Graphene, in its ideal form, is a two-dimensional (2D) material consisting of a single layer of carbon atoms arranged in a hexagonal lattice. The richness in morphological, physical, mechanical, and ...optical properties of ideal graphene has stimulated enormous scientific and industrial interest, since its first exfoliation in 2004. In turn, the production of graphene in a reliable, controllable, and scalable manner has become significantly important to bring us closer to practical applications of graphene. To this end, chemical vapor deposition (CVD) offers tantalizing opportunities for the synthesis of large-area, uniform, and high-quality graphene films. However, quite different from the ideal 2D structure of graphene, in reality, the currently available CVD-grown graphene films are still suffering from intrinsic defective grain boundaries, surface contaminations, and wrinkles, together with low growth rate and the requirement of inevitable transfer. Clearly, a gap still exits between the reality of CVD-derived graphene, especially in industrial production, and ideal graphene with outstanding properties. This Review will emphasize the recent advances and strategies in CVD production of graphene for settling these issues to bridge the giant gap. We begin with brief background information about the synthesis of nanoscale carbon allotropes, followed by the discussion of fundamental growth mechanism and kinetics of CVD growth of graphene. We then discuss the strategies for perfecting the quality of CVD-derived graphene with regard to domain size, cleanness, flatness, growth rate, scalability, and direct growth of graphene on functional substrate. Finally, a perspective on future development in the research relevant to scalable growth of high-quality graphene is presented.
Due to its excellent temperature resistance, 316 L stainless steel (SS) is widely used in integral impellers; however, as the engine performance requirements have increased, the shape of integral ...impellers has become increasingly complex. Directed energy deposition (DED), with a high production rate and low cost, is used to directly fabricate complex structural geometries. Nevertheless, the surface quality is lower than that achieved by conventional methods, i.e., milling. To overcome this problem, a novel hybrid approach with DED followed by a subtractive milling process within a single workstation is developed. This method can directly produce internal and highly complex structural parts with ideal dimensional accuracy. However, the process parameters and mechanical properties of DED and subtractive thermal milling (starting milling temperature of 200−300℃) after each deposition of a set of layers have rarely been evaluated. The purpose of this study is to address these research limitations. The densification, phase composition, microstructure and mechanical behaviour are studied, and a correlation between process parameters and performance is newly established. The results indicate that the nearly fully dense 316 L SS specimens exhibit high microhardness and tensile strength under the optimum process parameters, which is attributed to the high density and fine microstructure. Moreover, the highest tensile strength (683.3 MPa) among all tensile samples is obtained with v = 8 mm/s. The tensile strength values for wrought (hot work-annealed), wrought (cold-worked), cast samples, and for the industry requirement for 316 L SS are 480, 574, 552 and 450 MPa, which are 42.97 %, 19.56 %, 24.33 %, and 52.51 % lower, respectively, than that for the hybrid DED and thermal milling process. The test results and a comparison analysis show that the components from the hybrid DED and thermal milling process can satisfy the industry requirements for 316 L SS.
The development of efficient photocatalysts for the degradation of organic pollutants and production of hydrogen peroxide (H2O2) is an attractive two‐in‐one strategy to address environmental ...remediation concerns and chemical resource demands. Graphitic carbon nitride (g‐C3N4) possesses unique electronic and optical properties. However, bulk g‐C3N4 suffers from inefficient sunlight absorption and low carrier mobility. Once exfoliated, ultrathin nanosheets of g‐C3N4 attain much intriguing photocatalytic activity. Herein, a mussel‐inspired strategy is developed to yield silver‐decorated ultrathin g‐C3N4 nanosheets (Ag@U‐g‐C3N4‐NS). The optimum Ag@U‐g‐C3N4‐NS photocatalyst exhibits enhanced electrochemical properties and excellent performance for the degradation of organic pollutants. Due to the photoformed valence band holes and selective two‐electron reduction of O2 by the conduction band electrons, it also renders an efficient, economic, and green route to light‐driven H2O2 production with an initial rate of 0.75 × 10−6 m min−1. The improved photocatalytic performance is primarily attributed to the large specific surface area of the U‐g‐C3N4‐NS layer, the surface plasmon resonance effect induced by Ag nanoparticles, and the cooperative electronic capture properties between Ag and U‐g‐C3N4‐NS. Consequently, this unique photocatalyst possesses the extended absorption region, which effectively suppresses the recombination of electron–hole pairs and facilitates the transfer of electrons to participate in photocatalytic reactions.
