2022 Vol. 7, No. 4

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Research highlight
Multivariate MOF for optimizing atmospheric water harvesting
Ao Ma, Hengjiang Cong, Hexiang Deng
2022, 7(4): 575-577. doi: 10.1016/j.gee.2022.02.004
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Atmospheric water harvesting offers a powerful and promising solution to address the problem of global freshwater scarcity. In the past decade, significant progress has been achieved in utilizing hydrolytically stable metal-organic frameworks as recyclable water-sorbent materials under low relative humidity, especially in those arid areas. Recently, Yaghi's group has employed a combined crystallographic and theoretical technique to decipher the water filling mechanism in MOF-303, where the polar organic linkers rather than the inorganic units of MOF are demonstrated as the key factor. Hence, the hydrophilic strength of the water-binding pocket in MOFs can be optimized through the approach of multivariate modulations, resulting in enhanced water harvesting properties.
Review article
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.
Charactering and optimizing cathode electrolytes interface for advanced rechargeable batteries: Promises and challenges
Zhongyang Zhang, Xinran Wang, Ying Bai, Chuan Wu
2022, 7(4): 606-635. doi: 10.1016/j.gee.2021.05.012
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With the advancement of secondary batteries, interfacial properties of electrode materials have been recognized as essential factors to their electrochemical performance. However, the majority of investigations are devoted into advanced electrode materials synthesis, while there is insufficient attention paid to regulate their interfaces. In this regard, the solid electrolyte interphase (SEI) at anode part has been studied for 40 years, already achieving remarkable outcomes on improving the stability of anode candidates. Unfortunately, the study on the cathode electrolyte interfaces (CEI) remains in infancy, which constitutes a potential restriction to the capacity contribution, stability and safety of cathodes. In fact, the native CEI generally possesses unfavorable characteristics against structural and compositional stability that requires demanding optimization strategies. Meanwhile, an in-depth understanding of the CEI is of great significance to guide the optimization principles in terms of composition, structure, growth mechanism, and electrochemical properties. In this literature, recent progress and advances of the CEI characterization methods and optimization protocols are summarized, and meanwhile the mutually-reinforced mechanisms between detection and modification are explained. The criteria and the potential development of the CEI characterization are proposed with insights of novel optimization directions.
Metal-organic frameworks-derived metal phosphides for electrochemistry application
Xinru Tang, Nan Li, Huan Pang
2022, 7(4): 636-661. doi: 10.1016/j.gee.2021.08.003
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Metal-organic frameworks (MOFs) with high porosity and variable structure have attracted extensive attention in the field of electrochemistry, but their poor conductivity and stability have limited their development. Materials derived from MOFs can maintain the structural diversity and porosity characteristics of MOFs while improving their electrical conductivity and stability. Metal phosphides play an important role in electrochemistry because they possess rich active sites, unique physicochemical properties, and a porous structure. Published results show that MOF-derived metal-phosphides materials have great promise in the field of electrochemistry due to their controllable structure, high specific surface area, high stability and excellent electrical conductivity. MOF-derived metal-phosphides with significant electrochemical properties can be obtained by simply, economical and scalable synthetic methods. This work reviews the application of MOF-derived metal phosphides in electrochemistry. Specifically, the synthesis methodology and morphological characterization of MOFs derived metal-phosphides and their application in electrochemistry are described. Based on recent scientific advances, we discuss the challenges and opportunities for future research on MOF-derived metal-phosphides materials.
Research papers
Surface-mediated iron on porous cobalt oxide with high energy state for efficient water oxidation electrocatalysis
Jingsha Li, Tao Hu, Changhong Wang, Chunxian Guo
2022, 7(4): 662-671. doi: 10.1016/j.gee.2020.11.009
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Surface engineering of active materials to generate desired energy state is critical to fabricate high-performance heterogeneous catalysts. However, its realization in a controllable level remains challenging. Using oxygen evolution reaction (OER) as a model reaction, we report a surface-mediated Fe deposition strategy to electronically tailor surface energy states of porous Co3O4 (Fe-pCo3O4) for enhanced activity towards OER. The Fe-pCo3O4 exhibits a low overpotential of 280 mV to reach an OER current density of 100 mA cm-2, and a fast-kinetic behavior with a low Tafel slop of 58.2 mV dec-1, outperforming Co3O4-based OER catalysts recently reported and also the noble IrO2. The engineered material retains 100% of its original activity after operating at an overpotential of 350 mV for 100 h. A combination of theoretical calculations and experimental results finds out that the surface doped Fe promotes a high energy state and desired coordination environment in the near surface region, which enables optimized OER intermediates binding and favorably changes the rate-determining step.
