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A Tunable and Universal Catalyst for Efficient One-Pot Conversion of Xylose to γ-Valerolactone
Qiwen Zhan, Ruonan Zhu, Qingchong Xu, Xingjie Wang, Lihong Zhao, Fengxia Yue, Junli Ren
 doi: 10.1016/j.gee.2025.10.012
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Abstract:
The one-pot synthesis of γ-valerolactone (GVL) from xylose is pivotal for sustainable biofuel and fine chemical production. This study introduces a novel catalyst, Hf-LS-Beta, which is tailored for efficient xylose conversion to GVL, subsequently applied in a tandem process for wheat straw pre-hydrolysate catalysis. The catalyst features dispersed Lewis acid active sites formed through Hf and lignosulfonate sodium (LS) coordination within the Beta porous structure, enhancing accessibility. Both the structure and acidic properties of the catalyst were tunable by varying precursor dosages, with optimal performance achieved at a total Lewis acid content of 118-128 μmol/g and a specific surface area of 171-186 m2/g. Under optimized conditions, the Hf (1.5)-LS-Beta (0.4) catalyst delivered the highest GVL yield of 45.71% from xylose and maintained high stability over five cycles. Furthermore, a GVL yield of 29.37% was attained from xylose-rich hydrolysate from wheat straw. This catalyst achieves record-high xylose conversion in isopropanol, efficiently promoting cascade reactions involving dehydration, hydrogenation, ring-opening, and lactonization for GVL formation. Substrate versatility was also demonstrated with the successful conversion of glucose and arabinose, indicating the strong potential for integrated two-step GVL production from lignocellulosic biomass.
Selective Hydrogenolysis of Lignin to Alkene-Functionalized Monomers over ZnO-Modified Carbon Nanotube Supported Pd Catalysts
Wen Zhao, Qun Yu, Bingqing Wei, Lei Nie, Fabio Souza Toniolo, Zhenglong Li
 doi: 10.1016/j.gee.2025.10.011
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Abstract:
Although current methods enable lignin extraction and depolymerization, the selective hydrogenolysis of lignin into alkene-functionalized monomers remains a significant scientific challenge. These monomers can be further functionalized into diverse natural products or pharmaceutical intermediates, thereby enabling higher-value utilization of biomass resources. Here, we report a catalyst with low Pd loading (0.4 wt%) supported on ZnO-modified carbon nanotubes (Pd/ZnNC) for the selective catalytic hydrogenolysis of the dimer β-O-4 lignin model compound (veratrylglycerol-β-guaiacyl ether, VG) via distinct reaction pathways. The Pd/ZnNC catalyst achieves a selectivity of 37.5% toward alkene-functionalized monomers (1,2-dimethoxy-4-allylbenzene and 1,2-dimethoxy-4-propenylbenzene), approaching 75% of the theoretical maximum selectivity (50%). In contrast, the Pd/CNT catalyst predominantly produces 3-(3,4-dimethoxyphenyl)-1-propanol, and excessive side-chain saturation of monomers are not conducive to subsequent utilization processes. Moreover, the Pd/ZnNC catalyst achieves a conversion rate seven-fold higher than that of commercial catalysts Pd/C (5 wt%). Experimental characterization results demonstrate that the ZnO sites on carbon nanotubes facilitate the dispersion of Pd nanoparticles, resulting in a reduction in particle size. Furthermore, the synergistic effect between ZnO and Pd active sites promotes the selective catalytic formation of monomers containing unsaturated C=C bonds. The DFT calculations reveal that the Cγ-OH elimination is facilitated by Pd nanoparticles supported on ZnO, which reduces the reaction energy barrier and promotes the generation of propenyl-substituted monomers. The pathway enabled by Pd/ZnNC catalyst offers a great potential for lignin depolymerization into high-value products.
Single Sodium Atoms Anchored on N-Doped Porous Carbon: Solid Strongly Basic Catalysts with Uncommon Activity and Stability
Sai Liu, Xiang-Bin Shao, Zhi-Wei Xing, Xing-Ru Song, Kai Zhang, Yang Wang, Peng Tan, Lin-Bing Sun
 doi: 10.1016/j.gee.2024.12.003
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Abstract:
Solid strong base catalysts have high potentials in a variety of reactions due to the advantages of negligible corrosion, easy separation, and high efficiency. However, two issues hinder the applications of such catalysts seriously, namely aggregation of basic sites and leaching of active species during reactions. The development of solid strong base catalysts with active sites that are highly dispersed and stable remains a pronounced challenge. In this work, we employed a two-step reduction strategy to anchor Na single atoms on nitrogen-doped porous carbon (NPC) support, producing a high-performance solid strongly basic catalyst named as Na1/NPC. The alkali precursor NaNO3 was converted to Na2O on NPC at 400 oC, in which conventional solid base catalyst Na2O/NPC was generated. Upon heat treatment at 850 oC, Na2O was further reduced to Na single atoms anchored on NPC, creating Na1/NPC. Experimental studies and theoretical calculations show that Na is structurally embedded on the support in penta-coordinated configuration (Na-C3N2). The synergistic effect of highly dispersed Na atoms and nitrogen doping results in uncommon catalytic activity and stability. In transesterification between methanol and ethylene carbonate to produce dimethyl carbonate (DMC), the yield of DMC reaches 48.4% over Na1/NPC, corresponding to a turnover frequency (TOF) of 129.4 h-1, which is far beyond the conventional counterpart Na2O/NPC (63.3 h-1) and various reported solid base catalysts. The catalytic activity of Na1/NPC almost keeps constant during five cycles, while 87% of activity is lost for Na2O/NPC due to the leaching of basic sites. This work might offer new ideas for the development of efficient single-atom solid strong base catalysts with high efficiency.
