Increasing demand for sustainable and clean energy is calling for the next‐generation energy conversion and storage technologies such as fuel cells, water electrolyzers, CO2/N2 reduction ...electrolyzers, metal–air batteries, etc. All these electrochemical processes involve oxygen electrocatalysis. Boosting the intrinsic activity and the active‐site density through rational design of metal–organic frameworks (MOFs) and metal–organic gels (MOGs) as precursors represents a new approach toward improving oxygen electrocatalysis efficiency. MOFs/MOGs afford a broad selection of combinations between metal nodes and organic linkers and are known to produce electrocatalysts with high surface areas, variable porosity, and excellent activity after pyrolysis. Some recent studies on MOFs/MOGs for oxygen electrocatalysis and their new perspectives in synthesis, characterization, and performance are discussed. New insights on the structural and compositional design in MOF/MOG‐derived oxygen electrocatalysts are summarized. Critical challenges and future research directions are also outlined.
Boosting the intrinsic activity and the active‐site density through rational design of metal–organic frameworks (MOFs) and metal–organic gels (MOGs) as precursors represents a new approach of improving oxygen electrocatalysis efficiency. Several key compositional and structural considerations for the MOF/MOG design and new perspectives between synthesis, characterization, and performance are comprehensively discussed.
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.
Capacitive deionization (CDI) represents one of the most thermodynamically efficient technologies for brackish water desalination. Its performance is highly reliant on the surface properties of ...carbon-based electrodes. Zeolitic-imidazolate framework (ZIF)-derived carbon materials have emerged among the most promising candidates owing to their high structural and compositional tuneability. However, the impacts of the precursory ZIF structure on the properties of the final carbon, and therefore, CDI capacity and efficiency remain to be further explored. In this work, four Zn-based ZIFs with different side-chain substitutions on the imidazolates were synthesized on a gram scale with high yields to produce N-doped carbons by pyrolysis. The resulting carbons along with four commercial carbon blacks were characterized physically and electrochemically to explore the structure-performance relationship. We demonstrated that the imidazole side-chain substitution alters the ZIF's decomposition during pyrolysis, influencing the elemental compositions, surface properties, wettability and graphitization levels. The diverse carbon properties result in variable double layer capacitance and charge-transfer resistance, ultimately impacting the CDI performance. Among these carbons, Zn (4abIm)2-C afforded the greatest salt adsorption capacity of 14.19 mgNaCl·gC−1, while Zn (mIm)2-C showed the highest overall salt adsorption capacity and rate; both exceeded the performance of the commercial carbon blacks.
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•An array of zeolitic-imidazolate frameworks are converted to carbon materials.•ZIF-derived carbons show tunable surface area, conductivity, and wettability.•An optimal ZIF-carbon shows a CDI salt adsorption capacity of 14.19 mgNaCl·gC−1.•Graphitization is correlated with CDI charge efficiency and energy consumption.
Background
Femoral head collapse and coxa vara lead to internal fixator failure in elderly patients with hip fracture. External fixator application is an optimal choice; however, the existing methods ...have many disadvantages.
Methods
Type 31-A1.3 hip fracture models were developed in nine pairs of 1-year-old fresh bovine corpse femur specimens. Each left femur specimen was fixed by a dynamic hip screw (control group), and each right femur specimen was fixed by the slide-poking external fixator (experimental group). Vertical loading and torsion tests were then performed in both groups.
Results
In the vertical loading experiment, a 1000-N load was implemented. The mean vertical downward displacement of the femoral head in the experimental and control groups was 1.49322 ± 0.116280 and 2.13656 ± 0.166374 mm, respectively. In the torsion experiment, when the torsion was increased to 10.0 Nm, the mean torsion angle in the experimental and control groups was 7.9733° ± 1.65704° and 15.4889° ± 0.73228°, respectively. The slide-poking external fixator was significantly more resistant to compression and rotation than the dynamic hip screw.
Conclusion
The slide-poking external fixator for hip fractures that was designed and developed in this study can provide sufficient stability to resist compression and rotation in hip fractures.
In the present study, density functional theory (DFT) calculations were performed to investigate the reaction mechanism of methane oxidation catalyzed by ZSM-5-supported binuclear iron species. A ...variety of binuclear iron sites such as Fe(μ-O)Fe2+, Fe(μ-O)2Fe2+, Fe(μ-O)(μ-OH)Fe+, and HOFe(μ-O)FeOH2+ were considered. The conversion of methane to methanol is decomposed into two processes: C–H activation and methanol formation. It is found that the anhydrous Fe(μ-O)Fe2+ sites exhibit the lowest reactivity for methane oxidation due to high energy barriers for both C–H activation and methanol formation steps, while the Fe(μ-O)(μ-OH)Fe+ and HOFe(μ-O)FeOH2+ sites are found to exhibit higher reactivity for methane oxidation in comparison with the anhydrous sites. This high reactivity is mainly attributed to the presence of the terminal or bridged hydroxyls, which can either provide a significant coordination effect or act as an oxidant for methane oxidation. Moreover, we find that on both Fe(μ-O)Fe2+ and Fe(μ-O)2Fe2+ sites the existence of solvent water molecule can effectively enhance the reactivity of the methanol formation step. Our results confirm the experimental observation of methane oxidation at the low-temperature range (<500 K) and suggest a significant role of water in methane oxidation in Fe/ZSM5 catalyst. This may provide an important guide in designing catalysts with high activity of methane oxidation.
