Latest ArticlesThe low cost and facile scalable exfoliation route for two-dimensional hexagonal boron nitride (h-BN) was still indispensable for potential applications. In this work, we presented a convenient and scalable exfoliation for few-layer BNNSs. Taking advantage of the advantages of swift heating of microwave and ultra low temperature vaporization of liquid nitrogen, bulk h-BN was high-efficiently exfoliated into fewlayer BNNSs. The as-exfoliated BNNSs had a 2-6 nm thickness and approximately 7.91% yield, exhibiting scalable, facile and environment-friendly features. Furthermore, the as-exfoliated BNNSs were applied as additive in oil for reducing friction of oil. The COF of the BNNSs-based grease reduced by 20.10% compared to grease, and the antiwear performance decreased by 55.8% and 45.1% relative to grease and h-BN-based grease.
Porous nanomaterials are classified as a kind of materials with great potential for development in the field of electrocatalysis, but there is still room for further improvement as catalysts. We develop a threedimensional (3D) porous structure of Cu/Cu2O as an electrocatalyst for the glucose oxidation reaction (GOR) using the method of calcining the precursor CuC2O4·2H2O in N2. The obtained porous Cu/Cu2O nanostructure can provide more opportunities for effective reactions between particles, which can explain their efficient electrocatalytic performance. Additionally, the as-synthesized Cu/Cu2O nanostructure exhibits outstanding electrocatalytic performance for the glucose, including good stability, excellent sensitivity and remarkable selectivity.
Herein, we have presented a novel and easy to operate seed-mediated system for fabricating gold bipyramids (AuBPs) with 85% yields without any separation/purification processes. The used gold seeds are reduced by tannin and citrate, two kinds of air stable ligands, and conventionally employed unstable NaBH4 are thoroughly cast off. In addition, the as-proposed gold seeds can also be employed for AuNRs fabrication with rather larger diameters (22.2-60.3 nm), which is difficult to be achieved by conventional seed mediated fabrication system.
Zeolites have been widely applied in many chemical processes owing to their featured microporous framework structures. Organic structure-directing agents (OSDAs) play an important role during of the formation of zeolite frameworks via non-bonding host-guest interactions. Understanding these interactions is crucial to the design of OSDAs and the synthesis of target zeolites. Here, we report a molecular simulation study in the host-guest interactions between zeolite framework STW and 21 alkylated imidazolium and pyrazolium cations that have been used as the OSDAs for the synthesis of STW-type zeolites. We find that OSDAs that have successfully directed the formation of STW exhibit stronger host-guest interactions than unsuccessful ones. Furthermore, we find all successful OSDAs possess relatively more negative atomic charges on nitrogen atoms and smaller dipole moments. According to this finding, we have designed seven new alkylated imidazolium and pyrazolium cations that may be suitable for zeolite STW, and verified their structure-directing capability by molecular simulation calculations.
The effective extracting Cr(VI) from chromite ore processing residue (COPR) is the key to achieve COPR detoxification and recovery. We developed an effective method to extract Cr(VI) from COPR via controlling the phase transformation of Cr(VI)-containing minerals. Characteristic analysis showed that Cr(VI) was mainly incorporated in the hydrocalumite (NaCa4Al2O6(SO4/CrO4)1.5·15H2O) in COPR, which was a layered-double hydroxide (LDH) with multilayer structure. In the hydrothermal treatment experiments, the Na2CO3 solution showed significant extraction effect of Cr(VI) and detoxification effect of COPR. After treatment, 95% of Cr(VI) was removed and the Cr(VI) concentration in the leachate was decreased to 1.6 mg/L by the toxicity characteristic leaching procedure (TCLP), within the regulatory limit disposal standard (HJ/T 301-2007, 3 mg/L). Further study revealed that, during the treatment, hydrocalumite transformed into calcite (CaCO3) under the effect of mineralizer, therefore, the layered structure collapsed and the incorporated Cr(VI) was released to the supernatant. Meanwhile, the Cr(VI) desorbed from calcite with the calcite particles grew into large size with smooth surface. Stir-flow experiment revealed that the amount of chromium released from CORP to the environment was significantly reduced after treatment, and it is safer for landfill disposal. This work will provide an instructive guidance for the detoxification and recovery of COPR.
