查找使用阿拉丁产品的科研文献

Boosting the oxygen reduction activity of a three-dimensional network Co–N–C electrocatalyst via space-confined control of nitrogen-doping efficiency and the molecular-level coordination effect

Chaozhong Guo,Yanrong Li,Wenli Liao,Yao Liu,Zhongbin Li,Lingtao Sun,Changguo Chen,Jin Zhang,Yujun Si,Lu Li

The improvement of total nitrogen content and nitrogen-doping efficiency in carbon-based electrocatalysts is greatly significant to boost the electrocatalytic activity for the oxygen reduction reaction (ORR). Here, we report a new strategy for the synthesis of a highly mesoporous cobalt and nitrogen co-doped carbon electrocatalyst (3D-Co–N–C) with a three-dimensional network structure and a high BET surface area (∼638 m2 g−1) via using a novel cobalt-2,4,6-tri(2-pyridyl)-1,3,5-triazine complex with a strong molecular-level coordination effect as a single-source precursor and self-assembled sodium chloride aggregates as a space-confined nanoreactor for effective control of a high-temperature calcination process to reduce the thermal loss of nitrogen atoms and promote the nitrogen-doping efficiency, facilitating boosting of the ORR electrocatalytic activity in alkaline medium. The prepared 3D-Co–N–C catalyst exhibits unexpectedly excellent ORR activity with an onset potential of ∼1.0 V and a half-wave potential of ∼0.83 V, which is comparable to that of the commercial 20 wt% Pt/C catalyst. Additionally, the H2O2 yield (<17.0%) and the average electron transfer number of ∼3.8 for 3D-Co–N–C indicate a quasi four-electron pathway for ORR catalysis, suggesting that 3D-Co–N–C is a promising carbon-based electrocatalyst. It is proposed that the formation of the Co–Nx active structure can effectively enhance the electrocatalytic activity, but high contents of pyridinic- and graphitic-N can be mainly responsible for the ORR activity, which may be the electrocatalytically active site centers for the ORR. Besides, high BET surface area, highly mesoporous characteristics and outstanding electronic conductivity are also significant for the improvement of ORR activity. This study can provide a new, facile and green method for building high-performance carbon-based ORR electrocatalysts derived from easily available and innoxious transition metal–organic complexes, which can also help us to better understand the origin of the activity, active sites and their catalysis mechanism.

Engineering Electrolytic Silicon–Carbon Composites by Tuning the In Situ Magnesium Oxide Space Holder: Molten-Salt Electrolysis of Carbon-Encapsulated Magnesium Silicates for Preparing Lithium-Ion Battery Anodes

Muya Cai,Xianbo Zhou,Zhuqing Zhao,Qiang Ma,Hongwei Xie,Xianyang Li,Huayi Yin

Fabricating hollow space between a Si core and C shell has been recognized as an efficient strategy for tailoring lithium-storage performances of the silicon–carbon composite anode by resolving the extreme volume expansion of Si. Here, we report a molten-salt electrolysis method for electroreducing carbon-encapsulated magnesium silicate to prepare a Si@void@C composite in MgCl2-containing molten salt. The void space between carbon and silicon comes from the transition from silicate to Si as well as the removal of the in situ generated MgO, and the SiC is suppressed by tailoring the electrode potentials in MgCl2-containing molten salt. In other words, MgO serves as an inert space holder that can be removed by an acid leaching process to create void space. The obtained Si@void@C composite delivers a specific discharge capacity of 900 mAh/g at 1 A/g, even after 300 cycles with a discharge capacity retention rate of 75.5%. Therefore, this study paves an electrochemical pathway to prepare Si@void@C composite anodes using inexpensive feedstocks, and the void space can be tuned by adjusting the amount of MgO space holder.

A Comparative Study of Gas-phase Fluorination and Nano-Al2O3 Doping on Space Charge Behavior and Trap Level in Epoxy Resin

Zijia Shen,Feipeng Wang,Muhammad Zeeshan Khan,Zhengyong Huang,Li He,Yushuang He,Jian Li

Space-confined growth of lead-free halide perovskite Cs3Bi2Br9 in MCM-41 molecular sieve as an efficient photocatalyst for CO2 reduction at the gas−solid condition under visible light

Zihao Cui,Peng Wang,Yaqiang Wu,Xiaolei Liu,Guoqiang Chen,Peng Gao,Qianqian Zhang,Zeyan Wang,Zhaoke Zheng,Hefeng Cheng,Yuanyuan Liu,Ying Dai,Baibiao Huang

A facile and effective impregnation method is employed to synthesize the space-confined growth of lead-free halide perovskite Cs 3 Bi 2 Br 9 in MCM-41 molecular sieve. This MCM-41 @CBB (Cs 3 Bi 2 Br 9 ) composite shows an outstanding performance for the photocatalytic reduction of CO 2 to CO at the gas−solid condition under visible-light irradiation. The CO production rate of the MCM-41 @ 50 wt% CBB is determined to be 17.24 μmol g −1 h −1 , which greatly exceeds that of pure CBB (1.89 μmol g −1 h −1 ). The composite is highly stable showing no apparent decrease in the catalytic activity after 8 cycles of repeated experiment. The performance of space-confined growth of CBB nanoparticles in the serial molecular sieve exhibits 2.97–13.4 fold higher than that of pure CBB, respectively, which is superb than CPB (CsPbBr 3 ) and MCM-41 @CPB prepared in the same condition. The results are comparable with those reported for many lead halide perovskites, and are in the top among the lead-free perovskites, especially bismuth halide perovskites.

Determination of the Volatiles in Fermented Bamboo Shoots by Head Space – Solid-Phase Micro Extraction (HS-SPME) with Gas Chromatography – Olfactory – Mass Spectrometry (GC-O-MS) and Aroma Extract Dilution Analysis (AEDA)

Rongcan Guo,Futian Yu,Chenghua Wang,Hongrui Jiang,Lian Yu,Mouming Zhao,Xiaoling Liu

Suansun is a sour Chinese traditional fermented bamboo shoot product popular in Central and South Asia due to its unique flavor. The volatile compounds and their odor-activities in suansun are unknowns, which hinders the control of the fermentation and causes variations in the flavor and other properties. In order to assess the odor characteristics of suansun and its unique volatile components, headspace solid phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS) and aroma extract dilution analysis (AEDA) coupled with gas chromatography-olfactometry (GC-O) were used in this study to analyze three types of suansun samples. The results showed that a total of 43 volatiles were identified and quantified. Sixteen compounds, including five alcohols, four aromatics, four aldehydes, two carboxylic acids, and one ester, had high odor activity values exceeding 1. Fifteen odorants, including four unknowns, were detected by AEDA; eight of these compounds, 1-octen-3-ol, geraniol, p-cresol, nonanal, decanal, (E)-2-nonenal, phenylethyl alcohol, and octanoic acid, had high flavor dilution factors exceeding 243. Triangle difference tests showed that a mixture of p-cresol and octanoic acid revealed a high similarity to one of the symbolic “fermentation” odors in commercial suansun. The composition of the unique odor of suansun is better understood, which provides a theoretical basis for solving the quality control problems existing in the production process and lays a foundation for the modern production of this important product.