Carbon-hosted Fe–N-coordinated (Fe/N/C) materials, especially those derived from thermolysis of iron-added zinc-based zeolite-imidazolate frameworks (ZIFs), have emerged as the most promising ...platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) catalysts. However, the impacts of the precursory ZIF structure and their conversion chemistry during thermal activation to the final catalytic activity remain to be further explored in the process of continuously refining the catalyst performance. Herein, we synthesized a series of Fe-doped ZIFs with different imidazolate ligands and systematically studied the correlation between the crystal structures with the final ORR catalytic activity in an alkaline electrolyte. We also investigated the ZIF decomposition chemistry during pyrolysis using a thermogravimetric mass-spectroscopic analysis. We demonstrated that imidazole side-chain substitution alters the ZIF’s decomposition during pyrolysis, influencing the elemental compositions, surface properties, graphitization levels, and ultimately the catalytic performance. The Zn(mIm)2TPIBP catalyst affords the highest ORR activity with a half-wave potential of 0.93 V vs RHE, representing the best among all PGM-free catalysts studied.
The selection of a correct level in lumbar spinal stenosis (LSS) remains a common problem and is critically important to the effectiveness of this surgical treatment. Surgery is invasive, and ...extended laminectomy may lead to secondary surgical complications. The application of diffuse tensor imagining (DTI) and paraspinal mapping (PM) in addition to conventional magnetic resonance imaging (cMRI) may be helpful in this respect. However, the superiority of cMRI + DTI over cMRI+ (DTI or PM) in reducing decompression has not yet been established.
We compared the surgical levels, determined by cMRI + DTI and cMRI+ (DTI or PM) (self-control). Treatment outcome measurements were performed at two weeks, three months, six months, and twelve months postoperatively.
The surgical levels determined by cMRI ± DTI showed less than that determined by cMRI± (DTI or PM) with statistically significant differences (p value = 0.0199) and cMRI ± PM with no statistically significant differences (p value = 0.5503).
The effectiveness of cMRI ± DTI in the reduction of the surgical levels in degenerative lumbar spinal stenosis is superior than that of cMRI± (DTI or PM).
In lumbar spinal stenosis (LSS), at most times, several levels are impaired and selecting the correct level remains a common problem for surgeons, as surgery remains invasive, and extended ...laminectomy may lead to secondary surgical complications. Therefore, helping to select the correct level may be useful for surgeons. The use of diffuse tensor imaging (DTI) and paraspinal mapping (PM) in addition to conventional magnetic resonance imaging (MRI) may be helpful (Chen et al., J Orthop Surg Res 11:47, 2016). However, with decompression levels determined by conventional magnetic resonance imaging (MRI) increasing, whether the benefits of reducing decompression level of conventional MRI + (DTI or PM) will be more obvious is unknown.
Reduced surgical levels that were different between levels determined by conventional MRI + (DTI or PM) and conventional MRI + neurogenic examination (NE) between groups were compared. Treatment outcome measures were performed at 2 weeks, 3 months, 6 months, and 12 months postoperatively.
The reduced levels of three groups showed no statistically significant differences between each other except for two levels and four levels (two levels/three levels, p = 0.085; two levels/four levels, p = 0.039; three levels/ four levels, p = 0.506, respectively).
With surgical levels determined by conventional MRI increasing, the benefits of DTI and PM will be uncertainly more obvious.
In lumbar spinal stenosis, correlating symptoms and physical examination findings with decompression levels based on common imaging is not reliable. Paraspinal mapping (PM) and diffusion tensor ...imaging (DTI) may be possible to prevent the false positive occurrences with MRI and show clear benefits to reduce the decompression levels of lumbar spinal stenosis than conventional magnetic resonance imaging (MRI) + neurogenic examination (NE). However, they must have enough positive rate with levels which should be decompressed at first. The study aimed to confirm that the positive of DTI and PM is enough in levels which should be decompressed in lumbar spinal stenosis.
The study analyzed the positive of DTI and PM as well as compared the preoperation scores to the postoperation scores, which were assessed preoperatively and at 2 weeks, 3 months 6 months, and 12 months postoperatively.
96 patients underwent the single level decompression surgery. The positive rate among PM, DTI, and (PM or DTI) was 76%, 98%, 100%, respectively. All post-operative Oswestry Disability Index (ODI), visual analog scale for back pain (VAS-BP) and visual analog scale for leg pain (VAS-LP) scores at 2 weeks postoperatively were measured improvement than the preoperative ODI, VAS-BP and VAS-LP scores with statistically significance (p-value = 0.000, p-value = 0.000, p-value = 0.000, respectively).
In degenetive lumbar spinal stenosis, the positive rate of (DTI or PM) is enough in levels which should be decompressed, thence using the PM and DTI to determine decompression levels will not miss the level which should be operated.
For the deep desulfurization of fuel oil, adsorptive desulfurization (ADS) and oxidative desulfurization (ODS) may be the most viable alternatives to the conventional HDS process. In this work, a ...highly cross-linked vanadate based polyionic liquid (V-PIL) was synthesized by reacting poly(vinylimidazole) (PVIM) with peroxy-vanadic acid. The as-prepared V-PIL is mesoporous with specific area of 163 m2·g–1 and good adsorptivity for the oxidized sulfur compounds. Further, it can efficiently catalyze the oxidation of dibenzothiophene and benzothiophene with cumene hydroperoxide (CHP), achieving a unified desulfurization processes of ODS and ADS. Its catalytic activity and reusability is superior to the supported vanadate catalysts, e.g. V2O5@active carbon and V2O5@zeolite. The desulfurization capacity of V-PIL is 99% in the first run under specified conditions, i.e. stirring 4 h at 323 K for 500 ppmS DBT oil, with CHP/S being 4 in mole ratio and 3 wt % V-PIL with respect to oil. And over 80% of its desulfurization capacity can be retained after five successive uses without regeneration under the above conditions. The V-PIL may represent a new type of bulk catalyst with potential application considering its rich porosity, good dispersion, accessible catalytic sites, and no soluble loss of the bonded vanadates in the recycling uses.
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