MXenes have recently emerged as a new class of electrocatalysts for diverse energy conversion reactions, but they are generally considered to be catalytically inert. Herein, a strategy of interfacial ...polarization is put forward to improve the catalytic activity of MXenes, with the construction of an interfacial structure consisting of black phosphorus (BP) nanoflakes and Nb2C MXene nanosheets for electrochemical nitrate reduction to ammonia as a proof of concept. The experimental and computational results reveal that a strong interfacial polarization is built between BP nanoflakes and Nb2C nanosheets in the prepared BP/Nb2C composite. The polarization of Nb centers by adjacent BP sites gives rise to the formation of positively centered Nb atoms and BP‐polarized Nb atoms, which synergistically catalyze the cleavage of N–O bonds in HNO2* to form NO*. In addition, the stabilization of monatomic *N by the BP/Nb2C composite is also enhanced compared with BP nanoflakes and Nb2C nanosheets. As a result, both the ammonia yield rate and Faraday efficiency of the BP/Nb2C composite are much higher than that of BP nanoflakes and Nb2C nanosheets. Overall, this work shows the great potential for constructing a strong interfacial polarization to improve the catalytic performance of MXenes‐based electrocatalysts.
The study reveals that the interfacial polarization between black phosphorus (BP) nanoflakes and Nb2C nanosheets is vital to the enhanced nitrate reduction performance of the BP/Nb2C composite. The resulting black phosphorus‐polarized Nb and positively centered Nb tend to bind with both sides of N–O bonds in HNO2*, respectively, synergistically promoting the cleavage of N–O bonds to form NO*.
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•α-MnO2 nanorods have been in-situ supported on 3D-G via a facile hydrothermal method.•α-MnO2 nanorods are evenly deposited on 3D-G surface which possesses more defects.•The ...synergistic interaction between α-MnO2 nanorods and 3D-G improve ORR performance.•α-MnO2/3D-G catalyst exhibites excellent activity and durability for ORR in MFCs.
Magnesium-air fuel cells are considered as a potential energy conversion device owing to a high theoretical specific capability, economic viability and environmental friendliness. In this work, α-MnO2 nanorods are supported on three-dimensional graphene (3D-G) which is fabricated with coal tar pitch as the carbon precursor and MgO as the template via hydrothermal reaction. The synergistic interactions between α-MnO2 nanorods and 3D-G improve the activity and durability performance for oxygen reduction reaction in 0.1 mol L−1 KOH solution. α-MnO2/3D-G exhibits a high half-wave potential (0.81 V) and superior to α-MnO2/C (0.72 V) and α-MnO2/rGO (0.76 V), and close to 20 wt% Pt/C (0.83 V). α-MnO2/3D-G also possesses higher durability than commercial Pt/C. Furthermore, the magnesium-air fuel cells based on α-MnO2/3D-G, air-cathode display the peak power density (106.2 mW cm−2), and continuously durability (discharge for 16 h at 50 mA cm−2 with the mere decay of cell voltage by 7.6%). These results prove that α-MnO2/3D-G catalyst with high activity and durability can be a promising electrocatalyst in magnesium-air fuel cells.
Attenuated Salmonella can invade tumor cells and acts as a eukaryotic expression vector for gene propagation. We constructed a bi-gene, eukaryotic co-expression DNA vaccine of Mycobacterium ...tuberculosis heat shock protein 70 (mtHSP70) and Herpes simplex virus-thymidine kinase (HSV-tk) and used attenuated Salmonella as a vector to treat murine melanoma. In vitro, recombinant Salmonella can carry plasmid stably and can invade into the cytoplasm of B16 tumor cells expressing the protein of the mtHSP70/HSV-tk gene by Western blot assay. In vivo, after the recombinant Salmonella was injected into tumors, the HSV-tk precursor drug ganciclovir (GCV) was administered to start the HSV-tk killing of tumor cells. We found that the mtHSP70/HSV-tk recombinant bacteria can raise CD8+ T lymphocytes in peripheral blood by flow cytometry and in tumor tissues by immunofluorescence detection, increase IFN‑γ contents in tumor tissue by ELISA and significantly suppress tumor growth.
