Ru/CeO2 catalysts with different amounts of surface oxygen vacancies were prepared by changing the morphology of CeO2. The conversion of Ce4+ to Ce3+ and the formation of Ru–O–Ce bonds led to ...enhancement of the amount of oxygen vacancies. Ru species of low crystallinity enriched with Ru4+ ions exist on the surface of CeO2 nanorods, while metallic Ru particles exist on CeO2 nanocubes. The low crystallinity of Ru species and high concentration of oxygen vacancies enhanced the adsorption of hydrogen and nitrogen and also led to desorption of surface hydrogen in the form of H2. Therefore, Ru/CeO2 nanorods showed high ammonia synthesis activities. On the contrary, lower catalytic activity was observed over Ru/CeO2 nanocubes catalyst because H2 and N2 adsorption was less favorable plausibly due to the large particle size of Ru species and low concentration of oxygen vacancies, and most of the hydrogen species were consumed in H2O formation.
Ammonia is an important chemical for synthesized fertilizers traditionally and for a potential energy vector increasingly. Industrial ammonia synthesis through the Haber–Bosch process is ...energy-intensive and requires advanced materials to catalyze ammonia synthesis under mild conditions, whereas the utilization of ammonia as a hydrogen carrier via ammonia decomposition is facing a similar situation as well. The developed second-generation Ru-based catalysts performs superior activities over commercial Fe- or Ni-based catalysts; however, it remains challenging to construct effective Ru catalysts to achieve the usage of Ru metal affordably as well as further understanding the nature of Ru catalysis. This Perspective summarizes the recent contributions in engineering Ru-based catalysts via various strategies and related catalysis in ammonia synthesis and decomposition, and it discusses the similarities and differences of Ru catalysis in these reactions. Finally, an overview of this area and opportunities for further investigation are also provided.
•An AuNPs based colorimetric method is developed for organophosphous pesticide analysis.•The detection mechanism is based on dissolution of AuNPs and AChE hydrolysis reaction.•The colorimetric method ...has high sensitivity and good stability.•The colorimetric method could be applied in aqueous solutions with high salinity.
A simple and sensitive colorimetric method is developed for organophosphrous pesticides (OPs) analysis based on the enzymatic hydrolysis reaction of acetylcholinesterase and the dissolution of gold nanoparticles (AuNPs) in Au3+-cetyltrimethylammonium bromide (Au3+-CTAB) solution. In the absence of OPs, the enzymatic hydrolysis product, thiocholine, would reduce Au3+ and protect the AuNPs from dissolution by the Au3+-CTAB. In the presence of OPs, however, the activity of AChE is inhibited, which could not or could only produce a small amount of thiocholine to consume the Au3+. In this case, the large amount of residual Au3+ dissolves the AuNPs and decreases both the concentration and size of the AuNPs, thus leading to an obvious red-to-light pink or red-to-colorless color change. Under optimal conditions, the colorimetric method could indicate the presence of OPs, with the concentration down to 0.7ppb. After loading AuNPs on a cellulose paper, an AuNPs-coated dipstick is developed for the detection of OPs, which is highly sensitive with an observable limit of detection of 35ppb. Practical sample analyses in tap water, apple washing solution, and sea water indicate the colorimetric method has acceptable accuracy and good stability, even in the system containing 5M of NaCl. Regarding these merits, the as-proposed method could be applied for the point-of-care analysis of OPs in complex systems.
The increase of alumina calcination temperature from 800 °C to 1300 °C results in the transformation of γ-Al2O3 to α-Al2O3 phase accompanying a decrease of specific surface area and the amount of ...tetrahedral Al3+ sites. Over Ru–Ba/alumina catalysts, an increase in alumina calcination temperature would broaden the size distribution of Ru particles, enlarge the metal-to-oxide ratio of Ru, decrease the amount of surface hydroxyl groups, as well as lower the temperature for N2 desorption. As a result, the increase of alumina calcination temperature lessens the effect of hydrogen poisoning and decreases the activation energy for ammonia synthesis. The Ru–Ba/Al2O3 catalyst with alumina calcined at 980 °C having both θ-Al2O3 and α-Al2O3 shows ammonia synthesis rate three times higher than that with alumina calcined at 800 °C having a γ-Al2O3 phase.
Abscisic acid (ABA) is known to play roles in regulating plant tolerance to various abiotic stresses, but whether ABA's effects on heat tolerance are associated with its regulation of heat stress ...transcription factors (HSFs) and heat shock proteins (HSPs) is not well documented. The objective of this study was to determine whether improved heat tolerance of tall fescue (
Schreb.) by ABA was through the regulation of HSFs and HSPs. ABA-responsive transcriptional factors, ABA-responsive element binding protein 3 (FaAREB3) and dehydration-responsive element binding protein 2A (FaDREB2A) of tall fescue, were able to bind to the
-elements in the promoter of tall fescue heat stress transcription factor A2c (Fa
). Exogenous ABA (5 μM) application enhanced heat tolerance of tall fescue, as manifested by increased leaf photochemical efficiency and membrane stability under heat stress (37/32 °C, day/night). The expression levels of
, several tall fescue
(
), and ABA-responsive transcriptional factors were up-regulated in plants treated with ABA. Deficiency of Arabidopsis heat stress transcription factor A2 (
) suppressed ABA-induction of
expression and ABA-improved heat tolerance in Arabidopsis. These results suggested that HSFA2 plays an important role in ABA-mediated plant heat tolerance, and FaAREB3 and FaDREB2A may function as upstream
-acting factors and regulate transcriptional activity of
and the downstream
, leading to improved heat tolerance.
