Browsing by Department "Tianjin University"

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  • Catalytic Ethanolysis of Enzymatic Hydrolysis Lignin over an Unsupported Nickel Catalyst : The Effect of Reaction Conditions
    (2021-01-07) Sang, Yushuai; Wu, Kai; Liu, Qingfeng; Bai, Yunfei; Chen, Hong; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The effect of reaction conditions on ethanolysis of enzymatic hydrolysis lignin (EHL) with an unsupported nickel catalyst, that is, Ni(220H), was investigated. The two-dimensional heteronuclear single quantum coherence-nuclear magnetic resonance (2D-HSQC NMR) analysis of liquid products revealed that both the ether and C-C linkages in EHL were cleaved during the reaction and the ether linkages were completely cleaved under mild reaction conditions, while the cleavage of C-C linkages needed harsh reaction conditions. At 280 °C under 2 MPa H2 within 6 h, the highest aromatic monomer yield of 28.5 wt % was achieved. Further increasing the reaction temperature to 300 °C or decreasing the initial hydrogen pressure to 0 MPa was conducive to the repolymerization reaction. The ortho-alkyl phenol monomers originated from the alkyl free radicals produced from ethanol. Under 0 MPa H2, the hydrogenation of -HCCH- in side chains was inefficient, and hence, the decarboxylation and alkenyl elimination reactions of side chains were favorable.
  • Coupling Tetraalkylammonium and Ethylene Glycol Ether Side Chain To Enable Highly Soluble Anthraquinone-Based Ionic Species for Nonaqueous Redox Flow Battery
    (2022-04-20) Zhen, Yihan; Zhang, Cuijuan; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Nonaqueous redox flow batteries (NARFBs) have promise for large-scale energy storage with high energy density. Developing advanced active materials is of paramount importance to achieve high stability and energy density. Herein, we adopt the molecular engineering strategy by coupling tetraalkylammonium and an ethylene glycol ether side chain to design anthraquinone-based ionic active species. By adjusting the length of the ethylene glycol ether chain, an ionic active species 2-((9,10-dioxo-9,10-dihydroanthracen-1-yl)amino)-N-(2-(2-methoxyethoxy)ethyl)-(N,N-dimethylethan-1-aminium)-bis(trifluoromethylsulfonyl)imide (AQEG2TFSI) with high solubility and stability is obtained. Paired with a FcNTFSI cathode, the full battery provides an impressive cycling performance with discharge capacity retentions of 99.96% and 99.74% per cycle over 100 cycles with 0.1 and 0.4 M AQEG2TFSI, respectively.
  • An Efficient and Stable Lithium-Oxygen Battery Based on Metal-Organic Framework Separator Operating at 160 °C
    (2023-12-21) Qiu, Qianyuan; Yuan, Jiashu; Li, Gen; Pan, Zheng-ze; Yao, Penghui; Zhao, Yicheng; Zhang, Cuijuan; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A lithium oxygen battery (LOB) with molten salt electrolyte operating at elevated temperature has aroused great interest because it enables fast reaction kinetics. However, there is still a lack of open literature on the separator (membrane) of this kind of LOB. Metal-organic framework (MOF) materials are widely used as components of separators in many kinds of energy storage devices, due to their regular crystalline and well-defined pore structures. In this work, a MOF material, zirconium (II) 1,4-benzenedicarboxylate after lithiation (UiO-66-SO3Li) with a narrow pore size (6 Å), is used as a key component of the separator for LOB operating at elevated temperature. A “rolling dough” method is adopted to prepare the separator, which achieves 100% material utilization. The LOB with this membrane operates at 160 °C and delivers a specific capacity of 5.1 mAh cm−2 with an overpotential as low as 40 mV at 0.1 mA cm−2 and a prolonged cycle life, 180 cycles with a high coulombic efficiency of 99.9% at 0.5 mA cm−2. This MOF-based membrane provides efficient Li+ transfer and restricts discharge product migration during battery operation, which is promising for the development of LOB in large-scale practical applications.
