Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe3C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction reaction (ORR) ...electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe3C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm−2 in peak power density) and an aprotic Li–O2 battery (8749 mAh g−1 in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe3C contribution to the catalyst performance, suggesting Fe3C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.
An Fe–N–C catalyst is derived from dual metal–organic frameworks through facile pyrolysis, affording excellent oxygen reduction catalytic performance in alkaline/acidic half‐cells, a H2–O2 proton exchange membrane fuel cell, and a Li–O2 battery. The excellent catalytic performance benefits from density populated Fe–Fe3C@Fe–N–C dual active sites, hierarchical porosities for mass transport, and partial carbon graphitization for charge transfer.
Co core@Co oxide shell (Co@CoOx) catalysts represent a large family with promising oxygen reduction reaction (ORR) catalytic activity. However, inadequate understanding of Co@CoOx synergy prohibits ...further pursuit of catalytic performance enhancement. Herein, a Co zeolitic−imidazolate framework was converted into metallic Co, followed by controlled air treatment to form Co@CoOx. The composition and structure evolution as a function of air treatment temperature were studied thoroughly through conventional and synchrotron (both ex‐situ and in‐situ) characterizations, confirming the coexistence of CoO and Co3O4 in the shell. The optimal catalyst showed an ORR half‐wave potential of 0.87 V (vs. RHE) in an alkaline half‐cell and delivered high discharge capacity in an aprotic Li−O2 battery (7,124 mAh gCat+C−1) and an aqueous Zn−air battery (694 mAh gZn−1) with good performance retention after durability test. Modeling simulation and density functional theory calculation confirmed the charge donation from metal core to oxide shell and shed light on new insights of how metal@metal oxide synergy impacted the ORR via tuning the charge conductivity, oxygen affinity and intermediate transfer pathway. This work opens up a venue to boost ORR catalytic activity from an interfacial synergy perspective.
Fine tuning: Charge donation from metallic Co core to Co oxide shell is verified in a metal−organic framework‐derived Co@CoOx system, enabling the surface of Co oxide more electron enriched. Such synergy alters the charge conductivity, oxygen affinity, and intermediate transfer mechanism during the ORR. Adequate understanding of such correlations aids in further improving the activity of Co@CoOx ORR catalysts.
Abstract
Dual metal–organic frameworks (MOFs, i.e., MIL‐100(Fe) and ZIF‐8) are thermally converted into Fe–Fe
3
C‐embedded Fe–N‐codoped carbon as platinum group metal (PGM)‐free oxygen reduction ...reaction (ORR) electrocatalysts. Pyrolysis enables imidazolate in ZIF‐8 rearranged into highly N‐doped carbon, while Fe from MIL‐100(Fe) into N‐ligated atomic sites concurrently with a few Fe–Fe
3
C nanoparticles. Upon precise control of MOF compositions, the optimal catalyst is highly active for the ORR in half‐cells (0.88 V in base and 0.79 V versus RHE in acid in half‐wave potential), a proton exchange membrane fuel cell (0.76 W cm
−2
in peak power density) and an aprotic Li–O
2
battery (8749 mAh g
−1
in discharge capacity), representing a state‐of‐the‐art PGM‐free ORR catalyst. In the material, amorphous carbon with partial graphitization ensures high active site exposure and fast charge transfer simultaneously. Macropores facilitate mass transport to the catalyst surface, followed by oxygen penetration in micropores to reach the infiltrated active sites. Further modeling simulations shed light on the true Fe–Fe
3
C contribution to the catalyst performance, suggesting Fe
3
C enhances oxygen affinity, while metallic Fe promotes *OH desorption as the rate‐determining step at the nearby Fe–N–C sites. These findings demonstrate MOFs as model system for rational design of electrocatalyst for energy‐based functional applications.
Abstract
Co core@Co oxide shell (Co@CoO
x
) catalysts represent a large family with promising oxygen reduction reaction (ORR) catalytic activity. However, inadequate understanding of Co@CoO
x
synergy ...prohibits further pursuit of catalytic performance enhancement. Herein, a Co zeolitic−imidazolate framework was converted into metallic Co, followed by controlled air treatment to form Co@CoO
x
. The composition and structure evolution as a function of air treatment temperature were studied thoroughly through conventional and synchrotron (both ex‐situ and in‐situ) characterizations, confirming the coexistence of CoO and Co
3
O
4
in the shell. The optimal catalyst showed an ORR half‐wave potential of 0.87 V (vs. RHE) in an alkaline half‐cell and delivered high discharge capacity in an aprotic Li−O
2
battery (7,124 mAh g
Cat+C
−1
) and an aqueous Zn−air battery (694 mAh g
Zn
−1
) with good performance retention after durability test. Modeling simulation and density functional theory calculation confirmed the charge donation from metal core to oxide shell and shed light on new insights of how metal@metal oxide synergy impacted the ORR via tuning the charge conductivity, oxygen affinity and intermediate transfer pathway. This work opens up a venue to boost ORR catalytic activity from an interfacial synergy perspective.
