2018 Vol. 3, No. 2

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Short review
Recent advances in two-dimensional nanomaterials-based electrochemical sensors for environmental analysis
Shao Su, Shimou Chen, Chunhai Fan
2018, 3(2): 97-106. doi: 10.1016/j.gee.2017.08.005
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With the rapidly increased concerns in environmental pollution, there have been urgent needs to develop fast, sensitive, low-cost and multiplexed sensing devices for the detection of environmental pollutants. Two-dimensional (2D) nanomaterials hold great promise due to their unique chemical and physical properties, which have been extensively employed to monitor the environmental pollutants combined with different detection techniques. In this review, we summarize recent advances in 2D nanomaterials-based electrochemical sensors for detecting heavy metal ions, organic compounds, pesticides, antibiotics and bacteria. We also discuss perspectives and challenges of 2D nanomaterials in environmental monitoring.
High-throughput computational screening and design of nanoporous materials for methane storage and carbon dioxide capture
Minman Tong, Youshi Lan, Qingyuan Yang, Chongli Zhong
2018, 3(2): 107-119. doi: 10.1016/j.gee.2017.09.004
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The globally increasing concentrations of greenhouse gases in atmosphere after combustion of coal- or petroleum-based fuels give rise to tremendous interest in searching for porous materials to efficiently capture carbon dioxide (CO2) and store methane (CH4), where the latter is a kind of clean energy source with abundant reserves and lower CO2 emission. Hundreds of thousands of porous materials can be enrolled on the candidate list, but how to quickly identify the really promising ones, or even evolve materials (namely, rational design high-performing candidates) based on the large database of present porous materials? In this context, high-throughput computational techniques, which have emerged in the past few years as powerful tools, make the targets of fast evaluation of adsorbents and evolving materials for CO2 capture and CH4 storage feasible. This review provides an overview of the recent computational efforts on such related topics and discusses the further development in this field.
Research paper
Molecular dynamics study of room temperature ionic liquids with water at mica surface
Huanhuan Zhang, Mengyang Zhu, Wei Zhao, Song Li, Guang Feng
2018, 3(2): 120-128. doi: 10.1016/j.gee.2017.11.002
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Water in room temperature ionic liquids (RTILs) could impose significant effects on their interfacial properties at a charged surface. Although the interfaces between RTILs and mica surfaces exhibit rich microstructure, the influence of water content on such interfaces is little understood, in particular, considering the fact that RTILs are always associated with water due to their hygroscopicity. In this work, we studied how different types of RTILs and different amounts of water molecules affect the RTIL-mica interfaces, especially the water distribution at mica surfaces, using molecular dynamics (MD) simulation. MD results showed that (1) there is more water and a thicker water layer adsorbed on the mica surface as the water content increases, and correspondingly the average location of K+ ions is farther from mica surface; (2) more water accumulated at the interface with the hydrophobic [Emim][TFSI] than in case of the hydrophilic [Emim][BF4] due to the respective RTIL hydrophobicity and ion size. A similar trend was also observed in the hydrogen bonds formed between water molecules. Moreover, the 2D number density map of adsorbed water revealed that the high-density areas of water seem to be related to K+ ions and silicon/aluminum atoms on mica surface. These results are of great importance to understand the effects of hydrophobicity/hydrophicility of RTIL and water on the interfacial microstructure at electrified surfaces.
Enhanced efficiency in Concentrated Parabolic Solar Collector (CPSC) with a porous absorber tube filled with metal nanoparticle suspension
Mohammad Hatami, Jiafeng Geng, Dengwei Jing
2018, 3(2): 129-137. doi: 10.1016/j.gee.2017.12.002
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In this study, effects of different nanoparticles and porosity of absorber tube on the performance of a Concentrating Parabolic Solar Collector (CPSC) were investigated. A section of porous-filled absorber tube was modeled as a semi-circular cavity under the solar radiation which is filled by nanofluids and the governing equations were solved by FlexPDE numerical software. The effect of four physical parameters, nanoparticles type, nanoparticles volume fraction (φ), Darcy number (Da) and Rayleigh number (Ra), on the Nusselt number (Nu) was discussed. It turns out that Cu nanoparticle is the most suitable one for such solar collectors, compared to the commonly used Fe3O4, Al2O3, TiO2. With the increased addition of Cu nanoparticles all the parameters φ, Da and Ra shows a significant increase against the Nu, indicates the enhanced heat transfer in such cases. As a result, low concentration of Cu nanoparticle suspension combined with porous matrix was supposed to be beneficial for the performance enhancement of concentrating parabolic solar collector.
DMC-grafted cellulose as green-based flocculants for agglomerating fine kaolin particles
Meng Li, Yulong Wang, Xiaobang Hou, Xia Wan, Hui-Ning Xiao
2018, 3(2): 138-146. doi: 10.1016/j.gee.2017.11.005
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Novel cellulose based flocculants C-g-P (DMC) with various chain architectures are synthesized through a situ graft copolymerization. The cationic ammonium chloride group (DMC) is grafted onto cellulose by two separate inverse emulsion polymerization with γ-methacryloxypropyl trimethoxy silane (KH-570) and double bond addition reactions, which is a new and simple method to employ KH-570 as a bridge for the connection of cellulose matrix and DMC group. The effects of pH, flocculant dose, standing time on turbidity of kaolin suspensions and particle sizes have been studied systematically. In addition, the response surface methodology (RSM) study confirms that PAC and C-g-P (DMC) have synergy in turbidity removal with a higher removal efficiency of 98.32%. Moreover, C-g-P (DMC) 1 has higher removal efficiency with 96.5% at a low dosage of 0.6 mg L−1 and better floc properties than C-g-P (DMC) 2 and C-g-P (DMC) 3 , suggesting that the length and quantity of cationic branch chains play a crucial role in Kaolin flocculation due to their dramatically enhanced bridging effects.
