The development of designing and searching inexpensive electrocatalysts with high activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is significant to enable ...water splitting as a future renewable energy source. Herein, we synthesize a new CoP(MoP)-CoMoO3 heterostructure coated by a N-doped carbon shell CoP(MoP)-CoMoO3@CN via thermal decomposition and phosphatizing of the CoMoO4·0.9H2O nanowires encapsulated in N-doped carbon. At 10 mA·cm–2, this CoP(MoP)-CoMoO3@CN nanocomposite exhibits superior electrocatalytic activity at low overpotentials of 296 mV for OER and 198 mV for HER in alkaline media. More importantly, we achieve a current density of 10 mA·cm–2 at 1.55 V by using this CoP(MoP)-CoMoO3@CN as both cathode and anode for overall water splitting. This promising performance could be due to the high activity of CoP(MoP)-CoMoO3 and the good conductivity of the external mesoporous N-carbon shell, which makes the CoP(MoP)-CoMoO3@CN nanowires a competitive alternative to noble-metal-based catalysts for water splitting.
Hepatitis C virus (HCV), a Hepacivirus, is a major cause of viral hepatitis, liver cirrhosis, and hepatocellular carcinoma. HCV envelope glycoproteins E1 and E2 mediate fusion and entry into host ...cells and are the primary targets of the humoral immune response. The crystal structure of the E2 core bound to broadly neutralizing antibody AR3C at 2.65 angstroms reveals a compact architecture composed of a central immunoglobulin-fold â sandwich flanked by two additional protein layers. The CD81 receptor binding site was identified by electron microscopy and site-directed mutagenesis and overlaps with the AR3C epitope. The x-ray and electron microscopy E2 structures differ markedly from predictions of an extended, three-domain, class II fusion protein fold and therefore provide valuable information for HCV drug and vaccine design.
Despite being technically possible, the hydrogen production by means of electrocatalytic water splitting is still practically unreachable mainly because of the lack of inexpensive and high active ...catalysts. Herein, a novel and facile approach by melamine polymerization, exfoliation and Co2+-assisted thermal annealing is developed to fabricate Co nanoparticles embedded in bamboo-like and nitrogen-rich carbonitride nanotubes (Co@NCN). The electronic interaction between the embedded Co nanoparticles and N-rich carbonitride nanotubes could strongly promote the HER performance. The optimized Co@NCN-800 exhibits outstanding HER activity with an onset potential of −89 mV (vs RHE), a large exchange current density of 62.2 μA cm–2, and small Tafel slope of 82 mV dec–1, as well as excellent stability (5000 cycles) in acid media, demonstrating the potential for the replacement of Pt-based catalysts. Control experiments reveal that the superior performance should be ascribed to the synergistic effects between embedded Co nanoparticles and N-rich carbonitride nanotubes, which originate from the high pyridinic N content, fast charge transfer rate from Co particles to electrodes via electronic coupling, and porous and bamboo-like carbonitride nanotubes for more active sites in HER.
Controlled integration of ultrafine metal nanoparticles （MNPs） and metal- organic frameworks （MOFs） has drawn much attention due to their unique physical and chemical properties. However, the ...development of a one-step strategy for preparing ultrafine MNPs within MOFs still remains a great challenge. Herein, a facile synthetic approach toward the abovementioned composites was developed. In contrast to the conventional approach, these hybrids were prepared by the direct mixing of metal and MOF precursors in the reaction solution assisted by microwave irradiation. Impressively, the Au/MOF-199 composite with uniformly distributed ultrafine Au nanoparticles could be fabricated in only two minutes, and the Au loading could be increased up to a level of 5.13%. The multifunctional Au/MOF-199 catalysts exhibited high turnover numbers （TONs） and turnover frequencies （TOFs） in the three-component coupling reaction of formaldehyde, phenylacetylene, and piperidine （AB-coupling）. Owing to the confinement effect of MOF-199, the 5.13%Au/MOF-199 catalyst could be recycled for five runs without serious loss of activity, with no obvious aggregation of Au NPs detected.
A silicon carbide shielded fin-shaped gate metal-oxide-semiconductor field effect transistor (SF-MOS) is proposed in this letter, which utilizes a well-grounded p-region to shield the fin-shaped ...trench gate. Numerical simulations by Sentaurus TCAD are carried out to study the performance of SF-MOS, and comparisons with conventional trench MOSFET and the state-of-the-art double-trench MOSFET are presented. The maximum electric field in gate oxide of the SF-MOS is effectively lowered to below 3 MV/cm, which is a widely accepted criterion for long-term gate oxide reliability. Furthermore, with the shielding effects, the gate-to-drain charge of the SF-MOS is significantly reduced, leading to lower switching loss.
Auxiliary-source bond wires and connections are widely used in power modules with paralleled mosfets or insulated gate bipolar transistor (IGBTs). This paper investigates the operation mechanism of ...the auxiliary-source connections in multichip power modules. It reveals that the auxiliary-source connections cannot fully decouple the power loop and the gate loop such as the Kelvin-source connection, owing to their involvement in the loop of the power source current. Three effects of the auxiliary-source connections are then analyzed, which are 1) the common source stray inductance reduction, 2) the transient drain-source current imbalance mitigation, and 3) the influence on the steady-state current distribution. Finally, simulations and experimental results validate the theoretical analysis.