Degradation and Utilization of Polyvinyl Chloride (PVC): Challenges and Opportunities Toward a Circular Economy
Rui Huang, Jiaolong Meng, Xuefeng Jiang
 doi: 10.1016/j.gee.2025.10.010
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Abstract:
Polyvinyl chloride (PVC) poses persistent environmental and recycling challenges due to its high chlorine content, complex additives, and structural resistance to degradation. Recent research has shifted focus from traditional disposal methods toward chemically informed strategies that valorize PVC within the framework of a circular economy. This review systematically summarizes three emerging pathways for PVC transformation. The first involves catalytic deconstruction into small molecules such as chlorinated olefins, hydrocarbons, and oxygenates through thermal, photocatalytic, and electro-assisted processes. The second explores backbone-preserving reconstruction into functional materials including porous carbons, membranes, ion-conducting films, and vitrimer-type polymers by leveraging selective dechlorination and structural reprogramming. The third addresses the co-processing of PVC with mixed plastic wastes through synergistic catalytic systems that tolerate chlorine-rich streams and promote selective transformation. Across all pathways, emphasis is placed on structure–property correlations, chlorine management, additive compatibility, and downstream utility. Summary tables and schematic diagrams are included to compare system efficiencies, product selectivities, and application scopes. By integrating mechanistic understanding with materials innovation, this review highlights how PVC can be reimagined as a tunable molecular platform rather than a persistent pollutant.
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Catalytic conversion of lignocellulosic biomass into chemicals and fuels
Weiping Deng, Yunchao Feng, Jie Fu, Haiwei Guo, Yong Guo, Buxing Han, Zhicheng Jiang, Lingzhao Kong, Changzhi Li, Haichao Liu, Phuc T.T. Nguyen, Puning Ren, Feng Wang, Shuai Wang, Yanqin Wang, Ye Wang, Sie Shing Wong, Kai Yan, Ning Yan, Xiaofei Yang, Yuanbao Zhang, Zhanrong Zhang, Xianhai Zeng, Hui Zhou
2023, 8(1): 10-114.   doi: 10.1016/j.gee.2022.07.003
[Abstract](1676) [PDF 23019KB](106)
摘要:
In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future, lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock. This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels. Following a brief introduction on the structure, major resources and pretreatment methods of lignocellulosic biomass, the catalytic conversion of three main components, i.e., cellulose, hemicellulose and lignin, into various compounds are comprehensively discussed. Either in separate steps or in one-pot, cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF, furfural, polyols, and organic acids, or even nitrogen-containing chemicals such as amino acids. On the other hand, lignin is first depolymerized into phenols, catechols, guaiacols, aldehydes and ketones, and then further transformed into hydrocarbon fuels, bioplastic precursors and bioactive compounds. The review then introduces the transformations of whole biomass via catalytic gasification, catalytic pyrolysis, as well as emerging strategies. Finally, opportunities, challenges and prospective of woody biomass valorization are highlighted.
Application of deep eutectic solvents in biomass pretreatment and conversion
Yu Chen, Tiancheng Mu
2019, 4(2): 95-115.   doi: 10.1016/j.gee.2019.01.012
[Abstract](951) [FullText HTML](419) [PDF 3331KB](125)
摘要:
Biomass is renewable, abundant, cheap, biocompatible, and biodegradable materials and has been used to produce chemicals, materials, energy, and fuels. However, most of the biomass, especially most of the biomass polymers are not soluble in common solvents, which hinders their pretreatment and conversion. Deep eutectic solvents (DESs) are environmental-friendly, cheap, and highly tunable, with high solubility, which renders them potential applications in biomass pretreatment and conversion. They could be used as solvents or catalysts and so on. This paper intends to review the application of DESs for the pretreatment of biomass and conversion of biomass to value-added products. We focus on the following topics related to biomass and DESs: (1) DESs for the pretreatment of biomass; (2) DESs for the dissolution and separation of biomass or extraction of chemicals from biomass; (3) DESs for biomass conversion; (4) Drawbacks, and recyclability of DESs for pretreatment and conversion of biomass.
Overview of acidic deep eutectic solvents on synthesis, properties and applications
Hao Qin, Xutao Hu, Jingwen Wang, Hongye Cheng, Lifang Chen, Zhiwen Qi
2020, 5(1): 8-21.   doi: 10.1016/j.gee.2019.03.002
[Abstract](1001) [FullText HTML](443) [PDF 1576KB](116)
摘要:
This review divides the acidic deep eutectic solvents (ADES) into Brønsted and Lewis DES according to their diversity of acidic character. The hydrogen bond donors and halide salts for formulating an ADES are classified, the synthesis methods are described, and the physicochemical properties including freezing point, acidity, density, viscosity and conductivity are presented. Furthermore, the applications of Brønsted acidic deep eutectic solvents (BADES) and Lewis acidic deep eutectic solvents (LADES) are overviewed, respectively, covering the fields in dissolution, extraction, organic reaction and metal electrodeposition. It is expected that the ADES has great potential to replace the pollutional mineral acid, expensive and unstable solid acid, and costly ionic liquid in many acid-employed chemical processes, thus meeting the demands of green chemistry.
