2024 Vol. 9, No. 2

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Research highlight
New possibility for PET plastic recycling by a tailored hydrolytic enzyme
Shijie Yu, Qinghai Li, Yanguo Zhang, Hui Zhou
2024, 9(2): 163-165. doi: 10.1016/j.gee.2023.02.007
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Plastic waste puts a huge burden on the ecosystem due to the current lack of mature recycling technology. Poly (ethylene terephthalate) (PET) is one of the most produced plastics in the world. Enzymatic decomposition holds the promise of recovering monomers from PET plastic, and the monomers can be used to regenerate new PET products. However, there are still limitations in the activity and thermal stability of the existing PET hydrolases. The recent study by Lu et al. introduced a novel PET hydrolase via machine learning-aided engineering. The obtained PET hydrolase showed excellent activity and thermal stability in the hydrolysis of PET and is capable of directly degrading large amounts of postconsumer PET products. This approach provides an effective method for recycling PET waste and is expected to improve the current state of plastic pollution worldwide.
Review articles
Engineering g-C3N4 based materials for advanced photocatalysis: Recent advances
Xin-Lian Song, Lei Chen, Li-Jiao Gao, Jin-Tao Ren, Zhong-Yong Yuan
2024, 9(2): 166-197. doi: 10.1016/j.gee.2022.12.005
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Photocatalysis driven by abundant yet intermittent solar energy has considerable potential in renewable energy generation and environmental remediation. The outstanding electronic structure and physicochemical properties of graphitic carbon nitride (g-C3N4), together with unique metal-free characteristic, make them ideal candidates for advanced photocatalysts construction. This review summarizes the up-to-date advances on g-C3N4 based photocatalysts from ingenious-design strategies and diversified photocatalytic applications. Notably, the advantages, fabrication methods and limitations of each design strategy are systemically analyzed. In order to deeply comprehend the inner connection of theory–structure–performance upon g-C3N4 based photocatalysts, structure/composition designs, corresponding photocatalytic activities and reaction mechanisms are jointly discussed, associated with introducing their photocatalytic applications toward water splitting, carbon dioxide/nitrogen reduction and pollutants degradation, etc. Finally, the current challenges and future perspectives for g-C3N4 based materials for photocatalysis are briefly proposed. These design strategies and limitations are also instructive for constructing g-C3N4 based materials in other energy and environment-related applications.
Strategies of selective electroreduction of aqueous nitrate to N2 in chloride-free system: A critical review
Fukuan Li, Weizhe Zhang, Peng Zhang, Ao Gong, Kexun Li
2024, 9(2): 198-216. doi: 10.1016/j.gee.2022.09.007
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Electroreduction of nitrate has been gaining wide attention in recent years owing to it's beneficial for converting nitrate into benign N2 from the perspective of electrocatalytic denitrification or into value-added ammonia from the perspective of electrocatalytic NH3 synthesis. By reason of the undesired formation of ammonia is dominant during electroreduction of nitrate-containing wastewater, chloride has been widely used to improve N2 selectivity. Nevertheless, selective electroreduction of nitrate to N2 gas in chloride-containing system poses several drawbacks. In this review, we focus on the key strategies for efficiently enhancing N2 selectivity of electroreduction of nitrate in chloride-free system, including optimal selection of elements, combining an active metal catalyst with another metal, manipulating the crystalline morphology and facet orientation, constructing core–shell structure catalysts, etc. Before summarizing the strategies, four possible reaction pathways of electroreduction of nitrate to N2 are discussed. Overall, this review attempts to provide practical strategies for enhancing N2 selectivity without the aid of electrochlorination and highlight directions for future research for designing appropriate electrocatalyst for final electrocatalytic denitrification.
Porous framework materials for energy & environment relevant applications: A systematic review
Yutao Liu, Liyu Chen, Lifeng Yang, Tianhao Lan, Hui Wang, Chenghong Hu, Xue Han, Qixing Liu, Jianfa Chen, Zeming Feng, Xili Cui, Qianrong Fang, Hailong Wang, Libo Li, Yingwei Li, Huabin Xing, Sihai Yang, Dan Zhao, Jinping Li
2024, 9(2): 217-310. doi: 10.1016/j.gee.2022.12.010
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Carbon peaking and carbon neutralization trigger a technical revolution in energy & environment related fields. Development of new technologies for green energy production and storage, industrial energy saving and efficiency reinforcement, carbon capture, and pollutant gas treatment is in highly imperious demand. The emerging porous framework materials such as metal–organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs), owing to the permanent porosity, tremendous specific surface area, designable structure and customizable functionality, have shown great potential in major energy-consuming industrial processes, including sustainable energy gas catalytic conversion, energy-efficient industrial gas separation and storage. Herein, this manuscript presents a systematic review of porous framework materials for global and comprehensive energy & environment related applications, from a macroscopic and application perspective.
