Silica particles were prepared by flame spray pyrolysis (FSP) as a support for nickel catalysts. The impact of precursor feed rate (3, 5 and 7 mL/min) during FSP on the silica characteristics and the ...ensuing effect on catalytic performance for the carbon dioxide, or dry, reforming of methane (DRM) was probed. Increasing the precursor feed rate: (i) progressively lowered the silica surface area from ≈340 m2/g to ≈240 m2/g; (ii) altered the silanol groups on the silica surface; and (iii) introduced residual carbon-based surface species to the sample at the highest feed rate. The variations in silica properties altered the (5 wt %) nickel deposit characteristics which in turn impacted on the DRM reaction. As the silica surface area increased, the nickel dispersion increased which improved catalyst performance. The residual carbon-based species also appeared to improve nickel dispersion, and in turn catalyst activity, although not to the same extent as the change in silica surface area. The findings illustrate both the importance of silica support characteristics on the catalytic performance of nickel for the DRM reaction and the capacity for using FSP to control these characteristics.
Ni‐based hydroxides are promising electrocatalysts for biomass oxidation reactions, supplanting the oxygen evolution reaction (OER) due to lower overpotentials while producing value‐added chemicals. ...The identification and subsequent engineering of their catalytically active sites are essential to facilitate these anodic reactions. Herein, the proportional relationship between catalysts’ deprotonation propensity and Faradic efficiency of 5‐hydroxymethylfurfural (5‐HMF)‐to‐2,5 furandicarboxylic acid (FDCA, FEFDCA) is revealed by thorough density functional theory (DFT) simulations and atomic‐scale characterizations, including in situ synchrotron diffraction and spectroscopy methods. The deprotonation capability of ultrathin layer‐double hydroxides (UT‐LDHs) is regulated by tuning the covalency of metal (M)‐oxygen (O) motifs through defect site engineering and selection of M3+ co‐chemistry. NiMn UT‐LDHs show an ultrahigh FEFDCA of 99% at 1.37 V versus reversible hydrogen electrode (RHE) and retain a high FEFDCA of 92.7% in the OER‐operating window at 1.52 V, about 2× that of NiFe UT‐LDHs (49.5%) at 1.52 V. Ni–O and Mn–O motifs function as dual active sites for HMF electrooxidation, where the continuous deprotonation of Mn–OH sites plays a dominant role in achieving high selectivity while suppressing OER at high potentials. The results showcase a universal concept of modulating competing anodic reactions in aqueous biomass electrolysis by electronically engineering the deprotonation behavior of metal hydroxides, anticipated to be translatable across various biomass substrates.
The selective and efficient electrooxidation of biomass substrates provides a route forward for the production of sustainable hydrocarbon chemistries and simultaneous green hydrogen. Here, ultrathin NiMn layered double hydroxides are engineered with oxygen defects for the selective conversion of 5‐HMF to 2,5‐FDCA (FE > 90%) well within the oxygen evolution reaction potential window, owing to the catalyst propensity toward deprotonation chemistry.
Zika virus (ZIKV), which can cause devastating disease in fetuses of infected pregnant women, can be transmitted by mosquito inoculation and sexual routes. Little is known about immune protection ...against sexually transmitted ZIKV. In this study, we show that previous infection through intravaginal or subcutaneous routes with a contemporary Brazilian strain of ZIKV can protect against subsequent intravaginal challenge with a homologous strain. Both routes of inoculation induced high titers of ZIKV-specific and neutralizing antibody in serum and the vaginal lumen. Virus-specific T cells were recruited to and retained in the female reproductive tract after intravaginal and subcutaneous ZIKV infection. Studies in mice with genetic or acquired deficiencies in B and/or T cells demonstrated that both lymphocyte populations redundantly protect against intravaginal challenge in ZIKV-immune animals. Passive transfer of ZIKV-immune IgG or T cells significantly limited intravaginal infection of naive mice, although antibody more effectively prevented dissemination throughout the reproductive tract. Collectively, our experiments begin to establish the immune correlates of protection against intravaginal ZIKV infection, which should inform vaccination strategies in nonpregnant and pregnant women.
