Ion-exchange between Na2Ti3O7 and H2Ti3O7 nanosheets at different pH levels: An experimental and first-principles study

• An experimental and theoretical study of titanate nanosheets.
• pH dependence of formation energies of ion-exchange.
• The negative formation energies of ion-exchange decrease with decreasing pH.
• Titanate nanosheet is favorable for ion-exchange in a wide pH range.
• The composition of titanate nanosheet should be Na2−xHxTi3O7 (0

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