One‐dimensional materials exhibit fascinating properties in electrocatalytic applications but their fabrication faces the challenge of tedious and complicated operations. We have developed a ...bottom‐up strategy to construct a 1D metal carbide catalyst (Mo2C@NC) consisting of ultrafine Mo2C nanoparticles embedded within nitrogen‐doped carbon layers by simply calcining a mixture of ammonium molybdate, urea and melamine. Experimental results and thermodynamic calculations demonstrate that the retainable pyrolysis‐generated self‐supporting atmosphere plays a crucial role in the crystalline phase and morphology of materials. When functioned as an electrocatalyst for the hydrogen evolution reaction (HER), the achieved Mo2C@NC presents an excellent catalytic activity as well as outstanding stability. This work could shed fresh light onto the facile synthesis of effective HER catalysts with 1D nanostructure.
A very fine catalyst: A 1D catalyst consisting of ultrafine Mo2C nanoparticles and nitrogen‐doped carbon has been fabricated for the hydrogen evolution reaction. Self‐supporting gases play a vital role in building the 1D and porous structure of the materials, which facilitates charge and mass transfer during the catalytic process. The optimized catalyst exhibits a superior overpotential and Tafel slope.
In an attempt to develop high-activity and earth-abundant electrocatalysts for hydrogen evolution reaction (HER), tungsten carbide/carbon composites are prepared readily via annealing a ...polyaniline/tungstic acid hybrid precursor under vacuum condition. By simply changing the mass ratio of polyaniline and tungstic acid, a variety of products with different structures can be obtained. The varying mass ratio causes the change of crystalline sizes of carbides, existential state of carbon and carbides/carbon content of final products. The composite produced at mass ratio of 1/1 shows the worst HER activity among all the catalysts due to its minimal content of active ingredients and the lowest degree of graphitization. In the case of the mass ratio of 1/3, an excess of tungsten source results in increasing graphitic carbon layers and decreasing electrochemical active surface area, which leads to the limited charge transfer process and less exposed active sites for HER. The composite fabricated at the mass ratio of 1/2 presents favorable electrocatalytic activity and excellent stability in both acidic and alkaline solutions, indicating its great potential to serve as a HER catalyst for water splitting.
•Facile synthesis of tungsten carbide/carbon composites is demonstrated.•The increase in tungsten content leads to higher degree of crystallization of WC.•The increase in tungsten content causes a change of existential state of carbon.•The structure-performance correlation is investigated.•The catalyst presents favorable HER activity and excellent stability.
Abstract
One‐dimensional materials exhibit fascinating properties in electrocatalytic applications but their fabrication faces the challenge of tedious and complicated operations. We have developed a ...bottom‐up strategy to construct a 1D metal carbide catalyst (Mo
2
C@NC) consisting of ultrafine Mo
2
C nanoparticles embedded within nitrogen‐doped carbon layers by simply calcining a mixture of ammonium molybdate, urea and melamine. Experimental results and thermodynamic calculations demonstrate that the retainable pyrolysis‐generated self‐supporting atmosphere plays a crucial role in the crystalline phase and morphology of materials. When functioned as an electrocatalyst for the hydrogen evolution reaction (HER), the achieved Mo
2
C@NC presents an excellent catalytic activity as well as outstanding stability. This work could shed fresh light onto the facile synthesis of effective HER catalysts with 1D nanostructure.
The arginine-glycine-aspartic （RGD） acid peptide was grafted to the surface of apatitewollastonite （AW） ceramic in an effort to improve its cell adhesion, proliferation and osteoinduction. RGD ...peptide was covalently immobilized onto the surface of AW ceramic via the synthetic cross linker AA.PTS-E and 1-ethyl-3-（3-dimethylaminopropyl）carbodiimide （EDC）. The modified surfaces were characterized by attenuated total reflectance Fourier transform infrared spectroscopy （ATR-FTIR） and X-ray photoelectron spectroscopy （XPS）. The chemical analysis indicated that RGD peptide had been immobilized onto the AW surface successfully. The growth of osteoblast-like cells （MG63） showed that modifying the AW surface with RGD peptide enhanced the cell adhesion and proliferation. And the histological evaluation of RGD-AW showed that the bone regeneration and remodeling process were significantly enhanced compared to the original AW ceramics after 2, 4 and 8 weeks implantation in rabbit＇s femoral condyles.
For purpose of developing noble-metal-free electrocatalysts with high activity toward hydrogen evolution reaction (HER), tungsten-cased carbides are synthesized with ammonium metatungstate as ...tungsten source, resorcinol and formaldehyde as carbon source. Systematic experiments demonstrate that the introduction of iron nitrate complexed with trisodium citrate has a clear impact on the structural and morphological features of final products. Moreover, various crystalline phases involving WC, W2C, W and Fe3W3C can be readily tuned by altering the Fe/W atomic ratio. Electrochemical measurements reveal that the HER activity of Fe3W3C is superior to those of other control groups, giving a η10 (the overpotential for driving a current density of 10 mA cm−2) of −226 mV and Tafel slope of 91 mV dec−1 in acid solution. Theoretical calculations suggest the improved electrocatalytic performance of Fe3W3C may be attributed to the hydrogen spillover from W sites to Fe sites. This work may open up new opportunities to develop high-performance catalysts via accelerating hydrogen adsorption and hydrogen evolution at different components.