MnO2 nanorods adsorbed with different supports (non-support, carbon black, and MWCNTs) were prepared through hydrothermal method for magnesium–air fuel cells (MAFCs). The morphological ...characteristics of the catalysts indicate that the combination modes of nanorods and MWCNTs are parallel, cross, and bend intersect, which provide a large surface areas and enhance electron transfer process. X-ray diffraction pattern illustrates the crystal form of MnO2, and X-ray photoelectron spectroscopy reveals that the existing form of manganese is Mn4+. The ORR performance investigated using a rotating disk electrode shows that the initial reduction potential of MnO2/C and MnO2/MWCNTs in the LSV curves are −0.02 and 0.03 V vs. Hg/HgO (+0.098 V vs. NHE), respectively. The electron transfer number of MnO2/MWCNTs is 3.86, which corresponds to four electrons. In the I–t curves, the oxygen reduction current density of MnO2/MWCNTs decreases by 18.1% and MnO2/C decays by 27.9% after 60 h. The CVs reveal that the current density losses of MnO2/MWCNTs and MnO2/C are 0.4 and 0.8 mA cm−2 after scanning for 5000 cycles. The potential values of the air electrode loaded with MnO2/C and MnO2/MWCNTs catalysts are −0.78 and −0.62 V vs. SCE, respectively, at 150 mA cm−2, respectively. The discharge performance of a single-chamber MAFC shows that the peak power densities of MnO2/C and MnO2/MWCNTs are 60.95 and 70.47 mW cm−2, respectively, 20 °C in 10 wt% NaCl solutions. The single cells of MnO2/MWCNTs can continuously discharge for more than 24 h at a current density of 20 mA cm−2. The EIS proves that the conductivity of MnO2/MWCNTs is higher than MnO2/C.
•MnO2 nanorod adsorbed with supports (non-support, carbon black, and MWCNT) is prepared.•Structures between nanorod and MWCNT are parallel, cross and bend intersect.•The MnO2/MWCNTs possess good ORR performance and durability.•The magnesium–air cell of MnO2/MWCNTs has excellent discharge performance and stability.
Three-dimensional nitrogen-doped graphene (3D-NG@SiO2) is prepared by pyrolyzing poly (o-phenylenediamine) (POPD) with high nitrogen content. POPD is prepared via an in situ chemical oxidation ...polymerization of o-phenylenediamine (OPD) in acetic acid with silica colloid as templates. The optimum parameter is OPD:SiO2 = 1:2, pyrolysis @ 900 °C. SEM and TEM images show the wrinkled and porous graphene structures. Raman spectra indicate that 3D-NG@SiO2 consists of 4–6 layers graphene. N2 adsorption–desorption isotherms reveal that the pore size distributions mainly centralize at 5–10 nm. XRD illustrates the amorphous structure. XPS analysis shows that the nitrogen content is 3.6% and nitrogen mainly exists in the form of pyridinic nitrogen and pyrrolic nitrogen. The oxygen reduction reaction (ORR) performance investigated using a rotating disk electrode shows that the initial potential of 3D-NG@SiO2 is 0.08 V (vs. Hg/HgO). The electron transfer number is 3.92 @ −0.3 V (vs. Hg/HgO), indicating that 3D-NG@SiO2 mainly occurs via a four-electron process. The oxygen reduction current density decreases by 21% after 60 h in the chronoamperometry test. The CVs manifests a current density loss of 0.16 mA cm−2 after scanning for 5000 cycles. The high activity and durability indicate the promising potential of 3D-NG@SiO2 as ORR catalysts.
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•3D-NG@SiO2-2-900 is prepared by pyrolyzing POPD, with silica colloid as templates.•The number of graphene layers and the pore diameter of 3D-NG@SiO2 are controllable.•3D-NG@SiO2-2-900 has super ORR catalytic performance and durability in 0.1 M KOH.•High porosity, many planar nitrogen and mass transmission channel benefit the ORR.
Cerium sulfophenyl phosphate (CeSPP) doped polybenzimidazole (PBI) composite membranes were prepared by hot-pressing method as promising candidates for high temperature proton exchange membranes. In ...order to improve the oxidative stability of the composite membrane (PBI/CeSPP), the active vicinal diamino groups on polymer ends were protected by transformation into benzimidazolones. It was found that the membranes prepared from end-group protected PBI (e-PBI) had an evidently enhanced oxidative stability in comparison with the membrane made from unprotected PBI (u-PBI). CeSPP was found to be well dispersed in the polymer matrix due to its organic-inorganic nature and the strong ionic/hydrogen bonding between PBI and it. The composite membrane exhibited good mechanical strength and thermal stability up to 200 °C. The temperature and relative humidity dependence of the proton conductivity was investigated. The proton conductivity of e-PBI/CeSPP (25 wt%) at 180 °C reached 0.11, 0.039 and 0.0024 S cm−1 at 100%, 50% and 0 relative humidity, respectively.
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•e-PBI with higher oxidative stability was prepared by end-group protection of PBI.•Homogeneous e-PBI/CeSPP composite membranes were prepared by hot-pressing.•Strong hydrogen bonding network was formed in the composite membranes.•Good proton conductivity was achieved at different humidity at high temperature.
