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742 results on '"Zhu, Wenkun"'

157. In Situ Metal‐Oxygen‐Hydrogen Modified B‐Tio2@Co2P‐X S‐Scheme Heterojunction Effectively Enhanced Charge Separation for Photo‐assisted Uranium Reduction.

Author

Zhang, Fucheng, Dong, Huanhuan, Li, Yi, Fu, Dengjiang, Yang, Lu, Shang, Yupeng, Li, Qiuyang, Shao, Yuwen, Gang, Wu, Ding, Tao, Chen, Tao, and Zhu, Wenkun

Subjects
URANIUM, METALLIC bonds, HETEROJUNCTIONS, URANIUM mining, PHOTOREDUCTION, CHARGE carriers
Abstract

Photo‐assisted uranium reduction from uranium mine wastewater is expected to overcome the competition between impurity ions and U(VI) in the traditional process. Here, B‐TiO2@Co2P‐X S‐scheme heterojunction with metal‐oxygen‐hydrogen (M‐O‐H) is developed insitu modification for photo‐assisted U(VI) (hexavalent uranium) reduction. Relying on the DFT calculation and Hard‐Soft‐Acid‐Base (HSAB) theory, the introduction of metal‐oxygen‐hydrogen (M‐O‐H, hard base) metallic bonds in the B‐TiO2@Co2P‐X is found to enhance the hydrophilicity and the capture capability for uranyl ion (hard acid). Accordingly, B‐TiO2@Co2P‐500 hybrid nanosheets exhibit excellent U(VI) reduction ability (>98%) in the presence of competing ions. By self‐consistent energy band calculations and in‐situ KPFM spectral analysis, the formation of the internal electric field between B‐TiO2 and Co2P at the heterojunction is proven, offering a strong driving force and atomic transportation highway for accelerating the S‐scheme charge carriers directed migration and promoting the photocatalytic reduction of uranium. This work provides a valuable route to explore the functionally modified photocatalyst with high‐efficiency photoelectron separation for U(VI) reduction. [ABSTRACT FROM AUTHOR]

Published
2024
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158. Air oxidation in surface engineering of biochar-based materials: a critical review.

Author

Sun, Zhuozhuo, Dai, Lichun, Lai, Penghui, Shen, Feng, Shen, Fei, and Zhu, Wenkun

Subjects
BIOCHAR, OXIDATION, AIRWAYS (Aeronautics), ENERGY conversion, BIOMASS conversion, ENERGY storage
Abstract

Biochar always suffers from low porosity and/or poor surface functionality, which limit its performances. Among various surface engineering strategies, air oxidation favors both pore development and surface oxygenation for biochar. However, there is still a lack of systematic knowledge and critical perspective on air oxidation in surface engineering of biochar-based materials for various applications. Herein, this review analyzed the mechanisms of air oxidation, summarized the routes of air oxidation in surface engineering of biochar-based materials, investigated the impacts of controlling factors (including operation parameters and intrinsic biochar structure) on pore development and surface oxygenation during air oxidation, and discussed the performances of the resultant materials in pollution control, biomass catalytic conversion and energy storage. This review suggested that air oxidation could be conducted in oxidative torrefaction/pyrolysis, and applied as post-modification or pretreatment processes. Interestingly, air oxidation is efficient in enriching the heteroatoms in the heteroatom-doped biochar, and promoting the doping of metal species on biochar by enriching the anchor sites. This review also highlighted the future challenges concerning air oxidation in the surface engineering of biochar-based materials. Finally, this review was intended to attract broad attention and inspire new discoveries for promoting the application of air oxidation in surface engineering of biochar-based materials for various advanced applications. Highlights: • Air oxidation favors pore development and/or surface oxygenation for biochar. • Air oxidation can be conducted in oxidative torrefaction/pyrolysis, and applied as post-modification or pretreatment processes. • Mechanisms and controlling factors for air oxidation were analyzed, and future challenges were highlighted. [ABSTRACT FROM AUTHOR]

Published
2023
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175. Effects of Torrefaction Pretreatment on the Structural Features and Combustion Characteristics of Biomass-Based Fuel.

Author

Yang, Xu, Zhao, Yaying, Zhang, Lei, Wang, Zhuozhi, Zhao, Zhong, Zhu, Wenkun, Ma, Jiao, and Shen, Boxiong

Subjects
WHEAT straw, SOLID waste, COMBUSTION, FUEL quality, IGNITION temperature
Abstract

Wheat straw, a typical agricultural solid waste, was employed to clarify the effects of torrefaction on the structural features and combustion reactivity of biomass. Two typical torrefaction temperatures (543 K and 573 K), four atmospheres (argon, 6 vol.% O2, dry flue gas and raw flue gas) were selected. The elemental distribution, compositional variation, surface physicochemical structure and combustion reactivity of each sample were identified using elemental analysis, XPS, N2 adsorption, TGA and FOW methods. Oxidative torrefaction tended to optimize the fuel quality of biomass effectively, and the enhancement of torrefaction severity improved the fuel quality of wheat straw. The O2, CO2 and H2O in flue gas could synergistically enhance the desorption of hydrophilic structures during oxidative torrefaction process, especially at high temperatures. Meanwhile, the variations in microstructure of wheat straw promoted the conversion of N-A into edge nitrogen structures (N-5 and N-6), especially N-5, which is a precursor of HCN. Additionally, mild surface oxidation tended to promote the generation of some new oxygen-containing functionalities with high reactivity on the surface of wheat straw particles after undergoing oxidative torrefaction pretreatment. Due to the removal of hemicellulose and cellulose from wheat straw particles and the generation of new functional groups on the particle surfaces, the ignition temperature of each torrefied sample expressed an increasing tendency, while the Ea clearly decreased. According to the results obtained from this research, it could be concluded that torrefaction conducted in a raw flue gas atmosphere at 573 K would improve the fuel quality and reactivity of wheat straw most significantly. [ABSTRACT FROM AUTHOR]

Published
2023
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