Oxygen-deficient SnO2 nanoparticles with ultrathin carbon shell for efficient electrocatalytic N2 reduction
Guangkai Li, Haeseong Jang, Zijian Li, Jia Wang, Xuqiang Ji, Min Gyu Kim, Xien Liu, Jaephil Cho
2022, 7(4): 672-679. doi: 10.1016/j.gee.2020.11.004
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For high-efficiency NH3 synthesis via ambient-condition electrohydrogenation of inert N2, it is pivotal to ingeniously design an active electrocatalyst with multiple features of abundant surfacial deficiency, good conductivity and large surface area. Here, oxygen-deficient SnO2 nanoparticles encapsulated by ultrathin carbon layer (d-SnO2@C) are developed by hydrothermal deposition coupled with annealing process, as promising catalysts for ambient electrocatalytic N2 reduction. d-SnO2@C exhibits high activity and excellent selectivity for electrocatalytic conversion of N2 to NH3 in acidic electrolytes, with Faradic efficiency as high as 12.7% at -0.15 V versus the reversible hydrogen electrode (RHE) and large NH3 yield rate of 16.68 μg h-1 mgcat-1 at -0.25 V vs. RHE in 0.1 mol L-1 HCl. Benefiting from the structural superiority of enhanced charge transfer efficiency and optimized surface states, d-SnO2@C also achieves excellent long-term stability.
Design and in-situ construct BiOI/Bi/TiO2 photocatalysts with metal-mediated heterostructures employing oxygen vacancies in TiO2 nanosheets
Chenchen Zhang, Wenbin Chen, Dairong Hu, Hanjie Xie, Yibing Song, Binbin Luo, Yiwen Fang, Wenhua Gao, Ziyi Zhong
2022, 7(4): 680-690. doi: 10.1016/j.gee.2020.11.013
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The conventional p-n heterojunction photocatalysts suffer from the incompatibility between the interfacial charge transfer efficiency and the redox ability of charge carriers. To optimize the interfacial charge transfer of the conventional BiOI/TiO2 p-n photocatalyst, we synthesized the BiOI/Bi/TiO2 ternary photocatalyst with sandwiched metallic bismuth (Bi0) by the oxygen-vacancy assisted method. The DFT calculation and structural characterizations confirmed the reaction of the electron-rich oxygen vacancies in the 2D-TiO2 nanosheets (TiO2-NS) with the adsorbed BiO+ species. This reaction broke the Bi-O bonds to form Bi0 nanoparticles in-situ at the interface but still maintained the p-n heterojunction well. The NO-TPD and XRD analyses for samples correlated the Bi0 formation with the oxygen vacancy concentrations well. The sandwiched Bi0 functioned as an electronic transfer mediator like that in the Z-scheme heterostructure. Comparing with 0.20 BiOI/TiO2-NP (NP, Nanoparticles), 0.20 BiOI/Bi/TiO2-NS-a (NS, Nanosheet) showed a much improved catalytic performance, i.e., duplicated apparent quantum yield (AQY) and triplicated reaction rate constant (k). Also, the formation mechanism and the reaction mechanism were investigated in detail. This work provides a new strategy for the improving of the conventional p-n photocatalysts and new insights into the nature of the photocatalysis.
Vicinal hydroxyl group-inspired selective oxidation of glycerol to glyceric acid on hydroxyapatite supported Pd catalyst
Difan Li, Xiuge Zhao, Qingqing Zhou, Bingjie Ding, Anna Zheng, Qingpo Peng, Zhenshan Hou
2022, 7(4): 691-703. doi: 10.1016/j.gee.2020.11.018
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Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals. Herein, the hydroxyapatite (HAP) supported palladium (Pd) species were fabricated by impregnation and subsequent calcination. The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid (GLA) up to 90% with 59% conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions. The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation. Notably, it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca2+ sites on HAP-derived catalysts. In this catalytic process, the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group, while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA. Additionally, this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding α-hydroxycarboxylic acids selectively. Isotope labeling experiment using H218O confirmed that H2O not only acted as solvent but also was involved in the catalytic cycles. On the basis of the results, a possible reaction mechanism has been proposed. The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.
