2023 Vol. 8, No. 2

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Research Highlight
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.
Short communication
Tunable vacancy defect chemistry on free-standing carbon cathode for lithium-sulfur batteries
Xi Zhang, Xiaohong Liu, Wei Zhang, Yingze Song
2023, 8(2): 354-359. doi: 10.1016/j.gee.2022.03.006
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The defect chemistry is successfully modulated on free-standing and binder-free carbon cathodes for highly efficient Li–S redox reactions. Such rationally regulated defect engineering realizes the synchronization of ion/electron-conductive and defect-rich networks on the three-dimension carbon cathode, leading to its tunable activity for both relieving the shuttle phenomenon and accelerating the sulfur redox reaction kinetics. As expected, the defective carbon cathode harvests a high rate capacity of 1217.8 mAh g-1 at 0.2 C and a superior capacity retention of 61.7% at 2 C after 500 cycles. Even under the sulfur mass loading of 11.1 mg cm-2, the defective cathode still holds a remarkable areal capacity of 8.5 mAh cm-2.
Review article
Atomically dispersed metal sites in COF-based nanomaterials for electrochemical energy conversion
Yaqi Cao, Wenchao Peng, Yang Li, Fengbao Zhang, Yuanzhi Zhu, Xiaobin Fan
2023, 8(2): 360-382. doi: 10.1016/j.gee.2021.11.005
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Atomically dispersed metal sites (ADMSs) play key roles in electrochemical energy conversion. The covalent organic frameworks (COFs) enable the precise control of the chemical compositions and structures at the molecular level, making them ideal substrates for supporting ADMSs. In this review, we systematically summarize the recent progress on the design and synthesis of ADMSs in COFs, including embedding molecular catalysts into COFs, immobilizing ADMSs on heteroatom-containing COFs, and preparing COF-derived carbon materials through pyrolysis. The electrocatalytic performance of the resulting catalysts is presented for various electrochemical reactions, involving oxygen reduction reaction (ORR), carbon dioxide reduction reaction (CO2RR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and nitrogen reduction reaction (NRR). The modulation strategies of AMDSs in COFs for enhanced activity, selectivity, and stability are highlighted, together with a perspective of the current challenges and the future opportunities in this field.
Radical and (photo)electron transfer induced mechanisms for lignin photo-and electro-catalytic depolymerization
Kejia Wu, Minglong Cao, Qiang Zeng, Xuehui Li
2023, 8(2): 383-405. doi: 10.1016/j.gee.2022.02.011
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As one of the three major components of woody biomass, lignin is a kind of natural organic polymer and the only abundant natural renewable resource with aromatic nucleus. Chemical catalysis induced depolymerization is an important and effective approach for lignin utilization. In particular, photocatalysis and electrocatalysis show great potential in accurately activating C–O/C–C bonds, which is a critical point of selective cleavage of lignin. In this contribution, we focus on radical and (photo)electron transfer induced reaction mechanisms of the photo(electro)catalytic depolymerization of lignin. Primarily, the general situation of Carbon-centered radicals and active oxygen species mediated lignin conversion has been discussed. Then the mechanisms for (photo)electron transfer mediated lignin depolymerization have been summarized. At the end of this review, the challenges and opportunities of photo(electro)catalysis in the applications of lignin valorization have been forecasted.
A review on the synthesis of transition metal nitride nanostructures and their energy related applications
Qiao Luo, Congcong Lu, Lingran Liu, Maiyong Zhu
2023, 8(2): 406-437. doi: 10.1016/j.gee.2022.07.002
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Transition metal nitrides (TMN) have recently grabbed immensely appealing as ideal active materials in energy storage and catalysis fields on account of their remarkable electrical conductivity, excellent chemical stability, wide band gap and tunable morphology. Both pure TMN and TMN-based materials have been extensively studied concerned with their preparation approaches, nanostructures, and favored performance in various applications. However, the processes towards synthesis of TMN are numerous and complex. Choosing appropriate method to obtain target TMN with desired structure is crucial, which further affects its practical application performance. Herein, this review offers a timely and comprehensive summary of the synthetic ways to TMN and their application in energy related domains. The synthesis section is categorized into in-situ and ex-situ based on where the N element in TMN origins from. Then, overviews on the energy related applications including energy storage, electrocatalysis and photocatalysis are discussed. In the end, the problems to be solved and the development trend of the synthesis and application of transition metal nitrides are prospected.