A facile and green strategy is developed to craft silver‐decorated ultrathin graphitic carbon nitride nanosheets (Ag@U‐g‐C3N4‐NS) through a post gas‐etching treatment of bulk g‐C3N4 in conjunction with the uniform growth of Ag nanoparticles on its surface via a mussel‐inspired dopamine polymerization. The optimum Ag@U‐g‐C3N4‐NS photocatalyst exhibits excellent electrochemical properties and performance for the degradation of organic pollutants and H2O2 production.
Potassium‐ion hybrid capacitors (KICs) reconciling the advantages of batteries and supercapacitors have stimulated growing attention for practical energy storage because of the high abundance and low ...cost of potassium sources. Nevertheless, daunting challenge remains for developing high‐performance potassium accommodation materials due to the large radius of potassium ions. Molybdenum diselenide (MoSe2) has recently been recognized as a promising anode material for potassium‐ion batteries, achieving high capacity and favorable cycling stability. However, KICs based on MoSe2 are scarcely demonstrated by far. Herein, a diatomite‐templated synthetic strategy is devised to fabricate nitrogen‐doped MoSe2/graphene (N‐MoSe2/G) composites with favorable pseudocapacitive potassium storage targeting a superior anode material for KICs. Benefiting from the unique biomorphic structure, high electron/K‐ion conductivity, enriched active sites, and the conspicuous pseudocapacitive effect of N‐MoSe2/G, thus‐derived KIC full‐cell manifests high energy/power densities (maximum 119 Wh kg−1/7212 W kg−1), outperforming those of recently reported KIC counterparts. Furthermore, the potassium storage mechanism of N‐MoSe2/G composite is systematically explored with the aid of first‐principles calculations in combination of in situ X‐ray diffraction and ex situ Raman spectroscopy/transmission electron microscopy/X‐ray photoelectron spectroscopy.
Nitrogen‐doped MoSe2/graphene composites prepared via a biotemplated strategy are employed as highly effective anodes for potassium‐ion hybrid capacitors, manifesting high energy/power density (119 Wh kg−1/7212 W kg−1) and long lifespan.
Ongoing technological advances in diverse fields including portable electronics, transportation, and green energy are often hindered by the insufficient capability of energy-storage devices. By ...taking advantage of two different electrode materials, asymmetric supercapacitors can extend their operating voltage window beyond the thermodynamic decomposition voltage of electrolytes while enabling a solution to the energy storage limitations of symmetric supercapacitors. This review provides comprehensive knowledge to this field. We first look at the essential energy-storage mechanisms and performance evaluation criteria for asymmetric supercapacitors to understand the wide-ranging research conducted in this area. Then we move to the recent progress made for the design and fabrication of electrode materials and the overall structure of asymmetric supercapacitors in different categories. We also highlight several key scientific challenges and present our perspectives on enhancing the electrochemical performance of future asymmetric supercapacitors.
3D printing technology has stimulated a burgeoning interest to fabricate customized architectures in a facile and scalable manner targeting wide ranged energy storage applications. Nevertheless, ...3D-printed hybrid capacitor devices synergizing favorable energy/power density have not yet been explored thus far. Herein, we demonstrate a 3D-printed sodium-ion hybrid capacitor (SIC) based on nitrogen-doped MXene (N-Ti3C2T x ) anode and activated carbon cathode. N-Ti3C2T x affording a well-defined porous structure and uniform nitrogen doping can be obtained via a sacrificial template method. Thus-formulated ink can be directly printed to form electrode architecture without the request of a conventional current collector. The 3D-printed SICs, with a large areal mass loading up to 15.2 mg cm–2, can harvest an areal energy/power density of 1.18 mWh cm–2/40.15 mW cm–2, outperforming the state-of-the-art 3D-printed energy storage devices. Furthermore, our SIC also achieves a gravimetric energy/power density of 101.6 Wh kg–1/3269 W kg–1. This work demonstrates that the 3D printing technology is versatile enough to construct emerging energy storage systems reconciling high energy and power density.