High performance of TiO2/CuxO photoelectrodes for regenerative solar energy storage in a vanadium photoelectrochemical cell
Harin Yoo, Doohwan Lee, Jung Hyeun Kim
2022, 7(4): 704-711. doi: 10.1016/j.gee.2020.11.012
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Photocatalysts for harvesting solar energy to either electricity or chemical fuels have attracted much attention recently, but they have big obstacles such as wide bandgaps and rapid charge recombinations to overcome for final applications. In this study, we investigates a useful method to utilize vanadium redox pairs, which are commonly applied for vanadium redox flow batteries, to diminish charge recombinations and thus to enhance photocurrent response in regenerative solar energy storage. The results reveal significant improvements in photocurrent density by forming cuprous and cupric oxides in TiO2/CuxO electrodes under solar AM 1.5 illuminations using the vanadium photoelectrochemical storage cell at 0.025 mol L-1 of vanadium redox species in the acid electrolytes. In addition, the stabilized photocurrent density of the copper content optimized TiO2/CuxO electrodes is almost tripled from the TiO2 only electrode because the charge recombinations can be mitigated with the content optimized TiO2/CuxO electrodes. Therefore, the optimized TiO2/CuxO electrode results in the highest charge storing performance in the catholyte chamber, and the roles of vanadium redox species are also clearly demonstrated.
Visible light-driven oxidant-free dehydrogenation of alcohols in water using porous ultrathin g-C3N4 nanosheets
Wei Zhang, Jiajun Wang, Zewei Liu, Yibing Pi, Rong Tan
2022, 7(4): 712-722. doi: 10.1016/j.gee.2020.11.019
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Graphitic carbon nitride (g-C3N4) is a fascinating photocatalyst for solar energy utilization in photo-catalysis. Nevertheless, it often suffers from moderate photo-catalytic activity due to its low specific surface area and fast recombination rate of photogenerated electrons upon photo-excitation. Herein, we overcome the bottlenecks by constructing a porous g-C3N4 nanosheet ( PCNS ) through a simple thermal oxidation etching method. Benefited from its porous layer structure, the obtained PCNS exhibits large specific surface area, efficient separation of photogenerated charge carriers, as well as high exposure of active sites. As a result, it is robust and universal in visible light-driven dehydrogenation of alcohols in water under oxidant-free condition. Almost quantitative yields (> 99%) of various valuable carbonyl compounds were obtained over PCNS , while bulk g-C3N4 was far less efficient. Moreover, the photo-catalyst was highly stable and could be facilely recovered from the aqueous system for efficient reuse. The easy preparation and excellent performance made PCNS a promising and competitive photocatalyst for the solar applications.
High mass loading NiCo2O4 with shell-nanosheet/core-nanocage hierarchical structure for high-rate solid-state hybrid supercapacitors
Wang Yang, Liqiang Hou, Peng Wang, Yun Li, Rui Li, Bo Jiang, Fan Yang, Yongfeng Li
2022, 7(4): 723-733. doi: 10.1016/j.gee.2020.11.014
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Rational design of advanced structure for transition metal oxides (TMOs) is attractive for achieving high-performance supercapacitors. However, it is hampered by sluggish reaction kinetics, low mass loading, and volume change upon cycling. Herein, hierarchical NiCo2O4 architectures with 2D-nanosheets-shell and 3D-nanocages-core (2D/3D h-NCO) are directly assembled on nickel foam via a facile one-step way. The 2D nanosheets are in-situ generated from the self-evolution of initial NCO nanospheres. This 2D/3D hierarchical structures ensure fast ion/electron transport and maintain the structural integrity to buffer the volume expansion. The 2D/3D h-NCO electrode with an ultrahigh mass loading (30 mg cm-2) achieves a high areal capacity of 4.65 C cm-2 (equivalent to 1.29 mAh cm-2) at a current density of 4 mA cm-2, and retains 3.7 C cm-2 even at 50 mA cm-2. Furthermore, the assembled solid-state hybrid supercapacitor yields a high volumetric energy density of 4.25 mWh cm-3 at a power density of 39.3 mW cm-3, with a high capacity retention of 92.4% after 5000 cycles. Therefore, this work provides a new insight to constuct hierarchical electrodes for energy storage application.