Research paper
Selectively reductive amination of levulinic acid with aryl amines to N-substituted aryl pyrroles
Cailing Wu, Mengjie Lou, Mingming Sun, Huiyong Wang, Zhiyong Li, Jikuan Qiu, Jianji Wang, Zhimin Liu
2023, 8(2): 438-443. doi: 10.1016/j.gee.2021.04.010
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Synthesizing nitrogen (N)-containing molecules from biomass derivatives is a new strategy for production of this kind of chemicals. Herein, for the first time we present the synthesis of N-substituted aryl pyrroles via reductive amination/cyclization of levulinic acid (LA) with primary aromatic amines and hydrosilanes (e.g., PMHS) over CsF, and a series of N-substituted aryl pyrroles could be obtained in good to excellent yields at 120 °C. The mechanism investigation indicates that the reaction proceeds in two steps: the cyclization between amine and LA occurs first to form intermediate 5-methyl-N-alkyl-1,3-dihydro-2H-pyrrolones and their isomeride ( B ), and then the chemo-and region-selective reduction of intermediates take place to produce the final products. This approach for synthesis of N-substituted aryl pyrroles can be performed under mild and green conditions, which may have promising applications.
Phthalocyanine-derived catalysts decorated by metallic nanoclusters for enhanced CO2 electroreduction
Jiacheng Chen, Jiayu Li, Jing Xu, Minghui Zhu, Yi-Fan Han
2023, 8(2): 444-451. doi: 10.1016/j.gee.2021.05.006
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Electrochemical CO2 reduction (CO2RR) over molecular catalysts is a paramount approach for CO2 conversion to CO. Herein, we report a novel phthalocyanine-derived catalyst synthesized by a two-step method with a much improved electroconductivity. Furthermore, the catalyst contains both Ni–N4 sites and highly dispersed metallic Ni nanoclusters, leading to an increased CO2RR currents by two folds. Isotope labelling study and in situ spectroscopic analysis demonstrate that the existence of metallic Ni nanoclusters is the key factor for the activity enhancement and can shift the CO2RR mechanism from being electron transfer (ET)-limited (forming *COO-) to concerted proton-electron transfer (CPET)-limited (forming CO).
Complete degradation of high-loaded phenol using tungstate-based ionic liquids with long chain substituent at mild conditions
Yingying Yang, Honglei Fan, Tianbin Wu, Guanying Yang, Buxing Han
2023, 8(2): 452-458. doi: 10.1016/j.gee.2021.05.009
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Phenol in waste water threatens human health and is difficultly to be decomposed by nature. Efficient degradation of high-loaded phenol in water under mild condition is still a great challenge. Herein, ionic liquids with tungstate anion were designed and prepared. It was found that dodecyltrimethylammonium tungstate could catalyzed degradation of phenol into gases and water thoroughly at 323 k in 8 h. Tungstate anion revealed good catalytic oxidative activity and long carbon chain group connecting with cation of ionic liquids enriched phenol around catalysts, which induced the complete degradation of phenol at mild conditions. Increasing the amounts of hydrogen peroxide benefited to the total degradation of phenol. In addition, the ionic liquid could be reused for its excellent thermal stability. Our work provided a different strategy to treat waste water containing phenol efficiently.
