Jiangtao Li,Xiaoxia Hu,Hong Liu,Jiansen Zhao,Mingchao Wang,Haiyan Du
Asymmetric ceramic membranes with disordered layer prepared by directional freeze-casting can be used as filter materials. However, there are few research achievements on the structural and permeability of disordered layers. Here, we obtained alumina asymmetric ceramic membranes with different disordered layer by adjusting the amount of alumina in the ceramic slurry. The results show that there are two kinds of structures in the disordered layer: spherical micropores and interconnected meshy pores, which lead to the change of airflow state. With the increase of the alumina content, the pore size of the disordered layer decreases and the network structure becomes complex, resulting in the decrease of the velocity of the inertial flow. The filter resistance of disordered layer increases obviously, but its proportion in the total filter resistance increases first and then decreases. The permeability is related to the pore size, specific surface area and channel complexity of the membrane.
Hui Han,Yanling Qiu,Hui Zhang,Tianyi Bi,Qian Yang,Mengyao Liu,Jian Zhou,Xuqiang Ji
The structural symmetry breaking of a highly crystalline substance towards a chaotic non-crystal phase construction, particularly involving a self-healing process after crystalline grain destruction, is beset by difficulties and is critical for high-performance water splitting. Taking CO32−-intercalated carbonate hydroxides as initial high-crystallinity crystals, controllable interfacial structure destruction was designed on the basis of surface-wetting invasion from Fe relevant Lewis-acidic metal salts. A spontaneous self-treatment course occurs via the in situ formation of an ultrathin lattice-disordered layer (∼7.5 nm in thickness) due to the interfacial hydrolysis of the escaped CO32− encountering positive-valence iron ions. As-obtained NiCoCH@Fe–OH, with Co(CO3)0.5(OH)·0.11H2O@Ni2(OH)2CO3 (NiCoCH) as the core and amorphous Fe(OH)3 as the shell, shows excellent catalytic performance toward water splitting, with a current density of 50 mA cm−2 at overpotentials of 221 mV for the oxygen evolution reaction and 233.8 mV for the hydrogen evolution reaction in 1.0 M KOH. Assembling a two-electrode alkaline electrolytic cell, only 1.69 V is required to drive a current density of 50 mA cm−2. This work merges structural destruction and in situ regeneration into a one-material system through a single-step surface-wetting strategy for precise surficial nanostructure design, and it displays a mild/scalable approach for high-activity catalyst development.
Fengan Han,Yanting Liu,Guangyi Li,Lin Yuan,Aiqin Wang,Feng Wang,Tao Zhang,Ning Li
Selective hydrodeoxygenation (HDO) of lignocellulose-derived ketones to olefins is a promising method for upgrading lignocellulosic biomass-derived molecules. Herein, zinc molybdate (ZnMoO4–E) with a disordered layered stacking structure was first prepared using a facile and environmentally friendly evaporation method and it exhibited outstanding catalytic performance for the selective HDO of lignocellulose-derived ketones to olefins. Using it, 4-heptanone, a representative of lignocellulose-derived ketones, was totally converted, and a high carbon yield of heptene (90%) was achieved at 673 K. On the basis of the characterization results, the outstanding catalytic performance of ZnMoO4–E was attributed to its porous structure, higher oxygen vacancy (or the Mo5+ species) concentration and higher acidity. Analogously, ZnMoO4–E also exhibited good catalytic performances for the selective HDO of other lignocellulose-derived ketones (such as acetone, butanone, 2-pentanone, 3-pentanone, cyclohexanone, acetophenone and 5-nonanone) to their corresponding olefins.
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