Engineering electronic structures of titanium vacancies in Ti1-xO2 nanosheets enables enhanced Li-ion and Na-ion storage
Huiqin Wang, Fengchu Zhang, Jing Xia, Fei Lu, Bo Zhou, Ding Yi, Xi Wang
2022, 7(4): 734-741. doi: 10.1016/j.gee.2020.11.006
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Up to now, three kinds of ion-storage mechanisms are summarized towards anode materials in lithium/sodium-ion batteries, but they have low capacity and poor cyclic performance. Therefore, it is necessary to develop a new approach to optimize ion storage. Herein, we report an adsorption/desorption storage route through engineering electronic structure of cation-deficient Ti1-xO2 nanosheets. Ti1-xO2 nanosheets indeed exhibit higher capacity (332.1 mA h g-1 vs. 137.7 mA h g-1 for LIBs, 195.7 mA h g-1 vs. 111 mA h g-1 for SIBs), and more stable cyclic performance (296 mA h g-1 vs. 99 mA h g-1 for LIBs, 178.1 mA h g-1 vs. 80.2 mA h g-1 for SIBs after 100 cycles) at 0.1 A g-1 than TiO2 nanosheets. Kinetics analysis and density functional theory (DFT) calculations reveal that electronic structures of vacancy within Ti1-xO2 nanosheets encourage a novel adsorption-desorption storage route. These results highlight the benefits of the engineered electronic structures within electrode material and implement novel ion-storage mechanism towards broad energy storage applications.
The regulating effect of doping Cu on the catalytic performance of CO oxidative coupling to DMO on PdxCuy/GDY: A DFT study
Juan Zhao, Min Han, Zhanhui Wang, Lixia Ling, Riguang Zhang, Baojun Wang
2022, 7(4): 742-754. doi: 10.1016/j.gee.2020.11.011
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Rely on the density functional theory (DFT) calculation, the catalytic performance of PdxCuy/GDY (x = 1, 2, 3, 4; x + y ≤ 4) for CO oxidative coupling reaction was obtained. The Pdx/GDY (x = 1, 2, 3, 4) are not ideal catalyst for dimethyl oxalate (DMO) formation because by-product dimethyl carbonate (DMC) is easily formed on Pd1/GDY and Pd2/GDY, and high activation energies are needed on Pd3/GDY and Pd4/GDY. Therefore the second metal Cu is doped to regulate the performance of Pdx/GDY (x = 1, 2, 3, 4). Doping Cu not only improve the activity of DMO formation, but more importantly, controlling the ratio of Cu:Pd can effectively regulate the selectivity of DMO. Thus taking into account the activity and selectivity of the reaction for the preparation of DMO by CO oxidative coupling, the Pd1Cu1/GDY and Pd1Cu2/GDY with the activation energies of 105.2 and 99.2 kJ mol-1 to generate DMO show excellent catalytic activity and high DMO selectivity, which are considered as good catalysts for CO oxidative coupling. The differential charge density analysis shows the decrease in the charge density of metal clusters is an important reason for improving the selectivity of the catalyst.
Sulfur vacancies-doped Sb2S3 nanorods as high-efficient electrocatalysts for dinitrogen fixation under ambient conditions
Xuyan Wang, Jianwei Bai, Yantao Wang, Xiaoying Lu, Zehua Zou, Junfeng Huang, Cailing Xu
2022, 7(4): 755-762. doi: 10.1016/j.gee.2020.11.016
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Tuning surface electron transfer process by sulfur (S)-vacancies engineering is an efficient strategy to develop high-efficient catalysts for electroreduction N2 reaction (NRR). Herein, the distinct Sb2S3 nanorods with S-vacancies (Sv-Sb2S3) have been synthesized by a simple two-step method including hydrothermal and hydrogenation in H2/Ar atmosphere, which shows improved performance for NRR with the NH3 yield rate of 10.85 μg h-1 mgcat-1 at -0.4 V vs. RHE, the faradaic efficiency (FE) of 3.75% at -0.3 V vs. RHE and excellent stability for 24 h, largely outperforming bulk Sb2S3. X-ray photoelectron spectroscopy (XPS) and density function theory (DFT) calculations demonstrate that the abundant S-vacancies can create an electron-deficient environment and modulate the electron delocalization in Sv-Sb2S3, which can not only facilitate the N2 molecule adsorption, but also activate the N≡N, resulting in the enhanced performance for NRR.