  • Efficient Selective Oxidation of 5-Hydroxymethylfurfural with Oxygen over a ZnCrAl Mixed Oxide Catalyst Derived from Hydrotalcite-like Precursor
    (2022-08-10) Li, Yingying; Ma, Xueli; Lv, Wei; Chen, Hong; Yu, Linhao; Ma, Zewei; Wang, Sen; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cr-doped ZnAl mixed oxide catalysts (Zn0.75CrAl-x-c) were obtained via calcining the Zn0.75CrAl-x hydrotalcite precursors and were applied in the selective oxidation of 5-hydroxymethylfurfural (5-HMF) to 2,5-furandicarboxylic acid (FDCA). Cr doping significantly enhanced the catalytic activity. A 95.1% 5-HMF conversion with an 88.1% FDCA selectivity was achieved over the Zn0.75CrAl-6-c catalyst at 130 °C under 0.6 MPa oxygen for 4 h. The good performance was associated with the high specific surface area and high oxygen vacancy concentration. Moreover, the Zn0.75CrAl-6-c catalyst was used for five cycles without a significant activity loss indicating excellent stability.
  • Engineering the Mechanically Mixed BaMnO3-CeO2 Catalyst for NO Direct Decomposition: Effect of Thermal Treatment on Catalytic Activity
    (2023-02) Ning, Huanghao; Ji, Wenxue; Li, Yongdan; Zhang, Cuijuan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A 5 wt% BaMnO3-CeO2 composite catalyst prepared by the one-pot method exhibits extraordinary catalytic performance for nitrogen monoxide (NO) direct decomposition into N2 and O2; however, the reasons for the high activity remain to be explored. Here, the catalyst was prepared by mechanical mixing and then subjected to thermal treatment at different temperatures (600–800 °C) to explore the underlying reasons. The thermal pre-treatment at temperatures higher than 600 °C can improve the catalytic activity of the mechanically mixed samples. The 700 °C-treated 5%BaMnO3-CeO2 sample shows the highest activity, with NO conversion to N2 of 13.4%, 40.6% and 57.1% at 600, 700, and 800 °C, respectively. Comparative activity study with different supports (ZrO2, TiO2, SiO2, Al2O3) reveals that CeO2 is indispensable for the high performance of a BaMnO3-CeO2 composite catalyst. The Ce species (mainly Ce3+) in CeO2 components diffuse into the lattice of BaMnO3, generating oxide ion vacancy in both components as evidenced by X-ray photoelectron spectroscopy and Raman spectra, which accelerates the rate-determining step and thus higher activity. The chemisorption results show that the interaction between BaMnO3 and CeO2 leads to higher redox activity and mobility of lattice oxygen. This work demonstrates that engineering the oxide ion vacancy, e.g., by thermal treatment, is an effective strategy to enhance the catalytic activity towards NO direct decomposition, which is expected to be applicable to other heterogeneous catalysts involving oxide ion vacancy.
  • Physical Layer Authentication for Massive MIMO Systems with Hardware Impairments
    (2020-03) Zhang, Pinchang; Taleb, Tarik; Jiang, Xiaohong; Wu, Bin
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We study transmitter authentication in massive multiple-input multiple-output (MIMO) systems with non-ideal hardware for the fifth generation (5G) and beyond networks. A new channel-based authentication scheme is proposed by taking hardware impairments into account. Based on signal processing theory, we first formulate channel estimation under hardware impairments and determine error covariance matrix to assess the quantity caused by hardware impairments on authentication performance. With the help of hypothesis testing and matrix transformation theories, we are then able to derive exact expressions for the probabilities of false alarm and detection under different channel covariance matrix models. Extensive simulations are carried out to validate theoretical results and illustrate the efficiency of the proposed scheme. Impacts of system parameters on performance are revealed as well.