Strengthening absorption ability of Co-N-C as efficient bifunctional oxygen catalyst by modulating the d band center using MoC
Jianwen Liu, Ying Guo, Xian-Zhu Fu, Jing-Li Luo, Chunyi Zhi
2023, 8(2): 459-469. doi: 10.1016/j.gee.2021.05.008
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Co–N–C is a promising oxygen electrochemical catalyst due to its high stability and good durability. However, due to the limited adsorption ability improvement for oxygen-containing intermediates, it usually exhibits inadequate catalytic activity with 2-electron pathway and high selectivity of hydrogen peroxide. Herein, the adsorption of Co–N–C to these intermediates is modulated by constructing heterostructures using transition metals and their derivatives based on d-band theory. The heterostructured nanobelts with MoC core and pomegranate-like carbon shell consisting of Co nanoparticles and N dopant (MoC/Co–N–C) are engineered to successfully modulate the d band center of active Co–N–C sites, resulting in a remarkably enhanced electrocatalysis performance. The optimally performing MoC/Co–N–C exhibits outstanding bi-catalytic activity and stability for the oxygen electrochemistry, featuring a high wave-half potential of 0.865 V for the oxygen reduction reaction (ORR) and low overpotential of 370 mV for the oxygen evolution reaction (OER) at 10 mA cm-2. The zinc air batteries with the MoC/Co–N–C catalyst demonstrate a large power density of 180 mW cm-2 and a long cycling lifespan (2000 cycles). The density functional theory calculations with Hubbard correction (DFT + U) reveal the electron transferring from Co to Mo atoms that effectively modulate the d band center of the active Co sites and achieve optimum adsorption ability with “single site double adsorption” mode.
Anchoring nitrogen-doped Co2P nanoflakes on NiCo2O4 nanorod arrays over nickel foam as high-performance 3D electrode for alkaline hydrogen evolution
Xiaohao Ji, Xiaoyu Chen, Lijuan Zhang, Cheng Meng, Yilei He, Xing Zhang, Zumin Wang, Ranbo Yu
2023, 8(2): 470-477. doi: 10.1016/j.gee.2021.05.010
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Effective and robust electrocatalysts are mainly based on innovative materials and unique structures. Herein, we designed a flakelike cobalt phosphide-based catalyst supporting on NiCo2O4 nanorods array, which in-situ grew on the nickel foam (NF) current collector, referring as N–Co2P/NiCo2O4/NF electrode. By optimizing the microstructure and electronic structure through 3D hierarchy fabrication and nitrogen doping, the catalyst features with abundant electrochemical surface area, favorable surface wettability, excellent electron transport, as well as tailored d band center. Consequently, the as-prepared N–Co2P/NiCo2O4/NF electrode exhibits an impressive HER activity with a low overpotentials of 58 mV at 10 mA cm-2, a Tafel slop of 75 mV dec-1, as well as superior durability in alkaline medium. This work may provide a new pathway to effectively improve the hydrogen evolution performance of transition metal phosphides and to develop promising electrodes for practical electrocatalysis.
Mesoporous poly(ionic liquid)s with dual active sites for highly efficient CO2 conversion
Yawen Fu, Yanan Xu, Zepeng Zeng, Abdul-Rauf Ibrahim, Jin Yang, Shuliang Yang, Yaqiang Xie, Yanzhen Hong, Yuzhong Su, Hongtao Wang, Yanliang Wang, Li Peng, Jun Li, Wendy L. Queen
2023, 8(2): 478-486. doi: 10.1016/j.gee.2021.05.013
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Atmospheric CO2 concentrations are soaring due to the continued use of fossil fuels in energy production, an anthropogenic activity that is playing a leading role in global warming. Thus, research aimed at the capture and conversion of CO2 into value-added products, such as cyclic carbonates, is booming. While CO2 is an abundant, cheap, non-toxic, and readily accessible C1 feedstock, its thermodynamic stability necessitates the development of highly efficient catalysts that are able to promote chemical reactions under mild conditions. In this work, a novel mesoporous poly(ionic liquid) with dual active sites was synthesized through a facile method that involves co-polymerization, post-synthetic metalation, and supercritical CO2 drying. Due to a high density of nucleophilic and electrophilic sites, the as-prepared poly(ionic liquid), denoted as P2D-4BrBQA-Zn , offers excellent performance in a CO2 cycloaddition reaction using epichlorohydrin as the substrate (98.9% conversion and 96.9% selectivity). Moreover the reaction is carried out under mild, solvent-free, and additive-free conditions. Notably, P2D-4BrBQA-Zn also efficiently promotes the conversion of various other epoxide substrates into cyclic carbonates. Overall, the catalyst is found to have excellent substrate compatibility, stability, and recyclability.