Enhanced electrode kinetics and properties via anionic regulation in polyanionic Na3+xV2(PO4)3-x(P2O7)x cathode material
Mei-Yi Wang, Xin-Xin Zhao, Jin-Zhi Guo, Xue-Jiao Nie, Zhen-Yi Gu, Xu Yang, Xing-Long Wu
2022, 7(4): 763-771. doi: 10.1016/j.gee.2020.11.026
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Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P2O74- is selected to substitute the PO43- in Na3V2(PO4)3 (NVP) lattice and regulate the ratio of polyanion groups to prepare Na3+xV2(PO4)3-x(P2O7)x (NVPPx, 0 ≤ x ≤ 0.15) materials. The optimal Na3.1V2(PO4)2.9(P2O7)0.1 (NVPP0.1) material can deliver remarkably elevated specific capacity (104 mAh g-1 at 0.1 C, 60 mAh g-1 at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP0.1 exhibits outstanding cyclic stability (91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+ migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.
Improved methanol synthesis performance of Cu/ZnO/Al2O3 catalyst by controlling its precursor structure
Fan Zhang, Xiaoying Xu, Zhengpu Qiu, Bo Feng, Yuan Liu, Aihua Xing, Maohong Fan
2022, 7(4): 772-781. doi: 10.1016/j.gee.2020.11.027
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Methanol, a versatile chemical, fuel additive and potential H2 carrier, has attracted great attention. Despite of the wide industrialization, improvement of Cu-based methanol-synthesis catalysts is highly anticipated. Accordingly, a series of Cu/ZnO/Al2O3 with designed precursor structures were prepared, and its structure-function relationship was investigated to make progress on this area. Results showed the catalyst derived from highly zinc-substituted malachite demonstrated the best catalytic performance in this work. It was found that the well-behaved catalyst possessed relatively high Cu specific surface area and exposed Cu concentration, and the well Cu/ZnO synergy. CuZn alloy was found by In-situ XRD tests, and its effect on the catalyst's thermostability was discussed. Fractional precipitation, which facilitated the Cu2+ substitution by Zn2+ in malachite lattice, could be an efficient preparation method of the Cu/ZnO/Al2O3 catalyst.
A reaction density functional theory study of solvent effect in the nucleophilic addition reactions in aqueous solution
Cheng Cai, Weiqiang Tang, Chongzhi Qiao, Bo Bao, Peng Xie, Shuangliang Zhao, Honglai Liu
2022, 7(4): 782-791. doi: 10.1016/j.gee.2020.11.028
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Whereas the proper choice of reaction solvent constitutes the cornerstone of the green solvent concept, solvent effects on chemical reactions are not mechanistically well understood due to the lack of feasible molecular models. Herein, by taking the case study of nucleophilic addition reaction in aqueous solution, we extend the proposed multiscale reaction density functional theory (RxDFT) method to investigate the intrinsic free energy profile and total free energy profile, and study the solvent effect on the activation and reaction free energy for the nucleophilic addition reactions of hydroxide anion with methanal and carbon dioxide in aqueous solution. The predictions of the free energy profile in aqueous solution for these two nucleophilic addition reactions from RxDFT have a satisfactory agreement with the results from the RISM and MD-FEP simulation. Meanwhile, the solvent effect is successfully addressed by examining the difference of the free energy profile between the gas phase and aqueous phase. In addition, we investigate the solvent effect on the reactions occurred near solid-liquid interfaces. It is shown that the activation free energy is significantly depressed when reaction takes place in the region within 10 Å distance to the substrate surface owing to the decrease of hydration free energy at the solid-liquid interface.
