Transition metal carbide nanocrystalline M3C (M: Fe, Co, Ni) encapsulated in graphitic shells supported with vertically aligned graphene nanoribbons (VA-GNRs) are synthesized through a hot filament ...chemical vapor deposition (HF-CVD) method. The process is based on the direct reaction between iron group metals (Fe, Co, Ni) and carbon source, which are facilely get high purity carbide nanocrystals (NCs) and avoid any other impurity at relatively low temperature. The M3C-GNRs exhibit superior enhanced electrocatalystic activity for oxygen reduction reaction (ORR), including low Tafel slope (39, 41, and 45 mV dec–1 for Fe3C-GNRs, Co3C-GNRs, and Ni3C-GNRs, respectively), positive onset potential (∼0.8 V), high electron transfer number (∼4), and long-term stability (no obvious drop after 20 000 s test). The M3C-GNRs catalyst also exhibits remarkable hydrogen evolution reaction (HER) activity with a large cathodic current density of 166.6, 79.6, and 116.4 mA cm–2 at an overpotential of 200 mV, low onset overpotential of 32, 41, and 35 mV, small Tafel slope of 46, 57, and 54 mV dec–1 for Fe3C-GNRs, Co3C-GNRs, and Ni3C-GNRs, respectively, as well as an excellent stability in acidic media.
Single nanocrystalline tungsten carbide (WC) was first synthesized on the tips of vertically aligned carbon nanotubes (VA-CNTs) with a hot filament chemical vapor deposition (HF-CVD) method through ...the directly reaction of tungsten metal with carbon source. The VA-CNTs with preservation of vertical structure integrity and alignment play an important role to support the nanocrystalline WC growth. With the high crystallinity, small size, and uniform distribution of WC particles on the carbon support, the formed WC–CNTs material exhibited an excellent catalytic activity for hydrogen evolution reaction (HER), giving a η10 (the overpotential for driving a current of 10 mA cm–2) of 145 mV, onset potential of 15 mV, exchange current density@ 300 mV of 117.6 mV and Tafel slope values of 72 mV dec–1 in acid solution, and η10 of 137 mV, onset potential of 16 mV, exchange current density@ 300 mV of 33.1 mV and Tafel slope values of 106 mV dec–1 in alkaline media, respectively. Electrochemical stability test further confirms the long-term operation of the catalyst in both acidic and alkaline media.
Developing cost-effective electrocatalysts operated in the same electrolyte for water splitting, including oxygen and hydrogen evolution reactions, is important for clean energy technology and ...devices. Defects in electrocatalysts strongly influence their chemical properties and electronic structures, and can dramatically improve electrocatalytic performance. However, the development of defect-activated electrocatalyst with an efficient and stable water electrolysis activity in alkaline medium remains a challenge, and the understanding of catalytic origin is still limited. Here, we highlight defect-enriched bifunctional eletrocatalyst, namely, three-dimensional iron fluoride-oxide nanoporous films, fabricated by anodization/fluorination process. The heterogeneous films with high electrical conductivity possess embedded disorder phases in crystalline lattices, and contain numerous scattered defects, including interphase boundaries, stacking faults, oxygen vacancies, and dislocations on the surfaces/interface. The heterocatalysts efficiently catalyze water splitting in basic electrolyte with remarkable stability. Experimental studies and first-principle calculations suggest that the surface/edge defects contribute significantly to their high performance.
The thermal conduction of suspended few-layer hexagonal boron nitride （h-BN） sheets was experimentally investigated using a noncontact micro-Raman spectroscopy method. The first-order temperature ...coefficients for monolayer （1L）, bilayer （2L） and nine-layer （9L） h-BN sheets were measured to be -（3.41 ± 0.12）× 10-2, -（3.15 ± 0.14） × 10-2 and -（3.78 ±0.16）× 10-2 cm-1.K-1, respectively. The room-temperature thermal conductivity of few-layer h-BN sheets was found to be in the range from 227 to 280 W.m-1-K-1, which is comparable to that of bulk h-BN, indicating their potential use as important components to solve heat dissipation problems in thermal management configurations.
The scarcity and high cost of platinum-based electrocatalysts for the oxygen reduction reaction (ORR) has limited the commercial and scalable use of fuel cells. Heteroatom-doped nanocarbon materials ...have been demonstrated to be efficient alternative catalysts for ORR. Here, graphene quantum dots, synthesized from inexpensive and earth-abundant anthracite coal, were self-assembled on graphene by hydrothermal treatment to form hybrid nanoplatelets that were then codoped with nitrogen and boron by high-temperature annealing. This hybrid material combined the advantages of both components, such as abundant edges and doping sites, high electrical conductivity, and high surface area, which makes the resulting materials excellent oxygen reduction electrocatalysts with activity even higher than that of commercial Pt/C in alkaline media.
Preeclampsia (PE) is a major cause of maternal mortality and morbidity worldwide. Although there has been great progress in the understanding of PE, the exact cause for the disease development is ...still unclear. Recently, studies showed that genetic deletion of ELABELA (ELA, also known as APELA) could induce PE-like symptoms in mice. However, the role of ELA in the disease development of PE remains elusive. Our objective was to measure the changes of ELA levels in maternal serum, urine, and placenta from preeclamptic pregnant women and healthy pregnant women and evaluate the correlation between ELA levels and the occurrence of PE. Additionally, we investigated the effect of ELA on the migration and proliferation of human trophoblast cells. ELA levels are significantly decreased in late-onset PE pregnancies compared with normal pregnancies. The mRNA and protein expressions of ELA and the apelin receptor (APLNR or APJ) in late-onset PE placental tissues are also decreased. Furthermore, our in vitro study showed that the addition of ELA significantly increased the invasion ability and proliferation of trophoblast cells, which were inhibited by the APJ-specific antagonist ML221. Our study identified ELA as significantly decreased in late-onset PE; therefore, it might play an important role in the pathogenesis of late-onset PE.