The newly-assisted catalytic mechanism of surface hydroxyl species performed as the promoter in syngas-to-C2 species on the Cu-based bimetallic catalysts
Chenyang Li, Yuan Zhang, Debao Li, Baojun Wang, Christopher K. Russell, Maohong Fan, Riguang Zhang
2023, 8(2): 487-498. doi: 10.1016/j.gee.2021.06.001
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In the conversion process of syngas-to-C2 species, the OH species are inevitably produced accompanying the production of key intermediates CHx(x = 1–3), traditionally , the function of surface OH species is generally accepted as the hydrogenating reactive species. This work for the first time proposed and confirmed the assisted catalytic mechanism of surface OH species that performed as the promoter for syngas-to-C2 species on Cu-based catalysts. DFT and microkinetic modeling results reveal that the produced OH species accompanying the intermediates CHx production on the MCu (M = Co, Fe, Rh) catalysts can stably exist to form OH/MCu catalysts, on which the presence of surface OH species as the promoter not only presented better activity and selectivity toward CHx(x = 1–3) compared to MCu catalysts, but also significantly suppressed CH3OH production, providing enough CH sources to favor the production of C2 hydrocarbons and oxygenates. Correspondingly, the electronic properties analysis revealed the essential relationship between the electronic feature of OH/MCu catalysts and catalytic performance, attributing to the unique electronic micro-environment of the catalysts under the interaction of surface OH species. This new mechanism is called as OH-assisted catalytic mechanism, which may be applied in the reaction systems related to the generation of OH species.
Green rusts-derived iron oxide nanostructures catalyze NO reduction by CO
Ping Wang, Xiaoling Mou, Yong Li, Wenjie Shen
2023, 8(2): 499-508. doi: 10.1016/j.gee.2021.06.002
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Green rusts with brucite-like layers of hydroxide intercalated with anions constitute a family of diverse precursors for the synthesis of iron oxides via dehydration, but precise structural control of the resulting oxides with respect to the size and shape at the nanometer level remains challenging due to the easy oxidation of the ferrous species. Herein, we report a new synthetic strategy for the facile preparation of fibrous-like green rusts by using appropriate balancing anions (CO32- and SO42-) in ethylene glycol to regulate the morphology. Depending on the type of the intercalating anion, the green rusts were converted into hematite with fibrous-or plate-like shapes upon thermal activation. When evaluated in the reaction of NO reduction by CO, these iron oxides showed a prominent shape-dependent catalytic behavior. The fibrous-like Fe2O3 was much more catalytically active and structurally robust than the plate-like analogue. Combined spectroscopic and microscopic characterizations on the nanostructured iron oxides revealed that the superior performance of the fibrous-like Fe2O3 stemmed from a facile Fe2O3/Fe3O4 redox cycle and a higher density of active sites for NO activation.
