Dynamic evolution of the active center driven by hemilabile coordination in Cu/CeO2 single-atom catalyst

Abstract Hemilability is an important concept in homogeneous catalysis where both the reactant activation and the product formation can occur simultaneously through a reversible opening and closing of the metal-ligand coordination sphere. However, this effect has rarely been discussed in heterogeneous catalysis. Here, by employing a theoretical study on CO oxidation over substituted Cu1/CeO2 single atom catalysts, we show that dynamic evolution of metal-support coordination can significantly change the electronic structure of the active center. The evolution of the active center is shown to either strengthen or weaken the metal-adsorbate bonding as the reaction proceeds from reactants, through intermediates, to products. As a result, the activity of the catalyst can be increased. We explain our observations by extending hemilability effects to single atom heterogenous catalysts and anticipate that introducing this concept can offer a new insight into the important role active site dynamics have in catalysis toward the rational design of more sophisticated single atom catalyst materials

Screening of insecticides against the mulberry fruit gall midge

In recent years, a kind of mulberry pests which were known as the mulberry gall midge Cotarina sp. in different mulberry planting areas occurred popularly in China. This study aims to screening high efficacy and low toxicity insecticides for controlling Cotarina sp.. The current study can help understand integrated pest management (IPM) of Cotarina sp. by scientific and reasonable insecticide use. Field experiment was carried out to investigate eight insecticides, treated with 3 concentration gradients. The result shows that Imidacloprid, Thiamethoxam, Cyromazine, Bifenthrin and Cypermethrin·Profenofos had high control effect on the mulberry gall midge.Their pesticide residues were all less than Chinese Standard GB2763-2016, which means that they were feasible to control this pest. This paper shows that, to control Cotarina sp. in fruit mulberry production, 10% Imidacloprid WP with 2000~3000 dilution and 25% Thiamethoxam WDG with 1500~2500 dilution and 80% Cyromazine WDG with 1500~2000 dilution are the best. 2.5% Bifenthrin EW with 1000~1500 dilution and 440g/l Cypermethrin·Profenofos EC with 1000~2000 dilution should be used by selection. However, Bifenthrin or Cypermethrin·Profenofos cannot be used in mulberry field for both fruits and leaves, so as to avoid causing silkworm poisoning

Effects of Soil Types and Moisture Contents on Emergence Rate of Contarinia morulae Jiang

In order to explore the relationship between soil moisture content and the severity of occurrence of Contarinia morulae Jiang, the effects of different soil types and moisture contents on the emergence rate of C. morulae were investigated. The results showed that soil moisture contents had a significant effect on the emergence rate of C. morulae. When the soil moisture content was 10%, the emergence rate of C. morulae was the highest in both soil types. When the soil moisture content was too high or too low, the emergence rate of C. morulae was significantly reduced. Within the suitable water content range, the emergence rate of C. morulae in sandy soil was significantly higher than that in sandy loam soil. The trend of emergence of C. morulae in the two soil types was basically the same. The number of adults of C. morulae began to increase slowly on March 18, peaked on March 28 and then peaked again on early April

Screening of Effective Insecticides Against

In recent years, with the rapid development of the sericulture industry, the pests of mulberry trees are also increasing. Diaghania pyloalis Walker is one of the main pests of mulberry trees, has strong fecundity and very large food intake, especially in Sichuan and Chongqing areas. In order to find out the insecticides which can effectively control D. pyloalis, the screening test of high-efficiency control efficacy was carried out. In the summer of 2020, the 3rd instar larvae of D. pyloalis were selected as the test objects, and the indoor bioassay of 10 insecticides on D. pyloalis was carried out, and the results of the indoor bioassay were tested by field experiments in the autumn. The results show that 2000 times liquid of Dursban, Spinetoram, Chlorantraniliprole, and 1000 times liquid of Dichlorvos and Phoxim had the best control effect on D. pyloalis. Secondly, 2000 times liquid of Imidacloprid and Chlorfenapyr had the better control effect on D. pyloalis. Finally 2000 times liquid of Pymetrozine and Cyromazine had poor control effect, and 1000 times liquid of Azadirachtin had the worst control effect on D. pyloalis. To control D. pyloalis, 2000 dilution of Dursban and Spinetoram, and 1000 times liquid of Dichlorvos can be used in sericultural production. When using Chlorantraniliprole to control D. pyloalis, the leaves of mulberry should be picked with long interval to avoid affecting the quality of cocoons, and it is not recommended to use Cyromazine, Azadirachtin to control D. pyloalis