Background: Competition for freshwater between cities and agriculture is projected to grow due to rapid urbanization, particularly in the Global South. Water reallocation from rural to urban regions ...has become a common strategy to meet freshwater needs in growing cities. Conceptual issues and associated measurement problems have impeded efforts to compare and learn from global experiences. This review examines the status and trends of water reallocation from rural to urban regions based on academic literature and policy documents. Methods: We conduct a systematic literature review to establish the global reallocation database (GRaD). This process yielded 97 published studies (academic and policy) on rural-to-urban reallocation. We introduce the concept of reallocation 'dyads' as the unit of analysis to describe the pair of a recipient (urban) and donor (rural) region. A coding framework was developed iteratively to classify the drivers, processes and outcomes of water reallocation from a political economy perspective. Results: The systematic review identified 69 urban agglomerations receiving water through 103 reallocation projects (dyads). Together these reallocation dyads involve approximately 16 billion m3 of water per year moving almost 13 000 kilometres to urban recipient regions with an estimated 2015 population of 383 million. Documented water reallocation dyads are concentrated in North America and Asia with the latter constituting the majority of dyads implemented since 2000. Synthesis: The analysis illustrates how supply and demand interact to drive water reallocation projects, which can take many forms, although collective negotiation and administrative decisions are most prevalent. Yet it also reveals potential biases and gaps in coverage for parts of the Global South (particularly in South America and Africa), where reallocation (a) can involve informal processes that are difficult to track and (b) receives limited coverage by the English-language literature covered by the review. Data regarding the impacts on the donor region and compensation are also limited, constraining evidence to assess whether a water reallocation project is truly effective, equitable and sustainable. We identify frameworks and metrics for assessing reallocation projects and navigating the associated trade-offs by drawing on the concept of benefit sharing.
Improving the hydrogen evolution reaction (HER) performance of Pt based catalysts in alkaline environment is of key importance in various industrial processes and remains a challenge so far. Given ...the lower energy barriers of water dissociation upon the undercoordinated Pt and oxophilic species, engineering Pt based catalysts possessed the high density of surface atomic steps, ledges, and kinks with Ni(OH)2 are an effective way to endow Pt with high catalytic HER activity. Based on density functional theory (DFT) models, we demonstrated that the energy barrier of water dissociation process could be significantly reduced by the synergistic effect of undercoordinated Pt atoms and defective Ni(OH)2. This hypothesis has been further validated by experimental results that concave nanocube (CNC) Pt-Mn particles exposed by high indexed facets (HIFs) supported on the Ni(OH)2 nanosheets exhibited 6.88 times specific current density (4.80 times mass current density) higher than nanocube Pt-Mn particles mainly exposing non-defective surface. Moreover, the in situ electrochemical etching experiments suggested that the enhanced HER performance was attributed to the synergistic effect of Ni(OH)2 and Pt, rather than the increase of active sites for Pt via calculating the electrochemical surface area (ECSA) values. Thus, this work provides an insight for rational design of Pt based nanocomposite with enhanced catalytic properties for alkaline HER under the guidance of computational modeling.
The synergistic effect between undercoordinated Pt atoms and defective Ni(OH)2 nanosheets has an benefit on water dissociation in alkaline solution, in which the specific current density (mass current density) of concave cube (CNC) Pt-Mn/Ni(OH)2 for HER is 6.88 (4.80) times higher than that of nanocube Pt-Mn catalyst. Display omitted
•The undercoordinated Pt atoms has a benefit on higher HER performance, resulting from lower energy barrier for water dissociation.•The HER performance in basic solution can be further enhanced at the interface of undercoordinated Pt atoms and defective Ni(OH)2 by reducing water dissociation barrier.•Introduction of moderate Ni(OH)2 nanosheets can inspire the activity of Pt on HER.
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•After combining PtNi with Ni(OH)2, PtNi restructures.•The open-framework structure exposed more active sites for both HER and MOR.•Ni(OH)2 contribute to obvious enhancement of ...activity and stability for HER.•PtNi/Ni(OH)2 with an enhanced CO tolerance led to better performance for MOR.
Due to the negative impact of overusing traditional fossil fuels on the environment, electrochemical reactions that can minimize the generation of toxic materials during the process, including hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR), have been drawing increasing attention. In order to get more outstanding catalysts for both HER and MOR, we combined well-defined PtNi concave nanocubes (CNCs) bounded by high-index facets (HIFs) with Ni(OH)2 nanosheets via a facile hydrothermal process and successfully obtained hybrid PtNi/Ni(OH)2−x, where x means the initial mass of Ni(OH)2 in the synthesis. Remarkably, after the combination, the smooth surfaces of as-prepared PtNi CNCs were transmuted into rough ones made up of PtNi nanospheres (5–7 nm), with Ni(OH)2 nanosheets serving as the substrate. Therefore, benefiting from the merging step, the open-framework structure with more active sites exposed was formed. Besides, the unique synergistic effect and electronic effect inside PtNi alloy and between PtNi to Ni(OH)2, as well as the appropriate mass ratio of the two components make PtNi/Ni(OH)2-4.0 an excellent electrocatalyst with enhanced activity and promoted stability for both HER and MOR, which is superior to that of commercial Pt black and PtNi CNCs enclosed by HIFs. We believe that this work may potentially be applied in effective electrocatalyst construction and energy conversion.
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