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Early sex determination of Ginkgo biloba based on the differences in the electrocatalytic performance of extracted peroxidase
No full textGinkgo biloba is a dioecious plant. Male ginkgoes are mainly used in landscaping, while females are mainly used for fruit production. However, sex identification of ginkgo is a difficult task, especially at the seedling stage. In this work, we present for the first time the use of electrochemical techniques for the identification of ginkgo sex based on the differences in peroxides within male and female ginkgos. Graphene was used to concentrate peroxides in ginkgo extract, thereby improving electrochemical signal sensitivity. The electrochemical reduction of hydrogen peroxide catalyzed by peroxidase was used as a prob for sex determination in ginkgo. This electrochemical identification technique can be used not only for the analysis of adult ginkgo, but also successfully for the analysis of tissue culture seedlings and live seedlings. This electrochemical sensor has excellent discrimination ability due to the difference in peroxidase content in the leaves and petiole of ginkgo of different sexes. This electrochemical sensor allows for a rapid identification of the sex of ginkgo and has a very strong potential for field analysis. (c) 2021 Elsevier B.V. All rights reserved
Computational Screening of Single Atoms Anchored on Defective Mo2CO2 MXene Nanosheet as Efficient Electrocatalysts for the Synthesis of Ammonia
No full textThe electrochemical nitrogen reduction reaction (NRR) over single-atom catalysts (SACs) anchored on Mo vacancies of Mo2CO2 MXene nanosheets under ambient conditions suffers from poor selectivity, low yield, and low Faradaic efficiency because of their sluggish kinetics and the competing hydrogen evolution reaction. Herein, density functional theory calculations are performed to improve the understanding of the selectivity and yielding of ammonia through NRR over various isolated SACs, that is, from Sc to Au, anchored on the Mo vacancy of the Mo2CO2 MXene nanosheet (denoted as MO2CO2-M-SA). The potential-determining step of the NRR shows that eight candidates (i.e., Y, Zr, Nb, Hf, Ta, W, Re, and Os) confined on the defective Mo2CO2 layer could promote the electroreduction from N-2 to NH3. Among these, Mo2CO2-Y-SA presented the lowest reported reaction Presents the lowest reported reaction energy barrier (0.08 eV) through the distal pathway and high selectivity to NRR compared with the previously synthesized Mo2CO2-Ru-SA with a relatively high energy barrier (0.65 eV) and poor selectivity. In addition, the formation energy of Mo2CO2-Y-SA is more negative than that of the Mo2CO2-Ru-SA catalyst, suggesting that the experimental preparation of the Mo2CO2-Y-SA catalyst is highly feasible. This work lays a solid foundation for improving the rational design of MXene-based systems as efficient electrocatalysts for the synthesis of ammonia
Efficient and Stable Large-Area Perovskite Solar Cells with Inorganic Perovskite/Carbon Quantum Dot-Graded Heterojunction
No full textThis work reports on a compositionally graded heterojunction for photovoltaic application by cooperating fluorine-doped carbon quantum dots (FCQDs in short) into the CsPbI2.5Br0.5 inorganic perovskite layer. Using this CsPbI2.5Br0.5/FCQDs graded heterojunction in conjunction with low-temperature-processed carbon electrode, a power conversion efficiency of 13.53% for 1 cm(2) all-inorganic perovskite solar cell can be achieved at AM 1.5G solar irradiation. To the best of our knowledge, this is one of the highest efficiency reported for carbon electrode based all-inorganic perovskite solar cells so far, and the first report of 1 cm(2) carbon counter electrode based inorganic perovskite solar cell with PCE exceeding 13%. Moreover, the inorganic perovskite/carbon quantum dot graded heterojunction photovoltaics maintained over 90% of their initial efficiency after thermal aging at 85 degrees for 1056 hours. This conception of constructing inorganic perovskite/FCQDs graded heterojunction offers a feasible pathway to develop efficient and stable photovoltaics for scale-up and practical applications
Coordination-driven assembly of actinide-organic polyrotaxanes involving crown ether macrocycles (May, 10.1039/D1QO00536G, 2021)
No full textCompetitive Coordination of Chloride and Fluoride Anions Towards Trivalent Lanthanide Cations (La3+ and Nd3+) in Molten Salts
No full textMolten salt electrolysis is a vital technique to produce high-purity lanthanide metals and alloys. However, the coordination environments of lanthanides in molten salts, which heavily affect the related redox potential and electrochemical properties, have not been well elucidated. Here, the competitive coordination of chloride and fluoride anions towards lanthanide cations (La3+ and Nd3+) is explored in molten LiCl-KCl-LiF-LnCl(3) salts using electrochemical, spectroscopic, and computational approaches. Electrochemical analyses show that significant negative shifts in the reduction potential of Ln(3+) occur when F- concentration increases, indicating that the F- anions interact with Ln(3+) via substituting the coordinated Cl- anions, and confirm [LnCl(x)F(y)](3-x-y) (y(max)=3) complexes are prevailing in molten salts. Spectroscopic and computational results on solution structures further reveal the competition between Cl- and F- anions, which leads to the formation of four distinct Ln(III) species: [LnCl(6)](3-), [LnCl(5)F](3-), [LnCl(4)F(2)](3-) and [LnCl(4)F(3)](4-). Among them, the seven-coordinated [LnCl(4)F(3)](4-) complex possesses a low-symmetry structure evidenced by the pattern change of Raman spectra. After comparing the polarizing power (Z/r) among different metal cations, it was concluded that Ln-F interaction is weaker than that between transition metal and F- ions
Optical thermostability and weatherability of TiN/TiC-Ni/Mo cermet-based spectral selective absorbing coating by laser cladding
