JOURNAL OF COLLOID AND INTERFACE SCIENCE
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2020
·
IF 7.489
Zhengxiang Gu,Yijing Chen,Zengxi Wei,Linping Qian,Abdullah M. Al-Enizi,Jianmin Ma,Gang Zhou,Gengfeng Zheng
The electrochemical dinitrogen reduction represents an attractive approach of converting N 2 and water into ammonia, while the rational design of catalytic active centers remains challenging. Investigating model molecular catalysts with well-tuned catalytic sites should help to develop a clear structure-activity relationship for electrochemical N 2 reduction. Herein, we designed several polycyclic aromatic hydrocarbon (PAH) molecules with well-defined positions of boron and nitrogen atoms. Theoretical calculations revealed that the boron atoms possess high local positive charge densities as Lewis acid sites, which are beneficial for N 2 adsorption and activation, thus serving as major catalytic active sites for N 2 electrochemical reduction . Furthermore, the close vicinity of two boron atoms can further enhance the local positive density and subsequent catalytic activity. Using the PAH molecule with two boron atoms separated by two carbon atoms (B-2C-B), a high NH 3 production rate of 34.58 μg·h −1 ·cm −2 and a corresponding Faradaic efficiency (5.86%) were achieved at −0.7 V versus reversible hydrogen electrode, substantially exceeding the other PAHs with single boron or nitrogen-containing molecular structures.
研究领域:
化学
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材料科学
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电化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CRYSTENGCOMM
·
2022
·Vol. 24
·期 11
·2118-2125
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IF 3.756
Yufang Ma,Lei Wang,Lei Chen,Meikun Shen,Xue Yang,Tengteng Wang,Feixiang Yuan,Yu Zhou,Jun Wang,Hongjun Zhu
Regulating heteroatom-substituted tetrahedral sites (T sites) within a zeolite crystal significantly influences the zeolite properties. Herein, the as-synthesized MFI zeolite with tailored boron locations at various T sites is unveiled by powder X-ray crystallography. The experimental results imply that four similar but structurally different imidazolium-based organic structure-directing agents (OSDAs) adopted in the synthetic system can effectively control the location of final boron-enriched T sites. It is demonstrated that the specific boron location depends on the corresponding OSDA coordinates and their molecular structures. Furthermore, boron-enriched composite building units in the MFI framework are derived as well. Such boron-enriched T sites tailored by zeolite framework (host) and OSDA molecule (guest) interactions afford an effective strategy for the rational design of zeotype catalysts.
研究领域:
材料科学
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化学工程
✓ 已验证
DOI
高影响因子
Nano Research
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2020
·Vol. 13
·期 8
·2079-2084
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IF 8.183
Wang Hong-Hui,Lv Li-Bing,Zhang Shi-Nan,Su Hui,Zhai Guang-Yao,Lei Wei-Wei,Li Xin-Hao,Chen Jie-Sheng
The rational design of highly active and stable atomically dispersed M-X 4 (M = Fe, Co, Ni, etc., X = C, N) -based catalysts holds promises for wide application in almost all realms of catalysis. Despite great effort in the construction of specific M-X 4 centers, the possible effect of non-coordinated heteroatoms on the catalytic activity of metal centers has been rarely explored. Herein, we develop a new type of M-X 4 catalyst composed of Fe-N 4 centers and non-coordinated B heteroatoms (FeNC+B) and find the key role of non-coordinated B adjacent to Fe-N 4 centers in tailoring their electron density and final catalytic selectivity. The experimental and theoretical results demonstrated that non-coordinated boron atoms could decrease the electron density of Fe-N 4 centers to a suitable level and thus boost the selective production of nitriles from amine oxidation by depressing the formation of imines due to the flattened energy barrier of the reversible conversion of imines back to amines. As a reusable heterocatalyst, the state-of-the-art FeNC+B catalyst provides a turn-over frequency (TOF) value of 21.6 mol benzonitrile ·mol Fe −1 ·h −1 (100 °C), outpacing that of bench-marked nonnoble-metal-based homogeneous catalyst by a factor of 3.4.
研究领域:
催化化学
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材料科学
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理论化学
✓ 已验证
DOI
高影响因子
ChemElectroChem
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2020
·Vol. 7
·期 15
·3353-3360
·
IF 4.154
Ran Zhang,Zhaoyang Wei,Weiwei Lei,Tao Jiang,Qunchao Zhang,Dean Shi
Graphical Take cover : The shielding effects of ether oxygen atoms in Poly(ethylene glycol) (PEG) molecular chains on the B atoms can be alleviated by introducing siloxane oxygens in between them (B-Si x -PEGs). The deshielding effects of siloxane spacing groups on B atoms increase along with the increase of x in the B-Si x -PEGs polymer electrolytes. Doping boron (B) atoms into poly(ethylene glycol) (PEG)-based solid polymer electrolytes (B-PEG) is believed to be an attractive method to increase the lithium-ion transference number ( ) because of the interaction between the electropositive B atoms and the anions of lithium salts. However, this effect can be largely impeded by the interaction between B and the electronegative ether oxygen atoms in the attached PEG molecular chains, which is referred to as a shielding effect. Enlarging the distance between the center B atoms and the electronegative ether oxygens is believed to be an effective way to reduce such shielding effect. In this work, different number of siloxane spacing groups (Si x ) are introduced in between the B atom and ether oxygen in the B-PEG macromolecules (B-Si x -PEGs x =0,1,3,5). As the siloxane oxygen has less electronegativity to ether oxygen, the shielding effects should be weakened and the ability of B atoms to trap the anions of lithium salt will increase. As the introduction of siloxane groups into the B-Si x -PEGs polymer electrolytes will also reduce the neat contents of both B and PEG, which has the opposite effect on the whole ionic conductivities and values, both the ionic conductivities and values of B-Si x -PEGs electrolytes first increase then decrease along with x increases from 0 to 5 when the [Li + ]:[EO] mole ratio is fixed at 1 : 10. The peak value exists at x =1. Meanwhile, both the mobilities of Li + ions (confirmed via 7 Li nuclear magnetic resonance (NMR) results) and bis(trifluoromethane) sulfonimide (TFSI − ) anions (confirmed from Raman spectra analysis) get their maximum values when x =1. However, if both the concentrations of TFSI − and B atoms in B-Si x -PEGs electrolytes are taken into consideration, the normalized diffusion coefficient of TFSI − anions obtained by molecular dynamic (MD) simulation decrease monotonically when x increases from 0 to 5. As the diffusion coefficient of TFSI − anions is determined by the interaction probability and strength of TFSI − and B atoms; these results confirm that the interaction between the B atoms and TFSI − anions increase with x . Namely, the deshielding effects of siloxane spacing groups on B atoms increase along with the increase of x in the B-Si x -PEGs polymer electrolytes, while it levels off when x exceeds 3.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）