The electrochemical behavior of TiO2-NTAs electrode in H+ and Al3+ coexistent aqueous solution

• In the AlCl3 aqueous solution, TiO2-NTAs are electrochemical active to both of H+ and Al3+.
• H+ is preferential to hydroxylate on the TiO2-NTAs surface rather than to intercalate in the TiO2-NTAs lattice as compared with Al3+.
• Considerable Al3+ could be intercalated in the TiO2-NTAs lattice with the assistance of Cl- in the AlCl3 aqueous solution with lower acidity.

The concept of aqueous solution Al-ion battery inspires much enthusiasm in developing a novel chemical power source. In this work, the electrochemical behavior of TiO2-NTAs electrode in Al3+aqueous solution with different acidity is evaluated.Electrochemical studies showed that both of H+ and Al3+ in aqueous solution are electrochemical active to TiO2-NTAs, however, H+ is preferential to hydroxylate on the TiO2-NTAs surface rather than to intercalate in the TiO2-NTAs lattice as compared with Al3+under the assistance of Cl−. The surface hydroxylation of TiO2-NTAs can retard Al3+ diffusion in the TiO2-NTAs lattice as evidenced by the increase of faradic resistance RF (by EIS) at initial cathodic polarization process, however, the subsequent decrease of RF is due to the conductance improvement of TiO2-NTAs with the Al3+ intercalation. Here it can be concluded that for Al3+ aqueous solution battery with TiO2-NTAs as electrode, the suitable acidity (pH≈3) is required to minimizing the effect of H+.