The recent ZIKV epidemic resulted in devastating outcomes in fetuses and may affect reproductive health. Unlike other flaviviruses, ZIKV can be spread by sexual contact as well as a mosquito vector. While previous studies have identified correlates of protection for mosquito-mediated infection, few have focused on immunity against sexual transmission. As exposure to ZIKV via mosquito bite has likely occurred to many living in areas where ZIKV is endemic, our study addresses whether this route of infection can protect against subsequent sexual exposure. We demonstrate that subcutaneous ZIKV infection can protect against subsequent vaginal infection by generating both local antiviral T cell and antibody responses. Our research begins to define the immune correlates of protection for ZIKV infection in the vagina and provides a foundation for testing ZIKV vaccines against sexual transmission.
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•Cu oxidation state was tailored by heat treatment in a reducing (H2/Ar) atmosphere.•Initially present CuO was reduced to Cu2O by photoexcited electrons.•H2-treated metallic Cu was ...retained over the entire photocatalytic reaction.•Both Cu2O and metallic Cu on TiO2 are able to photocatalytically generate hydrogen, albeit by distinctly different mechanisms.
In-depth characteristic studies with H2 activity and theoretical calculations were used to reveal the copper oxidation states most effective for photocatalytic hydrogen production when loaded on TiO2. When the copper was originally present as CuO, photogenerated electrons initially reduced the Cu2+ to Cu+ in preference to proton reduction. The resulting Cu2O then behaved as a secondary photocatalyst on the TiO2 surface acting to improve the hydrogen production rate (1.4 times greater than neat TiO2). When the copper was originally present as Cu0, an improved hydrogen generation rate was also evident (2.4 times greater than Cu2O/TiO2) and the metallic state was retained over the course of the reaction. In this case, the Cu0 deposits function as a co-catalyst for proton reduction. The findings reconcile past disagreements associated with this system, demonstrating both Cu+ (following reduction from Cu2+) and Cu0 are able to photocatalytically generate hydrogen, albeit by distinctly different mechanisms.
Versatile superstructures composed of nanoparticles have recently been prepared using various disassembly methods. However, little information is known on how the structural disassembly influences ...the catalytic performance of the materials. Here we show how the disassembly of an ordered porous La
Sr
MnO
perovskite array, to give hexapod mesostructured nanoparticles, exposes a new crystal facet which is more active for catalytic methane combustion. On fragmenting three-dimensionally ordered macroporous (3DOM) structures in a controlled manner, via a process that has been likened to retrosynthesis, hexapod-shaped building blocks can be harvested which possess a mesostructured architecture. The hexapod-shaped perovskite catalyst exhibits excellent low temperature methane oxidation activity (T
=438 °C; reaction rate=4.84 × 10
mol m
s
). First principle calculations suggest the fractures, which occur at weak joints within the 3DOM architecture, afford a large area of (001) surface that displays a reduced energy barrier for hydrogen abstraction, thereby facilitating methane oxidation.
The influence of La-doping on Cu/ZnO catalyst for low-temperature water–gas shift reaction showed improvement on activation energy and stability of the catalysts to a certain extent, however La ...loadings above 2.3
wt% promoted H
2O adsorption at the expense of CO, thus lowering catalyst activity.
The influence of lanthanum (La) doping on the performance of 37
wt% Cu/ZnO catalysts for the low-temperature water–gas shift (LT-WGS) reaction was investigated. A 2.3
wt% La loading improved catalyst activity compared to the neat Cu/ZnO and Cu/ZnO/Al
2O
3 systems and was accompanied by a lowering of the activation energy. Higher La loadings promoted the adsorption of H
2O at the expense of CO, resulting in a decrease in LT-WGS activity. Additionally, 2.3
wt% La acted to stabilise catalyst activity compared with the neat Cu/ZnO. XPS and H
2-TPR assessment demonstrated a strong interaction between Cu and La components, while data from CO and H
2O-TPD studies favoured the associative WGS mechanism in this instance. Activity and stability findings also suggested metallic Cu was not responsible for LT-WGS activity.