A novel strategy for loading metal cocatalysts onto hollow nano-TiO2 inner surface with highly enhanced H2 production activity
Nan Chen, Yu Zhou, Songtao Cao, Ruixin Wang, Weizhou Jiao
2023, 8(2): 509-518. doi: 10.1016/j.gee.2021.07.002
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The loading strategy of cocatalysts affects its activity exerting and atom utilization. Here, a novel strategy for loading precious metal (Pt) cocatalysts by means of ultrathin N-doped carbon layer is reported. The strategy is based on a pyrolysis process of predesigned N-containing polymers and Pt complexes on hard-template surface, during which Pt can be reduced by carbon from pyrolysis at high temperatures. Finally, the hollow TiO2 composite with stable and dispersed Pt on its inner surface was prepared. It shows an ultrahigh photocatalytic H2 production activity as high as 25.7 mmol h-1 g-1 with methanol as sacrificial regent, and displays an apparent quantum yield as 13.2%. The improved photocatalytic activity and stability can be attributed to the highly dispersed and ultrafine Pt nanoparticles, enhanced interaction between Pt-species and carbon support, fast photo-excited electron transport from the high graphitization degree of NC layers, ample oxygen vacancies/defects, as well as the manipulated local charge distribution of Pt/NC-layer configuration. Additionally, the universality of the proposed strategy was demonstrated by replacing metal sources (such as, Ru and Pd). This work presented a promising strategy for the design and development of novel photocatalysts, which shows a broad application prospect.
Efficient synthesis of bioetheric fuel additive by combining the reductive and direct etherification of furfural in one-pot over Pd nanoparticles deposited on zeolites
Xiaowen Guo, Haihong Wu, Peng Wu, Mingyuan He, Yejun Guan
2023, 8(2): 519-529. doi: 10.1016/j.gee.2021.07.001
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Furfuryl ethers have been considered to be a promising fuel additive. One step reduction etherification of furfural over supported Pd catalysts provides a facile way for the preparation of furfuryl ether. However, the preparation of a reusable Pd catalyst for reductive etherification remains to be a great challenge. In this study, a series of SiO2 supported Pd catalysts with particle size ranging from 2.2 nm to 28 nm were prepared. Their textural properties and catalytic performance in furfural reductive etherification have been systematically studied. The results herein shed light on the particle size effect on the competition between hydrogenation/hydrogenolysis of C=O in furfural over Pd surface. We found out that Pd nanoparticles larger than 3 nm are preferred for one step reductive etherification. Based on this finding, we prepared a Pd/ZSM-5 bifunctional catalyst comprising Pd nanoparticles larger than 3 nm and decreased acidity in presence of amino organosilane, which served as a bifunctional catalyst succeeding in one-pot synthesis of ether via reductive-etherification and direct-etherification. This strategy showed significant advantage in efficiently converting furfuryl acohol, a major side-product, into ether, while suppressing the undesired side-reactions.
Insights into the size effect of ZnCr2O4 spinel oxide in composite catalysts for conversion of syngas to aromatics
Yi Fu, Youming Ni, Wenhao Cui, Xudong Fang, Zhiyang Chen, Zhaopeng Liu, Wenliang Zhu, Zhongmin Liu
2023, 8(2): 530-537. doi: 10.1016/j.gee.2021.07.003
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Direct conversion of syngas to aromatics (STA) over oxide-zeolite composite catalysts is promising as an alternative method for aromatics production. However, the structural effect of the oxide component in composite catalysts is still ambiguous. Herein, we investigate the size effect by selecting ZnCr2O4 spinel, as a probe oxide, mixing with H-ZSM-5 zeolite as a composite catalyst for STA reaction. The CO conversion, aromatics selectivity and space-time yield (STY) of aromatics are all significantly improved with the crystal size of ZnCr2O4 oxide decreases, which can mainly attribute to the higher oxygen vacancy concentration and thus the rapid generation of more C1 oxygenated intermediate species. Based on the understanding of the size–performance relationship, ZnCr2O4-400 with a smaller size mixing with H-ZSM-5 can achieve 32.6% CO conversion with 76% aromatics selectivity. The STY of aromatics reaches as high as 4.79 mmol gcat-1 h-1, which outperforms the previously reported some typical catalysts. This study elucidates the importance of regulating the size of oxide to design more efficient oxide-zeolite composite catalysts for conversion of syngas to value-added chemicals.
