Defect-engineered hexagonal boron nitride nanosheets as a new atomic-level directional ion conductor

With electron-conducting information technology, ion-conducting energy and environmental technology are promising for wide applications in a carbon-neutral world, but it has been challenging to achieve directional ion conduction in fast ion conductors, especially at the microscopic or even atomic scale. Here, the authors report a new atomic-level directional ion conductor of defect-engineered hexagonal boron nitride (h-BN) nanosheets for bioinspired nanofluidic iontronic devices, and propose a vacancy-defect-controlled strategy to achieve atomiclevel directional hydrogen ion conduction in h-BN nanosheets. The adsorption and migration behaviors of hydrogen ions in h-BN nanosheets with both B and N vacancy defects were systematically investigated through the first-principle method. The best hydrogen adsorption sites are directly above N and B atoms in the B-vacancy and N-vacancy h-BN, respectively. It is found that the migration barriers of hydrogen ion in B-vacancy and Nvacancy h-BN are as high as 1.83-2.47 eV and 1.71-2.30 eV, respectively, which are much higher than the 0.72 eV of intrinsic h-BN nanosheets. This means that hydrogen ions can conduct in defect-free h-BN, while they cannot conduct in B/N-vacancy defects. Accordingly, hydrogen ion conduction in h-BN nanosheets can be directionally controlled by controlling the position of vacancy defects, which can be artificially constructed by femtosecond laser plasma lithography. This work provides a new technology of vacancy-defect-controlled atomic-level directional ions conduction in 2D materials for ion-conductor integrated circuit, and opens the door for constructing bioinspired nanofluidic iontronic devices in future neuronal-computer interfaces.