The efficacy of electroacupuncture (EA) for treating patients with diarrhea-predominant IBS has been confirmed in the authors’ former research, but the regulatory mechanism of EA in IBS is still ...unknown. The aim of this study was to explore the relationship between the effect of EA on treating IBS rats and the activation and proliferation of mast cell (MC), the secretion of substance P(SP), and vasoactive intestinal polypeptide (VIP). The IBS rat model was set up with stress of binding limbs and colorectal distention. All rats were randomly assigned to four groups (Normal, Model, Tegaserod and EA). Hematoxylin and eosin staining has been used to observe the pathological change in the rats’ colonic mucosa and an AWR scoring system has been applied to evaluate improvement of visceral hypersensitivity in various methods of the different groups. Toluidine blue improved method (TBI) and immunohistochemistry have also been involved in observations of mucous mast cells in the colon, change of c-fos positive cells, and secretion of SP, SPR, VIP, VIPR in the local colon. Firstly, the threshold of visceral sensitivity in the rats model with IBS was remarkably reduced (
P
< 0.01). The MC count in colonic mucosa and c-fos positive cells count increased significantly (
P
< 0.01) with positive correlation within each. Secondly, EA on ST-25 and Tegaserod pouring into the stomach can inhibit the proliferation and activation of MC in the colon and regulate secretion of SP, SPR, VIP, VIPR (
P
< 0.01,
P
< 0.05), while the effect of EA is obviously superior to Tegaserod. We concluded, firstly, that the abnormal proliferation and activation of mucous mast cells in the colon, and oversecretion of neuropeptides such as SP, VIP and their receptors could be one of key mechanisms of etiology of IBS. Secondly, the inhibition of activation and proliferation and the secretion of SP, VIP could be major effects of EA when treating rats with IBS.
A novel, magnetic three-phase fluidized bed reactor (MTFBR) was designed with magnetic immobilized cellulase (MIC) as the biocatalyst for preparing chitooligosaccharides from chitosan. The MIC showed ...higher enzyme activity in a pulse magnetic field (PMF) than that in a steady magnetic field (SMF) or alternating magnetic field (AMF) under certain operating parameters. The application of a magnetic field increased the maximum reaction rate (V max) and Michaelis constant (K m), and the reaction rates of the MIC-catalyzed reaction in PMF and SMF at high concentration of chitosan solution (C s, 5 < C s < 20 mg/mL) increased as the intensity of the magnetic field increased. The concentrations of chitosan pentamer and hexamer produced were higher in the PMF than in the SMF and AMF, and the application of a magnetic field greatly reduced (by as much as 37.5%) the biocatalytic reaction time required to reach the maximum concentration of the desired chitooligosaccharides. These results suggest that the customized MTFBR supplemented with MIC is a reusable and effective piece of biocatalytic equipment, indicating that it has potential applications for large industrial-scale chitooligosaccharide syntheses.
A safe organic solvent mixture
n-heptane/ethanol was used as dispersion medium in reversal micelle to replace the commonly used toxic and highly volatile organic solvent such as chloroform and other ...solvents. This method overcame the obstacle for preparing hydrophobic nanoparticles by microwave irradiation method. The hydrophobic gold nanoparticles capped with octadecylamine (C
18NH
2) were prepared by using ethanol reduction in reverse micelle through microwave dielectric heating. The shape of obtained Au nanoparticles is nearly spherical and the size of them is sharply distributed in the 3–6
nm range, where 97% of the whole particles are included. The average diameter is determined to be 4.46
nm and the standard deviation is 0.44
nm. In addition to that, those particles obtained by this method could readily form the self-assembly two-dimensional arrangement on the water or membrane surface.
Synthesis of pillar[7]arene Chen, Yu; Tao, Hong Qi; Kou, Yu Hui ...
Chinese chemical letters,
05/2012, Letnik:
23, Številka:
5
Journal Article
Recenzirano
The first synthesis of pillar7arene is reported with two methods.Method A：the FeCl_3-catalyzed condensation reaction of 1,4- dimethoxybenzene（1） with paraformaldehyde in CHCl_3 gave ...dimethoxypillar7arene（3）.Method B：the p-toluenesulfonic acid catalyzed condensation reaction of 2,5-bis（benzyloxymethyl）-1,4-dimethoxybenzene（2） in CH_2Cl_2 gave compound 3.Demethylation of 3 with BBr_3 gave pillar7arene（4）.The pillar7arene might be a perspective macrocyclic host in host-guest chemistry.
The phyA^m gene encoding acid phytase and optimized neutral phytase phyCs gene were inserted into expression vector pPIC9K in correct orientation and transformed into Pichiapastoris in order to ...expand the pH profile ofphytase and decrease the cost of production. The fusion phytase phyA^m-phyCs gene was successfully overexpressed in P. pastoris as an active and extracellular phytase. The yield of total extracellular fusion phytase activity is （25.4±0.53） U/ml at the flask scale and （159.1±2.92） U/ml for high cell-density fermentation, respectively. Purified fusion phytase exhibits an optimal temperature at 55 ℃ and an optimal pH at 5.5-6.0 and its relative activity remains at a relatively high level of above 70% in the range ofpH 2.0 to 7.0. About 51% to 63% of its original activity remains after incubation at 75 ℃ to 95 ℃ for 10 min. Due to heavy glycosylation, the expressed fusion phytase shows a broad and diffuse band in SDS-PAGE （sodium dodecyl sulfate-polyacrylamide gel electrophoresis）. After deglycosylation by endoglycosidase H （EndoHf）, the enzyme has an apparent molecular size of 95 kDa. The characterization of the fusion phytase was compared with those ofphyCs andphyA^m.
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