Minimizing exposure of the fetus to medication and reducing adverse off-target effects in the mother are the primary challenges in developing novel drugs to treat pregnancy complications. ...Nanomedicine has introduced opportunities for the development of novel platforms enabling targeted delivery of drugs in pregnancy. This review sets out to discuss the advances and potential of surface-functionalized nanoparticles in the targeted therapy of pregnancy complications. We first describe the human placental anatomy, which is fundamental for developing placenta-targeted therapy, and then we review current knowledge of nanoparticle transplacental transport mechanisms. Meanwhile, recent surface-functionalized nanoparticles for targeting the uterus and placenta are examined. Indeed, surface-functionalized nanoparticles could help prevent transplacental passage and promote placental-specific drug delivery, thereby enhancing efficacy and improving safety. We have achieved promising results in targeting the placenta via placental chondroitin sulfate A (plCSA), which is exclusively expressed in the placenta, using plCSA binding peptide (plCSA-BP)-decorated nanoparticles. Others have also focused on using placenta- and uterus-enriched molecules as targets to deliver therapeutics via surface-functionalized nanoparticles. Additionally, we propose that placenta-specific exosomes and surface-modified exosomes might be potential tools in the targeted therapy of pregnancy complications. Altogether, surface-functionalized nanoparticles have great potential value as clinical tools in the targeted therapy of pregnancy complications.
Mo2C nanocrystals (NCs) anchored on vertically aligned graphene nanoribbons (VA-GNR) as hybrid nanoelectrocatalysts (Mo2C–GNR) are synthesized through the direct carbonization of metallic Mo with ...atomic H treatment. The growth mechanism of Mo2C NCs with atomic H treatment is discussed. The Mo2C–GNR hybrid exhibits highly active and durable electrocatalytic performance for the hydrogen-evolution reaction (HER) and oxygen-reduction reaction (ORR). For HER, in an acidic solution the Mo2C–GNR has an onset potential of 39 mV and a Tafel slope of 65 mV dec–1, and in a basic solution Mo2C–GNR has an onset potential of 53 mV, and Tafel slope of 54 mV dec–1. It is stable in both acidic and basic media. Mo2C–GNR is a high-activity ORR catalyst with a high peak current density of 2.01 mA cm–2, an onset potential of 0.93 V that is more positive vs reversible hydrogen electrode (RHE), a high electron transfer number n (∼3.90), and long-term stability.
A three-dimensional nanoporous Ni(OH)2 thin-film was hydrothermally converted from an anodically formed porous layer of nickel fluoride/oxide. The nanoporous Ni(OH)2 thin-films can be used as ...additive-free electrodes for energy storage. The nanoporous layer delivers a high capacitance of 1765 F g–1 under three electrode testing. After assembly with porous activated carbon in asymmetric supercapacitor configurations, the devices deliver superior supercapacitive performances with capacitance of 192 F g–1, energy density of 68 Wh kg–1, and power density of 44 kW kg–1. The wide working potential window (up to 1.6 V in 6 M aq KOH) and stable cyclability (∼90% capacitance retention over 10 000 cycles) make the thin-film ideal for practical supercapacitor devices.
Due to the lack of highly efficient and low-cost oxygen reduction reaction/oxygen evolution reaction (ORR/OER) catalyst and alkaline anion exchange membrane (AEM), advanced rechargeable zinc-air ...batteries are largely hindered in many applications from wearable electronics to electric vehicles. Herein, a hybrid of porous Co3O4 anchoring on MnO2, then interpenetrating with CNTs (Co3O4/MnO2-CNTs) is synthesized via facile hydrothermal process, and an AEM (CS/EMImC-Co-EP/GO) employing semi-interpenetrating network structure is fabricated with a simple solution-casting method. The porous nanoparticles and chrysalis-like hybrid as well as strong bi-metallic coupling effect build highways and buffer zones for reactant and electrons transfer for ORR/OER. In addition, due to the competition of bottom Co atoms, the density functional theory (DFT) proves that the neighbor Mn sites (Mn1 and Mn2) of the MnO2(110) surface are evidently activated, which prompts the catalytic activity of hybrids by making the Mn1, Mn2 3d density of states move forward lower energy entirely. As a result, Co3O4/MnO2-CNTs exhibit superior ORR/OER activities with the low potential difference (ΔE) of 0.85 V and impressive performances in rechargeable aqueous zinc-air batteries (power density: 534 mW cm−2). Moreover, combining AEM integrated into rechargeable flexible all-solid-state zinc-air batteries and stack, the enhancement natures of wearable devices are achieved even under different bending angles benefiting from high hydroxyl anion conductivity and remarkable flexibility of AEM semi-interpenetrating network, which accelerates ion transport by the synergy of hopping and vehicle mechanisms. Furthermore, the flexible all-solid-state zinc-air batteries show excellent tolerance toxicity of CO2.
A high-performing flexible all-solid-state Zn-air battery is achieved by coordinated hierarchical chrysalis-like Co/Mn electrocatalyst and heterostructure GO-enhanced anion exchange membrane. Display omitted
•Co/Mn double oxide intertwined CNTs bifunctional chrysalis-like air cathodes have been developed.•The single Zn-air cell delivers a discharge peak power density over 500 mW/cm2, four times that using Pt/C.•The 3-cell Zn-air stack represents an advanced level consistency of each cell, which has not been reported previously.•°°°°°°The flexible batteries show strong durability to CO2 penetration due to the use of flexible anion-exchange membranes.•DFT proves that MnO2(110) surface are activated, making Mn1, Mn2 3d density of states move forward lower energy.
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