Ion-exchange between Na2Ti3O7 and H2Ti3O7 nanosheets at different pH levels: An experimental and first-principles study |
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| Institution: | 1. School of Materials Science and Engineering, Heilongjiang University of Science and Technology, Harbin 150022, China;2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;1. Institute of Physics, National Academy of Sciences of Ukraine, 46 pr. Nauki, Kiev 03028, Ukraine;2. Physical–technical Research Institute, Nizhni Novgorod State University, Nizhni Novgorod 603950, Russia;1. CIC Energigune, C/Albert Einstein 48, Parque Tecnológico de Álava, Miñano, 01510, Spain;2. Departamento de Química Inorgánica, Universidad del País Vasco, UPV/EHU, P.O.Box.664, Leioa, 48080, Spain;1. State Key Laboratory of Fine Chemical, School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, PR China;2. Key Lab of Heat Transfer Enhancement and Energy Conservation of Ministry of Education, School of Chemistry & Chemical Engineering, South China University of Technology, Guangzhou, 510640, PR China;3. Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Nankai University, Tianjin, 300071, PR China;4. Discipline of Chemistry, School of Environmental & Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia |
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| Abstract: | The models of Na2?xHxTi3O7 (x=0, 1, and 2) nanosheets were proposed to investigate the formation energies of ion-exchange using first-principles calculations. The calculated results demonstrated that sodium titanate nanosheet is energetically favorable for ion-exchange in a wide pH range, from acidic solution to even highly concentrated alkaline aqueous solution due to the negative formation energies. Therefore, the composition of sodium titanate nanosheet in alkaline solution should be Na2?xHxTi3O7 (0<x≤2) rather than Na2Ti3O7. The formation energies of ion-exchange decrease with the pH decreasing. As a result, the thermodynamic driving force of ion-exchange is enhanced at low pH level. To further verify the calculated results, the ion-exchange properties of a series of titanate nanosheets in aqueous solutions at different pH levels were investigated. The experimental results are in good agreement with the theoretical deduction. |
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| Keywords: | Nanosheet Ion-exchange First-principle |
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