  • Recent development in two-dimensional material-based membranes for redox flow battery
    (2022-12) Yuan, Jiashu; Xia, Yonggao; Chen, Xiaoping; Zhao, Yicheng; Li, Yongdan
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Redox flow battery (RFB) has been widely considered to be one of the most promising grid-scale energy-storage technology. The membrane, namely separator, serves as preventing the crossover of the positive and negative active species, while facilitating the transport of the supporting electrolyte ions, is crucial to achieve a high performance and a long-term stability for an RFB. Advances in RFBs require high-performance and low-cost membranes with high ion-selective transport for the application of large-scale energy storage. Two-dimensional (2D) materials have emerged as promising functional materials owing to their atomic-scale thickness and unique physical/chemical properties, which have great potential in the application of RFB membrane. Focusing on the recent state-of-the-art of 2D materials, in this mini review, various 2D materials applied in the membrane for RFB are briefly introduced. A perspective on the near-future developments of 2D materials in RFB membranes is presented.
  • Recent Progress in the Integration of CO2 Capture and Utilization
    (2023-06) Ning, Huanghao; Li, Yongdan; Zhang, Cuijuan
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    CO2 emission is deemed to be mainly responsible for global warming. To reduce CO2 emissions into the atmosphere and to use it as a carbon source, CO2 capture and its conversion into valuable chemicals is greatly desirable. To reduce the transportation cost, the integration of the capture and utilization processes is a feasible option. Here, the recent progress in the integration of CO2 capture and conversion is reviewed. The absorption, adsorption, and electrochemical separation capture processes integrated with several utilization processes, such as CO2 hydrogenation, reverse water–gas shift reaction, or dry methane reforming, is discussed in detail. The integration of capture and conversion over dual functional materials is also discussed. This review is aimed to encourage more efforts devoted to the integration of CO2 capture and utilization, and thus contribute to carbon neutrality around the world.
  • Solvent- And Base-Free Oxidation of 5-Hydroxymethylfurfural over a PdO/AlPO4-5 Catalyst under Mild Conditions
    (2021-09-22) Yu, Linhao; Chen, Hong; Wen, Zhe; Ma, Xueli; Li, Yingying; Li, Yongdan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A solvent-free method was proposed to upgrade the biomass-derived compound 5-hydroxymethylfurfural (HMF). The oxidation of HMF to produce 2,5-furandicarboxylic acid (FDCA) has been examined in the presence of O2 without the addition of solvent and base. Different from the conversion of the aldehyde group on HMF as the initial oxidation step in H2O solvent, the hydroxyl group on HMF was first oxidized and FDCA was finally generated without the addition of solvent. The role of O2 is to replenish the consumption of active oxygen species on the catalyst surface. The oxidation of HMF to FDCA proceeded due to the solvent-free effect. A 83.6% FDCA selectivity at 38.8% HMF conversion was measured with a PdO/AlPO4-5 catalyst at 80 °C for 5 h and the reaction mechanism was proposed.
  • Tuning the Catalytic Activity of Complex Metal Oxides Prepared by a One-Pot Method for NO Direct Decomposition
    (2021-07-07) Wei, Miao; Xie, Pingping; Yong, Xin; Li, Yongdan; Zhang, Cuijuan
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The complex metal oxides xLa-Sr-Co-Fe/MgO (x = 10-80 wt %) were prepared via a one-pot method for NO direct decomposition. The X-ray diffraction results show a gradual transformation of La-Sr-Co-Fe oxide from the Ruddlesden-Popper structure (A2BO4) to the perovskite structure (ABO3) with increasing x accompanied with Mg doping into the lattice of La-Sr-Co-Fe oxide. The NO direct decomposition activity decreases with x when x ≤ 60% and then increases with further loading. The 10% La-Sr-Co-Fe/MgO sample shows high activity and high oxygen resistance with a NO conversion to N2 of ∼46% in the presence of 10% O2 at 850 °C (W/F = 1.5 g s/cm3). Several characterization techniques have been employed to reveal the composition-structure-activity relationship. The MgO component increases the sintering resistance of catalysts, and thus, the surface area increases with the MgO content. The reducibility of Co/Fe species, content of oxide ion vacancies at the surface, mobility of lattice oxygen, and content of NO sorption decrease with x for x ≤ 60% and then increase with a further increase in x, which are responsible for the activity variation.