Research papers
Dealuminated Hβ zeolite for selective conversion of fructose to furfural and formic acid
Rui Li, Qixuan Lin, Junli Ren, Xiaobao Yang, Yingxiong Wang, Lingzhao Kong
2024, 9(2): 311-320. doi: 10.1016/j.gee.2022.06.003
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The fructose-to-furfural transformation is facing major challenges in the selectivity and high efficiency. Herein, we have developed a simple and effective approach for the selective conversion of fructose to furfural using Hβ zeolite modified by organic acids for dealuminization to regulate its textural and acidic properties. It was found that citric acid-dealuminized Hβ zeolite possessed high specific surface areas, wide channels and high Brønsted acid amount, which facilitated the selective conversion of fructose to furfural with a maximum yield of 76.2% at 433 K for 1 h in the γ-butyrolactone (GBL)-H2O system, as well as the concomitant formation of 83.0% formic acid. The 13C-isotope labelling experiments and the mechanism revealed that the selective cleavage of C1–C2 or C5–C6 bond on fructose was firstly occurred to form pentose or C5 intermediate by weak Brønsted acid, which was then dehydrated to furfural by strong Brønsted acid. Also this dealuminized Hβ catalyst showed the great recycling performance and was active for the conversion of glucose and mannose.
CO2 methanation boosted by support-size-dependent strong metal-support interaction and B–O–Ti component
Shaoyu Yuan, Yushan Yang, Zhangyi Xiong, Peijing Guo, Sufang Sun, Zejiang Li, Jianlong Du, Yongjun Gao
2024, 9(2): 321-332. doi: 10.1016/j.gee.2022.05.010
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Strong metal-support interaction (SMSI) has a great impact on the activity and selectivity of heterogeneous catalysts, which was usually adjusted by changing reduction temperature or processing catalyst in different atmosphere. However, few researches concentrate on modulating SMSI through regulating the structure of the support. Herein, we show how changing the surface environment of the anatase TiO2 (B–TiO2) can be used to modulate the SMSI. The moderate TiOx overlayer makes the Ni metal highly dispersed on the high specific surface area of support, resulting in a substantially enhanced CO2 methanation rate. Besides, a novel phenomenon was observed that boron dopants promote the formation of the B–O–Ti interface site, enhancing the catalytic performance of CO2 hydrogenation. DFT calculations confirm that the B–O–Ti structure facilitates the activation of CO2 and further hydrogenation to methane.
Integration of morphology and electronic structure modulation on cobalt phosphide nanosheets to boost photocatalytic hydrogen evolution from ammonia borane hydrolysis
Chao Wan, Yu Liang, Liu Zhou, Jindou Huang, Jiapei Wang, Fengqiu Chen, Xiaoli Zhan, Dang-guo Cheng
2024, 9(2): 333-343. doi: 10.1016/j.gee.2022.06.007
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The controllable and safe hydrogen storage technologies are widely recognized as the main bottleneck for the accomplishment of sustainable hydrogen energy. Ammonia borane (AB) has regarded as a competitive candidate for chemical hydrogen storage. However, developing efficient yet high-performance catalysts towards hydrogen evolution from AB hydrolysis remains an enormous challenge. Herein, cobalt phosphide nanosheets are synthesized by a facile salt-assisted along with low-temperature phosphidation strategy for simultaneously modulating its morphology and electronic structure, and function as hydrogen evolution photocatalysts. Impressively, the Co2P nanosheets display extraordinary performance with a record high turnover frequency of 44.9 min-1, outperforming most of the noble-metal-free catalysts reported to date. This remarkable performance is attributed to its desired nanosheets structure, featuring with high specific surface area, abundant exposed active sites, and short charge diffusion paths. Our findings provide a novel strategy for regulating metal phosphides with desired phase structure and morphology for energy-related applications and beyond.
