Advanced adjustable ionic conductivity of polybenzimidazole membranes with arrayed two-dimensional AlOOH nanosheets for water electrolysis

Abstract

The polybenzimidazole (PBI) membrane is promising but limited by its lower ion conductivity when used in the energy field. Two-dimensional (2D) layered hydroxides with abundant hydroxyl groups could accelerate ion transport. However, the ionic conductivity cannot be adjusted when the 2D nanosheet is introduced by blending or spraying methods. Here, a series of novel arrayed 2D AlOOH-PBI composite membranes with adjustable ionic conductivity were prepared via the in situ growth–etching method through the control of the thickness of nanosheets. The hydroxide ion conductivity of the proposed membrane was about 3.1-fold higher than that of the pristine PBI membrane. The proton conductivity also showed about 1.5-fold enhancement. Meanwhile, the membrane electrode assembly with novel membranes showed a superior voltage performance of 2.06 V at a current density of 1 A cm⁻², and the long-term stability was confirmed for over 200 h at a current density of 500 mA cm⁻² in water electrolysis. These results look promising for the preparation of new membranes for energy applications.