filler materials that are capable of enhancing the CO2/CH4 separation performance of polymeric membranes. Specifically, we highlight novel synthetic strategies for engineering filler materials to develop high-performance composite membranes. Besides, as the matrix components (polymers) of composite membranes largely dictate the overall gas separation performances, we introduce a new empirical metric, the “Filler Enhancement Index” (F index), to aid researchers in assessing the effectiveness of the fillers from a big data perspective. The F index systematically decouples the effect of polymer matrices and critically evaluates both conventional and emerging fillers to map out a future direction for next-generation (bio)gas separation membranes. Beyond biogas separation, this review is of relevance to a broader community with interests in composite membranes for other gas separation processes, as well as water treatment applications.
Advances in microfluidic technology towards flexibility, transparency, functionality, wearability, scale reduction or complexity enhancement are currently limited by choices in materials and assembly ...methods. Organized microfibrillation is a method for optically printing well-defined porosity into thin polymer films with ultrahigh resolution. Here we demonstrate this method to create self-enclosed microfluidic devices with a few simple steps, in a number of flexible and transparent formats. Structural colour, a property of organized microfibrillation, becomes an intrinsic feature of these microfluidic devices, enabling in-situ sensing capability. Since the system fluid dynamics are dependent on the internal pore size, capillary flow is shown to become characterized by structural colour, while independent of channel dimension, irrespective of whether devices are printed at the centimetre or micrometre scale. Moreover, the capability of generating and combining different internal porosities enables the OM microfluidics to be used for pore-size based applications, as demonstrated by separation of biomolecular mixtures.
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Graphene hydrogels hold great potential for the disinfection of bacteria-contaminated water. However, the intrinsic antibacterial activity of graphene hydrogels is not satisfactory, ...and the incorporation of other antibacterial agents often results in their unwanted releases. Here, we present a new strategy to improve the antibacterial activities of graphene hydrogels. We first synthesized a new pi-conjugated molecule containing five aromatic rings and two side-linked quaternary ammonium (QA) groups, denoted as piQA. Next, we fabricated composite gravity filters by assembling piQA with reduced graphene oxide (rGO) hydrogel. The rGO hydrogel helps to form a sponge-like physical sieve, contributes to the overall antibacterial activity, and provides abundant pi-rich surfaces. The large aromatic cores of piQA allow the formation of collectively strong pi-pi interactions with rGO, resulting in a high piQA mass loading of ∼31 wt%. Due to the sieving effect of rGO hydrogel and the synergistic antibacterial activity of rGO and piQA, the filters prepared based on piQA-rGO assemblies can remove over 99.5% of Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) cells with a high-water treatment capacity of 10 L g−1. Furthermore, the piQA-rGO assemblies show low toxicity towards two different mammalian cell lines (L929 and macrophages), and the release of piQA is also negligible. Overall, the new piQA-rGO assembly demonstrates high potential for water disinfection applications.
Graphene-based laminate membranes have recently demonstrated unique advantages over the traditional separation membranes made of polymers or ceramics. For both gas and liquid separations, various ...designs of crosslinker-stabilized graphene oxide (GO) membranes have been reported. However, the preparation methods used for those are poorly scalable for industrial applications. Herein, we report the fabrication of large-area (1333 cm2) GO-based membranes via doctor-blade casting of gel-like slurries prepared by incorporating calcium ions (Ca2+), ferric ions (Fe3+), polyethylene oxide (PEO), or polyethyleneimine (PEI) as crosslinkers. We found that all crosslinkers tested are suitable for the gelation of dilute GO dispersions (1–5 mg/mL) for doctor-blade casting. Besides, all crosslinked-GO membranes demonstrated outstanding stability under sonication compared to a GO-only membrane prepared via vacuum-assisted filtration. In aqueous nanofiltration tests, Fe3+-crosslinked GO membranes achieved virtually complete rejection of different organic dyes. PEO-crosslinked GO membranes, on the other hand, exhibited an outstanding performance for the separation of carbon dioxide (CO2) and nitrogen (N2) gases with a CO2/N2 selectivity of 52. Given the scaleup potential of doctor-blade casting and the practicality of crosslinking-based gelation approach, the proposed approach is promising to increase the industrial relevance of GO-based laminate membranes.