Carbon nanofluids are engineered materials with controllable thermal and optical properties. Stable, high temperature operation (>20) of these fluids would enable them to improve upon – and ...eventually replace – pure fluids in many important commercial and industrial applications including applications in solar thermal collectors. To date, however, much of the nanofluids research focuses on low temperature (<100°C) applications and testing. For solar thermal collector applications, carbon nanofluids are uniquely well-suited due to their high absorptivity over the entire solar spectral range. This study pushes well beyond the 100°C mark by conducting a range of experiments to identify appropriate base fluids and functionalization methods to produce stable carbon nanotube (CNT)-based nanofluid dispersions at temperatures of up to 250°C to ensure their suitability for industrial heating applications (typically 100–250°C). Different forms of CNTs including, single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes were chemically functionalized to obtain stable dispersions in water, glycol and Therminol (a synthetic heat transfer oil). The stability of chemically functionalized carbon nanotube dispersions at different temperatures, 20, 80, 100, 150, 200 and 250°C, was investigated. The results of broadband UV–VIS–NIR spectroscopy showed no agglomeration in mildly oxidized multi-walled carbon nanotubes dispersed in Therminol when heated to 250°C, highlighting this low-cost composite medium as a potential candidate for use in high temperature nanofluid-based solar thermal collectors.
•High thermal stability is crucial for nanofluids used in solar thermal collectors.•The thermal stability of twenty seven CNT-based nanofluids was investigated.•A higher thermal stability was observed for MWCNTs than DWCNTs and SWCNTs.•KPS functionalized CNTs showed higher thermal stability than acid-treated CNTs.•KPS-MWCNTs were identified as a potential nanofluid for solar thermal applications.
Optimizing interfacial contact between graphene and a semiconductor has often been proposed as essential for improving their charge interactions. Herein, we fabricated bismuth vanadate-reduced ...graphene oxide (BiVO4/rGO) composites with tailored interfacial contact extents and revealed their disparate behavior in photoelectrochemical (PEC) and powder suspension (PS) water oxidation systems. BiVO4/rGO with a high rGO coverage on the BiVO4 surface (BiVO4/rGO HC) exhibited an 8-fold enhancement in the PEC photocurrent density with respect to neat BiVO4 at 0 V versus Ag/AgCl, while BiVO4/rGO with a low rGO coverage (BiVO4/rGO LC) gave a lesser 3-fold enhancement. In contrast, BiVO4/rGO HC delivered a detrimental effect, while BiVO4/rGO LC exhibited an enhanced performance for oxygen evolution in the PS system. The phenomenon is attributed to changes in the hydrophobicity of the BiVO4/rGO composite in conjunction with the interfacial contact configuration. A better BiVO4/rGO interfacial contact was found to improve the charge separation efficiency and charge transfer ability of the composite material, explaining the superior PEC performance of BiVO4/rGO HC. Additionally, optimization of the interfacial contact extent was revealed to further improve the energetics of the composite material, as evidenced by a Fermi level shift to a more negative potential. However, the high hydrophobicity of BiVO4/rGO HC arising from the higher rGO reduction extent triggered poor water miscibility, reducing the surface wettability and therefore hampering the photocatalytic O2 evolution activity of the sample. The study underlines water miscibility as a governing issue in the PS system.
The incursion of a plant pathogen into a new geographic area initiates a series of decisions about appropriate control or eradication efforts. Incomplete, erroneous, and/or selective information may ...be used by diverse stakeholders to support individual goals and positions on how an incursion should be managed. We discuss the complex social, political, and technical factors that shape a biosecurity response prior to reviewing information needs and common stakeholder misunderstandings. Selected examples focus on the rust fungi (order Pucciniales). We then explore how plant pathologists, as technical experts, can interact with biosecurity stakeholders to build empathy and understanding that in turn allows a shift from being a distant subject matter expert to an active participant helping to structure problems and shape knowledge flows for better outcomes.
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