A highly dispersed Pt/copper modified-MnO2 catalyst for the complete oxidation of volatile organic compounds: The effect of oxygen species on the catalytic mechanism
Xunxun Li, Yaru Wang, Dongyun Chen, Najun Li, Qingfeng Xu, Hua Li, Jinghui He, Jianmei Lu
2023, 8(2): 538-547. doi: 10.1016/j.gee.2021.07.004
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Manganese oxide (MnO2) exhibits excellent activity for volatile organic compound oxidation. However, it is currently unknown whether lattice oxygen or adsorbed oxygen is more conducive to the progress of the catalytic reaction. In this study, novel hollow highly dispersed Pt/Copper modified-MnO2 catalysts were fabricated. Cu2+ was stabilized into the δ-MnO2 cladding substituting original K+, which produced lattice defects and enhance the content of adsorbed oxygen. The 2.03 wt% Pt Cu0.050-MnO2 catalyst exhibited the highest catalytic activity and excellent stability for toluene and benzene oxidation, with T100= 160 °C under high space velocity (36,000 mL g-1 h-1). The excellent performance of catalytic oxidation of VOCs is attributed to the abundant adsorbed oxygen content, excellent low-temperature reducibility and the synergistic catalytic effect between the Pt nanoparticles and Cu0.050-MnO2. This study provides a comprehensive understanding of the Langmuir–Hinshelwood (L-H) mechanism occurring on the catalysts.
Coral-like and binder-free carbon nanowires for potassium dual-ion batteries with superior rate capability and long-term cycling life
Min Wang, Qirong Liu, Guangming Wu, Jianmin Ma, Yongbing Tang
2023, 8(2): 548-558. doi: 10.1016/j.gee.2021.03.007
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Owing to the advantages of high operating voltage, environmental benignity, and low cost, potassium-based dual-ion batteries (KDIBs) have been considered as a potential candidate for large-scale energy storage. However, KDIBs generally suffer from poor cycling performance and unsatisfied capacity, and inactive components of conductive agents, binders, and current collector further lower their overall capacity. Herein, we prepare coral-like carbon nanowires (CCNWs) doped with nitrogen as a binder-free anode material for K+-ion storage, in which the unique coral-like porous nanostructure and amorphous/short-range-ordered composite feature are conducive to enhancing the structural stability, to facilitating the ion transfer and to boosting the full utilization of active sites during potassiation/de-potassiation process. As a result, the CCNW anode possesses a hybrid K+-storage mechanism of diffusive behavior and capacitive adsorption, and stably delivers a high capacity of 276 mAh g-1 at 50 mA g-1, good rate capability up to 2 A g-1, and long-term cycling stability with 93% capacity retention after 2000 cycles at 1 A g-1. Further, assembling this CCNW anode with an environmentally benign expanded graphite (EG) cathode yields a proof-of-concept KDIB, which shows a high specific capacity of 134.4 mAh g-1 at 100 mA g-1, excellent rate capability of 106.5 mAh g-1 at 1 A g-1, and long-term cycling stability over 1000 cycles with negligible capacity loss. This study provides a feasible approach to developing high-performance anodes for potassium-based energy storage devices.
Stable NiPt-Mo2C active site pairs enable boosted water splitting and direct methanol fuel cell
Jing Li, Zhu Guo, Wenjie Zhang, Jing Guo, Konggang Qu, Weiwei Cai
2023, 8(2): 559-566. doi: 10.1016/j.gee.2021.08.005
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Sluggish kinetics of methanol oxidation reaction (MOR) and alkaline hydrogen evolution reaction (HER) even on precious Pt catalyst impede the large-scale commercialization of direct methanol fuel cell (DMFC) and water electrolysis technologies. Since both of MOR and alkaline HER are related to water dissociation reaction (WDR), it is reasonable to invite secondary active sites toward WDR to pair with Pt for boosted MOR and alkaline HER activity on Pt. Mo2C and Ni species are therefore employed to engineer NiPt–Mo2C active site pairs, which can be encapsulated in carbon cages, via an in-situ self-confinement strategy. Mass activity of Pt in NiPt–Mo2C@C toward HER is boosted to 11.3 A mgpt-1, 33 times higher than that of Pt/C. Similarly, MOR catalytic activity of Pt in NiPt–Mo2C@C is also improved by 10.5 times and the DMFC maximum power density is hence improved by 9-fold. By considering the great stability, NiPt–Mo2C@C exhibits great practical application potential in DMFCs and water electrolysers.