Enhanced CO2 electroreduction to ethylene via strong metal-support interaction
Mengen Chu, Chunjun Chen, Yahui Wu, Xupeng Yan, Shuaiqiang Jia, Ruting Feng, Haihong Wu, Mingyuan He, Buxing Han
2022, 7(4): 792-798. doi: 10.1016/j.gee.2020.12.001
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The CuO/CeO2 composites with strong metal-support interaction were synthesised, which can efficiently electroreduct CO2 to C2H4. The Faradaic efficiency (FE) of C2H4 could reach 50.5% with a current density of 18 mA cm-2. The strong metal-support interaction could not only enhance the adsorption and activation of CO2, but also can stablize the CuO.
Hierarchical and self-supporting honeycomb LaNi5 alloy on nickel foam for overall water splitting in alkaline media
Yanze Wu, Yalan Liu, Kui Liu, Lin Wang, Lei Zhang, Degao Wang, Zhifang Chai, Weiqun Shi
2022, 7(4): 799-806. doi: 10.1016/j.gee.2021.09.005
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Ni-based metallic foams possessing large specific surfaces and open cell structures are of specific interest as catalysts or catalyst carriers for electrolysis of water. Traditional fabrication of Nickel foam limits the element modification choices to several inert transition metals only on polymer foam precursor and subsequent preparation of foam-based catalysts in aqueous solution or organic electrolyte. To expand the modification horizon, molten salt with wide electrochemical window and fast ion diffusion can achieve the reduction of highly active elements. Herein, we reported is a general and facile method to deposit directly of highly reactive element La and prepare hierarchical honeycomb LaNi5 alloy on Ni foam (ho-LaNi5/NF). This self-supporting electrode presents excellent electrical coupling and conductivity between the Ni foam and LaNi5, which provides a 3D self-supported heterostructure with outstanding electrocatalytic activity and excellent durability for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It exhibits excellent overpotential (1.86 V) comparable to commercial coupled IrO2//Pt/C (1.85 V) at a high current density of 100 mA cm-2. This work may pave the way for fabricating novel 3D self-supported honeycomb alloy that can be applied as electrode for usage of clean energy.
The feasibility study of the indium oxide supported silver catalyst for selective hydrogenation of CO2 to methanol
Kaihang Sun, Zhitao Zhang, Chenyang Shen, Ning Rui, Chang-jun Liu
2022, 7(4): 807-817. doi: 10.1016/j.gee.2021.05.004
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Silver catalyst has been extensively investigated for photocatalytic and electrochemical CO2 reduction. However, its high activity for selective hydrogenation of CO2 to methanol has not been confirmed. Here, the feasibility of the indium oxide supported silver catalyst was investigated for CO2 hydrogenation to methanol by the density functional theoretical (DFT) study and then by the experimental investigation. The DFT study shows there exists an intense Ag-In2O3 interaction, which causes silver to be positively charged. The positively charged Ag species changes the electronic structure of the metal, facilitates the formation of the Ag-In2O3 interfacial site for activation and dissociation of carbon dioxide. The promoted CO2 dissociation leads to the enhanced methanol synthesis via the CO hydrogenation route as CO2*→CO*→HCO*→H2CO*→H3CO*→H3COH*. The Ag/In2O3 catalyst was then prepared using the deposition-precipitation method. The experimental study confirms the theoretical prediction. The methanol selectivity of CO2 hydrogenation on Ag/In2O3 reaches 100.0% at reaction temperature of 200 ℃. It remains more than 70.0% between 200 and 275 ℃. At 300 ℃ and 5 MPa, the methanol selectivity still keeps 58.2% with a CO2 conversion of 13.6% and a space-time yield (STY) of methanol of 0.453 gmethanol gcat-1 h-1, which is the highest methanol STY ever reported for silver catalyst. The catalyst characterization confirms the intense Ag-In2O3 interaction as well, which causes high Ag dispersion, increases and stabilizes the oxygen vacancies and creates the active Ag-In2O3 interfacial site for the enhanced CO2 hydrogenation to methanol.