Synthesis and applications of MOF-derived porous nanostructures
Min Hui Yap, Kam Loon Fow, George Zheng Chen
2017, 2(3): 218-245.   doi: 10.1016/j.gee.2017.05.003
[Abstract](731) [FullText HTML](307) [PDF 6267KB](105)
摘要:
Metal organic frameworks (MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area, large pore volume, and excellent chemical stability. Research on synthesis, structures and properties of various MOFs has shown that they are promising materials for many applications, such as energy storage, gas storage, heterogeneous catalysis and sensing. Apart from direct use, MOFs have also been used as support substrates for nanomaterials or as sacrificial templates/precursors for preparation of various functional nanostructures. In this review, we aim to present the most recent development of MOFs as precursors for the preparation of various nanostructures and their potential applications in energy-related devices and processes. Specifically, this present survey intends to push the boundaries and covers the literatures from the year 2013 to early 2017, on supercapacitors, lithium ion batteries, electrocatalysts, photocatalyst, gas sensing, water treatment, solar cells, and carbon dioxide capture. Finally, an outlook in terms of future challenges and potential prospects towards industrial applications are also discussed.
A comprehensive review on recent progress in aluminum–air batteries
Yisi Liu, Qian Sun, Wenzhang Li, Keegan R. Adair, Jie Li, Xueliang Sun
2017, 2(3): 246-277.   doi: 10.1016/j.gee.2017.06.006
[Abstract](1033) [FullText HTML](476) [PDF 14207KB](179)
摘要:
The aluminum–air battery is considered to be an attractive candidate as a power source for electric vehicles (EVs) because of its high theoretical energy density (8100 Wh kg−1), which is significantly greater than that of the state-of-the-art lithium-ion batteries (LIBs). However, some technical and scientific problems preventing the large-scale development of Al–air batteries have not yet to be resolved. In this review, we present the fundamentals, challenges and the recent advances in Al–air battery technology from aluminum anode, air cathode and electrocatalysts to electrolytes and inhibitors. Firstly, the alloying of aluminum with transition metal elements is reviewed and shown to reduce the self-corrosion of Al and improve battery performance. Additionally for the cathode, extensive studies of electrocatalytic materials for oxygen reduction/evolution including Pt and Pt alloys, nonprecious metal catalysts, and carbonaceous materials at the air cathode are highlighted. Moreover, for the electrolyte, the application of aqueous and nonaqueous electrolytes in Al–air batteries are discussed. Meanwhile, the addition of inhibitors to the electrolyte to enhance electrochemical performance is also explored. Finally, the challenges and future research directions are proposed for the further development of Al–air batteries.
Progress in aqueous rechargeable batteries
Jilei Liu, Chaohe Xu, Zhen Chen, Shibing Ni, Ze Xiang Shen
2018, 3(1): 20-41.   doi: 10.1016/j.gee.2017.10.001
[Abstract](508) [FullText HTML](210) [PDF 6967KB](81)
摘要:
Over the past decades, a series of aqueous rechargeable batteries (ARBs) were explored, investigated and demonstrated. Among them, aqueous rechargeable alkali-metal ion (Li+, Na+, K+) batteries, aqueous rechargeable-metal ion (Zn2+, Mg2+, Ca2+, Al3+) batteries and aqueous rechargeable hybrid batteries are standing out due to peculiar properties. In this review, we focus on the fundamental basics of these batteries, and discuss the scientific and/or technological achievements and challenges. By critically reviewing state-of-the-art technologies and the most promising results so far, we aim to analyze the benefits of ARBs and the critical issues to be addressed, and to promote better development of ARBs.
Cellulose-based materials in wastewater treatment of petroleum industry
Baoliang Peng, Zhaoling Yao, Xiaocong Wang, Mitchel Crombeen, Dalton G. Sweeney, Kam Chiu Tam
2020, 5(1): 37-49.   doi: 10.1016/j.gee.2019.09.003
[Abstract](528) [FullText HTML](240) [PDF 2482KB](68)
摘要:
The most abundant natural biopolymer on earth, cellulose fiber, may offer a highly efficient, low-cost, and chemical-free option for wastewater treatment. Cellulose is widely distributed in plants and several marine animals. It is a carbohydrate polymer consisting of β-1,4-linked anhydro-D-glucose units with three hydroxyl groups per anhydroglucose unit (AGU). Cellulose-based materials have been used in food, industrial, pharmaceutical, paper, textile production, and in wastewater treatment applications due to their low cost, renewability, biodegradability, and non-toxicity. For water treatment in the oil and gas industry, cellulose-based materials can be used as adsorbents, flocculants, and oil/water separation membranes. In this review, the uses of cellulose-based materials for wastewater treatment in the oil & gas industry are summarized, and recent research progress in the following aspects are highlighted: crude oil spill cleaning, flocculation of solid suspended matter in drilling or oil recovery in the upstream oil industry, adsorption of heavy metal or chemicals, and separation of oil/water by cellulosic membrane in the downstream water treatment.
Recent progress on synthesis of ZIF-67-based materials and their application to heterogeneous catalysis
Chongxiong Duan, Yi Yu, Han Hu
2022, 7(1): 3-15.   doi: 10.1016/j.gee.2020.12.023
[Abstract](844) [FullText HTML](391) [PDF 3992KB](66)
摘要:
In recent years, an increasing amount of interest has been dedicated to the synthesis and application of ZIF-67-based materials due to their exceptionally high surface area, tunable porosity, and excellent thermal and chemical stabilities. This review summarizes the latest strategies of synthesizing ZIF-67-based materials by exploring the prominent examples. Then, the recent progress in the applications of ZIF-67-based materials in heterogeneous catalysis, including catalysis of the redox reactions, addition reactions, esterification reactions, Knoevenagel condensations, and hydrogenation-dehydrogenation reactions, has been elaborately discussed. Finally, we end this work by shedding some light on the large-scale industrial production of ZIF-67-based materials and their applications in the future.