Visible light triggered exfoliation of COF micro/nanomotors for efficient photocatalysis
Kai Feng, Liang Zhang, Jiang Gong, Jinping Qu, Ran Niu
2023, 8(2): 567-578. doi: 10.1016/j.gee.2021.09.002
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We report a new facile light-induced strategy to disperse micron-sized aggregated bulk covalent organic frameworks (COFs) into isolated COFs nanoparticles. This was achieved by a series of metal-coordinated COFs, namely COF-909-Cu, -Co or -Fe, where for the first time the diffusio-phoretic propulsion was utilized to design COF-based micro/nanomotors. The mechanism studies revealed that the metal ions decorated in the COF-909 backbone could promote the separation of electron and holes and trigger the production of sufficient ionic and reactive oxygen species under visible light irradiation. In this way, strong light-induced self-diffusiophoretic effect is achieved, resulting in good dispersion of COFs. Among them, COF-909-Fe showed the highest dispersion performance, along with a drastic decrease in particle size from 5 μm to 500 nm, within only 30 min light irradiation, which is inaccessible by using traditional magnetic stirring or ultrasonication methods. More importantly, benefiting from the outstanding dispersion efficiency, COF-909-Fe micro/nanomotors were demonstrated to be efficient in photocatalytic degradation of tetracycline, about 8 times faster than using traditional magnetic stirring method. This work opens up a new avenue to prepare isolated nanosized COFs in a high-fast, simple, and green manner.
Nitrogen-doped porous carbon nanosheets as both anode and cathode for advanced potassium-ion hybrid capacitors
Quanzhou Du, Yuhua Zhao, Yujuan Chen, Jianming Liu, Huanhuan Li, Guangyue Bai, Kelei Zhuo, Jianji Wang
2023, 8(2): 579-588. doi: 10.1016/j.gee.2022.02.013
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Potassium-ion hybrid capacitors (PIHCs) as a burgeoning research hotspot are an ideal replacement for lithium-ion hybrid capacitors (LIHCs). Here, we report nitrogen-doped porous carbon nanosheets (NPCNs) with enlarged interlayer spacing, abundant defects, and favorable mesoporous structures. The structural changes of NPCNs in potassiation and depotassiation processes are analyzed by using Raman spectroscopy and transmission electron microscopy. Due to the unique structure of NPCNs, the PIHC device assembled using NPCNs as both the anode and cathode material (double-functional self-matching material) exhibits a superior energy density of 128 Wh kg-1 with a capacity retention of 90.8% after 9000 cycles. This research can promote the development of double-functional self-matching materials for hybrid energy storage devices with ultra-high performance.