Molecular-level proton acceptor boosts oxygen evolution catalysis to enable efficient industrial-scale water splitting
Yaobin Wang, Qian Lu, Xinlei Ge, Feng Li, Le Chen, Zhihui Zhang, Zhengping Fu, Yalin Lu, Yang Song, Yunfei Bu
2024, 9(2): 344-355. doi: 10.1016/j.gee.2022.07.001
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Industrial water splitting has long been suppressed by the sluggish kinetics of the oxygen evolution reaction (OER), which requires a catalyst to be efficient. Herein, we propose a molecular-level proton acceptor strategy to produce an efficient OER catalyst that can boost industrial-scale water splitting. Molecular-level phosphate (-PO4) group is introduced to modify the surface of PrBa0.5Ca0.5Co2O5+δ (PBCC). The achieved catalyst (PO4-PBCC) exhibits significantly enhanced catalytic performance in alkaline media. Based on the X-ray absorption spectroscopy results and density functional theory (DFT) calculations, the PO4 on the surface, which is regarded as the Lewis base, is the key factor to overcome the kinetic limitation of the proton transfer process during the OER. The use of the catalyst in a membrane electrode assembly (MEA) is further evaluated for industrial-scale water splitting, and it only needs a low voltage of 1.66 V to achieve a large current density of 1 A cm-2. This work provides a new molecular-level strategy to develop highly efficient OER electrocatalysts for industrial applications.
Lamellar water induced quantized interlayer spacing of nanochannels walls
Yue Zhang, Chenlu Wang, Chunlei Wang, Yingyan Zhang, Junhua Zhao, Ning Wei
2024, 9(2): 356-365. doi: 10.1016/j.gee.2022.06.009
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The nanoscale confinement is of great important for the industrial applications of molecular sieve, desalination, and also essential in biological transport systems. Massive efforts have been devoted to the influence of restricted spaces on the properties of confined fluids. However, the situation of channel-wall is crucial but attracts less attention and remains unknown. To fundamentally understand the mechanism of channel-walls in nanoconfinement, we investigated the interaction between the counter-force of the liquid and interlamellar spacing of nanochannel walls by considering the effect of both spatial confinement and surface wettability. The results reveal that the nanochannel stables at only a few discrete spacing states when its confinement is within 1.4 nm. The quantized interlayer spacing is attributed to water molecules becoming laminated structures, and the stable states are corresponding to the monolayer, bilayer and trilayer water configurations, respectively. The results can potentially help to understand the characterized interlayers spacing of graphene oxide membrane in water. Our findings are hold great promise in design of ion filtration membrane and artificial water/ion channels.
A novel Ag/ZnO core–shell structure for efficient sterilization synergizing antibiotics and subsequently removing residuals
Wenmei Han, Wenli Wang, Jie Fan, Runping Jia, Xuchun Yang, Tong Wu, Qingsheng Wu
2024, 9(2): 366-377. doi: 10.1016/j.gee.2022.07.004
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The massive use of antibiotics has led to the aggravation of bacterial resistance and also brought environmental pollution problems. This poses a great threat to human health. If the dosage of antibiotics is reduced by increasing its bactericidal performance, the emergence of drug resistance is certainly delayed, so that there's not enough time for developing drug resistance during treatment. Therefore, we selected typical representative materials of metal Ag and semiconductor ZnO nano-bactericides to design and synthesize Ag/ZnO hollow core–shell structures (AZ for short). Antibiotics are grafted on the surface of AZ through rational modification to form a composite sterilization system. The research results show that the antibacterial efficiency of the composite system is significantly increased, from the sum (34.7% + 22.8% = 57.5%) of the antibacterial efficiency of AZ and gentamicin to 80.2%, net synergizes 22.7%, which fully reflects the effect of 1 + 1 > 2. Therefore, the dosage of antibiotics can be drastically reduced in this way, which makes both the possibility of bacterial resistance and medical expenses remarkably decrease. Subsequently, residual antibiotics can be degraded under simple illumination using AZ-self as a photocatalyst, which cuts off the path of environmental pollution. In short, such an innovative route has guiding significance for drug resistance.