Lignin-based carbon fibers: Formation, modification and potential applications
Shichao Wang, Jixing Bai, Mugaanire Tendo Innocent, Qianqian Wang, Hengxue Xiang, Jianguo Tang, Meifang Zhu
2022, 7(4): 578-605.   doi: 10.1016/j.gee.2021.04.006
[Abstract](702) [FullText HTML](293) [PDF 7520KB](58)
摘要:
As an aromatic polymer in nature, lignin has recently attracted gross attention because of its advantages of high carbon content, low cost and bio-renewability. However, most lignin is directly burnt for power generation to satisfy the energy demand of the pulp mills. As a result, only a handful of isolated lignin is used as a raw material. Thus, increasing value addition on lignin to expand its scope of applications is currently a challenge demanding immediate attention. Many efforts have been made in the valorization of lignin, including the preparation of precursors for carbon fibers. However, its complex structure and diversity significantly restrict the spinnability of lignin. In this review, we provide elaborate knowledge on the preparation of lignin-based carbon fibers ranging from the relationships among chemical structures, formation conditions and properties of fibers, to their potential applications. Specifically, control procedures for different spinning methods of lignin, including melt spinning, solution spinning and electrospinning, together with stabilization and carbonization are deeply discussed to provide an overall understanding towards the formation of lignin-based carbon fibers. We also offer perspectives on the challenges and new directions for future development of lignin-based carbon fibers.
A survey of hybrid energy devices based on supercapacitors
Dan Gao, Zhiling Luo, Changhong Liu, Shoushan Fan
2023, 8(4): 972-988.   doi: 10.1016/j.gee.2022.02.002
[Abstract](354) [PDF 5056KB](30)
摘要:
Developing multifunctional energy storage systems with high specific energy, high specific power and long cycling life has been the one of the most important research directions. Compared to batteries and traditional capacitors, supercapacitors possess more balanced performance with both high specific power and long cycle-life. Nevertheless, regular supercapacitors can only achieve energy storage without harvesting energy and the energy density is still not very high compared to batteries. Therefore, combining high specific energy and high specific power, long cycle-life and even fast self-charging into one cell has been a promising direction for future energy storage devices. The multifunctional hybrid supercapacitors like asymmetric supercapacitors, batteries/supercapacitors hybrid devices and self-charging hybrid supercapacitors have been widely studied recently. Carbon based electrodes are common materials used in all kinds of energy storage devices due to their fabulous electrical and mechanical properties. In this survey, the research progress of all kinds of hybrid supercapacitors using multiple effects and their working mechanisms are briefly reviewed. And their advantages and disadvantages are discussed. The hybrid supercapacitors have great application potential for portable electronics, wearable devices and implantable devices in the future.
Cell-free biocatalysis coupled with photo-catalysis and electro-catalysis: Efficient CO2-to-chemical conversion
Junzhu Yang, Chi-Kit Sou, Yuan Lu
2024, 9(9): 1366-1383.   doi: 10.1016/j.gee.2023.10.002
[Abstract](393) [PDF 4824KB](192)
Abstract:
The increasing atmospheric carbon dioxide (CO2) concentration has exposed a series of crises in the earth's ecological environment. How to effectively fix and convert carbon dioxide into products with added value has attracted the attention of many researchers. Cell-free enzyme catalytic system coupled with electrical and light have been a promising attempt in the field of biological carbon fixation in recent years. In this review, the research progresses of photoenzyme catalysis, electroenzyme catalysis and photo-electroenzyme catalysis for converting carbon dioxide into chemical products in cell-free systems are systematically summarized. We focus on reviewing and comparing various coupling methods and principles of photoenzyme catalysis and electroenzyme catalysis in cell-free systems, especially the materials used in the construction of the coupling system, and analyze and point out the characteristics and possible problems of different coupling methods. Finally, we discuss the major challenges and prospects of coupling physical signals and cell-free enzymatic catalytic systems in the field of CO2 fixation, suggesting possible strategies to improve the carbon sequestration capacity of such systems.
Spectrophotometric determination of the formation constants of Calcium(II) complexes with 1,2-ethylenediamine, 1,3-propanediamine and 1,4-butanediamine in acetonitrile
Jacqueline González González, Mónica Nájera-Lara, Varinia López-Ramírez, Juan Antonio Ramírez-Vázquez, José J.N. Segoviano-Garfias
2017, 2(1): 51-57.   doi: 10.1016/j.gee.2017.01.002
[Abstract](215) [FullText HTML](98) [PDF 1052KB](98)
Abstract:
In this work, with the purpose to explore the coordination chemistry of calcium complexes which could work as a partial model of manganese–calcium cluster, a spectrophotometric study to evaluate the stability of the complexes: Calcium(II)-1,2-ethylendiamine, Calcium(II)-1,3-propanediamine and Calcium(II)-1,4-butanediamine in acetonitrile, were carried on. By processing the spectrophotometric data with the HypSpec program allows the determination of the formation constants. The logarithmic values of the formation constants obtained for Calcium(II)-1,2-ethylendiamine, Calcium(II)-1,3-propanediamine and Calcium(II)-1,4-butanediamine were log β110 = 4.69, log β110 = 5.25 and log β110 = 4.072, respectively.