No full textIn the present work, a monolayer of micro-nano scale TiN/TiC-Ni/Mo ceramic solar spectral selective coating was deposited on the stainless steel substrate by laser cladding. The absorptance (alpha) and emittance (epsilon) of the coating prepared at the mixed scale of TiN/TiC-Ni/Mo were 80.1% and 2.24%, respectively. After annealing at 600 degrees C for 24 h, the absorptance increased to 80.8% and the emittance was 1.9%. The ratio of absorptance to emittance is alpha/epsilon = 42.52. This study showed that the thermal stability and optical properties of the ceramic coating was excellent under high temperature. It also provides a new idea for the preparation of solar absorbing coatings in the future
Chemical Composition and Corrosion Behavior of a-C:H/DLC Film-Coated Titanium Substrate in Simulated PEMFC Environment
No full textThe amorphous hydrogenated (a-C:H) film-coated titanium, using different CH4/H-2 and deposition times, was prepared by the ion beam deposition (IBD) method, which has the advantage of high adhesion because of the graded interface mixes at the atomic level. The chemical characterizations and corrosion behaviors of a-C:H film were investigated and evaluated by SEM, AFM, Raman spectroscopy, EPMA, TEM and XPS. An a-C:H film-coated titanium was corroded at 0.8 V, 90 degrees C in a 0.5 mol/L H2SO4 solution for 168 h. The metal ion concentration in the H2SO4 corrosion solution and the potentiodynamic polarization behavior were evaluated. Results indicate that a higher CH4/H-2 of 1:0 and a deposition time of 12 h can result in a minimum I-D/I-G ratio of 0.827, Ra of 5.76 nm, metal ion concentration of 0.34 ppm in the corrosion solution and a corrosion current of 0.23 mu A/cm(2). The current density in this work meets the DOE's 2020 target of 1 mu A/cm(2). Electrical conductivity is inversely proportional to the corrosion resistance. The significant improvement in the corrosion resistance of the a-C:H film was mainly attributed to the increased sp(3) element and nanocrystalline TiC phase in the penetration layer. As a result, the a-C:H film-coated titanium at CH4/H-2 = 1:0 with improved anti-corrosion behavior creates a great potential for PEMFC bipolar plates
Enhanced Thermoelectric and Mechanical Performances in Sintered Bi0.48Sb1.52Te3-AgSbSe2 Composite
No full textBismuth telluride alloys have dominated the industrial application of thermoelectric cooling, but the relatively poor mechanical performance of commercial zone-melting material seriously limits the device integration and stability. Here, we exhibit synergistically enhanced thermoelectric and mechanical performances of sintered Bi0.48Sb1.52Te3-AgSbSe2 composites. It is found that the increased hole concentration improves the S-2 sigma to 40 mu W cm(-1) K-2 at room temperature, and the emerged various defects effectively suppress the kappa(l) to 0.57 W m(-1) K-1 at 350 K. All effects harvest a highest ZT = 1.2 at 350 K along with an average ZT = 1.0 between 300-500 K in the x = 0.2 sample. Notably, AgSbSe2 addition not only optimizes the thermoelectric properties, but also enhances the mechanical performance with a Vickers hardness of 0.75 GPa. Furthermore, the isotropy of thermoelectric properties is also observably promoted by solid-phase reaction combined with high-energy ball milling and hot pressing. Our study reveals a viable strategy to improve the comprehensive performance of sintered bismuth telluride materials
Effective Corrosion Inhibition of Carbon Steel in Hydrochloric Acid by Dopamine-Produced Carbon Dots
No full textIn present study, novel nitrogen doped carbon dots (NCDs) are synthesized using a green material-dopamine-as a precursor and studied as corrosion inhibitors for Q235 carbon steel in 1 M HCl solution. According to the electrochemical results, it is found that NCDs acting as a mixed-type corrosion inhibitor can effectively retard the acid corrosion of carbon steel, and their inhibition efficiency increases with the concentration increasing from 50 to 400 ppm. The highest inhibition efficiency is 96.1% in the presence of 400 ppm NCDs at room temperature. Additionally, the adsorption of NCDs obeys the Langmuir adsorption isotherm. In addition, weight loss results show that the inhibition efficiency in the presence of 400 ppm NCDs increases with prolonged exposure time and rising temperature (298-328 K), owing to the strong adsorption of NCDs on the steel surface, and the eta value is 92.2% at 60 h of immersion and 86.2%, 89.1%, 90.6% and 92.9% at 298, 308, 318 and 328 K, respectively. Surface analysis by scanning electron microscope (SEM), laser scanning confocal microscope (LSCM) and X-ray photoelectron spectroscopy (XPS) further proves the formation of a protective NCD film on the steel surface
Rhodium Encapsulated within Silicalite-1 Zeolite as Highly Efficient Catalyst for Nitrous Oxide Decomposition: From Single Atoms to Nanoclusters and Nanoparticles
No full textThe size of metal species plays a pivotal role in governing catalytic performance of supported metal catalysts. In this work, a series of Rh encapsulated within silicalite-1 catalysts with different sizes were prepared by one-pot hydrothermal method and employed to catalyze the decomposition of N2O. Detailed structure determinations by HAADF-STEM, XPS and CO-DRIFTS demonstrate that subtle modulation of the encapsulated Rh species were achieved easily from single-atom to nanoclusters and nanoparticles by controlling the loading and reduction conditions of Rh. The turnover frequency (TOF) of N2O decomposition showed a typical volcano-type dependence on Rh size. Kinetic studies revealed that this structure-sensitive catalysis was related to the difference in N2O and O-2 adsorption/desorption for various Rh species. Furthermore, a Rh@S-1 catalyst with a proper Rh size (ca. 1.6 nm) was identified as the best-performing catalyst with a maximum TOF (ca. 95 h(-1)), showing much superior activity than other reported Rh-based catalysts