Fabrication of hierarchical MXene-based AuNPs-containing core–shell nanocomposites for high efficient catalysts
Kaikai Li, Tifeng Jiao, Ruirui Xing, Guodong Zou, Qianran Zhao, Jingxin Zhou, Lexin Zhang, Qiuming Peng
2018, 3(2): 147-155. doi: 10.1016/j.gee.2017.11.004
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MXene is a new type of layered two-dimensional transition metal carbide materials differing from graphene, demonstrating intriguing chemical/physical properties. Here the chemical modification of MXene and next fabrication of core–shell MXene–COOH@(PEI/PAA)n composites have been investigated. The obtained MXene-based composites were treated with gold nanoparticles to form MXene–COOH@(PEI/PAA)n@AuNPs nanocomposites, and their catalytic properties for nitro-compounds were studied. The prepared nanocomposites demonstrated good catalytic activity and reproducibility, showing potential applications in composite catalysts and environmental fields.
α-Fe2O3 nanoplates with superior electrochemical performance for lithium-ion batteries
Li Xu, Yuhui Tian, Tiefeng Liu, Henan Li, Jingxia Qiu, Sheng Li, Huaming Li, Shouqi Yuan, Shanqing Zhang
2018, 3(2): 156-162. doi: 10.1016/j.gee.2018.01.005
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On account of the high theoretical capacity, high corrosion resistance, environmental benignity, abundant availability and low cost, the research on α-Fe2O3 has been gradually fastened on as promising anodes materials toward lithium-ion batteries (LIBs). A high-performance anode for LIBs based on α-Fe2O3 nanoplates have been selectively prepared. The α-Fe2O3 nanoplates can be synthesized with iron ion-based ionic liquid as iron source and template. The α-Fe2O3 nanoplates as the anode of LIBs can display high capacity of around 1950 mAh g−1 at 0.5 A g−1 which have exceeded the theoretical capacity of α-Fe2O3. On account of unique nanoplate structures and gum arabic as binder, the α-Fe2O3 nanoplates also exhibit high rate capability and excellent cycling performance.
NMR studies of stock process water and reaction pathways in hydrothermal carbonization of furfural residue
Fen Yue, Christian Marcus Pedersen, Xiuyin Yan, Yequn Liu, Danlei Xiang, Caifang Ning, Yingxiong Wang, Yan Qiao
2018, 3(2): 163-171. doi: 10.1016/j.gee.2017.08.006
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Hydrothermal carbonization (HTC) is a valuable approach to convert furfural residue (FR) into carbon material. The prepared biochars are usually characterized comprehensively, while the stock process water still remains to be studied in detail. Herein, a NMR study of the main components in stock process water generated at different HTC reaction conditions was reported. Various qualitative and quantitative NMR techniques (1H and 13C NMR, 1H–1H COSY and 1H13C HSQC etc.) especially 1D selective gradient total correlation spectroscopy (TOCSY NMR) were strategically applied in the analysis of HTC stock process water. Without separation and purification, it was demonstrated that the main detectable compounds are 5-hydroxymethylfurfural, formic acid, methanol, acetic acid, levulinic acid, glycerol, hydroxyacetone and acetaldehyde in this complicate mixture. Furthermore, the relationship between the concentration of major products and the reaction conditions (180–240 °C at 8 h, and 1–24 h at 240 °C) was established. Finally, reasonable reaction pathways for hydrothermal conversion of FR were proposed based on this result and our previously obtained characteristics of biochars. The routine and challenging NMR methods utilized here would be an alternative other than HPLC or GC for biomass conversion research and can be extended to more studies.
Heteroatom-doped porous carbon from methyl orange dye wastewater for oxygen reduction
Yiqing Wang, Mingyuan Zhu, Yingchun Li, Mengjuan Zhang, Xueyan Xue, Yulin Shi, Bin Dai, Xuhong Guo, Feng Yu
2018, 3(2): 172-178. doi: 10.1016/j.gee.2017.06.005
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Banana peel-derived porous carbon (BPPC) was prepared from banana peel and used as an adsorbent for methyl orange (MO) wastewater removal. BPPC-MO50 is a N,S-doped BPPC obtained via secondary carbonization. The BPPC-MO50 exhibited a high specific surface area of 1774.3 m2/g. Heteroatom-doped porous carbon (PC) was successfully synthesized from the BPPC absorbed MO at high temperature and used for oxygen reduction. The BPPC-MO50 displayed the highest ORR onset potential among all carbon-based electrocatalysts, i.e., 0.93 V vs. reversible hydrogen electrode (RHE). This is the first report to describe porous carbon-activated materials from agriculture and forestry waste that is used for adsorption of dyes from wastewater via an enhanced heteroatom (N,S) content. These results may contribute to the sustainable development of dye wastewater treatment by transforming saturated PC into an effective material and has potential applications in fuel cells or as energy sources.

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