A comprehensive review on recent progress in aluminum–air batteries
Yisi Liu, Qian Sun, Wenzhang Li, Keegan R. Adair, Jie Li, Xueliang Sun
2017, 2(3): 246-277.   doi: 10.1016/j.gee.2017.06.006
[Abstract](1033) [FullText HTML](476) [PDF 14207KB](476)
Abstract:
The aluminum–air battery is considered to be an attractive candidate as a power source for electric vehicles (EVs) because of its high theoretical energy density (8100 Wh kg−1), which is significantly greater than that of the state-of-the-art lithium-ion batteries (LIBs). However, some technical and scientific problems preventing the large-scale development of Al–air batteries have not yet to be resolved. In this review, we present the fundamentals, challenges and the recent advances in Al–air battery technology from aluminum anode, air cathode and electrocatalysts to electrolytes and inhibitors. Firstly, the alloying of aluminum with transition metal elements is reviewed and shown to reduce the self-corrosion of Al and improve battery performance. Additionally for the cathode, extensive studies of electrocatalytic materials for oxygen reduction/evolution including Pt and Pt alloys, nonprecious metal catalysts, and carbonaceous materials at the air cathode are highlighted. Moreover, for the electrolyte, the application of aqueous and nonaqueous electrolytes in Al–air batteries are discussed. Meanwhile, the addition of inhibitors to the electrolyte to enhance electrochemical performance is also explored. Finally, the challenges and future research directions are proposed for the further development of Al–air batteries.
Nitrogen-doping boosts *CO utilization and H2O activation on copper for improving CO2 reduction to C2+ products
Yisen Yang, Zhonghao Tan, Jianling Zhang, Jie Yang, Renjie Zhang, Sha Wang, Yi Song, Zhuizhui Su
2024, 9(9): 1459-1465.   doi: 10.1016/j.gee.2023.09.002
[Abstract](183) [PDF 1881KB](90)
Abstract:
To improve the electrocatalytic transformation of carbon dioxide (CO2) to multi-carbon (C2+) products is of great importance. Here we developed a nitrogen-doped Cu catalyst, by which the maximum C2+ Faradaic efficiency can reach 72.7% in flow-cell system, with the partial current density reaching 0.62 A cm-2. The in situ Raman spectra demonstrate that the *CO adsorption can be strengthened on such a N-doped Cu catalyst, thus promoting the *CO utilization in the subsequent C-C coupling step. Simultaneously, the water activation can be well enhanced by N doping on Cu catalyst. Owing to the synergistic effects, the selectivity and activity for C2+ products over the N-deoped Cu catalyst are much improved.
Recovery of greenhouse gas as cleaner fossil fuel contributes to carbon neutrality
Xin Zhang, Jian-Rong Li
2023, 8(2): 351-353.   doi: 10.1016/j.gee.2022.06.002
[Abstract](577) [PDF 438KB](252)
Abstract:
Under the context of carbon neutrality of China, it is urgent to shift our energy supply towards cleaner fuels as well as to reduce the greenhouse gas emission. Currently, coal is the main fossil fuel energy source of China. The country is striving hard to replace it with methane, a cleaner fossil fuel. Although China has rich geological resources of methane as coal bed methane (CBM) reserves, it is quite challenging to utilize them due to low concentration. The CBM is however mainly emitted directly to atmosphere during coal mining, causing waste of the resource and huge contribution to greenhouse effect. The recent work by Yang et al. demonstrated a potential solution to extract low concentration methane selectively from CBM through using MOF materials as sorbents. Such kind of materials and associated separation technology are promising to reduce greenhouse gas emission and promote the methane production capability, which would contribute to carbon neutrality in dual pathways.
Catalytic conversion of lignocellulosic biomass into chemicals and fuels
Weiping Deng, Yunchao Feng, Jie Fu, Haiwei Guo, Yong Guo, Buxing Han, Zhicheng Jiang, Lingzhao Kong, Changzhi Li, Haichao Liu, Phuc T.T. Nguyen, Puning Ren, Feng Wang, Shuai Wang, Yanqin Wang, Ye Wang, Sie Shing Wong, Kai Yan, Ning Yan, Xiaofei Yang, Yuanbao Zhang, Zhanrong Zhang, Xianhai Zeng, Hui Zhou
2023, 8(1): 10-114.   doi: 10.1016/j.gee.2022.07.003
Abstract HTML PDF
Abstract:
In the search of alternative resources to make commodity chemicals and transportation fuels for a low carbon future, lignocellulosic biomass with over 180-billion-ton annual production rate has been identified as a promising feedstock. This review focuses on the state-of-the-art catalytic transformation of lignocellulosic biomass into value-added chemicals and fuels. Following a brief introduction on the structure, major resources and pretreatment methods of lignocellulosic biomass, the catalytic conversion of three main components, i.e., cellulose, hemicellulose and lignin, into various compounds are comprehensively discussed. Either in separate steps or in one-pot, cellulose and hemicellulose are hydrolyzed into sugars and upgraded into oxygen-containing chemicals such as 5-HMF, furfural, polyols, and organic acids, or even nitrogen-containing chemicals such as amino acids. On the other hand, lignin is first depolymerized into phenols, catechols, guaiacols, aldehydes and ketones, and then further transformed into hydrocarbon fuels, bioplastic precursors and bioactive compounds. The review then introduces the transformations of whole biomass via catalytic gasification, catalytic pyrolysis, as well as emerging strategies. Finally, opportunities, challenges and prospective of woody biomass valorization are highlighted.
