Latest ArticlesThere is an urgent demand for tuning the selectivity and activity of the photocatalysts to remove co-existent pollutants simultaneously. Herein, we introduced the surficial activity sites into the bismuth oxybromide (BiOBr), including the Bi/Bi-O defects and hetero Cu atoms, and then the higher photocatalytic activity and selectivity of BiOBr were realized for degradation phenol and ciprofloxacin (CIP). It can be found that the Bi/Bi-O defects played more important role in enhancing the photocatalytic activity for degradation of phenol, while the Cu atoms significantly improved the photocatalytic activity for removing CIP. Moreover, the heterogeneous Cu atoms as the activity sites excited the reaction between phenol and CIP even under dark condition and were beneficial for synchronously removing phenol and CIP. This work provides a feasible way for BiOX photocatalyst to remove co-existent pollutants and may have a practical application.
Boron/nitrogen-co-doped carbon (BCN) nanosheets decorated with Fe2O3 nanocrystals (Fe2O3–BCN) were cast on a glassy carbon electrode (GCE) and applied as an electrochemical sensor to effectively detect paraquat (PQ), a toxic herbicide, in aqueous environments. A linear experiment performed using square wave voltammetry (SWV) under optimized experimental conditions produced a decent linear relationship and a low detection limit (LOD) of 2.74 nmol/L (S/N = 3). Repeatability, reproducibility, stability, and interference experiments confirmed that the Fe2O3–BCN/GCE system exhibited decent electrochemical sensing performance for PQ molecules. Notably, the designed sensor showed high selectivity and a decent linear relationship with PQ concentration in natural water samples. To the best of our knowledge, this is the first study on the preparation of Fe2O3–BCN nanosheets for PQ detection. The proposed sensor can be employed as an effective alternative tool for distinguishing and processing PQ.
To investigate the reactivity of homoatomic clusters [E9]4− (E = Si-Pb) and intermetalloid clusters [M@E9]−, the reactions of the Zintl anions [Sn9]4− and [Ni@Sn9]4− with the CdMes2 (Mes = Mesitylene) in the presence of 2.2.2-crypt were carried out. Two new compounds [K(2.2.2-crypt)]6[(Sn9)Cd(Sn9)].en (1) and [K(2.2.2-crypt)]6[(Ni@Sn9)Cd(Ni@Sn9)].en (2) were afforded. Both 1 and 2 were characterized by single-crystal X-ray diffraction, energy dispersive X-ray (EDX), and electrospray ionization mass spectrometry (ESI-MS), and can be viewed as two [Sn9]4− or [Ni@Sn9]4− subunits bridged by Cd ion in an η3: η3 coordination mode. Quantum chemical calculations reveal the relationships between the geometries and electronic structures of clusters 2a, [Ni3Ge18]4− and [Cu4@Sn18]4−. Further electron localization technique (AdNDP method) was performed to explain chemical bonding patterns of 1a.
Traditional methods of preparing metal-organic frameworks (MOFs) compounds have the disadvantages such as poor dispersion, inefficient and discontinuous process. In this work, microchannel reactor is used to prepare MOFs-derived zeolite-imidazole material via flash nanoprecipitation to form ZIF-67 + PEI(FNP), which reduces the MOF synthesis time down to millisecond time interval while keeping the synthesized ZIF-67 + PEI(FNP) highly dispersed. The Co@N–C(FNP)catalyst obtained by flash nanoprecipitation and carbonization has a higher Co content and thus more active sites for oxygen reduction reaction than the Co@N–C(DM) catalyst prepared by direct mixing method. Electrochemical tests show that the Co@N–C(FNP) catalyst prepared by this method has excellent oxygen reduction performance, good methanol resistance and high stability. The onset potential and half-wave potential of Co@N–C(FNP) are 0.92 VRHE and 0.83 VRHE, respectively, which are higher than that of Co@N–C(DM) (Eonset = 0.90 VRHE and E1/2 = 0.83 VRHE). Moreover, the Zn-air battery assembled with Co@N–C(FNP) as the cathode catalyst has high open circuit voltage, high power density and large specific capacity. The performance of these batteries has been comparable to that of Pt/C assembled batteries. Density functional theory (DFT) calculations confirm that the Co (220) crystal plane present in Co@N–C(FNP) have stronger adsorption energy than that of Co (111) crystal plane in Co@N–C(DM), leading to better electrocatalytic performance of the former.
Herein, phosphorus-mediated sulfur nanoparticles encapsulated in reduced graphene oxide nanosheets (P-SrGO-T) were successfully synthesized as the cathode for sodium ion battery by a ball milling and the following thermal treatment. A series of covalent bonds, such as P–S, C–S–C, C–O–P and C–S–P, are formed in this process, which are in favor of fixing the sulfur and suppressing the parasitic shuttle effect of polysulfide. Benefiting from the graphene sheets and these covalent bonds, a high reversible capacity of 637.4 mAh/g was achieved in P-SrGO-T after 100 cycles at the current density of 0.2 A/g. In addition, P-SrGO-T also delivers a high-rate capacity (330.7 mAh/g at 5 A/g) attributing to low charge transfer resistance and faster ion diffusion kinetic. This work pushes the progress forward in developing phosphosulfide cathode for sodium ion batteries.