A simple and easy-operation electrode modification strategy was proposed using Cu-MOF/GO nanohybrids for physiologists and pathologists for the feasible and reliable simultaneous electrochemical ...detections of DNA bases, namely guanine and adenine. The nanohybrids were prepared
via
a simple ultrasonic method and were employed for the fabrication of a sensing interface. SEM, TEM, XRD, FT-IR, and electrochemical characterizations were used to characterize the general morphology and structure of the nonohybrids. The proposed Cu-MOF/ERGO/GCE exhibited ultra-stable and high-sensitivity performance in the simultaneous electrochemical detection of guanine and adenine. The recorded DPV curves revealed a linear increase in the faradaic signals with increase in the concentrations of guanine and adenine in the range of 0.02-10 µM and 20-100 µM for guanine, and 0.005-20 µM and 40-200 µM for adenine. The relative standard deviation of guanine and adenine for 50 consecutive detections is 1.37% and 1.92%, respectively. It was proved that the proposed Cu-MOF/ERGO/GCE can be performed for the detection of guanine and adenine in real samples, such as Herring sperm DNA, and satisfactory results were obtained. This strategy does not require complicated modification procedures, professional modification techniques, or sophisticated instruments, but it can provide a highly sensitive and stable detection method, which is expected to expand and deepen the applications of electrochemical detection in life science research.
A simple and easy-operation electrode modification strategy was proposed using Cu-MOF/GO nanohybrids for physiologists and pathologists for the feasible and reliable simultaneous electrochemical detections of DNA bases, namely guanine and adenine.
This paper proposes a two-stage scheduling strategy for large-scale electric vehicles to reduce the adverse impact of the uncontrolled charging of the electric vehicles on the grid. Based on the ...statistical data of private car travel, the uncontrolled charging demand of individual electric vehicles and their aggregation are simulated. In the first stage, the electric vehicles and thermal power units are jointly scheduled. To minimize the total cost and standard deviation of the total load curve, the charging and discharging load guiding curve of the electric vehicles and the optimal output plans of the thermal power units in each period of the scheduled day are formulated. In the second stage, the electric vehicle load management and control centre formulates specific charging and discharging plans for the users through rolling optimization to follow the guiding load curve. The cost of vehicle discharge compensation is considered to improve the willingness of users to participate in scheduling and the user satisfaction. To avoid the "dimension disaster" caused by the centralized dispatching of large numbers of electric vehicles, the K-means clustering algorithm is used to divide the vehicles into different groups. Next, each group is scheduled as a unit, and the model is solved by using the particle swarm optimization algorithm. By comparing the optimization results of different scenarios, the feasibility and effectiveness of the proposed strategy are verified.
The industrial synthesis of ammonia (NH
) using iron-based Haber-Bosch catalyst requires harsh reaction conditions. Developing advanced catalysts that perform well at mild conditions (<400 °C, <2 ...MPa) for industrial application is a long-term goal. Here we report a Co-N-C catalyst with high NH
synthesis rate that simultaneously exhibits dynamic and steady-state active sites. Our studies demonstrate that the atomically dispersed cobalt weakly coordinated with pyridine N reacts with surface H
to produce NH
via a chemical looping pathway. Pyrrolic N serves as an anchor to stabilize the single cobalt atom in the form of Co
-N
that facilitates N
adsorption and step-by-step hydrogenation of N
to *HNNH, *NH-NH
and *NH
-NH
. Finally, NH
is facilely generated via the breaking of the *NH
-NH
bond. With the co-existence of dynamic and steady-state single atom active sites, the Co-N-C catalyst circumvents the bottleneck of N
dissociation, making the synthesis of NH
at mild conditions possible.
In the present work, LaCo1–x Ru x O3 perovskites (x = 0, 0.01, and 0.02) were synthesized, and the influences of the partial substitution of Co by Ru on the reducibility and structural properties of ...LaCoO3 perovskite were investigated by XRD, TPR, XPS, STEM, and XAFS techniques. The results indicate that Ru is incorporated into the LaCoO3 lattice, giving rise to a decrease of mean crystallite size as well as promotion of perovskite reducibility. At 450 °C and 1 MPa, LaCo0.98Ru0.02O3 shows an ammonia synthesis rate of 10.5 mmol/(gNH3·h) and insignificant decline of activity in a run of 50 h. On contrast, the ammonia synthesis rate over the Ru/LaCoO3 counterpart prepared by wet impregnation method gradually drops from 8.05 to 7.15 mmol/(gNH3·h). Moreover, there is strong synergy between Ru and Co species in LaCo0.98Ru0.02O3, affording enrichment of Ruδ+ clusters and surface Co2+ species that are beneficial to N2 adsorption and activation.
The spatial arrangements of Ti species would affect the electronic metal-support interactions and the proportion of Ce3+ sites for ceria-supported Ru catalysts. Ti-Surface-loaded CeO2 supported Ru ...catalysts exhibited excellent ammonia synthesis activity, which is attributed to a larger proportion of Ru metal, more electrons of Ru species and better adsorption ability of hydrogen and nitrogen.
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