Application of deep eutectic solvents in biomass pretreatment and conversion
Yu Chen, Tiancheng Mu
2019, 4(2): 95-115.   doi: 10.1016/j.gee.2019.01.012
Abstract HTML PDF
Abstract:
Biomass is renewable, abundant, cheap, biocompatible, and biodegradable materials and has been used to produce chemicals, materials, energy, and fuels. However, most of the biomass, especially most of the biomass polymers are not soluble in common solvents, which hinders their pretreatment and conversion. Deep eutectic solvents (DESs) are environmental-friendly, cheap, and highly tunable, with high solubility, which renders them potential applications in biomass pretreatment and conversion. They could be used as solvents or catalysts and so on. This paper intends to review the application of DESs for the pretreatment of biomass and conversion of biomass to value-added products. We focus on the following topics related to biomass and DESs: (1) DESs for the pretreatment of biomass; (2) DESs for the dissolution and separation of biomass or extraction of chemicals from biomass; (3) DESs for biomass conversion; (4) Drawbacks, and recyclability of DESs for pretreatment and conversion of biomass.
Overview of acidic deep eutectic solvents on synthesis, properties and applications
Hao Qin, Xutao Hu, Jingwen Wang, Hongye Cheng, Lifang Chen, Zhiwen Qi
2020, 5(1): 8-21.   doi: 10.1016/j.gee.2019.03.002
Abstract HTML PDF
Abstract:
This review divides the acidic deep eutectic solvents (ADES) into Brønsted and Lewis DES according to their diversity of acidic character. The hydrogen bond donors and halide salts for formulating an ADES are classified, the synthesis methods are described, and the physicochemical properties including freezing point, acidity, density, viscosity and conductivity are presented. Furthermore, the applications of Brønsted acidic deep eutectic solvents (BADES) and Lewis acidic deep eutectic solvents (LADES) are overviewed, respectively, covering the fields in dissolution, extraction, organic reaction and metal electrodeposition. It is expected that the ADES has great potential to replace the pollutional mineral acid, expensive and unstable solid acid, and costly ionic liquid in many acid-employed chemical processes, thus meeting the demands of green chemistry.
Synthesis and applications of MOF-derived porous nanostructures
Min Hui Yap, Kam Loon Fow, George Zheng Chen
2017, 2(3): 218-245.   doi: 10.1016/j.gee.2017.05.003
Abstract HTML PDF
Abstract:
Metal organic frameworks (MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area, large pore volume, and excellent chemical stability. Research on synthesis, structures and properties of various MOFs has shown that they are promising materials for many applications, such as energy storage, gas storage, heterogeneous catalysis and sensing. Apart from direct use, MOFs have also been used as support substrates for nanomaterials or as sacrificial templates/precursors for preparation of various functional nanostructures. In this review, we aim to present the most recent development of MOFs as precursors for the preparation of various nanostructures and their potential applications in energy-related devices and processes. Specifically, this present survey intends to push the boundaries and covers the literatures from the year 2013 to early 2017, on supercapacitors, lithium ion batteries, electrocatalysts, photocatalyst, gas sensing, water treatment, solar cells, and carbon dioxide capture. Finally, an outlook in terms of future challenges and potential prospects towards industrial applications are also discussed.
A comprehensive review on recent progress in aluminum–air batteries
Yisi Liu, Qian Sun, Wenzhang Li, Keegan R. Adair, Jie Li, Xueliang Sun
2017, 2(3): 246-277.   doi: 10.1016/j.gee.2017.06.006
Abstract HTML PDF
Abstract:
The aluminum–air battery is considered to be an attractive candidate as a power source for electric vehicles (EVs) because of its high theoretical energy density (8100 Wh kg−1), which is significantly greater than that of the state-of-the-art lithium-ion batteries (LIBs). However, some technical and scientific problems preventing the large-scale development of Al–air batteries have not yet to be resolved. In this review, we present the fundamentals, challenges and the recent advances in Al–air battery technology from aluminum anode, air cathode and electrocatalysts to electrolytes and inhibitors. Firstly, the alloying of aluminum with transition metal elements is reviewed and shown to reduce the self-corrosion of Al and improve battery performance. Additionally for the cathode, extensive studies of electrocatalytic materials for oxygen reduction/evolution including Pt and Pt alloys, nonprecious metal catalysts, and carbonaceous materials at the air cathode are highlighted. Moreover, for the electrolyte, the application of aqueous and nonaqueous electrolytes in Al–air batteries are discussed. Meanwhile, the addition of inhibitors to the electrolyte to enhance electrochemical performance is also explored. Finally, the challenges and future research directions are proposed for the further development of Al–air batteries.
Progress in aqueous rechargeable batteries
Jilei Liu, Chaohe Xu, Zhen Chen, Shibing Ni, Ze Xiang Shen
2018, 3(1): 20-41.   doi: 10.1016/j.gee.2017.10.001
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Over the past decades, a series of aqueous rechargeable batteries (ARBs) were explored, investigated and demonstrated. Among them, aqueous rechargeable alkali-metal ion (Li+, Na+, K+) batteries, aqueous rechargeable-metal ion (Zn2+, Mg2+, Ca2+, Al3+) batteries and aqueous rechargeable hybrid batteries are standing out due to peculiar properties. In this review, we focus on the fundamental basics of these batteries, and discuss the scientific and/or technological achievements and challenges. By critically reviewing state-of-the-art technologies and the most promising results so far, we aim to analyze the benefits of ARBs and the critical issues to be addressed, and to promote better development of ARBs.