•Facile synthesis of various tungsten-based carbides is demonstrated.•The structure-performance correlation is intensively investigated.•The enhanced HER activity of Fe3W3C may be due to the hydrogen spillover effect.
Kaolin, talc powder and alumina were used as raw materials to prepare ceramic foams using a protein foaming agent via direct foaming. CH3COOLi and Ti(OC4H9)4 were employed as lithium and titanium ...sources, respectively to synthesize Li2TiO3 by the sol–gel process during which Li2TiO3 was loaded on ceramic foams to address the problem that powdery Li2TiO3 is difficult to be used in extracting lithium directly from the sea water and salt lake brine for engineering troubles. Hydrochloric acid was used to treat Li2TiO3 to obtain H2TiO3–lithium adsorbent. The results indicate that ceramic foams with a high open porosity are observed, and Li2TiO3 with particle size 80–100nm is loaded on ceramic foams successfully. The Li+ drawn out ratio from Li2TiO3 reaches 50.2%, and the adsorptive capacity comes up to 21.0mgg−1 after a treatment 24h.
•Ceramic foams with a high open porosity are prepared with cheap raw materials.•Li2TiO3 is synthesized with CH3COOLi and Ti(OC4H9)4 by the sol–gel process.•Li2TiO3 is loaded on ceramic foams to solve the problems it suffers in engineering.•Rietveld refinement is done using the Reflex module in Materials Studio 5.5.•The Li+ drawn out ratio and the adsorptive capacity are 50.2% and 21.0mgg−1.
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Glass lubricants have great potential in industrial metal forming processes such as hot extrusion of titanium and titanium alloys. In this work, based on the extrusion process of ...commercial-purity titanium (TA2) at 800 °C, glass lubricants with low melting points are designed. The thermal properties, high-temperature oxidation resistance and friction properties of uncoated and glass-coated TA2 samples are systemically studied, which reveals the good lubricating and anti-oxidation properties of the samples. The glass lubricant melts into a viscoelastic film at 800 °C to insulate TA2 from oxygen and reduce friction, and automatically peel off during cooling due to the significantly mismatched thermal expansion between the glass coating and TA2 substrate. This work provides a guidance for designing glass-based lubricants used in hot extrusion of metals.
H2TiO3–lithium adsorbent was obtained from the acid-modified precursor Li2TiO3, which was synthesized via the solid-phase reaction between LiOH·H2O and a Ti-rich material. The Ti-rich material ...containing 88.35% TiO2 was prepared from low-grade titanium slag via an upgrading process primarily involving alkaline roasting and acid leaching-hydrolysis. The parameters for the synthesis and acid treatment of the Li2TiO3 precursor were investigated. It was observed that monoclinic β-Li2TiO3 with good crystallization could be synthesized at 750°C with a Li/Ti molar ratio of 2.5. The adsorbent obtained under the optimized preparation conditions exhibited an excellent lithium adsorption capacity of up to 27.8mg/g in LiOH solution with a Li+ concentration of 2g/L, and the adsorption capacity stabilized at 23 to 24mg/g after several cycles. The adsorbent had better Li+ selectivity in the synthetic salt-lake brine solution. The separation coefficients of Li+ to Na+ and K+ reached 37.5 and 26.9, respectively.
•Low-grade titanium slag was upgraded by alkaline roasting and acid leaching-hydrolysis processes.•The obtained Ti-rich material was first used to prepare H2TiO3–lithium adsorbent.•The obtained lithium adsorbent has excellent lithium adsorption performance.
Microbubbles are 10–100-μm bubbles with unique properties that find applications in chemical reactions, water aeration, sewage purification, biomedicine, skincare, and mineral flotation. Here, we ...review microbubbles with focus on basics, analysis, preparation, and applications. Microbubbles preparation can be done by lowering the pressure, by breaking the gas phase, or by electrochemistry. We present applications for improving gas–liquid reactions, wastewater treatment, mineral flotation, drug delivery, drinks, hyperoxia therapy, aquaculture, and agriculture. Industrial use of microbubbles is actually limited by the preparation of stable and uniformly sized microbubbles at large scale.
Aromatic and functional polymers with processibility derived from biobased starting materials are prerequisite considering sustainable society. Poly(2,5‐benzimidazole)s are rigid‐rod polymers to show ...ultrahigh thermal stability such as flame retardance, while usually suffer from poor solubility. Here, poly(benzimidazole‐co‐amide)s are synthesized from two biobased monomers, 3,4‐diaminobenzoic acid and a semirigid comonomer, 4‐aminohydrocinnamic acid. The copolymers with an amide composition of 80 mol% and higher are soluble in widely used polar solvents to fabricate the films keeping high flame retardance, which is comparable with popular high‐performance polymers such as aromatic polyimides, polyetheretherketone, polyphenylene sulfide, etc.
Polybenzimidazole (ABPBI) possesses ultrahigh thermostability and chemical resistance, yet its applications are limited due to low solubility and processability. This issue is attempted to be solved by introducing flexibility in the polymer backbone through the copolymerization of two biobased monomers 3,4‐diaminobenzoic acid and 4‐aminohydrocinnamic acid. The resulting copolymer becomes soluble in widely used organic solvents while keeping high flame retardance and mechanical toughness.