Graphene oxide (GO) with one-atom-thick exhibit remarkable molecule sieving properties, but its low permeance flux renders it difficult to be applied in practice as a high-permeance separation membrane. In this study, we design complex membrane from covalently crosslinked GO, polydopamine (PDA), and 3-aminopropytriethoxysilane (APTES) as building blocks to fabricate the high-permeance GO-based membrane via the vacuum filtration method. A branched crosslinking product (PDA/APTES) working as a clamp grasped the hydrophilic functional groups (hydroxyl, epoxy, carboxyl) on GO for improving the GO membrane flux. The interlayer structure of the GO membrane was optimized according to the crosslinker concentration, reaction time, initial pH, and temperature for RGO/PDA/APTES (RGPA) in this study. At the optimized reaction conditions including the crosslinker concentration of 1.4 mL/L, the temperature of 80 ℃, the time of 16 h, and the initial pH of 8.5 for RGPA mixture, the interlayer gallery of RGPA membrane was effectively tunes, endowing high flux ranging from 11.98 L m−2 h−1 to 1823.97 L m−2 h−1. Besides, the RGPA membrane ensured the high rejections to dye solutions such as methylene blue (MB) (> 99%) and congo red (CR) (> 90%). Meanwhile, the superior reusable performance of the RGPA membrane was achieved, together with the rejections for MB and CR to 96.32% and 93.1% after 4 cycles, respectively. Also, the RGPA membrane possessed superior anti-fouling performances for bovine serum albumin (BSA) aqueous solution and excellent stabilities in harsh conditions (pH 3, 7 and 11). Grafting the crosslinker onto GO nanosheets exhibits the distinct advantages of achieving the high flux, high rejections to dyes, and superior reusable performance of membranes, posing a great application potential for membrane separation technology in wastewater treatment.
Chemotherapy is restricted by efficient drug outflow due to the multiple drug resistance (MDR) in heterogenous nature of tumor. Herein, we present a dual-responsive hyaluronic acid (HA) nanocomposite hydrogel that can not only response to the tumor microenvironment but also enhance chemotherapy. This HA hydrogel consists of a core-shell SiO2 (GOD@SiO2-Arg) and mesoporous silica nanoparticles (MSNs) with doxorubicin (DOX) as the cargo (DOX@MSN). It could rapidly release the GOD@SiO2-Arg nanoparticles at the low pH tumor-specific environment due to the cleavage of imine bond. GOD@SiO2-Arg activated by over-expressed glutathione (GSH) in tumor cells releases GOD due to the cleavage of disulfide bonds, which could oxidize glucose to produce hydrogen peroxide (H2O2) for in situ NO generation via reaction between Arg and H2O2. The validity of this study might provide a method to modulate the tumor microenvironment for enhancing chemotherapy.
Bimetallic catalysts usually exhibit better performance than monometallic catalysts due to synergistic effect. However, there is a lack of exploring the synergistic effect on catalytic performance caused by the introduction of inactive metal ion. In this work, we design a molecular model system that can precisely regulate the metal site number and catalytic property. When these molecular metal compounds are used as homogeneous catalysts for photocatalytic CO2 reduction, the dinuclear heterometallic CuNi-L2 shows the highest CO2-to-CO conversion, which is 2.1 and 3.0 times higher than that of dinuclear homometallic Ni2-L2 and mononuclear Ni-L1. Density functional theory calculations demonstrate that, in CuNi-L2, the introduction of inactive CuII is easier to promote the photo-generated electrons transferring to the coupled active NiII site to achieve the highest activity. In addition, this work also provides insights to design and construct more efficient bimetallic catalysts in future.
Low-cost and efficient oxygen reduction reaction (ORR) electrocatalysts are the key to developing Zn-air batteries for renewable energy storage. Herein, the Mn-N-P doped carbon sphere was prepared through polymerization of hexachlorotripolyphosphazene (HCCP) and phloroglucinol, and then followed the calcination at 900 ℃. Theory calculations demonstrated the introduction of Mn in N-P doped carbon could lower the dissociation barrier of O2 into O* and promote the ORR through a 4e− pathway. The as-prepared catalysts exhibited a half-wave potential of 0.82 V vs. RHE and limiting current density of 5.2 mA/cm2 toward ORR, which was comparable to those of the commercial Pt/C catalysts. In addition, Zn-air batteries with 0.05 Mn-N-P-C catalysts showed a high specific capacity of 830 mAh/gZn and excellent cycle stability. This facile approach demonstrated herein could be a solution to develop optimum non-precious metal catalysts for the application in cathodes of proton exchange membrane fuel cells. This study also provides new insight to design the catalysts of multi-heteroatom coordinated metal in the carbon matrix for both fundamental researches and practical applications.
Photocatalytic selective transform native lignin into valuable chemicals is an attractive but challenging task. Herein, we report a mesoporous sulfur-doped carbon nitride (MSCN-0.5) which is prepared by a facile one-step thermal condensation strategy. It is highly active and selective for the cleavage Cα−Cβ bond in β−O−4 lignin model compound under visible light radiation at room temperature, achieving 99% substrate conversion and 98% Cα−Cβ bond cleavage selectivity. Mechanistic studies revealed that the Cβ−H bond of lignin model compounds activated by holes and generate key Cβ radical intermediates, further induced the Cα−Cβ bond cleavage by superoxide anion radicals (•O2−) to produce aromatic oxygenates. Waste Camellia oleifera shell (WCOS) was taken as a representative to further understand the reaction mechanisms on native lignin. 33.2 mg of monophenolic compounds (Vanillin accounted for 22% and Syringaldehyde for 34%) can be obtained by each gram of WCOS lignin, which is 2.5 times as that of the pristine carbon nitride. The present work offers useful guidance for designing metal-free heterogeneous photocatalysts for Cα−Cβ bond cleavage to harvest monophenolic compounds.
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