Cellulose-based materials in wastewater treatment of petroleum industry
Baoliang Peng, Zhaoling Yao, Xiaocong Wang, Mitchel Crombeen, Dalton G. Sweeney, Kam Chiu Tam
2020, 5(1): 37-49.   doi: 10.1016/j.gee.2019.09.003
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The most abundant natural biopolymer on earth, cellulose fiber, may offer a highly efficient, low-cost, and chemical-free option for wastewater treatment. Cellulose is widely distributed in plants and several marine animals. It is a carbohydrate polymer consisting of β-1,4-linked anhydro-D-glucose units with three hydroxyl groups per anhydroglucose unit (AGU). Cellulose-based materials have been used in food, industrial, pharmaceutical, paper, textile production, and in wastewater treatment applications due to their low cost, renewability, biodegradability, and non-toxicity. For water treatment in the oil and gas industry, cellulose-based materials can be used as adsorbents, flocculants, and oil/water separation membranes. In this review, the uses of cellulose-based materials for wastewater treatment in the oil & gas industry are summarized, and recent research progress in the following aspects are highlighted: crude oil spill cleaning, flocculation of solid suspended matter in drilling or oil recovery in the upstream oil industry, adsorption of heavy metal or chemicals, and separation of oil/water by cellulosic membrane in the downstream water treatment.
Recent progress on synthesis of ZIF-67-based materials and their application to heterogeneous catalysis
Chongxiong Duan, Yi Yu, Han Hu
2022, 7(1): 3-15.   doi: 10.1016/j.gee.2020.12.023
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In recent years, an increasing amount of interest has been dedicated to the synthesis and application of ZIF-67-based materials due to their exceptionally high surface area, tunable porosity, and excellent thermal and chemical stabilities. This review summarizes the latest strategies of synthesizing ZIF-67-based materials by exploring the prominent examples. Then, the recent progress in the applications of ZIF-67-based materials in heterogeneous catalysis, including catalysis of the redox reactions, addition reactions, esterification reactions, Knoevenagel condensations, and hydrogenation-dehydrogenation reactions, has been elaborately discussed. Finally, we end this work by shedding some light on the large-scale industrial production of ZIF-67-based materials and their applications in the future.
Lignin-based carbon fibers: Formation, modification and potential applications
Shichao Wang, Jixing Bai, Mugaanire Tendo Innocent, Qianqian Wang, Hengxue Xiang, Jianguo Tang, Meifang Zhu
2022, 7(4): 578-605.   doi: 10.1016/j.gee.2021.04.006
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As an aromatic polymer in nature, lignin has recently attracted gross attention because of its advantages of high carbon content, low cost and bio-renewability. However, most lignin is directly burnt for power generation to satisfy the energy demand of the pulp mills. As a result, only a handful of isolated lignin is used as a raw material. Thus, increasing value addition on lignin to expand its scope of applications is currently a challenge demanding immediate attention. Many efforts have been made in the valorization of lignin, including the preparation of precursors for carbon fibers. However, its complex structure and diversity significantly restrict the spinnability of lignin. In this review, we provide elaborate knowledge on the preparation of lignin-based carbon fibers ranging from the relationships among chemical structures, formation conditions and properties of fibers, to their potential applications. Specifically, control procedures for different spinning methods of lignin, including melt spinning, solution spinning and electrospinning, together with stabilization and carbonization are deeply discussed to provide an overall understanding towards the formation of lignin-based carbon fibers. We also offer perspectives on the challenges and new directions for future development of lignin-based carbon fibers.
A survey of hybrid energy devices based on supercapacitors
Dan Gao, Zhiling Luo, Changhong Liu, Shoushan Fan
2023, 8(4): 972-988.   doi: 10.1016/j.gee.2022.02.002
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Developing multifunctional energy storage systems with high specific energy, high specific power and long cycling life has been the one of the most important research directions. Compared to batteries and traditional capacitors, supercapacitors possess more balanced performance with both high specific power and long cycle-life. Nevertheless, regular supercapacitors can only achieve energy storage without harvesting energy and the energy density is still not very high compared to batteries. Therefore, combining high specific energy and high specific power, long cycle-life and even fast self-charging into one cell has been a promising direction for future energy storage devices. The multifunctional hybrid supercapacitors like asymmetric supercapacitors, batteries/supercapacitors hybrid devices and self-charging hybrid supercapacitors have been widely studied recently. Carbon based electrodes are common materials used in all kinds of energy storage devices due to their fabulous electrical and mechanical properties. In this survey, the research progress of all kinds of hybrid supercapacitors using multiple effects and their working mechanisms are briefly reviewed. And their advantages and disadvantages are discussed. The hybrid supercapacitors have great application potential for portable electronics, wearable devices and implantable devices in the future.