Wearable and portable self-powered units have stimulated considerable attention in both the scientific and technological realms. However, their innovative development is still limited by inefficient ...bulky connections between functional modules, incompatible energy storage systems with poor cycling stability, and real safety concerns. Herein, we demonstrate a flexible solar-charging integrated unit based on the design of printed magnesium ion aqueous asymmetric supercapacitors. This power unit exhibits excellent mechanical robustness, high photo-charging cycling stability (98.7% capacitance retention after 100 cycles), excellent overall energy conversion and storage efficiency (η
= 17.57%), and outstanding input current tolerance. In addition, the Mg ion quasi-solid-state asymmetric supercapacitors show high energy density up to 13.1 mWh cm
via pseudocapacitive ion storage as investigated by an operando X-ray diffraction technique. The findings pave a practical route toward the design of future self-powered systems affording favorable safety, long life, and high energy.
Visible light-responsive photocatalytic technology holds great potential in water treatment to enhance purification efficiency, as well as to augment water supply through the safe usage of ...unconventional water sources. This review summarizes the recent progress in the design and fabrication of visible light-responsive photocatalysts
via
various synthetic strategies, including the modification of traditional photocatalysts by doping, dye sensitization, or by forming a heterostructure, coupled with π-conjugated architecture, as well as the great efforts made within the exploration of novel visible light-responsive photocatalysts. Background information on the fundamentals of heterogeneous photocatalysis, the pathways of visible light-responsive photocatalysis, and the unique features of visible light-responsive photocatalysts are presented. The photocatalytic properties of the resulting visible light-responsive photocatalysts are also covered in relation to the water treatment,
i.e.
, regarding the photocatalytic degradation of organic compounds and inorganic pollutants, as well as photocatalytic disinfection. Finally, this review concludes with a summary and perspectives on the current challenges faced and new directions in this emerging area of research.
This review summarizes the recent progress in the design, fabrication, and application of visible light-responsive photocatalysts.
Grapefruit essential oil has been proven to have wide range of bioactivities. However, bioactivity of its molecular distillate has not been well studied. In this study, a light phase oil was obtained ...by molecular distillation from cold-pressed grapefruit essential oil and GC-MS was used to identify its chemical composition. The antimicrobial activity of the light phase oil was tested by filter paper diffusion method, and the anticancer activity was determined by the Cell Counting Kit-8 (CCK-8) assay. Twenty-four components were detected with a total relative content of 99.74%, including 97.48% of terpenes and 1.66% of oxygenated terpenes. The light phase oil had the best antimicrobial effect on
, followed by
,
and
. DPPH and ABTS assays demonstrated that the light phase oil had good antioxidant activity. The CCK-8 assay of cell proliferation showed that the light phase oil had a good inhibitory effect on the proliferation of HepG2 liver cancer cells and HCT116 colon cancer cells.
Lithium-sulfur (Li-S) batteries have garnered a lot of attention in the realm of electrochemical energy storage owing to their high energy and low cost. However, the serious polysulfide shuttle ...effect of the sulfur cathode poses a critical challenge for the development of Li-S batteries with elevated sulfur loadings. In addition, the poor robustness of traditional blade-casting cathodes greatly impedes the practical applications of flexible Li-S cells that display high areal capacity. To address these concerns, we report herein a freestanding hybrid sulfur host
via in situ
crafting of flexible carbon cloth (CC), vertically grown graphene nanoflakes over CC (G/CC) and metal-organic-framework derived CoP anchored on vertical graphene (CoP@G/CC). The thus-derived sulfur cathodes (CoP@G/CC-S) with a typical sulfur loading of 2 mg cm
−2
exhibit outstanding electrochemical performances, including excellent rate capability (930.1 mA h g
−1
at 3.0C) and impressive cycling stability (0.03% capacity decay per cycle after 500 cycles at 2.0C). A high areal capacity of 8.81 mA h cm
−2
at 0.05C can also be obtained even at an elevated sulfur loading of 10.83 mg cm
−2
. Furthermore, flexible pouch cells based on the self-supported CoP@G/CC-S showcase favorable rate and cycling performances with high mechanical robustness.
A self-supported and binder-free CoP@G/CC-S cathode affording high conductivity, a suppressed shuttle effect and favorable mechanical robustness enables high-performance flexible Li-S batteries for practical applications.
PDF