Metal organic framework supported niobium pentoxide nanoparticles with exceptional catalytic effect on hydrogen storage behavior of MgH2
Liuting Zhang, Farai Michael Nyahuma, Haoyu Zhang, Changshan Cheng, Jiaguang Zheng, Fuying Wu, Lixin Chen
2023, 8(2): 589-600. doi: 10.1016/j.gee.2021.09.004
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Nb2O5 nanoparticles with an average particle size of 10 nm supported on a rhombic dodecahedral metal organic framework (MOF) were successfully synthesized by a facile one-pot hydrothermal reaction and subsequent calcination process. Experimental results demonstrated that the prepared catalyst drastically improved the hydrogen storage behavior of MgH2. 7 wt% Nb2O5@MOF doped MgH2 started to desorb hydrogen at 181.9 °C and 6.2 wt% hydrogen could be released within 2.6 min and 6.3 min at 275 °C and 250 °C, respectively. The fully dehydrogenated composite also displayed excellent hydrogenation by decreasing the onset absorption temperature to 25 °C and taking up 4.9 wt% and 6.5 wt% hydrogen within 6 min at 175 °C and 150 °C, respectively. Moreover, the corresponding activation energy was calculated to be 75.57 ± 4.16 kJ mol-1 for desorption reaction and 51.38 ± 1.09 kJ mol-1 for absorption reaction. After 20 cycles, 0.5 wt% hydrogen capacity was lost for the MgH2+7 wt% Nb2O5@MOF composite, much lower than 1.5 wt% of the MgH2+7 wt% Nb2O5 composite. However, the addition of Nb2O5@MOF had limited effect on reducing the dehydrogenation enthalpy of MgH2. Microstructure analysis revealed that Nb2O5 particles were uniformly distributed on surface of the MgH2 matrix and synergistically improved the hydrogen storage property of MgH2 with MOF.
Vacancies and interfaces engineering of core-shell heterostuctured NiCoP/NiO as trifunctional electrocatalysts for overall water splitting and zinc-air batteries
Xiaolin Hu, Jichuan Fan, Ronghua Wang, Meng Li, Shikuan Sun, Chaohe Xu, Fusheng Pan
2023, 8(2): 601-611. doi: 10.1016/j.gee.2021.11.003
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The electronic structures and properties of electrocatalysts, which depend on the physicochemical structure and metallic element components, could significantly affect their electrocatalytic performance and their future applications in Zn-air battery (ZAB) and overall water splitting (OWS). Here, by combining vacancies and heterogeneous interfacial engineering, three-dimensional (3D) core–shell NiCoP/NiO heterostructures with dominated oxygen vacancies have been controllably in-situ grown on carbon cloth for using as highly efficient electrocatalysts toward hydrogen and oxygen electrochemical reactions. Theoretical calculation and electrochemical results manifest that the hybridization of NiCoP core with NiO shell produces a strong synergistic electronic coupling effect. The oxygen vacancy can enable the emergence of new electronic states within the band gap, crossing the Fermi levels of the two spin components and optimizing the local electronic structure. Besides, the hierarchical core–shell NiCoP/NiO nanoarrays also endow the catalysts with multiple exposed active sites, faster mass transfer behavior, optimized electronic strutures and improved electrochemical performance during ZAB and OWS applications.
Influence of MnOx deposition on TiO2 nanotube arrays for electrooxidation
Kaihang Zhang, Yuanzheng Zhang, Su Liu, Xin Tong, Junfeng Niu, Dong Wang, Junchen Yan, Zhaoyang Xiong, John Crittenden
2023, 8(2): 612-618. doi: 10.1016/j.gee.2022.11.005
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TiO2 has demonstrated outstanding performance in electrochemical advanced oxidation processes (EAOPs) due to its structural stability and high oxygen overpotential. However, there is still much room for improving its electrochemical activity. Herein, narrow bandgap manganese oxide (MnOx) was composited with TiO2 nanotube arrays (TiO2 NTAs) that in-situ oxidized on porous Ti sponge, forming the MnOx-TiO2 NTAs anode. XANES and XPS analysis further proved that the composition of MnOx is Mn2O3. Electrochemical characterizations revealed that increasing the composited concentration of MnOx can improve the conductivity and reduce oxygen evolution potential so as to improve the electrochemical activity of the composited MnOx-TiO2 NTAs anode. Meanwhile, the optimal degradation rate of benzoic acid (BA) was achieved using MnOx-TiO2 NTAs with a MnOx concentration of 0.1 mmol L-1, and the role of MnOx was proposed based on DFT calculation. Additionally, the required electrical energy (EE/O) to destroy BA was optimized by varying the composited concentration of MnOx and the degradation voltage. These quantitative results are of great significance for the design and application of high-performance materials for EAOPs.

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