Cell-free biocatalysis coupled with photo-catalysis and electro-catalysis: Efficient CO2-to-chemical conversion
Junzhu Yang, Chi-Kit Sou, Yuan Lu
2024, 9(9): 1366-1383.   doi: 10.1016/j.gee.2023.10.002
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The increasing atmospheric carbon dioxide (CO2) concentration has exposed a series of crises in the earth's ecological environment. How to effectively fix and convert carbon dioxide into products with added value has attracted the attention of many researchers. Cell-free enzyme catalytic system coupled with electrical and light have been a promising attempt in the field of biological carbon fixation in recent years. In this review, the research progresses of photoenzyme catalysis, electroenzyme catalysis and photo-electroenzyme catalysis for converting carbon dioxide into chemical products in cell-free systems are systematically summarized. We focus on reviewing and comparing various coupling methods and principles of photoenzyme catalysis and electroenzyme catalysis in cell-free systems, especially the materials used in the construction of the coupling system, and analyze and point out the characteristics and possible problems of different coupling methods. Finally, we discuss the major challenges and prospects of coupling physical signals and cell-free enzymatic catalytic systems in the field of CO2 fixation, suggesting possible strategies to improve the carbon sequestration capacity of such systems.
Spectrophotometric determination of the formation constants of Calcium(II) complexes with 1,2-ethylenediamine, 1,3-propanediamine and 1,4-butanediamine in acetonitrile
Jacqueline González González, Mónica Nájera-Lara, Varinia López-Ramírez, Juan Antonio Ramírez-Vázquez, José J.N. Segoviano-Garfias
2017, 2(1): 51-57.   doi: 10.1016/j.gee.2017.01.002
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In this work, with the purpose to explore the coordination chemistry of calcium complexes which could work as a partial model of manganese–calcium cluster, a spectrophotometric study to evaluate the stability of the complexes: Calcium(II)-1,2-ethylendiamine, Calcium(II)-1,3-propanediamine and Calcium(II)-1,4-butanediamine in acetonitrile, were carried on. By processing the spectrophotometric data with the HypSpec program allows the determination of the formation constants. The logarithmic values of the formation constants obtained for Calcium(II)-1,2-ethylendiamine, Calcium(II)-1,3-propanediamine and Calcium(II)-1,4-butanediamine were log β110 = 4.69, log β110 = 5.25 and log β110 = 4.072, respectively.
A comprehensive review on recent progress in aluminum–air batteries
Yisi Liu, Qian Sun, Wenzhang Li, Keegan R. Adair, Jie Li, Xueliang Sun
2017, 2(3): 246-277.   doi: 10.1016/j.gee.2017.06.006
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The aluminum–air battery is considered to be an attractive candidate as a power source for electric vehicles (EVs) because of its high theoretical energy density (8100 Wh kg−1), which is significantly greater than that of the state-of-the-art lithium-ion batteries (LIBs). However, some technical and scientific problems preventing the large-scale development of Al–air batteries have not yet to be resolved. In this review, we present the fundamentals, challenges and the recent advances in Al–air battery technology from aluminum anode, air cathode and electrocatalysts to electrolytes and inhibitors. Firstly, the alloying of aluminum with transition metal elements is reviewed and shown to reduce the self-corrosion of Al and improve battery performance. Additionally for the cathode, extensive studies of electrocatalytic materials for oxygen reduction/evolution including Pt and Pt alloys, nonprecious metal catalysts, and carbonaceous materials at the air cathode are highlighted. Moreover, for the electrolyte, the application of aqueous and nonaqueous electrolytes in Al–air batteries are discussed. Meanwhile, the addition of inhibitors to the electrolyte to enhance electrochemical performance is also explored. Finally, the challenges and future research directions are proposed for the further development of Al–air batteries.
Nitrogen-doping boosts *CO utilization and H2O activation on copper for improving CO2 reduction to C2+ products
Yisen Yang, Zhonghao Tan, Jianling Zhang, Jie Yang, Renjie Zhang, Sha Wang, Yi Song, Zhuizhui Su
2024, 9(9): 1459-1465.   doi: 10.1016/j.gee.2023.09.002
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To improve the electrocatalytic transformation of carbon dioxide (CO2) to multi-carbon (C2+) products is of great importance. Here we developed a nitrogen-doped Cu catalyst, by which the maximum C2+ Faradaic efficiency can reach 72.7% in flow-cell system, with the partial current density reaching 0.62 A cm-2. The in situ Raman spectra demonstrate that the *CO adsorption can be strengthened on such a N-doped Cu catalyst, thus promoting the *CO utilization in the subsequent C-C coupling step. Simultaneously, the water activation can be well enhanced by N doping on Cu catalyst. Owing to the synergistic effects, the selectivity and activity for C2+ products over the N-deoped Cu catalyst are much improved.
Recovery of greenhouse gas as cleaner fossil fuel contributes to carbon neutrality
Xin Zhang, Jian-Rong Li
2023, 8(2): 351-353.   doi: 10.1016/j.gee.2022.06.002
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Under the context of carbon neutrality of China, it is urgent to shift our energy supply towards cleaner fuels as well as to reduce the greenhouse gas emission. Currently, coal is the main fossil fuel energy source of China. The country is striving hard to replace it with methane, a cleaner fossil fuel. Although China has rich geological resources of methane as coal bed methane (CBM) reserves, it is quite challenging to utilize them due to low concentration. The CBM is however mainly emitted directly to atmosphere during coal mining, causing waste of the resource and huge contribution to greenhouse effect. The recent work by Yang et al. demonstrated a potential solution to extract low concentration methane selectively from CBM through using MOF materials as sorbents. Such kind of materials and associated separation technology are promising to reduce greenhouse gas emission and promote the methane production capability, which would contribute to carbon neutrality in dual pathways.

Editor-in-Chief:Buxing Han

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