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Liang H, Zou S, Liu M, Yin T, Xia X, Hua X, Fu Y, Bu Y. Highly Concentrated Electrolyte Superlubricants Enhanced by Interfacial Water Competition Around Chemically Active MgO Additives. ACS APPLIED MATERIALS & INTERFACES 2024; 16:11997-12006. [PMID: 38394677 DOI: 10.1021/acsami.3c15826] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/25/2024]
Abstract
The low concentration of water-based lubricants and the high chemical inertness of the additives involved are often regarded as basic norms in the design of liquid lubricants. Herein, a novel liquid superlubricant of an aqueous solution containing a relatively high concentration of salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), is reported for the first time, and the superlubricity stability and load-bearing capacity of the optimized system (MgO0.10/LiTFSI10) are effectively strengthened by the addition of only trace (0.10 wt %) water-chemically active MgO additives. It demonstrates higher applicable loads, lower COF (∼0.004), and stability relative to the base solution. Only a trace amount of MgO additive is needed for the superlubricity, which makes up for the cost and environmental deficiencies of LiTFSI10. The weak interaction region between free water and the outer-layer water of Li+ hydration shells becomes a possible ultralow shear resistance sliding interface; the Mg(OH)2 layer, generated by the reaction of MgO with water, further creates additional weakly interacting interfaces, leading to the formation of an asymmetric contact between the clusters/particles within the hydrodynamic film by moderating the competition between interfacial water and free water, thus achieving high load-bearing macroscopic superlubricity. This study deepens the contribution of electrolyte concentration to ionic hydration and superlubricity due to the low shear slip layer formed by interfacial water competition with water-activated solid additives, providing new insights into the next generation of high load-bearing water-based liquid superlubricity systems.
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Affiliation(s)
- Hongyu Liang
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Shijing Zou
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Manqiang Liu
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Tianqiang Yin
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Xiaojie Xia
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Xijun Hua
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Yonghong Fu
- Institute of Advanced Manufacturing and Modern Equipment Technology, School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Yongfeng Bu
- Institute for Energy Research, Jiangsu University, Zhenjiang 212013, China
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Tofoni A, Tavani F, Vandone M, Braglia L, Borfecchia E, Ghigna P, Stoian DC, Grell T, Stolfi S, Colombo V, D’Angelo P. Full Spectroscopic Characterization of the Molecular Oxygen-Based Methane to Methanol Conversion over Open Fe(II) Sites in a Metal-Organic Framework. J Am Chem Soc 2023; 145:21040-21052. [PMID: 37721732 PMCID: PMC10540213 DOI: 10.1021/jacs.3c07216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Indexed: 09/19/2023]
Abstract
Iron-based enzymes efficiently activate molecular oxygen to perform the oxidation of methane to methanol (MTM), a reaction central to the contemporary chemical industry. Conversely, a very limited number of artificial catalysts have been devised to mimic this process. Herein, we employ the MIL-100(Fe) metal-organic framework (MOF), a material that exhibits isolated Fe sites, to accomplish the MTM conversion using O2 as the oxidant under mild conditions. We apply a diverse set of advanced operando X-ray techniques to unveil how MIL-100(Fe) can act as a catalyst for direct MTM conversion. Single-phase crystallinity and stability of the MOF under reaction conditions (200 or 100 °C, CH4 + O2) are confirmed by X-ray diffraction measurements. X-ray absorption, emission, and resonant inelastic scattering measurements show that thermal treatment above 200 °C generates Fe(II) sites that interact with O2 and CH4 to produce methanol. Experimental evidence-driven density functional theory (DFT) calculations illustrate that the MTM reaction involves the oxidation of the Fe(II) sites to Fe(III) via a high-spin Fe(IV)═O intermediate. Catalyst deactivation is proposed to be caused by the escape of CH3• radicals from the relatively large MOF pore cages, ultimately resulting in the formation of hydroxylated triiron units, as proven by valence-to-core X-ray emission spectroscopy. The O2-based MTM catalytic activity of MIL-100(Fe) in the investigated conditions is demonstrated for two consecutive reaction cycles, proving the MOF potential toward active site regeneration. These findings will desirably lay the groundwork for the design of improved MOF catalysts for the MTM conversion.
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Affiliation(s)
- Alessandro Tofoni
- Dipartimento
di Chimica, Università degli Studi
di Roma “La Sapienza”, P.le A. Moro 5, I-00185 Rome, Italy
| | - Francesco Tavani
- Dipartimento
di Chimica, Università degli Studi
di Roma “La Sapienza”, P.le A. Moro 5, I-00185 Rome, Italy
| | - Marco Vandone
- Dipartimento
di Chimica & UdR INSTM di Milano, Università
degli Studi di Milano, Via Golgi 19, 20133 Milan, Italy
| | - Luca Braglia
- CNR-Istituto
Officina dei Materiali, TASC, 34149 Trieste, Italy
| | - Elisa Borfecchia
- Dipartimento
di Chimica & UdR INSTM di Torino, Università
di Torino, Via P. Giuria
7, 10125 Turin, Italy
| | - Paolo Ghigna
- Dipartimento
di Chimica, Università di Pavia, V.le Taramelli 13, I-27100 Pavia, Italy
| | - Dragos Costantin Stoian
- The Swiss-Norwegian
Beamlines (SNBL), European Synchrotron Radiation Facility, BP 220, 38043 Grenoble, France
| | - Toni Grell
- Dipartimento
di Chimica & UdR INSTM di Milano, Università
degli Studi di Milano, Via Golgi 19, 20133 Milan, Italy
| | - Sara Stolfi
- CNR-Istituto
Officina dei Materiali, TASC, 34149 Trieste, Italy
| | - Valentina Colombo
- Dipartimento
di Chimica & UdR INSTM di Milano, Università
degli Studi di Milano, Via Golgi 19, 20133 Milan, Italy
- CNR
− SCITEC − Istituto di Scienze e Tecnologie Chimiche
“Giulio Natta”, Via Golgi 19, 20133 Milan, Italy
| | - Paola D’Angelo
- Dipartimento
di Chimica, Università degli Studi
di Roma “La Sapienza”, P.le A. Moro 5, I-00185 Rome, Italy
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