The electrocatalytic reduction of CO2 is deemed to be a promising method to ease environmental and energy issues. However, achieving high efficiency and selectivity of CO2 electroreduction remains a ...bottleneck due to huge limitation of CO2 mass transfer and competition of hydrogen evolution reaction (HER) in aqueous solution. In this work, we propose to utilize triple-phase interface engineering over an In2O3 electrode to enhance its CO2 reduction reaction (CO2RR) performance. Notably, distinguishing from other research studies (doping, defect introduction, and heterojunction construction) that regulate the nature of In2O3-based catalysts themselves, we herein tune interfacial wettability of In2O3 using facile fluoropolymer coating for the first time. In contrast to the hydrophilic In2O3 electrode Faraday efficiency (FE)HCOOH ∼ 62.7% and FEH2 ∼ 24.1% at −0.67 V versus RHE, the hydrophobic fluoropolymer (taking polyvinylidene fluoride as an example)-coated In2O3 electrode delivers a significantly enhanced FEHCOOH of 82.3% and a decreased FEH2 of 5.7% at the same potential. Upon combining contact angle measurements, density functional theory calculation, and ab initio molecular dynamics simulation, the enhanced CO2RR performance is revealed to be attributed to the rich triple-phase interfaces formed after fluoropolymer coating as an “aerophilic sponge”, which increases the local concentration of CO2 near In2O3 active sites to improve CO2 reduction and meanwhile reduces the accessible water molecules to suppress competitive HER. This work presents a feasible approach for the enhanced selectivity of HCOOH yield over In2O3 by triple-phase interface engineering, which also provides a convenient and effective method for developing other materials used in gas-consumption reactions.
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•It is the first study on microbial diversity during persimmon wine fermentation.•Functional core microbiota was identified during the fermentation of persimmon wine.•Spontaneous ...fermentation increased the proportion of esters in persimmon wine.•Hanseniaspora and Rhodotorula play important roles in volatile compounds formation.
In this study, we determined the composition of microorganisms in the spontaneous/inoculated fermentation process of persimmon (Diospyros kaki L., China) wine for the first time and compared the similarities and differences of microbial succession, change in volatile compounds, and variations in amino acids. We found that spontaneous persimmon wine fermentation (SPF) resulted in lower bacterial community diversity and higher fungi community diversity than inoculated persimmon wine fermentation (IPF). SPF increased the proportion of esters in overall volatile compounds (29.9 % vs 18.9 %) at the end of fermentation. According to partial least squares (PLS, VIP > 1.0) analysis and Spearman’s correlation analysis, 18 (11 bacterial and 7 fungus) were identified as the functional core microbiotas in SPF. Among them, indigenous Saccharomyces, Hanseniaspora, Rhodotorula, Leuconostoc, and Lactobacillus play an important role in the formation of volatile compounds and are worthy of further study, while Escherichia-Shigella, Ralstonia and Zoogloea should be inhibited during the fermentation process. However, a key problem in SPF was the fermentation time, which was too long (about 27 days) and did not meet the needs of industrial production. Overall, the results showed the possibility of considering select indigenous aroma-producing microorganisms as persimmon wine fermentation starters to improve the unique characteristics of persimmon wine.
Poly4,4′-(diphenyl ether)-5,5′-bibenzimidazole (oPBI) based high temperature proton exchange membranes are prepared by covalent cross-linking with chloromethylated polysulfone (CMPSU) and doping with ...zirconium phytate (ZrPA). ZrPA is synthesized as the proton conductor through a facile method from zirconyl chloride and phytic acid which is abundant and readily available. oPBI is cross-linked by CMPSU and that hydrogen bonds are formed between ZrPA and oPBI-CMPSU. The composite membranes are dense without through holes when doping with ZrPA. The composite membranes exhibit good thermal stability below 140 °C. Meanwhile, the composite membranes reveal good mechanical strength and methanol resistance. The oxidative stability is improved because of cross-linking and the doping of ZrPA. Conductivities of oPBI-CMPSU/ZrPA at different temperatures and relative humidity (RH) are investigated. At 100% RH, 50% RH and 0 RH, the conductivity of oPBI-CMPSU(20%)/ZrPA(30%) can reach 0.072 S/cm, 0.025 S/cm and 0.012 S/cm at 140 °C, respectively. Although the proton conductivity of the composite membrane was not particularly high at 100% RH, the composite membrane comparatively exhibited good proton conductivity at high temperature and at 50% RH and 0 RH.
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The current theories of antimalarial mechanism of artemisinin are inadequate to fully explain the observed effects. In our study, "organism-like" formation of Schistosoma hemozoin granules by ...attaching to and utilizing erythrocytes to form new ones was observed. This indicates that heme iron is transferred from erythrocytes to hemozoin granules during their formation. However, as a disposal product of heme detoxification, these granules are not completely expelled from the Schistosoma gut, but decomposed again between microvilli in the posterior portion of the gut to transfer iron to eggs. Based on the function of iron transport supported by our observation of the unique process of Schistosoma hemozoin formation, here we propose a new viewpoint of antimalarial mechanism of artemisinin, which emphasizes the final outcome, i.e., interference of iron utilization in parasites by artemisinin, instead of focusing on the mode of interaction between artemisinin and heme or hemozoin. This suggests that artemisinin and its endoperoxides derivatives likely hit the Achilles' heel of hemozoin-producing and iron-dependent organisms.
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