Herein, we prepared novel three-dimensional (3D) gear-shaped Co3O4@C (Co3O4 modified by amorphous carbon) and sheet-like SnO2/CC (SnO2 grow on the carbon cloth) as anode and cathode to achieve efficient removal of 4-nitrophenol (4-NP) in the presence of peroxymonosulfate (PMS) and simultaneous electrocatalytic reduction of CO2, respectively. In this process, 4-NP was mineralized into CO2 by the Co3O4@C, and the generated CO2 was reduced into HCOOH by the sheet-like SnO2/CC cathode. Compared with the pure Co0.5 (Co3O4 was prepared using 0.5 g urea) with PMS (30 mg, 0.5 g/L), the degradation efficiency of 4-NP (60 mL, 10 mg/L) increased from 74.5%-85.1% in 60 min using the Co0.5 modified by amorphous carbon (Co0.5@C). Furthermore, when the voltage of 1.0 V was added in the anodic system of Co0.5@C with PMS (30 mg, 0.5 g/L), the degradation efficiency of 4-NP increased from 85.1%-99.1% when Pt was used as cathode. In the experiments of 4-NP degradation coupled with simultaneous electrocatalytic CO2 reduction, the degradation efficiency of 4-NP was 99.0% in the anodic system of Co0.5@C with addition of PMS (30 mg, 0.5 g/L), while the Faraday efficiency (FE) of HCOOH was 24.1% at voltage of -1.3 V using the SnO2/CC as cathode. The results showed that the anode of Co3O4 modified by amorphous carbon can markedly improve the degradation efficiency of 4-NP, while the cathode of SnO2/CC can greatly improve the FE and selectivity of CO2 reduction to HCOOH and the stability of cathode. Finally, the promotion mechanism was proposed to explain the degradation of organic pollutants and reduction of CO2 into HCOOH in the process of electrocatalysis coupled with advanced oxidation processes (AOPs) and simultaneous CO2 reduction.
Formaldehyde (HCHO) is one kind of common indoor toxic pollutant, the catalytic oxidation degradation of formaldehyde at room temperature is desired. In this work, a new single atomic catalyst (SAC), Al doped graphene, for the catalytic oxidation of HCHO molecules was proposed through density function theory (DFT) calculations. It is found that Al atoms can be adsorbed on graphene stably without aggression. Then HCHO can be effectively oxidized into CO2 and H2O in the presence of O2 molecules on Al doped graphene with a low energy barrier of 0.82 eV and releasing energy of 2.29 eV with the pathway of HCHO → HCOOH → CO → CO2. The oxidation reaction can happen promptly with reaction time τ = 56.9 s at the speed control step at room temperature. Therefore, this work proposed a high-performance catalyst Al-doped graphene without any noble metal for HCHO oxidation at ambient temperature, and corresponding oxidation pathway and mechanism are also deeply understood.
The biogeochemical transformation of gold (Au), i.e. its dissolution and re-precipitation, is critical in supergene transport of Au and formation of Au granules. Besides biogenic reduction, the formation Au granules can also be driven by chemical processes. Previous studies have showed the formation of Au nanoparticles (AuNPs) from ionic Au(Ⅲ) can be mediated by dissolved organic matter under sunlight. In this letter, we further demonstrated that these AuNPs can further slowly (in years) grow into visible Au granules. Different sized nano-flower and fractal dendrite-like branched gold structures (from tens of nanometres to over 100 μm) were observed in the Au granule sample. This growth of AuNPs into visible Au granules may play a critical role in the supergene mineralization and enrichment of secondary Au and drive the biogeochemical cycle of Au.
A new paradigm to remove toxic chromate anions from aqueous solution by crystallization of chromatewater clusters with imine-linked guanidinium cationic ligands is introduced. The guanidium-based cationic ligand was easily prepared through the imine condensation of an aldehyde and aminoguanidine hydrochloride. The cationic imine-linked guanidinium ligand (BBIG-Cl) showed a high removal capacity (292.5 mg/g) in the solutions. Rapid decontamination of chromate anions from the wastewater by this cationic ligand was resulted from an instantaneous crystallization. The produced guanidium chromate salts have an extremely low solubility (Ksp, BBIG = 8.19×10-9). Such superior removal performance of these materials was attributed to the charge-assisted hydrogen bonding between the cationic ligand and chromate-water hydrate anions, which was revealed by the single-crystal X-ray diffraction analysis and density functional theory (DFT) calculations. In addition, the successful recovery of the guanidium-based ligand makes it more attractive for real-world applications.
Fenton reaction is one of most promising approaches for efficient removal of various robust organic pollutants in wastewater, however it faces several intrinsic challenges such as acidic condition, sludge waste and sensitive to sulfide-containing compound. Here we reported a novel FeS1.92 as an efficient and sulfide resistant heterogeneous Fenton catalyst under mild condition. This novel FeS1.92 was facilely prepared through a mechanochemical synthesis of mackinawite (FeS) with sulfur powder (S) by ball milling. The sulfured mackinawite (FeS1.92) exhibits high performance in activating H2O2 to generate hydroxyle radicals for organic waste remediation. Furthermore, this FeS1.92 based heterogeneous Fenton catalyst is highly sulfide resistant and shows improved performance for degrading sulfide-containing organic pollutants. This study provides an effective mechanochemical approach to fabricate heterogeneous Fenton catalysts for sulfide-containing wastewater treatment.
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