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Water disinfection practices are critical for supplying safe drinking water. Existing water disinfection methods come with various drawbacks, calling for alternative or complementary solutions. ...Nanocarbon materials (NCMs) offer unique advantages for water disinfection owing to their high antimicrobial activity, often low environmental/human toxicity, and tunable physicochemical properties. Nevertheless, it is a challenge to assess the research progress made so far due to the structure and property diversity in NCMs as well as their different targeted applications. Because of these, here we provide a broad outline of this emerging field in three parts. First, we introduce the antimicrobial activities of the different types of NCMs, including fullerenes, nanodiamonds, carbon (nano)dots, carbon nanotubes, and graphene-family materials. Next, we discuss the current status in applying these NCMs for different water disinfection problems, especially as hydrogel filters, filtration membranes, recyclable aggregates, and electrochemical devices. We also introduce the use of NCMs in photocatalysts for photocatalytic water disinfection. Lastly, we put forward the key hurdles of the field that hamper the realization of the practical applications and propose possible directions for future investigations to address those. We hope that this minireview will encourage researchers to tackle these challenges and innovate NCM-based water disinfection platforms in the near future.
Selective synthesis of single-walled carbon nanotubes (SWCNTs) is highly desirable for various applications. Among the strategies proposed for achieving this, the method involving sulfur-containing ...compounds is a promising approach showing the conversion of common cobalt/silica catalysts (Co/SiO2) into chirality selective catalysts. However, the possible influence of sulfur-containing compounds in promoting the selectivity of non-cobalt-based metal/silica catalysts has not been studied. Here three metal sulfate based catalysts (MSO4/SiO2, M=Fe, Ni, or Co) were prepared for SWCNT synthesis under the same growth condition. Detailed SWCNT and catalyst characterizations show that well-dispersed Fe oxides and silicates are formed on Fe2(SO4)3/SiO2, favoring the formation of small diameter (6,5) nanotubes. NiSO4/SiO2 contains a portion of NiSO4 together with Ni silicate and relatively large NiO particles, leading to a wider diameter distribution centered around (8,7) nanotubes. CoSO4/SiO2 consists of dominantly well-dispersed CoSO4 and a small amount of Co silicates, showing the good selectivity toward the relatively larger diameter (9,8) nanotubes with an abundance of 40.6% among the semiconducting nanotubes. Sulfur retained on the catalysts influences the selectivity toward relatively larger diameter SWCNTs. Current work highlights the potential of using metal sulfates with varied decomposition temperatures to achieve the selective growth of SWCNTs.
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Translating the advantages of carbon nanomaterials into macroscopic energy storage devices is challenging because the desirable nanoscale properties often disappear during assembly processes. Here we ...describe a new nonequilibrium subcritical hydrothermal method capable of independently manipulating the temperature and pressure to create unique assembly conditions crossing the commonly used liquid-vapor boundary. Highly conductive and dense-packed yet ion-accessible nanocarbon microfibers can be obtained from graphene oxide sheets, single-walled carbon nanotubes, and a nitrogen-doping crosslinker under 20 min of hydrothermal assembly, 80% energy saving compared to standard hydrothermal methods, and one of the shortest time in the field of hydrothermal processing of carbon nanomaterials. Using those microfibers, we built microsupercapacitors that reach a high volumetric capacitance of 52 F cm−3, energy density of 7.1 mWh cm−3, and power density of 1645.7 mW cm−3, respectively. We further demonstrate the 3D integration of multiple fiber microsupercapacitors that reduces the device footprint by 75% while expanding the operational voltage and current window. This strategy is a promising tool for harmoniously assembling carbon nanostructures as energy storage components for various energy applications.
A new hydrothermal system is capable of controlling the temperature and pressure of water independently to create unique hydrothermal assembly conditions for achieving ultrafast assembly of carbon nanomaterials into carbon architectures. Display omitted
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