One-pot green mass production of hierarchically porous carbon via a recyclable salt-templating strategy
Changde Ma, Jiang Gong, Shuang Zhao, Xiaoguang Liu, Xueying Mu, Yanhui Wang, Xuecheng Chen, Tao Tang
2022, 7(4): 818-828. doi: 10.1016/j.gee.2020.12.004
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Porous carbon materials have exhibited a series of promising applications in supercapacitors and other research fields, yet still confronting the complicated synthetic procedures and massive usage of toxic reagents. Herein, we propose a green and one-pot method to produce heteroatom-doped hierarchical porous carbon materials in large-scale without any toxic reagents employed. Eventually, the as-prepared nitrogen-doped porous carbon (NPC) displays a high specific surface area of 2018 m2 g-1 together with abundant heteroatom dopants (14.8 wt% O and 1.03 wt% N). The potassium carbonate template can be recycled via a simple rinsing and re-precipitation process. Furthermore, the as-prepared nitrogen-doped porous carbon delivers a high specific capacitance of 361 F g-1 at 0.5 A g-1 and excellent rate capability of 240 F g-1 at 20 A g-1 (66.5% capacitance retention). Finally, considering the low-price raw materials and facile green synthesis procedure, the present approach can be easily scalable to prepare biomass-derived heteroatoms doped porous carbon, which is not only applicable for supercapacitor but also for other research fields.
Ni2P/MoS2 interfacial structures loading on N-doped carbon matrix for highly efficient hydrogen evolution
Yuelong Xu, Ran Wang, Zhan Liu, Lili Gao, Tifeng Jiao, Zhenfa Liu
2022, 7(4): 829-839. doi: 10.1016/j.gee.2020.12.008
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Electrochemical catalysts for the hydrogen evolution reaction (HER) have attracted increasing attentions. Noble metal-free cocatalysts play a vital role in HER applications. Herein, a novel strategy to prepare a Ni2P/MoS2 cocatalyst through a simple hydrothermal-phosphorization method was reported, and the prepared cocatalyst was then loaded on an N-doped carbon substrate with excellent conductive performance. The large surface area of the carbon substrate provided many active sites, and the interface between Ni2P and MoS2 improved the catalytic performance for the HER. Compared with pure Ni2P catalyst and MoS2 catalyst, the prepared Ni2P/MoS2 cocatalyst exhibited enhanced catalytic performance. In addition, the results indicate that the prepared cocatalyst has a wide pH range and low onset potential values of 280, 350 and 40 mV in acidic, phosphate-buffered saline and alkaline solutions, respectively, and the corresponding Tafel slopes are 75, 121 and 95 mV dec-1, respectively. Density functional theory (DFT) was adopted to calculate the hydrogen adsorption free energy (ΔGH*). The results showed that the interface between Ni2P and MoS2 reduced ΔGH*, which was beneficial to the adsorption of hydrogen. Present preparation of cocatalysts with unique interfaces provides a new strategy for improving the catalytic performance of HER.
Increasing the greenness of an organic acid through deep eutectic solvation and further polymerisation
Liteng Li, Xiaofang Li, Susu Zhang, Hongyuan Yan, Xiaoqiang Qiao, Hongyan He, Tao Zhu, Baokun Tang
2022, 7(4): 840-853. doi: 10.1016/j.gee.2021.02.006
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Abstract:
Acrylic acid (AA) is an important and widely used industrial chemical, but its high toxicity renders its use incompatible with the concept of green development. By leveraging its terminal carboxyl group and unsaturated bond, we designed and explored a new strategy to increase the greenness of AA via its eutectic melting using a quaternary ammonium salt (choline chloride) to form a deep eutectic solvent (DES), followed by polymerisation of the DES to form a polymer (poly(DES)). The greenness of AA, DES, and poly(DES) was evaluated via an in vitro test using MGC80-3 cells and an in vivo test using Kunming mice. The toxicity improved from Grade 2 (moderately toxic) for AA to Grade 1 (slightly toxic) for DESs and Grade 0 (non-toxic) for poly(DES) in the in vitro test. Moreover, the poly(DES)s showed a lower toxicity in mice than the DESs in the in vivo test. Thus, greenness enhancement was successfully achieved, with the greenness following the order AA < DES < poly(DES). Furthermore, the mechanisms underlying the change in toxicity were explored through microscopy and flow cytometry, which revealed that the DES can permeate the MGC80-3 cell membrane during the G0/G1 phase to adversely affect DNA synthesis in the S phase, but the poly(DES) cannot. Finally, the green poly(DES), which showed good adsorption properties and flexible functionality, was successfully applied as a carrier or excipient of drugs. Through the novel strategy reported herein, greenness enhancement and the broadening of the application scope of a toxic organic acid were achieved, making such acids applicable for green development.

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