Natural high-porous diatomaceous-earth based self-floating aerogel for efficient solar steam power generation
Aitang Zhang, Kai Wang, Md Julker Nine, Mengyu Cao, Hanwen Zong, Zhiqiang Liu, Hanwen Guo, Jingquan Liu, Dusan Losic
2024, 9(2): 378-389. doi: 10.1016/j.gee.2022.08.001
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The application of solar steam generation in seawater desalination is an effective way to solve the shortage of fresh water resources. At present, many kinds of photothermal conversion materials have been developed and used as evaporators in seawater desalination. However, some evaporators need additional thermal insulation or water supply devices to achieve efficient photothermal conversion. In addition, their complex, time consuming and no scalable preparation process, high cost of raw materials and poor salt resistance hinder the practical application of these evaporator. Owing to its distinctive nanoporous structure, diatomite as fossilized single-cells algae diatoms is a promising natural silica-based material for seawater desalination. They are taken from sea and that makes true sense to use them in the sea. Herein, we report the first example of synthesis robust three-dimensional (3D) natural-diatomite composite by assembling polyaniline nanoparticles covered diatomite into the polyvinyl alcohol pre-treated melamine foam frameworks and demonstrate its application as new evaporator for seawater desalination. The porous framework does not only improve the sunlight scattering efficiency, but also offer large network of channels for water transportation. The inherent mechanism behind salt desalination process involves the absorption of water molecules on the surface of the internal silica micro-nano pores, and evaporation under the heat induced by the polyaniline absorbed sunlight. Meanwhile, the metal ions are segregated by many available pores and channels to achieve the self-desalting effect. The developed evaporator possesses the superiority of multi-stage pore structure, strong hydrophilicity, low thermal conductivity, excellent light absorption, fast water transportation and salt-resistant crystallization as well as good durability. The evaporation rate without an additional device is found to be 1.689 kg m-2 h-1 under 1-Sun irradiation, and the energy conversion efficiency is as high as 95%. This work creates a platform and develops the prospect of employing green and sustainable natural-diatomite composite evaporator for practical applications of seawater desalination.
A sustainable process to 100% bio-based nylons integrated chemical and biological conversion of lignocellulose
Ruijia Hu, Ming Li, Tao Shen, Xin Wang, Zhuohua Sun, Xinning Bao, Kequan Chen, Kai Guo, Lei Ji, Hanjie Ying, Pingkai Ouyang, Chenjie Zhu
2024, 9(2): 390-402. doi: 10.1016/j.gee.2022.11.004
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Considerable progress has been made in recent years to the development of sustainable polymers from bio-based feedstocks. In this study, 100% bio-based nylons were prepared via an integrated chemical and biological process from lignocellulose. These novel nylons were obtained by the melt polymerization of 3-propyladipic acid derived from lignin and 1,5-pentenediamine/1,4-butanediamine derived from carbohydrate sugar. Central to the concept is a three-step noble metal free catalytic chemical funnelling sequence (Raney Ni mediated reductive catalytic fractionation - reductive funnelling - oxidative funnelling), which allowed for obtaining a single component 3-propyladipic acid from lignin with high efficiency. The structural and thermodynamic properties of the obtained nylons have been systematically investigated, and thus obtained transparent bio-based nylons exhibited higher Mw (>32,000) and excellent thermal stability (Td5% > 265 ℃). Considering their moderate Tg and good melt strength, these transparent bio-based nylons could serve as promising functional additives or temperature-responsive materials.
Comprehensive reutilization of herbal waste: Coproduction of magnolol, honokiol, and β-amyrin from Magnolia officinalis residue
Lukun Xiao, Anyi Zhao, Jie Qiu, An Liu, Sha Chen, Jinzhu Jiang, Jun Zhang, Cong Guo, Jipeng Di, Jintang Cheng, Chang Chen, Kangxin Hou, Aiping Zhang, Yan Liu, Caixia Wang
2024, 9(2): 403-412. doi: 10.1016/j.gee.2023.01.008
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Herbal extraction residues (HERs) cause serious environmental pollution and resource waste. In this study, a novel green route was designed for the comprehensive reutilization of all components in HERs, taking Magnolia officinalis residues (MOR) as an example. The reluctant structure of MOR was first destroyed by alkali pretreatment to release the functional ingredients (magnolol and honokiol) originally remaining in MOR and to make MOR more accessible for hydrolysis. A metal–organic frame material MIL-101(Cr) with a maximum absorption capacity of 255.64 mg g-1 was synthesized to absorb the released honokiol and magnolol from the pretreated MOR solutions, and 40 g L-1 reducing sugars were obtained with 81.8% enzymatic hydrolysis rate at 10% MOR solid loading. Finally, 382 mg L-1 β-amyrin was produced from MOR hydrolysates by an engineered yeast strain. In total, 1 kg honokiol, 8 kg magnolol, and 7.64 kg β-amyrin could produce from 1 ton MOR by this cleaner process with a total economic output of 170,700 RMB.

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