ENVIRONMENTAL SCIENCE & TECHNOLOGY
·
2019
·
IF 7.149
Yue Hu,Xing Peng,Zhihui Ai,Falong Jia,Lizhi Zhang
In this study, we report that liquid nitrogen treatment is a promising zero-valent iron activation method that does not remove the iron oxide shell; this can improve the apparent Cr(VI) removal rate constant of zero-valent iron by about 4–120 times, depending on the particle sizes and the suppliers of zero-valent iron. It was found that liquid nitrogen, with its low temperature of 77 K, could crack the iron oxide shell of zero-valent iron to produce abundant fractures because of the different thermal expansion coefficients of iron oxide and iron. These fractures provided suitable mass transfer channels for the inward transfer of water/oxygen molecules to the iron core and the subsequent in situ generation of Fe(II) for the reduction of Cr(VI) to Cr(III). More importantly, systematic characterizations confirmed the generation of an Fe(III)/Cr(III)/Cr(VI) composite on the surface of zero-valent iron during the removal, suggesting its environmental benignancy. This study provides a novel physical zero-valent iron activation method, sheds light on the importance of the iron oxide shell of zero-valent iron on Cr(VI) removal, and clarifies the intrinsic Cr(VI) removal mechanism of zero-valent iron.
研究领域:
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF SOLID STATE CHEMISTRY
·
2020
·
IF 2.726
Guoqiang Li,Feifei Li,Jianxin Liu,Caimei Fan
The nitrogen activation is the Achilles’ heel of photocatalytic nitrogen fixation . Herein, metal-organic frameworks (MOFs), for first time, are proposed to solve the above bottleneck. A series of Fe-Based MOFs (MIL-101(Fe), MIL-100(Fe), MIL-88(Fe)) demonstrated excellent photocatalytic nitrogen fixation activity. To gain insight into the reaction mechanism, MIL-101(Cr) and MIL-101(Fe), with same molecular structure except the central metal ions , selected for system comparison. Photocatalytic nitrogen fixation activity of MIL-101(Fe) and MIL-101(Cr) are 50.355 μmol L −1 h −1 and inactive, respectively. This suggested that the nitrogen fixation activity originated from the Fe catalytic center. The results of in situ FTIR and quantum computation verifies Fe catalytic center have a higher electron density, a lower reaction activation energy and more generation of N–H bond than those of Cr catalytic center. In view of the analogous outer electron configuration of Cr and Fe, it was suspect that two extra d-orbitals electronics of Fe element are the basic reason of the excellent photocatalytic nitrogen fixation activity. This work provides a new application of MOFs in photocatalytic nitrogen fixation field and emphasizes the vital of d-orbitals electronics during the nitrogen activation process.
研究领域:
材料科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2025
·
IF 3.9
Tongtong Zhang,Xibo Zhang,Fei Chang
The industrial production of ammonia predominantly relies on the well-established Haber-Bosch process, which operates under harsh conditions (350–500 °C and 15–35 MPa). This process consumes nearly 2% of the world’s energy production and is associated with significant carbon emissions. Consequently, there is an urgent need to develop efficient catalytic processes for ammonia synthesis that can operate at milder temperatures and pressures. In this work, we introduce a synergistic photothermal ammonia synthesis process using ruthenium (Ru) catalysts supported on defective titania (TiO2-x). A solid-state mechanical reduction method was employed to create oxygen vacancies in TiO2, resulting in the formation of TiO2-x. The Ru nanoparticles on TiO2-x with moderate oxygen vacancies exhibited high dispersion, with an average particle size of 2–3 nm. Owing to the plasmonic hybridization effect between TiO2-x and Ru nanoparticles, the Ru/TiO2–x system demonstrated full-spectrum solar-light absorption and enabled photothermal ammonia synthesis at low temperature (250 °C). This system achieved nearly a 300% enhancement in activity compared to that of traditional thermal catalytic processes. Kinetic studies revealed a decrease in apparent activation energy and reaction orders of N2 and NH3 upon solar illumination of Ru/TiO2–x, indicating its remarkable photothermal promotion of nitrogen activation and ammonia desorption. Our findings underscore the significance of the photothermal effect in activating inert nitrogen molecules and achieving ammonia synthesis under mild conditions, providing valuable insights into the design of future catalysts.
研究领域:
催化化学
·
材料科学
·
化学工程
·
纳米技术
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
Nature Communications
·
2020
·Vol. 11
·期 1
·1-10
·
IF 12.121
Wang Xiuyun,Peng Xuanbei,Chen Wei,Liu Guangyong,Zheng Anmin,Zheng Lirong,Ni Jun,Au Chak-tong,Jiang Lilong
The industrial synthesis of ammonia (NH 3 ) using iron-based Haber-Bosch catalyst requires harsh reaction conditions. Developing advanced catalysts that perform well at mild conditions (<400 °C, <2 MPa) for industrial application is a long-term goal. Here we report a Co-N-C catalyst with high NH 3 synthesis rate that simultaneously exhibits dynamic and steady-state active sites. Our studies demonstrate that the atomically dispersed cobalt weakly coordinated with pyridine N reacts with surface H 2 to produce NH 3 via a chemical looping pathway. Pyrrolic N serves as an anchor to stabilize the single cobalt atom in the form of Co 1 -N 3.5 that facilitates N 2 adsorption and step-by-step hydrogenation of N 2 to *HNNH, *NH-NH 3 and *NH 2 -NH 4 . Finally, NH 3 is facilely generated via the breaking of the *NH 2 -NH 4 bond. With the co-existence of dynamic and steady-state single atom active sites, the Co-N-C catalyst circumvents the bottleneck of N 2 dissociation, making the synthesis of NH 3 at mild conditions possible.
研究领域:
催化
·
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
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